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Recovery of zinc sulphate from industrial effluents by liquid–liquid extraction using D2EHPA (di-2-ethylhexyl phosphoric acid)
Abstract
The liquid–liquid extraction of zinc using D2EHPA as extractant has been investigated in this paper in order to recover zinc sulphate from an industrial effluent produced by Votorantim Co. (Brazil) which contains several metallic species such as cadmium, cobalt, iron, lead, calcium, magnesium, manganese and nickel. The study was carried out in two main steps: (1) extraction and stripping laboratory scale tests in order to assess adequate operational conditions for the favourable recovery of zinc from the effluent and (2) continuous pilot scale tests using a mixer-settler battery aiming to reproduce the bench results. In the laboratory scale experiments, operating variables such as the pH of the aqueous effluent (0.5–5.0), concentration of D2EHPA (5–50%,w/w) and aqueous/organic volumetric phase ratio (1/5–5/1) were investigated for the zinc extraction process; for the zinc stripping process, the organic/aqueous volumetric phase ratio (1/1–10/1) was studied by contacting a metal loaded organic phase with an industrial acid solution produced by the company in the electrolysis of zinc. The continuous mixer-settler tests have shown that zinc can be selectively and quantitatively removed from the effluent (around 98%) using 3 extraction stages (pH 2.5, [D2EHPA] = 20% (w/w) and A/O = 1), and other 3 stripping stages (O/A = 4). A final solution containing 125.7 g/L of zinc was obtained that could be sent directly to electrowinning.
... Use of D2EHPA, PC-88A, CYANEX 272, and CYANEX 301 as Zn extractant for the solvent extraction of Zn from Zn-bearing sulfate media is discussed in details [40][41][42]. D2EHPA [41,[43][44][45][46][47][48][49][50][51][52][53][54], TBP and D2EHPA [55], LIX 984 N [56], and Ionquest 801 [57] solvent extraction agents were used for the solvent extraction of Zn. Sze and Hue [58] investigated extraction of Zn and Cr from alloy electroplating wastewater using D2EHPA, PC-88A, Cyanex 272, and Cyanex 302 and determined the formation of a third phase when ammoniated Cyanex 272 and Cyanex 302 solvents used. ...
... Thus, pH 2.5 was considered as optimum pH value for the extraction experiments to avoid high Fe extraction and possible Fe precipitation during pH adjustment. Optimum pH values for the extraction Zn from Zn-bearing solutions by D2EHPA solvent extraction agent are reported as 2.5 and 3 in literature [46,52,73]. 71% of Zn, 54% of Fe, 28% of Ca, 18% of Mg, 15% of Mn, and 3% of Si are extracted at pH 2.5. ...
... In addition, low Zn extraction rates are obtained when diluted extractant used. 20% D2EHPA (vv) is found to be optimum extractant concentration to obtain considerable Zn extraction rate and low impurity extraction rate in this work and literature [44,46,59,74,75]. Fig. 11. Figure 11 shows that peaks in XRD diagram of the precipitate and sample are in good agreement with ZnC 2 O 4 •2H 2 O (ICDD 00-025-1029) and ZnO (ICDD 01-079-2205), respectively. ...
A large amount of electric arc furnace dust (EAFD) is produced as hazardous waste materials during steelmaking in electric arc furnace. EAFD includes a considerable amount of zinc. Recovery of Zn as ZnO from EAFD via mechanochemical leaching, solvent extraction, precipitation, and thermal decomposition route was investigated. Dissolution behavior of Zn, Fe, Mn, Si, Mg, and Ca during the mechanochemical leaching of EAFD in H2SO4 solution was determined. Optimum mechanochemical leaching parameters were considered as 10 g of EAFD, 2 M H2SO4, 240 min of reaction time, ball to the dust weight ratio of 20, and rotational speed of 500 rpm. D2EHPA solution (20%, vv) was used for solvent extraction of Zn from mechanochemical leach solution. McCabe–Thiele diagrams constructed for extraction and stripping stages indicated that 95% of zinc in the leach solution was extracted in three stages at A:O = 1:1, while 97% of Zn was stripped from loaded organic phase at operating line of A:O = 4:1. ZnC2O4∙2H2O powder was precipitated from strip solution obtained by solvent extraction by adding oxalic acid solution at pH 4. Thermal properties of ZnC2O4·2H2O precipitated were investigated by thermogravimetric–differential thermal analysis technique. High-purity ZnO was obtained by thermal decomposition of ZnC2O4∙2H2O precipitated.
... mol/L) have a synergetic effect on zinc extraction. In another research by Pereira et al., 98% of zinc has been extracted from a waste stream using 20% D2EHPA at pH 2.5 after three extraction steps [20]. Also, Balesini et al. [21] reported that 98.8% of zinc can be extracted from a solution containing zinc, cadmium, and nickel using 40% (v/v) D2EHPA, pH 2.5, O/A = 1:4 which is in agreement with the results obtained by Vahidi et al. [22]. ...
... This predictive GEP model is formulated in the form of Eqs. (17)(18)(19)(20)(21)(22)(23)(24)(25)(26) for genes number 1 to 10, respectively. Providing an accurate formula for estimating bioleaching problems is still attractive and advantageous. ...
Attempts to predict metal recovery accurately have been hindered by the complexity of the solvent extraction process, nonlinear effects, and the multitude of influencing factors. Conventional computing algorithms must be improved for solving practical problems due to insufficient or noisy data and complex multidimensional scenarios. In this study, a gene expression programming (GEP) model was developed to predict zinc extraction (ZE) from the bioleaching process utilizing the most influential parameters such as stirring speed (0–800 rpm), temperature (25–45 °C), pH (1–2.5), Di-(2-ethylhexyl) phosphoric acid (D2EHPA) concentration (5–20%), phase ratio (1:5–10:1), saponification degree (0–40%), and contact time (0–900 s) as the input parameters. Under optimal conditions of 20% D2EHPA, 15% saponification degree, 650 rpm stirring speed, pH2, and an A:O ratio of 1:1, zinc extraction reached 98.4%. The main motivation for constructing the GEP model is to present a rational mathematical model with more accurate results than statistical models. Furthermore, a model should be applicable for future usages to predict the value of metal recovery using independent variables accurately. The developed GEP model outperformed multiple linear regression and multiple nonlinear regression models with the adjusted R2 of 0.9551 and 0.9453, RMSE of 5.5100 and 7.2727, MAE of 0.0758 and 2.8308, MARE of 0.0260 and 0.0334, and VAF of 92.3069 and 87.9199 for the respective training and testing parts. Besides, the sensitivity analysis was performed using the cosine amplitude (CA) technique, and the stirring speed and D2EHPA concentration have the highest (rij = 0.931) and lowest (rij = 0.581) impact on the predicted ZE, respectively. The conducted study proves the appropriateness of the developed GEP model for ZE prediction.
... Studying a suitable extractant for zinc removal, organophosphorus extractants have been shown to selectively recover zinc from solutions (Mellah and Benachour, 2006;Owusu, 1998;Pereira et al., 2007). Among various organophosphorus extractants, El Dessouky et al. (2008) investigated the separation of Zn(II), Fe(II), Fe(III), and Cd(II) using tributylphosphate (TBP) and trioctyl phosphine oxide (CYANEX 921) in kerosene from a chloride medium and reported the better performance of TBP compared to Cyanex921. ...
... This shift leads to an increase in the consumption of zinc ions and, subsequently, raises efficiency. Our findings are in agreement with those of other studies in which the zinc extraction efficiency increases until the pH of 2.5 ± 0.1 (Asadi et al., 2018;Long et al., 2010;Pereira et al., 2007;Vahidi et al., 2009). Above this level, increasing the pH did not affect the metal extraction, and a saturation point is reached at pH = 2.5. ...
The efficiency of zinc(II) extraction with di(2-ethylhexyl) phosphoric acid (D2EHPA) diluted in kerosene has been investigated in batch and continuous extraction columns, enabling a comparison between the performance of spray and packed column. The effect of pH of the aqueous phase, reaction time, and extractant volume ratio were considered as the operational variables in a lab-scale mixer-settler in batch mode. The optimum values for each variable were determined and used as the constant values in the pilot-scale continuous setup for optimization of the extraction process in the columns. A pilot-scale setup can provide more relatable results to industrial-scale production. The effect of dispersed phase flow rate, system temperature, nozzle diameter, and height of packing were investigated in continuous mode in spray and packed pilot-scale columns. To minimize the number of experiments, the response surface methodology (RSM) design of experiments (DOE) was adopted using five levels for each parameter. The effect of each variable and their binary and ternary interactions were analyzed by analysis of variance (ANOVA) with a confidence level of 95%. Maximum zinc extraction efficiency in the batch mode was 93.63%, which occurred at the pH of 2, a reaction time of 25 min, and an extractant volume ratio of 15% (V/V D2EHPA to kerosene). Maximum zinc extraction in the spray and packed columns were 76.13% and 84.06%, respectively. Despite the lower extraction efficiency in the continuous mode, a considerably lower required organic to aqueous ratio make these setups more favorable over traditional mixers.
... The purification of the leachate can be done via several different stages, e.g., cementation [26,27], precipitation [28][29][30][31], or solvent extraction (SX) [17,[32][33][34][35][36][37]. The most commonly used SX reagents for Zn extraction are organophosphorus extractants, i.e., di(2-ethylhexyl)phosphoric acid (D2EHPA), 2-ethylhexyl phosphonic acid mono-2-ethyl hexyl ester (PC88A) and bis (2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) [34,[38][39][40]. ...
... Fig. 2 shows that extractions of Zn and Mn using D2EHPA ( Fig. 2A) and Cyanex 572 (Fig. 2B) are favored with increasing pH as predicted by Eq. (1) by cation exchange mechanism. Similar behaviors of Zn and Mn extraction with acidic extractants are also reported in the literature [32,[34][35][36][37][44][45][46][47]. ...
Electric arc furnace (EAF) dust is globally one of the biggest metal-containing waste fractions, with a composition that challenges the recycling of dust back to the steel process due to the high Zn and Pb content, which also prevents it from being landfilled. The current study presents a process flowsheet with zinc and lead removal from EAF dust via citric acid leaching, lead removal by precipitation, and further solvent extraction (SX) of zinc for recovery. The process produces fractions that can be directly routed back to a steel plant (leach residue), a zinc electrowinning process (pregnant leach solution, PLS), and a lead smelter (lead sulfate, PbSO4 precipitate). Moreover, zinc separation by solvent extraction from citric acid leach solution originating from EAF was performed successfully with minimal impurity content in the final electrolyte, using di(2-ethylhexyl)phosphoric acid (D2EHPA). The total lead removal from PLS was achieved with an addition of only 0.012 M sulfate ion (from sulfuric acid) at room temperature. The optimization of zinc separation via SX was performed at a temperature range of 25–55 °C varying the D2EHPA concentration (10–25 vol-%) with different O/A ratios. With an optimized EAF SX process (pH = 5, t = 15 min, T = 25 °C, CD2EHPA = 20 vol-%, O/A = 1:1) and stripping process (t = 15 min, T = 25 °C, CH2SO4 = 1 M, O/A = 3:1), the zinc content in the electrolyte could be enriched up to 50 g/L, and the amount of impurities in the solution decreased down to a level where they have no adverse effect on the zinc electrowinning process and final zinc recovery. Moreover, the iron-rich leach residue was also shown to be chemically suitable as a raw material for the EAF process. With the proposed roasting-leaching-precipitation-SX-EW unit operation, EAF dust can be converted into three different secondary raw material streams, suitable for integration into state-of-the-art processes.
... Owusu (1998) reported the use of di-(2-ethylhexyl) phosphoric acid for extracting Zn from plant cake leach solutions with approximately full recovery of Zn. Using the same solvent, Pereira et al. (2007) reported a similar Zn recovery rate from the industrial effluent. Other than Zn, other metal ions can also be effectively extracted by the di-(2-ethylhexyl) phosphoric acid. ...
The demand for 2-ethylhexanol is rising in several sectors, yet this chemical is actually almost exclusively produced from petroleum resources, calling for sustainable alternatives. Here we review the production of 2-ethylhexanol from lignocellulosic biomass-derived chemicals with emphasis on 2-ethylhexanol synthesis and applications. 2-Ethylhexanol can be synthesized from ethanol, butanol, butyraldehyde, and syngas. Applications comprise biofuels, lubricants, plasticizers, and surfactants.
... Over the years, SPE has been used to extract PhACs, pesticides, and PCPs and their TPs from aqueous matrices (Campos-Mañas et al., 2019;Gago-Ferrero et al., 2013;Pereira et al., 2007;Poirier-Larabie et al., 2016). SPE has several advantages, including improved analyte extraction, lesser organic solvent usage (acetonitrile, ethanol, etc.), and reduced emulsion formation (Ahadi et al., 2011). ...
Micropollutants have become ubiquitous in aqueous environments due to the increased use of pharmaceuticals, personal care products, pesticides, and other compounds. In this review, the removal of micropollutants from aqueous matrices using various advanced oxidation processes (AOPs), such as photocatalysis, electrocatalysis, sulfate radical-based AOPs, ozonation, and Fenton-based processes has been comprehensively discussed. Most of the compounds were successfully degraded with an efficiency of more than 90%, resulting in the formation of transformation products (TPs). In this respect, degradation pathways with multiple mechanisms, including decarboxylation, hydroxylation, and halogenation, have been illustrated. Various techniques for the analysis of
micropollutants and their TPs have been discussed. Additionally, the ecotoxicity posed by these TPs was determined using the toxicity estimation software tool (T.E.S.T.). Finally, the performance and cost-effectiveness of the AOPs at the pilot scale have been reviewed. The current review will help in understanding the treatment efficacy of different AOPs, degradation pathways, and ecotoxicity of TPs so formed.
... Di-(2ethylhexyl)phosphoric acid (D2EHPA) is one of the most popular acidic extractants due to its selectivity, versatility, commercial availability, good physicochemical properties, and chemical stability. For decades, D2EHPA has been employed in the separation of rare-earth elements [1][2][3], nickel and cobalt [4], indium and gallium [5], zinc [6], vanadium [7], and iron [8]. As an acidic extractant, D2EHPA extracts metal ions via the following (simplified) reaction mechanism: With M n+ the aqueous metal ion, HL and L − the undissociated and dissociated extractant, and (a) and (o) the aqueous and organic phases respectively. ...
... Medina et al. (2005) agreed that the carrier lost the ability to form a complex with the Zn ions at higher proton concentrations. Such behavior is found typical for metal cation extraction by cationic extractants where the increase in pH (lower concentration of proton) commonly results in enhanced metal extraction up to a threshold (Pereira et al. 2007). Other than that, Zn ion speciation at varying pH is another factor to be considered. ...
Zinc (Zn) was identified as one of the most toxic heavy metals and often found contaminating the water sources as a result of inefficient treatment of industrial effluent. A green emulsion liquid membrane (GELM) was proposed in this study as a method to minimize the concentration of Zn ions in an aqueous solution. Instead of the common petroleum-based diluent, the emulsion is reformulated with untreated waste cooking oil (WCO) collected from the food industry as a sustainable and cheaper diluent. It also includes Bis(2-ethylhexyl) phosphate (D2EHPA) as a carrier, Span 80 as a surfactant, sulfuric acid (H2SO4) as an internal phase, and ZnSO4 solution as an external phase. Such formulation requires a thorough understanding of the oil characteristics as well as the interaction of the components in the membrane phase. The compatibility of WCO and D2EHPA, as well as the external phase pH, was confirmed via a liquid–liquid extraction (LLE) method. To obtain the best operating conditions for Zn extraction using GELM, the extraction time and speed, carrier, surfactant and internal phase concentrations, and W/O ratio were varied. 95.17% of Zn ions were removed under the following conditions; 0.001 M of H2SO4 in external phase, 700 rpm extraction speed for 10 min, 8 wt% of carrier and 4 wt% of surfactant concentrations, 1:4 of W/O ratio, and 1 M of internal phase concentration.
... Numerous studies have been carried out on zinc solvent extraction from inorganic pregnant leach solution (PLS) using D2EHPA as extractant. [32][33][34][35][36][37][38][39] More than 95% of Zn extraction with D2EHPA was reported between 25 and 40°C at very low pH between 1 and 3 for most of the researchers. The solvent extraction of zinc from organic leach solutions using D2EHPA, on the other hand, has not been extensively reported compared to inorganic acids. ...
The recovery of zinc (Zn) and lead (Pb) from a citric leach solution of a non-sulfide type ore flotation tailing was examined utilizing sulfuric acid precipitation followed by solvent extraction using di(2-ethylhexyl) phosphoric acid (D2EHPA) as the extractant. Following lead precipitation (98.9%) with sulfuric acid, the pregnant leach solution was sent to solvent extraction stage with D2EHPA for the separation of zinc from the other impurities such as Ca, Mg and Fe. The best solvent extraction conditions were determined to be a concentration of 20% D2EHPA, temperature of 25 °C, contact time of 10 min and phase ratio of unity. Under the optimum conditions, 98.3% Zn was extracted into the organic phase in a single contact at a pH of 3.6, along with a significant amount of Ca (79%) and minor amounts of Mg (14.7%) and Fe (8.6%). At pH 4.5, the loaded organic solution was carried to the scrubbing stage, where 20 g/L zinc solution was used to remove approximately 91% Ca and 34% Mg from the organic solution. At a pH of 0.25, the loaded organic solution was almost completely stripped of zinc and 27% of calcium in two steps.
... The process is illustrated in Fig. 4. The H + ion activity in the external phase is closely related to the reaction rate of Zn extraction (Reis & Carvalho, 2004). As illustrated in Fig. 4, the extraction is governed by the cation exchange reaction in which the protons are released (Fouad, 2008 (Pereira et al., 2007). Other than that, Zn ions speciation at varying pH is another factor to be considered. ...
Zinc (Zn) was identified as one of the most toxic heavy metals and often found contaminating the water sources as a result of inefficient treatment of industrial effluent. A Green Emulsion Liquid Membrane (GELM) was proposed in this study as a method to minimize the concentration of Zn ions in an aqueous solution. Instead of the common petroleum-based diluent, the emulsion is reformulated with untreated waste cooking oil (WCO) collected from the food industry as a sustainable and cheaper diluent. It also includes Bis(2-ethylhexyl) phosphate (D2EHPA) as carrier, Span 80 as surfactant, sulfuric acid (H 2 SO 4 ) as internal phase and ZnSO 4 solution as external phase. Such formulation requires a thorough understanding of the oil characteristics as well as the interaction of the components in the membrane phase. The compatibility of WCO and D2EHPA, as well as the external phase pH was confirmed via liquid-liquid extraction (LLE) method. To obtain the best operating conditions for Zn extraction using GELM, the extraction time and speed, carrier, surfactant and internal phase concentrations, and W/O ratio were varied. 95.17% of Zn ions were removed under the following conditions; 0.001M of H 2 SO 4 in external phase, 700 rpm extraction speed for 10 minutes, 8 wt% of carrier and 4 wt% of surfactant concentrations, 1:4 of W/O ratio and 1 M of internal phase concentration.
... The main feature of the extractant D2EHPA, which is classified as an organophosphorus acid, is the formation of dimeric structures by hydrogen bonding between extracting molecules (Pereira et al., 2007). When metallic cations are extracted, D2EHPA releases hydrogen ions. ...
A novel and environmentally friendly three-liquid-phase extraction (TLPE) approach was developed for simultaneous separation of copper (Cu), magnesium (Mg) and zinc (Zn) from water samples. The proposed organic/two aqueous phase system consists of di(2-ethylhexyl)phosphoric acid (D2EHPA), Choline Chloride:urea (deep eutectic solvent (DES)), and salt (K2HPO4). The effects of various factors including amount of DES and K2HPO4, pH, D2EHPA concentration, phase-mixing time, and diluent on the preconcentration/separation of Cu, Mg and Zn were evaluated. The results showed that 96.6% of Zn was concentrated in the D2EHPA-rich top phase, whereas 97.8% of Cu and 98.1% of Mg were quantitatively extracted into the DES-rich middle phase and salt-rich bottom phase, respectively. Excellent recovery (>97%) of Cu, Mg and Zn was obtained by using 20% (v/v) D2EHPA in hexane, and 1.72 g DES and 3.12 g K2HPO4 in two lower aqueous phases at pH=4. The limits of detection were 1.58, 1.55 and 2.37 mg/L for Cu, Mg and Zn, respectively. Relative standard deviations (RSDs) for 0.5 mg/L and 1.0 mg/L of Cu, Mg and Zn in water samples were <6%. The accuracy of the procedure was confirmed by analyzing a certified reference material of water and tea (NIST SRM 1640a, GBW 07605). Under optimized conditions, excellent agreement was observed between the TLPE-flame atomic absorption spectrometry (FAAS) results and certified values using the student’s t-test (P=0.05). TLPE procedure was successfully applied for the determination of Cu, Mg and Zn in water samples.
... The extraction reaction of divalent metals like Ni and Zn metals using acidic extractant like D2EHPA can be represented as following [37]: ...
Present communication is aimed to investigate the reaction mechanism of Zn(II) and Ni(II) and thermodynamic modeling using di-(2-ethylhexyl) phosphoric acid (D2EHPA) as an organic extractant that is diluted in kerosene at T = 25 °C and the organic: aqueous phase ratio of 1:1 and pH range 2-6. The effect of two important parameters i.e. concentration of extractant and pH on the extraction of metals were investigated. The experimental tests allowed to define the best process conditions, among various investigated conditions, to extract Ni(II) and Zn(II) from filter cake. The optimized extraction values of Ni(II) and Zn(II) were 95.5 and 95.1%, respectively and these were obtained within one stage by 25% (v/v) concentration of D2EHPA, 60 min of contact time and rotation speed of 600 rpm. Moreover, the extraction reaction stoichiometry of Ni(II) and Zn(II) was determined using the slope analysis. Also, the activity coefficient of all ions in the aqueous phase and all of the organic components in the organic phase were predicted based on Electrolyte-universal quasichemical-NRF and universal quasichemical-NRF model. The obtained results indicated well agreement with the experimental data.
... However, at intermediate and high loading levels, there is a co-existence between the complexes ZnR.2RH and ZnR 2 , as indicated by the statistical analysis of Zn-D2EHPA equilibrium data by Mansur et al., 2002 [14]. The use of D2EHPA to extract Zn from inorganic leach solutions have been studied extensively by numerous investigators [15][16][17][18][19][20][21][22][23][24][25][26]. Most of these studies reported that more than 95% of Zn can be extracted with D2EHPA at pH between 1 and 3, a temperature between 25 and 40 • C and a contact time of less than 10 min. ...
The recovery of zinc and lead from a malic leach solution of a carbonate type ore flotation tailing by precipitation with sulfuric acid followed by solvent extraction using di(2-ethylhexyl)phosphoric acid (D2EHPA) as extractant was investigated. The separation of lead via precipitation was essentially complete from the malic acid leach solution by adding sulphuric acid to reach a pH of 0.25 at 25 °C. The precipitate product was identified by XRD as anglesite (PbSO4). The pregnant leach solution after lead precipitation was then subjected to solvent extraction using D2EHPA. The optimum solvent extraction conditions were determined as 10% D2EHPA concentration, 25 °C temperature, 10 min contact time and phase ratio of unity. Under these conditions, 99.3% of zinc was extracted into the organic phase at a pH of 4.2 in a single contact alongside a substantial amount of Ca (76.6%), and minor amounts of Fe (19.2%) and Mg (18%). Complete stripping of zinc and calcium from the loaded organic solution along with 47.8% of Mg was achieved at a pH 0.5 under room temperature. No iron stripping was observed from the loaded organic. The zinc content in the loaded strip solution could be enriched and then sent to the electrowinning (EW) stage. It is noted that the calcium and magnesium impurities in the loaded strip solution had no adverse effect on the zinc EW process. Based on the experimental results, a flowsheet was proposed for the recovery of Pb and Zn from the malic acid leach solution. With the proposed precipitation and solvent extraction process, two different material streams are produced.
... Di-2-ethylhexyl-phosphoric acid (D2EHPA) is extensively used as an extractant for the extraction of Sm(III) from aqueous solutions.2Other applications of this popular extractant include the removal of Zn(II) [5], Mn(II) [6], Fe(III) [7]. The objective of this study is to investigate the best conditions for samarium(III) extraction by D2EHPA by varying diverse parameters as shaking time, initial pH of aqueous solution, and the temperature. ...
The liquid-liquid extraction of samarium (III) from aqueous nitrate solution using D2EHPA (di-2-ethylhexyl phosphoric acid) as extractants is investigated to recover samarium (III) from aqueous solution. The effect of operating parameters, such as time, nitrate ion, aqueous phase acidity, concentration of the extractant, temperature on the samarium extraction. At pH=5.05, maximum extraction efficiency was obtained with 2 mmol L-1 D2EHPA in dichloromethane at initial concentration of Sm3+ 1 mmol L-1.
D2EHPA extracts Sm3+ very rapidly. Equilibrium was reached within 15 min. The synergistic effect showed that addition of D2EHPA to TOP (Tri-iso-octyl-phosphate) extraction was obtained for the volume ratio 4.5/0.5. The thermodynamic functions like free energy (∆G), enthalpy (∆H) and entropy (∆S) of extraction mechanism are discussed. By liquid-liquid extraction the removed quantity was 93.26 mg g-1. The stripping efficiency
was found to be quantitative in HNO3 and HCl 1 M. The robustness of the procedure is demonstrated by the average recoveries obtained (>99.6 %) for samarium (III).
Keywords: Samarium (III); D2EHPA; Optimization; Extraction
... Di-2-ethylhexyl-phosphoric acid (D2EHPA) is extensively used as an extractant for the extraction of Sm(III) from aqueous solutions.2Other applications of this popular extractant include the removal of Zn(II) [5], Mn(II) [6], Fe(III) [7]. The objective of this study is to investigate the best conditions for samarium(III) extraction by D2EHPA by varying diverse parameters as shaking time, initial pH of aqueous solution, and the temperature. ...
The liquid-liquid extraction of samarium (III) from aqueous nitrate solution using D2EHPA (di-2-ethylhexyl phosphoric acid) as extractants is investigated to recover samarium (III) from aqueous solution. The effect of operating parameters, such as time, nitrate ion, aqueous phase acidity, concentration of the extractant, temperature on the samarium extraction. At pH=5.05, maximum extraction efficiency was obtained with 2 mmol L-1 D2EHPA in dichloromethane at initial concentration of Sm3+ 1 mmol L-1. D2EHPA extracts Sm3+ very rapidly. Equilibrium was reached within 15 min. The synergistic effect showed that addition of D2EHPA to TOP (Tri-iso-octylphosphate) extraction was obtained for the volume ratio 4.5/0.5. The thermodynamic functions like free energy (∆G), enthalpy (∆H) and entropy (∆S) of extraction mechanism are discussed. By liquid-liquid extraction the removed quantity was 93.26 mg g-1. The stripping efficiency was found to be quantitative in HNO3
and HCl 1 M. The robustness of the procedure is demonstrated by
the average recoveries obtained (>99.6 %) for samarium (III).
... Zinc has been recovered from an industrial effluent by Pereira et al., and the results obtained show that 98% of zinc could be extracted using three extraction steps at pH 2.5, D2EHPA = 20%, A:O = 1:1, and three stripping steps at O:A = 4:1 in a continuous mixer-settler. The final solution containing 125.7 g/L zinc has then been sent directly to the electro-winning process [34]. ...
... A higher concentration of extractant (X o ) accelerates the complexes formation and zinc and iron distribution ratio as well as extraction. However, the higher extraction rate of zinc rather than iron leads to a higher Zn/Fe separation factor (Martins et al. 2020;Pereira, Rocha and Mansur 2007). The ANOVA results (not reported here) showed that only the interaction of D2EHPA concentration-time, D2EHPA concentration-A/O and time-A/O were meaningful. ...
The copper flue dust is an important secondary source for various metals and also a potential threat to the environment. In this study, a process was developed to convert a local copper flue dust containing 20.60% copper, 21% iron and 2.88% zinc into value-added products via a hydrometallurgical route. The response surface methodology was applied for the optimization of base metals leaching by sulfuric acid. Maximum recoveries of 96% for zinc and 76.7% for copper were achieved under the optimum conditions, whereas only 23.92% of the iron content was dissolved. Moreover, various parameters effective on Zn/Fe separation factor were assessed, and favorable separation obtained at pH 3, 2:1 A/O ratio, 20% V/V of D2EHPA in kerosene during 15 minutes. Stripping experiments also showed that 96.35% of zinc was successfully stripped at 1 M sulfuric acid and 2:1 A/O. The mathematical prediction models for leaching, solvent extraction and stripping were proposed and confirmed by statistical analysis and experiments. The proposed process in this study, enhances the copper production in the current leaching plant and makes it possible to recover zinc from industrial waste as a by-product.
... Generally, hydrometallurgy process consists of three basic steps: (1) leaching of zinc ores in dilute H 2 SO 4 (sulfuric acid is a leaching reactant used to recover zinc from oxidized zinc ores: for example, ZnO + H 2 SO 4 → ZnSO 4 + H 2 O), (2) refining of the resulting zinc sulfate solution, (3) electrolysis to recover the metallic zinc as a highpurity product (Abdel-Aal 2000; Hui et al. 2019;Pecina et al. 2008). Leaching of oxidized zinc ores with H 2 SO 4 , NH 4 OH and NaOH solutions have been studied, and it has been found that H 2 SO 4 leaching represents better results than NaOH and NH 4 OH (Parhi and Sarangi 2008;Pereira et al. 2007;Reddy and Priya 2005). An oxidized material containing a great amount of zinc have been leached with H 2 SO 4 to produce ZnSO 4 . ...
In the present study, the production process of zinc sulfate from the zinc oxide ore was experimentally investigated. The effect of main operating condition such as weight ratio of sulfuric acid to zinc content of ore (H 2 SO 4 /zinc), leaching temperature (°C), stirring speed (rpm), leaching time (min), particle size (mm), solid to liquid ratio (pulp density, wt. %), additives amount (kg/m ³ ) and leaching pH on dissolution process of zinc oxide ore in H 2 SO 4 solution were evaluated. Taguchi method and Aspen Plus software were used to determine the optimum condition and simulate the production process of zinc sulfate. Also, Aspen Plus software was used to determine the efficiency of zinc sulfate production. The experimental factors and their levels were as follows: 0.937–1.875 for the weight ratio of sulfuric acid to zinc content of ore, 50–80 °C for the leaching temperature, 100–400 rpm for stirring speed, 30–120 min for leaching time, 0.01–10 mm for particle size, 10–40 wt% for pulp density, 10–50 kg/m ³ for additives amount and 1.4–2 for solution pH. The optimum condition was found to be H 2 SO 4 /Zinc ratio, 1.25; temperature, 70 °C; agitation rate, 200 rpm; leaching time, 30 min; particle size, 1 mm; pulp density, 10 wt%; additives amount, 30 kg/m ³ and pH, 1.8. The most effective factors for maximizing the dissolution of ZnO in H 2 SO 4 was the leaching pH. The predicted results by Aspen Plus simulation indicated that the total efficiency of zinc recovery at optimum condition is more than 97%.
... Applications of liquid-liquid extraction can be found in industries such as petrochemical, pharmaceutical and hydrometallurgical. Hydrometallurgy helps concentrate metals like zinc or copper, for electrowinning as well as for separating the complex metallic system, for example, nickel/cobalt and other metal ions [1]. This method can be used for the selective separation of other metal ions: Zn(II), Cd(II), Al(III), Co(II), Ni(II) [2][3][4][5][6] or Cu(II) [7,8]. ...
A new compound 2,6-bis(4-methoxybenzoyl)-diaminopyridine (L) was used as an extractant for copper(II) ion recovery in a solvent extraction conducted at a temperature of 25 °C. The best results (99% recovery of copper(II) ions) were obtained when the aqueous phase contained 0.001 mol/dm3 Cu(II) and 0.2 mol/dm3 NH3 (pH~5.8), while the organic phase was a 0.001 mol/dm3 chloroform solution of 2,6-bis(4-methoxybenzoyl)-diaminopyridine. Spectrophotometry studies were used to determine the dissociation constant of the tested compound and determine the stability constant of the complex of subjected compound with copper(II) ions. The high-resolution mass spectrometry (HRMS) and higher energy collisional dissociation tandem mass spectrometry (HCD MS/MS) methods have been applied for the confirmation of the structure of 2,6-bis(4-methoxybenzoyl)-diaminopyridine and to determine its complexation with Cu(II) in solution.
... A study for recovering zinc sulfate from an industrial effluent containing several other metals (Mn, Fe, Cd, Pb, Cu, Co, and Ni at varying concentration levels) using D2EHPA was carried out in a batch scale and continuous pilot scale using a mixer-settler battery. It was demonstrated that zinc can be efficiently removed from the effluent [12]. ...
A blend of brass ashes containing 48.0% of zinc and 16.6% of copper was processed through selective leaching with dilute H2SO4 and solvent extraction, using D2EHPA as the extracting agent in order to separate zinc and copper. Solvent extraction tests performed in bench and pilot scales were designed to evaluate the following operating parameters: time, pH, D2EHPA concentration, A/O ratio in the extraction step, and O/A ratio in the stripping step. Zinc present in the brass ashes was efficiently leached by H2SO4 (recovery of 91.9%), whereas only 8.6% of copper was leached, producing a liquor containing zinc (28.6 g/L), copper (1.5 g/L), calcium (0.45 g/L), iron (0.43 g/L), and chloride (0.22 g/L), as well as fluoride, lead, nickel and cadmium, at levels below 0.01 g/L. Zinc was selectively extracted over copper by solvent extraction with D2EHPA. A continuous solvent extraction run in pilot scale was carried out using 4 extraction stages (pH = 2, A/O ratio = 1) and 2 stripping stages (O/A ratio = 2), where 91.8% of zinc extraction and 96.9% of zinc stripping were achieved. Iron extraction efficiency reached 85.9%, thus illustrating the need for its prior removal if required. The fluorine extraction was 29.9%, as compared to 10.4% for chlorine, whose respective extractions are related to the presence of iron and zinc in the liquor, as evidenced by species speciation analysis. A copper concentrate containing 42.2% was obtained in the leaching step.
... Scans were charge referenced to the sodium chloride Na 1s photoemission at 1072.6 eV. 56 Single-crystal X-ray crystallography was performed on an Agilent Xcalibur 3 E diffractometer (4-circle kappa geometry, sealed tube source, CCD detector). Water content was measured on either a Mettler Toledo volumetric V20 or Coulometric C20 Karl-fisher titrator. ...
The bis(trifluoromethanesulfonyl)imide, [NTf2]-, anion can be paired with organic cations to give hydrophobic ionic liquids that form a secondary phase with water. These ionic liquids are often identified as green solvents and considered as re-placements for traditional organic solvents in chemical processes, i.e. aqueous biphasic extractions. Here we consider a range of hydrophobic [NTf2]- ionic liquids as extraction phases with hypersaline brines for heavy metal remediation. Extrac-tion experiments were complicated by partial solubility of the hydrophobic ionic liquids, and ion chromatography was used to quantify the anion and cation losses to the aqueous phase. Although ionic liquid leaching was lower in hypersaline brine than water (i.e. salting out), ionic liquids losses were significant at relatively low volume ratios for short-chain and functional ionic liquids. Ionic liquid purity was also affected by ion exchange; more organic cations were lost to the aqueous phase than [NTf2]- anions. Solvent replenishment costs were extremely high due to loss to the aqueous phase and high ionic liquid prices. New separation technologies will be required if these ionic liquids are to be used industrially; recovery is unlikely to offset the cost with current separation methodologies. Prevention is advised over recovery and long-chain hydrophobic ionic liquids are recommended in this regard.
... with N-n-Heptylaniline as an Extractant: Analysis of Pharmaceutical and Commercial Sample zinc(II)sulphate from an industrial effluent produced by Votorantim Co. which contains several metallic species such as cadmium, cobalt, iron, lead, calcium, magnesium, manganese and nickel [17]. ...
... D2EHPA is commonly used to separate zinc from solutions that contain metals. Pereira et al., 2007) investigated the extraction of 11.9g/L of zinc from a solution with other metals like iron, magnesium, manganese and calcium. The work reported that zinc extraction using 20% (v/v) D2EHPA and an A/O ratio was possible with two theoretical stages. ...
Global generation of waste electrical and electronic equipment (WEEE) is increasing quickly. Metals from WEEE can be recovered by using unit operations of chemical engineering. This paper describes a combined hydrometallurgical route (sulfuric oxidant leaching + solvent extraction) to recover copper from printed circuit boards (PCBs). A non-magnetic fraction from comminuted PCBs was used to perform leaching tests at 75ºC for 6 hours in an oxidizing media (sulfuric acid + hydrogen peroxide). In order to separate zinc, aluminum, and copper from the leaching liquor, solvent extraction tests were carried out using D2EHPA. Parameters that influence the process, such as pH, extractant concentration, and the aqueous/organic (A/O) ratio were investigated. Solvent extraction experiments were carried out in two stages: i) separation of zinc, aluminum, and residual iron, and ii) copper separation. The results showed that the leaching obtained around 60% aluminum, 94% copper, 76% zinc, 50% nickel and residual iron from the non-magnetic fraction of PCBs. With the solvent experiments, in the first stage, 100 wt.% zinc, iron and aluminum were extracted at pH 3.5, 2:1 A/O, 10 % (v/v) D2EHPA, while, in the second stage 100% of the copper was extracted at pH 3.5, 1:1 A/O, 20 % (v/v) D2EHPA.
... In most of the proposed, and used, recoveries flow-sheets, zinc solvent extraction plays a decisive role in the overall scheme due to the operational characteristics mentioned above. Since zinc is mostly presented in the aqueous solutions generated from these recovery processes as Zn 2+ , the extractants used to extract the cation are, naturally, acidic or cationic reagents, and among them, alkylphosphorous derivatives are often used [1][2][3][4][5][6][7]. As in all general rules, and despite the above, there are exceptions and in the case of zinc(II) this occurs in the treatment of spent pickling solutions, in which, basic or solvation reagents had been proposed as extractants for the various neutral species and anionic zinc(II)-chloride complexes [8][9][10], whereas more recently, ionic liquids had been introduced as potential zinc extractants from this chloride and other aqueous media [11][12][13][14][15][16]. ...
The use of Cyanex 272 for extraction of zinc and iron from industrial wastes like chromium(III) passivation baths is investigated. The extraction of the metals is studied, in batch conditions, as a function of equilibration time, temperature, diluent of the organic solution, metals and extractant concentrations and pH values of the aqueous solutions. Also the stripping of the metals from loaded organic phases had been investigated using sulphuric acid solutions as strippant.
... The Zn (and Fe) removal with D2EHPA can be outlined by the following extraction equilibria, in which (HR) 2 represents the dimeric form of the extracting agent that acts like a liquid organic ion exchanger [33]: Fig. 9 presents the effects of the D2EHPA concentration and HCl content in the aqueous phase on the extraction of Zn(II) and Fe(II), in the case of the simulated effluent. As predictable, the metals extraction increases at low proton concentration and at high concentration of extracting agent. ...
... thors have previously employed several extractants for the recovery of zinc and iron, such as CYANEX 272 [5] and MIBK [6] for iron, DBBP [7], CYANEX 921 [1] and CYANEX 272 [8] for zinc. The main extractant used in zinc extraction is di (2-ethylhexyl) phosphoric acid (D2EHPA) [9] , which also extracts iron (III) [10]. In addition to the D2EHPA, Tri-n-butyl phosphate (TBP) has been reported as the most effective extractant for zinc extraction and stripping from chloride solutions [8,11]. ...
Waste chloride pickle liquors from hot-dip galvanizing plants, steel plants and flue dust contains reasonable amounts of heavy metals such as Zn, Cr, Ni, etc. Iron is invariably associated with most of these materials and comes into solution during leaching. Thus, synergistic effect of TBP with D2EHPA diluted in kerosene on the extraction of zinc (II) and iron (III) from leach solutions was investigated. The Zn and Fe concentration in the leach liquor used in the present study was 2 g/L. Experiments were carried out in the pH range of 0.5-4.0, temperature of 25 °C, using the sole D2EHPA, sole TBP and D2EHPA-TBP mixtures at different ratios. Results showed that the co-extraction of zinc (II) and iron (III) increased with increasing equilibrium pH using D2EHPA. It is demonstrated that the mixtures of TBP and D2EHPA are more efficient and selective than D2EHPA alone. At low pHs, the separation factor is low when pure D2EHPA is used as an extractant; however , using TBP as a synergist, the separation factor increases and results in a better separation of zinc from iron. Increasing TBP to D2EHPA ratios in the organic phase caused a slight shift to the right in the extraction isotherm of iron and a marked shift to the right in the extraction isotherm of zinc and thus, superior separation of iron over zinc was achieved.
... Nevertheless, in this technique iron cannot be recycled and is considered as a secondary resource. [29] Therefore, an appropriate extractant that can extract both zinc(II) and iron(III) separately should be used. Solvent extraction by several extractants such as CYANEX 272, [30] ionquest 801 [31] and MIBK [32] for iron, and DBBP, [27] CYANEX 921, [33] CYANEX 302 [28] and CYANEX 272 [34] for zinc has been carried out. ...
Waste chloride pickle liquors from hot-dip galvanizing plants, steel plants and flue dust contains reasonable amounts of heavy metals such as Zn, Cr, Ni, etc. Iron is invariably associated with most of these materials and comes into solution during leaching. Thus, synergistic extraction of zinc (II) and iron (III) from leach solutions in TBP (tri-n-butyl phosphate) - D2EHPA (di (2-ethylhexyl) phosphoric acid) system diluted in kerosene was investigated. The Zn and Fe concentration in the leach liquor used in the present study was 2 g/L. Experiments were carried out in the pH range of 0.5 - 4.0, temperature of 25 °C, using sole D2EHPA, sole TBP and D2EHPA-TBP mixtures at different ratios. Results showed that the co-extraction of zinc (II) and iron (III) increased with increasing equilibrium pH using D2EHPA. It is demonstrated that the mixtures of TBP and D2EHPA are more efficient and selective than D2EHPA alone. At low pH values, the separation factor is low when pure D2EHPA is used as an extractant; however, using TBP as a synergist, the separation factor increases and results in a better separation of zinc from iron. Increasing TBP to D2EHPA ratios in the organic phase caused a slight shift to the right in the extraction isotherm of iron and a marked shift to the right in the extraction isotherm of zinc and the maximum separation factor of 13.3×10³ was achieved at TBP to D2EHPA volume ratio of 4:1 (0.58 M TBP: 0.12 M D2EHPA). Furthermore, the effect of equilibrium pH, organic to aqueous phase ratio and Cl⁻ concentration on the selective extraction was investigated. Using two extraction stages at O/A ratio of 2:1 and pHe (equilibrium pH) of 3 and 1 for zinc and iron, respectively, 99% of zinc (II) and 96.25% of iron (III) were extracted.
... Nevertheless, in this technique iron cannot be recycled and is considered as a secondary resource. [29] Therefore, an appropriate extractant that can extract both zinc(II) and iron(III) separately should be used. Solvent extraction by several extractants such as CYANEX 272, [30] ionquest 801 [31] and MIBK [32] for iron, and DBBP, [27] CYANEX 921, [33] CYANEX 302 [28] and CYANEX 272 [34] for zinc has been carried out. ...
The extraction equilibrium of Zn(II) and Fe(III) from chloride solution by the mixture of TBP (tri-n-butyl phosphate) and D2EHPA (di(2-ethylhexyl) phosphoric acid), diluted in kerosene was studied. The results show that in TBP to D2EHPA volume ratio of 3:1 (0.55 M TBP:0.15 M D2EHPA) ΔpH0.5 increased to about 2.5 and Fe(III) and Zn(II) extracted separately with the percentage extraction of 99% and 80%, respectively. The Fourier transform infrared (FTIR) measurements were used in order to find the possible structural functionalities of extracted species in the organic phase. Moreover, the FTIR measurements indicated that there was a hydrogen bond between TBP and D2EHPA molecules. According to FTIR studies and slope analysis method, the reaction between TBP, D2EHPA and zinc was determined and the FTIR-ATR (attenuated total reflectance) method was also employed to verify the stoichiometry of Zn(II) - organic complexes in the organic phase. Both FTIR-ATR and slope analysis methods provided the same results that the ZnA2AH·TBP was probably the extracted specie in the organic phase.
... And LIX841 is another type of extractant [39]. Abundant of researches have been focused on this issue, which is not a knotty problem [40][41][42][43][44]. ...
An intensified oxidative acid leaching of copper–cadmium-bearing slag featuring using high-efficient oxygen carrier, such as activated carbon, was investigated to achieve high leaching rate of valuable metals. The effects of leaching variables, including agitation rate, sulfuric acid concentration, temperature, slag particle size, activated carbon and cupric ion concentration, were examined. It is found that leaching rates of cadmium and zinc both exceed 99 % in a very short time, but for copper, leaching rate of 99 % is achieved under the optimized leaching parameters, which are agitation rate of 100 r·min−1, sulfuric acid concentration of 15 wt%, leaching temperature of 80 °C, slag particle size of 48–75 μm, activated carbon concentration of 3 g·L−1, liquid-to-solid ratio of 4:1, oxygen flow rate of 0.16 L·min−1, and leaching time of 60 min. The macro-leaching kinetics of copper metal was analyzed, and it is concluded that the inner diffusion is the controlling step, with apparent activation energy of 18.6 kJ·mol−1. The leaching solution with pH value of 2–4 can be designed to selectively extract valuable metals without neutralization, and the leaching residue can be treated by prevailing Pb smelting process.
Graphical Abstract
The phase compositions of the leaching residue are PbSO4 and CaSO4. And the chemical composition analysis result shows that about 13 % Pb is contained in the residue, which can be recycled by Pb smelting technology in an Isa furnace. The way is that the Pb-containing concentrate and the PbSO4-containing leaching residue can be mixed and placed in the furnace.
... Zinc(II) can be extracted by a number of extractants such as TBP, β-diketones, oxine and its derivatives, TOPO, fatty acids, naphthenic and salicylic acid, β-isopropyltropolone, PAN, diethyldithiocarbamate, dithizone, thio-compounds etc. (Sekine and Hasegawa, 1977), D2EHPA (Begum et al., 2009;Vahidi et al., 2009;Perreira et al., 2007;Mansur et al., 2002), Alamine 336 (Sayar et al., 2007), 5-azidomethyl-8-hydroxyquinoline (Himmi et al., 2008), 1-phynyl-3-mryhyl-4benzoylpyrazol-5-one (Barkat et al., 2004), PC 88A (Nathsarma and Devi, 2006), Cyanex 921 ( Navarro et al., 2007), Cyanex 302 (Mansur et al., 2008;Jha et al., 2005), Cyanex 301 (Mansur et al., 2008;Jha et al., 2005), Cyanex 272 (Zhu et al., 2011;Awaad et al., 2009;Bari et al., 2009a;2009b;Deep and de Carvalho, 2008;Parhi and Sarangi, 2008;Mansur *Author for correspondence;E-mail: rkbiswas53@yahoo.com et al., 2008;Nathsarma and Devi, 2006;Ali et al., 2006;Jha et al., 2005;Salgado et al., 2003;Sarma and Reddy, 2002;Chah et al., 2002;Devi et al., 1997;Amer and Luis, 1995;Sole and Hiskey, 1992;Sastre et al., 1990) etc. ...
The equilibrium in the partitioning of Zn(II) from its sulphate solution to bis-(2,4,4-tri- methylpentyl) phosphinic acid (Cyanex 272, BTMPPA, H 2A2) solution in kerosene (paraffin) has been investigated extensively. The equilibration time is < 5 min. Extraction of Zn(II) is found to be increased with increasing equilibrium pH, extractant concentration and temperature; and independent of [Zn(II)] in the aqueous phase provided equilibrium pH and extractant concentration are kept constant. The pH dependence of extraction ratio (D) at a constant [H2A2](o,eq) is found to be 2. The extractant dependence plots at constant equilibrium pH values are not straight lines but are curves with asymptotic slopes of 1 and 2 at lower concentration region (LCR) and higher concentration region (HCR) of extractant, respectively. D is found to be an inverse function of (1 + 2[SO 42-]). The extraction at LCR of extractant is found to occur through the reaction: Zn2+ + H2A2 (o) ⇌ [ZnA2](o) + 2 H+; but at HCR of extractant, it occurs via the reaction: Zn2+ + 2 H2A2 ⇌ [ZnA2.H2A2](o) + 2 H+. The extraction equilibrium constants, Kex at LCR and HCR of extractant are estimated as 10-3.11 and 10-2.08, respectively, at 303 K. The extraction process is found to be endothermic but AH value increases with increasing extractant concentration. The maximum loading capacity is estimated to be 11.5 g Zn(II) per 100 g extractant. At a maximum loading, the species exists in organic phase is ZnA2. The stripping ability of various inorganic acids towards loaded zinc, as well as, the possibilities of separation of Zn(II) from its binary mixtures with 3d - block metal ions have also been investigated.
2-Ethylhexanol is a versatile platform chemical with extensive applications in various fields. Currently, 2-ethylhexanol is exclusively produced from petroleum resources. However, the increased market demand for it and the depletion of fossil resources would entail the production of 2-ethylhexanol in a more sustainable way. Production of 2-ethylhexanol from renewable lignocellulosic biomass could be an alternative pathway. Here, we reviewed the applications of 2-ethylhexanol in different fields, with a focus on the renewable production of bio-based fuels, plasticizer, lubricant and surfactant from 2-ethylhexanol. Moreover, the possible pathways for renewable production of 2-ethylhexanol from lignocellulosic biomass are also discussed. Finally, future perspectives on renewable production of 2-ethylhexanol are also provided.
The rapid development of advanced technologies has increased the demand for critical elements, such as Mn, Co, and Ni. A systematic study was conducted to develop a process for producing high-purity Mn, Co, and Ni products from an acid mine drainage (AMD). As major contaminants, Fe and Al in the solution were sequentially precipitated and eliminated by elevating the pH to around 4.00 and 6.50, respectively. After that, a pre-concentrated slurry containing 3,794 mg/L Mn, 59 mg/L Co, 127 mg/L Ni, and 300 mg/L Zn was obtained by collecting the precipitates formed in the pH range of 6.50 to 10.00. The pH of the pre-concentrated slurry was decreased to around 5.00 by adding HCl to re-dissolve Co, Ni, and Zn for further purification. At this pH, greater than 50% of Mn remained undissolved, and filtration of the undissolved material resulted in a product with around 30 wt.% Mn. Sodium sulfide was added into the re-dissolved solution to selectively precipitate Co, Ni, and Zn while remaining Mn in the solution. Almost 100% of Co, Ni, and Zn but only around 15% of Mn were precipitated using a sulfur to metal molar ratio of 1 at pH 4.00. The sulfide precipitate was calcined at 200 °C for 2 h and then completely dissolved in 1.2 M HCl. The critical elements existing in the dissolved solution were efficiently separated using a two-stage solvent extraction process. Ultimately, Co and Ni products with almost 94% and 100% purity were obtained by sulfide and alkaline precipitation, respectively.
The objective of this study is to develop a mathematical model based on the response surface methodology (RSM) for Liquid-liquid extraction and separation of Selenium and Tellurium from the aqueous nitric acid solution using Cyanex 301 as a potential organic extractant. For this purpose, three independent variables, i.e. nitric acid concentration (1–5 mol L⁻¹), Cyanex 301 concentration (0.02–0.1 mol L⁻¹), and extraction temperature (15–55 °C) were considered to evaluate their impacts on the responses of the percentage extractions (%E) of selenium and tellurium based on central composite design (CCD) approach. After conducting the experiments and statistically analyzing the results, correlations were proposed for selenium and tellurium extraction based on quadratic models. The results indicated that the Cyanex 301 concentration was the most paramount variable in extraction separation of Selenium and Tellurium. According to the obtained results the optimal condition for selective extraction of Se(IV) over Te(IV) was obtained at HNO3 concentration 2.7 mol L⁻¹, Cyanex 301 concentration 0.06 mol L⁻¹, and extraction temperature 25 °C. The optimum predicted extraction percentage of Se(IV) and Te(IV) was 99.77% and 28.47%, respectively and the actual values were 99.72%, and 28.12%, respectively. Also, the predicted and real separation factor was found to be 1089.87 and 910.37 respectively. These results showed the suitability of the implemented model and the prosperous application of RSM based on CCD in optimizing the selective extraction conditions of Se(IV) from Te(IV) in nitric acid medium.
Alkali agents could be used to enhance the extraction of zinc from solution of high concentration, but excess alkali can sensitively lead to emulsification of the solution. In this paper, the emulsification in the extraction process, demulsification, and extraction with different additives and its action mechanism were studied. The results indicate that the associated addition of alkali and organic acid could eliminate emulsification and improve zinc extraction. The extraction ratio of zinc reached 99.61% under the conditions of 104 mL/L organic acid, 80 g/L alkali, and 40% extractant concentration. Zinc hydroxide formed from hydroxyl and zinc ion at sensitively increased pH was the cause of emulsification during extraction. Associated addition of alkali and organic acid could contribute to the control solution pH in the range of 3.0–4.0, which is lower than that of the formation of zinc hydroxide, and therefore, improve zinc extraction.
Multiple purification of zinc sulfate solution is an important process for zinc hydrometallurgy, and large quantities of copper-cadmium residues are generated as byproducts in this process. Copper-cadmium residues contain a large number of valuable metals that must be recovered. A comprehensive extraction process has been proposed using sulfuric acid as the leaching reagent and hydrogen peroxide as the oxidizing reagent. The effects of acid concentration, leaching temperature, leaching time, liquid-to-solid ratio, hydrogen peroxide dosage and stirring speed on the leaching efficiency were investigated. The optimum conditions were determined as an acid concentration of 150 g/L, liquid-to-solid ratio of 4:1, hydrogen peroxide amount of 20 mL, time of 60 min, temperature of 30 °C, particle size of −d75 μm, and agitation rate of 300 r/min. It was concluded that the leaching efficiency of copper and cadmium reached 97%, but because of the existence of zinc sulfide in the residues, a lower leaching efficiency of zinc was obtained. Furthermore, the leaching kinetics of copper was also studied based on the shrinking core model. The activation energy for copper leaching was 5.06 kJ/mol, and the leaching process was controlled by the diffusion through the product layer.
Purification of concentrated manganese sulfate solution by solvent extraction is discussed in this paper. The use of bis(2-ethylhexyl) hydrogen phosphate (D2EHPA) and bis(2,4,4-trimethylpentyl)phosphinic acid (BTMPPA) was studied in removal of impurities from zinc electrowinning anode sludge leachates. Over 99 % of zinc and iron were removed by both extractants at around pH 3 in two mixer-settlers operating in continuous countercurrent mode at a solvent-to-feed (S/F) ratio of 0.43 and T = 22 ± 1 °C. BTMPPA had higher selectivity for zinc and iron over manganese than D2EHPA under all experimental conditions. Extraction of manganese was typically below 10 % and can be limited by crowding the extractants, since the fraction of manganese in both loaded extractants was decreased by decreasing organic to aqueous volumetric ratio (O/A). A significant amount of the co-extracted Mn was recovered by selective stripping with 0.5 M sulfuric acid. Extraction by BTMPPA was more sensitive to pH adjustment than extraction by D2EHPA. Increasing the mean residence time in mixer from 3.6 min to 6.0 min improved the removal of zinc and iron with BTMPPA but the change in residence time had little or no effect on zinc and iron removal with D2EHPA.
Conventional techniques for kinetic rate constant acquisition are limited by diffusive transport, which can be well addressed by microfluidic techniques. Segmented flow capillary microreactors were used for the first time in this study to obtain kinetic rate constants for a reactive zinc extraction system. The influences of initial zinc ion concentration, total flow velocity, pH of the aqueous phase, and ionic strength on the kinetic rate constant determination were investigated. The control regimes were determined with the ratio of reaction to total resistance R, and the Hatta number. The kinetic rate constants obtained at low initial zinc concentrations, low acidity and high flow velocities exhibited minor deviations, indicating that the zinc sulfate/D2EHPA system could be under the kinetic control regime with the capillary microreactors, which also demonstrated the viability of the segmented flow approach. The kinetic rate constant data obtained with the segmented flow capillary microreactor from this work were much higher than those obtained from previous studies, which may be attributed to the fact that the microreactor minimizes the influence of diffusive transport. The purpose of this work was to provide reliable kinetic data of the reactive zinc extraction system and to verify the efficiency and superiority of the segmented flow microreactor approach over other techniques.
Zinc recovery is extremely important due to the chemical and physical properties of this metal. Liquid-liquid extraction technique allows the selective recovery of zinc, leading to a high purity product. For the first time, a concentrated mining sulfuric liquor as a stock solution for in situ preparation of an Aqueous Two-Phase System (ATPS) in a hydrometallurgical process. This liquor is an overly complex solution with a high content of metal ions, especially Zn2+ and Mg2+. ATPS technique has already shown good results when compared to traditional solvent extraction techniques and can be considered a greener technique. The proposed method was optimized to obtain selective Zn2+ extraction by studying the parameters: the nature of the ATPS-forming polymer and their concentration in the stock solution; the effect of the salt added to the system; the concentration of extractant agent and the mass ratio between both phases. The optimized methodology made it possible to extract (91.5 ± 0.1)% of Zn2+ and (18.2 ± 0.1)% of Mg2+ from the liquor in three extraction steps. In the stripping step which used NaOH as the precipitating agent, about 65 % of Zn2+ was selectively recovered at pH = 6.00 and at pH = 9.00 the recovery of Zn2+was close to 80 %. Furthermore, for the first time it was proven that the polymer and the extracting agent (following the stripping step) are reusable components of the ATPS. A high extraction efficiency (%EZn ∼ 45 %) was achieved in one extraction step using the recycled extraction phase without any adjustment.
Selective extraction of zinc from sulphate effluents containing zinc, cadmium and manganese by liquid-liquid extraction with a capillary microreactor operating in the slug flow regime was elaborately investigated. Experiments were carried out at a flow rate ratio 1:1 of aqueous to organic phase, with a set-up consisting of a T-mixer connected to a PTFE capillary microreactor, and a subsequent membrane separator. The influences of extractant saponification degree, initial aqueous pH, residence time and mixture velocity on separation performance were studied, which indicated that separation enhancement of zinc from cadmium and manganese can be achieved by controlling the residence time and mixture velocity in the capillary microreactor without any aqueous pH adjustment. The βZn/Cd 2232.86 and βZn/Mn 1288.90 could be accomplished within 45 s in microfluidic extraction, whereas only 233.39 and 193.05 within 25 min in batch extraction, confirming the significant separation enhancement. Furthermore, the overall volumetric mass transfer coefficient kLa and overall mass transfer coefficient kL were also determined, high kLa of zinc (0.055 s⁻¹-0.472 s⁻¹) and low kLa of cadmium (0.009 s⁻¹-0.076 s⁻¹) and manganese (0.011 s⁻¹-0.083 s⁻¹) were responsible for the significant separation performance in the slug flow microfluidic system.
For the ever-growing demand of nickel (Ni) resources in industry, the Ni recovery from the mining residues or waste has received considerable interest. Zinc plant residue contains valuable metals it may be recovered using conventional pyrometallurgical or hydrometallurgical processes. The present communication is focused on the selective recovery of Ni from the real nitric acid leach solution of zinc plant residue by solvent extraction (i.e. 1-Butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) as ionic liquid, Di-(2-ethylhexyl) phosphoric acid (D2EHPA) and diphenylthiocarbazone (dithizone)). At first step, leaching of filter cake with the nitric acid solution was examined experimentally and it was observed that nitric acid as a relatively strong oxidant, can adequately dissolve Ni and Zn. After that, Ni and Zn extraction behavior in the leach solution was studied and the influence of pH and extractant concentration were investigated on the extraction of the metals. The results indicated Ni can be effectively separated by controlling the pH values. Moreover, Ni can be selectively separated using dithizone combined with [bmim][PF6] at pH = 5.5 and the separation factor βNi/Zn can reach 2.27×10⁵ in one extraction stage. The extraction mechanism of Ni was investigated using slope analysis and stripping efficiencies 100% have been achieved for Zn and Ni with 2.0 M HNO3. Thus, it can be concluded that the use of [bmim][PF6] as alternatives solvents which have a less significant environmental impact than the usual solvents in terms of emission of vapors is one of the promising approaches for nickel ion extraction from the real leaching solution of zinc plant residue.
In this work, the possibility of separation of Zn²⁺ and Cd²⁺ metal ions from chloride (brine) solutions was examined. For this purpose, simple solvent extraction (SX) experiments by di-2-ethylhexyl phosphoric acid (D2EHPA) in kerosene as a diluent was performed on synthetic and industrial chloride solution obtained from brine leaching of zinc filter cakes (by-product of zinc hydrometallurgical processing). The optimal conditions for separation were determined. The zinc extraction efficiency was 99% with negligible co-extraction of cadmium. Therefore, a high ΔpH0.5 value for Zn(II) and Cd(II) was achieved. FT-IR and slope analysis indicated that ZnClA ∙ 3HA and CdClA ∙ 3HA species were probably extracted.
Zn 2+ , Cu 2+ and Ni 2+ permeabilities through supported liquid membranes (SLMs) were determined experimentally from single, binary, and ternary ionic mixtures. Microporous polypropylene membrane was used as the frame to retain isopar-L solvent and di (2-ethylhexyl) phosphoric acid (D2EHPA) carrier. Sulfuric acid solution was used as a strip (receiving) solution. The ion permeability values were in the 10 − 7-10 − 6 cm 2 s − 1 range and increased with the concentrations of D2EHPA in isopar-L and the stripping sulfuric acid. The ion ideal selectivity ranged from 1.05 (Zn/Cu) to 8.40 (Zn/Ni), depending on the feed concentration. The single ion permeability was significantly higher than the binary mixtures, probably due to ion competition with D2EHPA carrier molecules. High selectivity was achieved using ternary mixtures: Zn 2+ was the fast-permeating species due to preferential sorption with D2EHPA. Separating Zn 2+ from Cu 2+ and/or Ni 2+ mixtures was most efficient with high D2EHPA concentration, concentrated H 2 SO 4 strip solution , concentrated feed solution, and from multiple ionic mixes.
A new process of extraction of zinc(II) ions with the use of liquid membranes under the conditions of galvanostatic electrodialysis with metal electrodeposition in the catholyte is presented. Liquid membranes represent solutions of di(2-ethylhexyl)phosphoric acid with addition of tri-n-octylamine in 1,2-dichloroethane. The effect of the electrodialysis current density and the composition of aqueous solutions and organic membranes on the rates of extraction, transmembrane transfer of metal ions, and electrodeposition of metal is studied. Fine-crystalline cathodic deposits of zinc are obtained from solutions of hydrochloric, sulfuric, perchloric, and acetic acids. It is shown that in the process under study, the virtually complete (>99.9%) extraction of zinc(II) ions by liquid membranes from their original solution containing 0.01 M ZnSO4 is achieved after 1–2.5 h of electrodialysis. The maximum degree of metal re-extraction is 98% and the degree of electrodeposition is 78%. It is shown that the shape of chronopotentiograms can serve as a criterion of completeness of zinc(II) extraction from the original solution.
In this study, separation of silver(I) and zinc(II) from nitrate leach solution of spent silver oxide batteries were carried out by extraction and selective stripping. Di-(2-ethylhexyl) phosphoric acid (D2EHPA) was used to extract Zn(II) and Ag(I) in the equilibrium pH range of 0.99–1.34. The extraction of Zn(II) was more affected by the pH value than that of Ag(I). Zn(II) and Ag(I) loaded in D2EHPA was separated by selective stripping with a mixture of 0.01 mol/dm³ nitric acid and 1 mol/dm³ thiourea and 0.5 mol/dm³ nitric acid for Ag(I) and Zn(II), sequentially. A process flowsheet for the separation and recovery of Zn(II) and Ag(I) from the nitrate leach solution of spent silver oxide batteries was proposed.
Fig. 10 Process flow sheet for the separation of Ag(I) and Zn(II) from nitrate leaching solution. Fullsize Image
Solvent extraction of zinc from sulphate leach solution obtained from the treatment of a sulphide-oxide sample, was investigated using D2EHPA and Cyanex 272 diluted in kerosene in a batch reactor. According to the results, D2EHPA exhibited the higher extraction efficiencies than Cyanex 272 at the organic/aqueous ratio of 1:1. The optimum concentration and pH for D2EHPA and Cyanex 272 were distinguished to be 0.5 mol/L and 2.5, and 0.035 mol/L and 3.5, respectively. Under these conditions, extraction efficiency was found to be ∼75% for D2EHPA against 41% for Cyanex 272. The plot of log D versus log [D2EHPA] confirmed the presence of 1 mole D2EHPA in dimeric form for 1 mole Zn in the extraction system. Thermodynamic data showed that the zinc extraction process is endothermic. For D2EHPA, two-stage simulated counter-current extraction experiments were performed on the basis of the McCabe-Thiele diagram and the extraction percentage of zinc was found to be about 88%. The synergistic effect of Cyanex 272 and TBP with D2EHPA was particularly investigated. It was found that the mixture of 80% D2EHPA and 20% Cyanex 272 exhibited the best synergistic effect for Zn-extraction with a synergistic coefficient of 1.04.
Soils contaminated with heavy metals represent a serious threat for humans and all ecosystems. In some cases, they can be remediated by metal phytoextraction, using accumulator or hyperaccumulator plants, however the fate of harvested metal-enriched biomass has to be addressed. Cadmium (Cd) and zinc (Zn) are very common contaminants of urban, industrial and agricultural soils. To date, no process has been developed to recover these metals from plant biomass.
This contribution presents a novel hydrometallurgical process designed to recover Cd and Zn from the biomass of a Zn/Cd hyperaccumulator plant Noccaea caerulescens. Dried plants are first ashed at 620 °C, a process which has been carefully investigated to avoid metal loss, and then the ash is acid leached. Following this, the process comprises two main steps: one to extract Cd and Zn and the other for Cd cementation using Zn powder and selective precipitation of Zn. Optimal cementation conditions have been determined with synthetic solutions using a Box-Behnken experimental design. In this context, a mole ratio Zn:Cd of 2:1, a temperature of 25 °C and a duration of 50 min proved optimal. The full process was tested on a sample of plant biomass. It demonstrated that Cd and Zn recovery was possible by cementation and precipitation. This new process still has to be optimized and up-scaled but it paves the way to Cd and Zn recovery from diverse types of soils, and even to ‘metal cultivation’, an emergent phytotechnology now referred to as agromining.
The reversed micelles formed in solvent extraction of thorium(IV) by bis(2-ethylhexyl) phosphoric acid (HDEHP) in n-heptane were studied. IR spectra, dynamic/static light scattering and zero shear viscosity measurements indicated that thorium complexes formed rodlike reversed micelles, and both the size of aggregates and the viscosity of the organic phase increased with the increasing loadage of thorium(IV). The entanglement of reversed micelles resulted in their transformation to wormlike reversed micelles, inducing the very high viscosity of the organic phase. The structural composition of thorium complexes was proposed to be Th(DEHP)3(NO3) according to the results of log -log plot and job method analysis. Furthermore, molecular modeling was employed to clarify the structures of reversed micelles as well as the state of water inside. It was found that the complexes linked together via hydrogen bonding and van der Waals forces and that the existence of NO3– and H2O improved the stability of reversed micelles.
Mixed extractants composed of di(2-ethylhexyl)phosphoric acid (P204) and ionic liquids (trihexyl(tetradecyl)phosphonium chloride (IL101) or methyltrioctylammonium chloride (A336)) for Zn(ii)/Cu(ii) separation were investigated. An antagonistic effect can be found for the extraction of both zinc and copper when mixing ionic liquids with P204, especially for Cu(ii), thus the Zn(ii)/Cu(ii) separation can be greatly improved by adjusting the kinds and mole fractions of ionic liquids in the mixed extractants. Attenuated total reflection infrared (ATR-IR) and nuclear magnetic resonance (NMR) spectroscopies elucidate that the diverse intermolecular interactions between P204 and ionic liquids can be tailored by changing their compositions. Two-dimensional correlation analysis on IR spectra further extracts the overlapped structural information of the mixed extractants. And the dependence of metal extraction on intermolecular interactions has been elucidated.
Kovohutě Příbram has developed a technology of portable zinc carbon and alkaline batteries treatment which consists of batteries crushing, sorting components and their utilization and in co-operation with the Department of Metals and Corrosion Engineering, VŠCHT Praha, a hydromet-allurgical method to utilize spent electrode material, so called active mass, which is the key factor to fill new goals for recycling efficiency set by Directive 2006/66/EU. This paper describes the developed method of spent Zn/Mn0 2 batteries treatment. After the dismantling of the batteries the active mass was analyzed and found to contain 28 % Zn and 22 % Mn. Batch laboratory experiments were carried out to establish an acid leaching procedure aiming at achieving maximum zinc extraction under simultaneous possible depressing manganese extraction. Leaching of active mass was performed in sulfuric acid originating from spent lead acid batteries. Leach liquors obtained were purified by alkalization and cementation. Zinc was recovered from refined liquors as zinc carbonate precipitate usable for zinc production or other purposes.
The development and operation of a continuous solvent extraction process for the separation of the middle (Sm, Eu, Gd, Tb) and light rare earth fractions (La, Ce, Pr, Nd) from a nitrate feed liquor is described. The process consists of extraction of the middle rare earths into a 15 vol% solution of D2EHPA in Shellsol AB in 8 counter-current stages, followed by scrubbing with 1 M nitric acid in 2–4 stages, and stripping with 1.5 M hydrochloric acid in 6–8 stages. Residual rare earth values in the organic phase (mainly Dy, with some Tb and Gd) were removed in a secondary stripping circuit using 2.5 M hydrochloric acid in 4 stages. More than 1000 1 of feed liquor were processed in two continuous counter-current trials lasting a total of 630 h. From a feed containing Sm 3.5, Gd 2.4, Eu 0.8 and Nd 20 g l−1 (together with 4–8 g l−1 each of the lighter rare earths), strip liquors containing Sm 35, Gd 20 and Eu 8 g l−1 were obtained, with neodymium (5 g l−1) as the main impurity. Recoveries of the middle rare earths to the strip liquors were high (95–100%), whereas losses of the light rare earths were low (0–4%).Addition of oxalic acid to the strip liquors, followed by calcination of the precipitated oxalate, gave a middle rare earth oxide containing 45% Sm2O3, 29% Gd2O3, 13% Eu2O3 and 6% Nd2O3. This oxide was dissolved in acetic acid and electrolysed in 1 M potassium citrate solution, using a mercury cathode and a platinum anode, to give a europium amalgam containing a small amount of samarium (Eu:Sm ≈ 66:1). The amalgam was treated with acetic acid, and the resulting acetate solution was again electrolysed to give a purified amalgam from which was recovered a final europium oxide product containing only traces of other rare earths (< 25 mg kg−1 Sm,
Southern Africa was the site of one of the first large solvent-extraction (SX) plants built, following smaller plants in the North American uranium industry and the Ranchers and Bagdad copper plants in Arizona. The copper Tailings Leach Plant at Nchanga, Zambia, was commissioned in 1973 with a capacity of 2800 m3/h. This was the largest SX plant in the world for more than a decade and is still operational today. South Africa witnessed the first commercial implementation of SX for the refining of the platinum-group metals. More recently, southern Africa has seen the implementation of SX for other base metals, precious metals, and specialty metals. These include the “world firsts” of primary production of zinc using SX by Skorpion Zinc in Namibia, and the large-scale refining of gold by SX at Harmony Gold, South Africa. Several other flowsheets that use SX technology are currently under commissioning, development, or feasibility study for implementation in this part of the world, including those for cobalt, nickel, vanadium, tantalum, and niobium.A review of SX operations in the African subcontinent is presented, with particular attention paid to advances since the turn of the millennium. Several interesting projects under development are also discussed, along with some innovative concepts in flowsheet chemistry that should soon reach commercial application.
It has been demonstrated in earlier works that zinc as an impurity can be effectively removed from cobalt sulphate solutions (Zn/Co < 1) by solvent extraction with D2EHPA. Some process residues from copper plants contain both cobalt and zinc as valuable metals, which have to be separately extracted for their recovery. Leaching of such residues leads to solutions with higher Zn/Co ratios (Zn/Co > 10). Again, solvent extraction with D2EHPA has been successfully used to separate cobalt and zinc into their respective solutions, which could further be treated by appropriate techniques for the production of these metals.The method mainly consists of selective copper extraction with LIX 984, iron removal by precipitation with CaCO3, simultaneous cobalt and zinc extraction with D2EHPA followed by their separation by selective stripping with sulphuric acid of different concentrations. The use of a specific cobalt extractant is not necessary. More than 95% copper has been recovered from the pregnant solution typically containing 1.0 g/l Co2+, 2.0 g/l Cu2+, 12.60 g/l Zn2+ and 8.4 g/l Fe3+. The cobalt and zinc recoveries were on an average of 90% each in their respective individual solutions.
An investigation was conducted of equilibria and reaction kinetics for the extraction of zinc from aqueous sulfate solutions by di(2-ethylhexyl) phosphoric acid in n-heptane. The overall stoichiometry of the reaction was established from equilibrium studies, whereas the rate measurements led to the identification of the possible rate-controlling step and a suggestion for a mechanism of the reaction. The effects of temperature and ionic strength were incorporated into an empirical correlation for the rate constant.
The extraction of Hg(II) from hydrochloric acid solutions has been investigated using Cyanex 471X in xylene as an extractant. The results demonstrate that Hg(II) is extracted into xylene as HgCl2·4L (L represents the extractant). The effect of the nature of the diluent on the extraction of Hg(II) with Cyanex 471X has been studied and correlated with the dielectric constant. The loading capacity of the extractant was also determined. IR spectral studies of the extracted complex were used to further clarify the nature of the extracted complex. The potential of the extractant for decontaminating mercury from the brine sludge of a Chlor-Alkali plant has been assessed.
The equilibrium behaviour in n-heptane of ZnSO4/di-2-ethylhexyl phosphoric acid (D2EHPA), the reactive test system of the European Federation of Chemical Engineering has been investigated in this study at changing loading conditions. The existence of two competitive zinc-complex species ZnR2RH and ZnR2 in the organic phase has been identified using Fourier transformed infrared (FT-IR) spectroscopy method. Analysis of FT-IR spectra of the organic phase indicates the complex ZnR2RH predominates at low loading conditions while both complexes ZnR2RH and ZnR2 co-exist at intermediate and high loading conditions.
An equilibrium model is proposed for the reactive system ZnSO4/di-2-ethylhexyl phosphoric acid (D2EHPA)/diluent being considered by the European Federation of Chemical Engineering as a test system, valid over a wide concentration range of extraction and stripping conditions. The model is supported by the statistical analysis of estimated parameters. Two simple consecutive reactions are assumed to give two zinc complexes with relative proportions changing as conditions change from extraction to stripping. The model was solved by Newton's method, and all parameters were estimated by data fitting using the direct search method of Hooke and Jeaves. The model predicts aqueous concentrations with an average relative error lower than 11% by assuming activity coefficients of 1.0. The incorporation of the activity coefficients may improve the model accuracy but cannot validate other simpler extraction mechanisms.
Extraction of zinc and other metals from aqueous solutions using D2EHPA as an extractant in organic phases has been investigated extensively in the past. Under the conditions of low loading of metal in organic phase, equilibrium behaviour is adequately explained through an interfacial reaction with constant stoichiometric coefficients. Experiments show that as the loading of metal in the organic phase increases, increasingly smaller number of molecules of D2EHPA are required to extract a metal ion. Reaction mechanisms which explain this behaviour through breakup of complexes formed on the interface to release free extractant for further extraction are shown to be untenable as they fail to explain experimental observations on viscosity variation and dependence of apparent equilibrium constant on loading ratio alone. A new reaction mechanism is proposed in this work. It considers that complex formed on the interface aggregates in the organic phase and releases free extractant for increased extraction. The proposed mechanism successfully explains the above hitherto unexplained features of metal–D2EHPA extraction systems. It also quantitatively predicts the extraction equilibria not just for zinc but also for cobalt and nickel, and may characterize other extraction systems as well.
The world mineral industry is experiencing an unprecedented interest in nickel–cobalt extraction from laterite ores through acid pressure leach and SX-EW processes. The recovery of cobalt and nickel from the leach solution through direct solvent extraction is of great interest as this would result in significant capital and operating cost savings. In the direct solvent extraction approach, the separation of zinc, calcium, copper and, in particular, manganese from cobalt and nickel is highly important. A series of shakeout tests was undertaken to investigate the fundamentals of the separation of the above impurities from cobalt and nickel using di-2-ethylhexyl phosphoric acid (D2EHPA) in kerosene.
A bench scale solvent extraction study has been carried out on mixed electrolyte solutions containing zinc, cadmium and cobalt as sulphates. Very high separation factors or ΔpH0.5 were obtained. These values indicate the ease of separation of these metals under appropriate conditions. In batch countercurrent experiments using a plant solution containing 83.2 g/l Zn, 52.8 g/l Cd, 2 g/l Co and 0.10 g/l Ni and 30 v/o di-2-ethylhexyl phosphoric acid (DEHPA) plus 4 v/o TBP in SX-1, stepwise (selective) extractions of zinc and cadmium from the mixed electrolyte solution were achieved, leaving cobalt and nickel in the raffinate. Zinc was extracted at pH 2.0 followed by cadmium extraction at pH 3.7. The Zn-loaded organic was scrubbed with ZnSO4 solution to remove any co-extracted cadmium and cobalt contaminants at equilibrium pH 2–2.2. Similarly, the Cd-rich organic phase was scrubbed with CdSO4 solution to remove any co-extracted cobalt and nickel species at pH 3.6–3.7. Under the experimental conditions, overall cobalt and nickel extractions were negligible.
The extraction of copper and zinc from sulphate media by di-2-ethylhexylphosphoric acid (D2EHPA) is reported. The equilibrium data for the extraction of (1) zinc alone (2–40 g/l), and (2) copper alone (2–60 g/l) by both 10 v/v % and 20 v/v % D2EHPA are given.The general case of extraction of two metals which compete for the same extractant is considered, and the data for the binary metal system zinc/copper extracted by 20 v/v % D2EHPA are reported. Specific chemical models and empirical models have been developed to correlate the data.Because the extractant has a high affinity for zinc in the presence of copper, the binary data can be modelled on the assumption that the interaction of copper with zinc can be neglected. However, the effect of zinc in reducing the extraction of copper is significant.We show that zinc can be decontaminated from copper and test the predictions with a laboratory scale counter current apparatus. Typical predictions show that in five stages, a 20 v/v % D2EHPA feed and an aqueous feed of 1.98 g/l Zn, 36.78 g/l Cu, zero g/l H2SO4 would give a 89.9% recovery of zinc with purity of 90%; with lower copper to zinc ratios in the feed the purity may be improved.
Kinetic studies of the extraction of zinc from aqueous sulfate solution by di(2-ethylhexyl) phosphoric acid in kerosene were made, using a constant interfacial area cell. Measurements of the extraction and stripping rates led to the identification of rate expressions and a suggested mechanism of this reaction. Based on the nature of the extractant and the reaction mechanism for the formation of zinc complex in the aqueous phase, a simple extraction scheme is proposed in which the rate-controlling step is interfacial. The mass-action constant obtained in the present kinetic study is considered to agree with the extraction constant obtained in the previous equilibrium study. Effects of the total sulfate concentration in the aqueous phase on the extraction and stripping rates were also investigated.
The extraction of Zn(II) with bis(2,4,4-trimethylpentyl) phosphinic acid, commonly known as CYANEX 272, in kerosene from aqueous sulphate, chloride and nitrate media was investigated. The extraction was found to increase with CYANEX 272 concentration, pH of the aqueous phase and ammonium sulphate concentrations. Stripping investigations using different stripping agents indicated that HCl and HNO3 are effective for stripping zinc. The experimental obtained capacity of CYANEX 272 was found to be 0.105M Zn(II) per mole extractant after four stages. Results on the effect of temperature indicate that the Zn(II) extraction in the investigated system is exothermic. Based on benchscale results, a continuous counter-current extraction flowsheet was developed and tested using a 15-stage horizontal type mixer-settler for the recovery of Zn(II) from simulated and real industrial waste resulting from rayon industry. The extraction efficiencies of the used system are 97 and 94% for a simulated waste solution and real solution, respectively, whereas the stripping efficiency is 96% for both processes.
The role of kinetics of extraction in the design of extraction equipment is becoming more important with the move to reduce organic inventories and phase residence times. This paper examines the influence of the kinetics of ZnSO4 extraction into di-2-ethylhexyl phosphoric acid (D2EHPA) in Shellsol 2046 in a 100 mm diameter, 1 m tall column packed with Super Mini Rings (SMR). Concentrations of zinc along the column in both phases could be simulated to within ±10% using an axial dispersion model with a diffusion-kinetic model incorporated.
Equilibria of aqueous solutions of ZnSO4 + H2SO4 with bis(2-ethylhexyl)phosphoric acid in isododecane (pentamethylheptane), a system which is proposed as an EFCE (European Federation of Chemical Engineering) test system for reactive extraction, and of aqueous solutions of ZnCl2 + HCl with bis(2-ethylhexyl)phosphoric acid in isododecane were investigated. Equilibrium concentrations and physical properties (density, viscosity, interfacial tension) are given at 298 K. The experimental data could be described well with a model that assumes the formation of one organic complex and regards the hydrogen sulfate equilibrium in the aqueous phase. The Pitzer equation was used for the aqueous phase, and the theory of Hildebrand and Scott was used to describe nonidealities in the organic phase. For quick estimations, shortcut formula for physical properties and the activities are given.
The rate of extraction of zinc(II) from aqueous perchlorate solutions at 1 M ionic strength by di(2-ethylhexyl) phosphoric acid (DEHPA) in Isopar-H (ESSO chemicals) was studied. The study was performed using a modified Lewis cell at 25°C. The experimental hydrodynamic conditions were chosen so that the contribution from diffusion on the measured rate of reaction was minimized. The rate of zinc extraction was measured at different chemical composition by varying zinc, hydrogen ion and DEHPA concentrations. The data were analysed in terms of pseudo-first order constants and a reaction mechanism was developed where a zinc-DEHPA complex is formed at the interface. The results of this kinetic model are in agreement with the equilibrium study reported previously for the same system.
Synergistic effects of Cyanex 272 mixed with D2EHPA and Cyanex 302 mixed with D2EHPA were investigated for the separation of cobalt and nickel from a dilute sulfate media with the aim of reducing the reagent cost. Selective extraction of cobalt over nickel improved with respect to D2EHPA, but worsened with respect to Cyanex 272. By the application of the slope analysis method, the stoichiometric coefficient of the extractant was found to be four for cobalt and five for nickel, in a mixture of D2EHPA with Cyanex 302. However, it was four for both cobalt and nickel in a mixture of D2EHPA with Cyanex 272. Fourier Transform Infrared Spectroscopy (FT-IR) was utilized to examine the organo-metallic complexes containing cobalt and nickel. Increasing the ratio of Cyanex 272 or Cyanex 302 to D2EHPA did not reveal a significant effect on the extraction curve of cobalt, but caused an increase in pH of the nickel extraction curve. Increasing the ratio of Cyanex 272 or Cyanex 302 to D2EHPA increased the pH50 difference (ΔpH50(Ni–Co)). Optimum separation was found with a Cyanex 302 to D2EHPA ratio of 0.3:0.3 when the pH50 difference (ΔpH50(Ni–Co)) was 0.9. Results showed that extraction of cobalt is more endothermic than that of nickel. Improved separation was hence achieved with a warm mixture.
The extraction equilibrium of the possible test system for reactive extraction zinc sulphate/bis (2-ethylhexyl)-phosphoric acid (D2EHPA)/n-heptane was studied at 25°C. The results from slope analysis, computer modelling and quantitative FT-IR spectroscopy have been compared. The computer program SXLSQA was used for modelling the equilibrium taking into account the non-ideality of both phases, based on the Pitzer approach for the aqueous phase and the regular solution theory of Hildebrand/Scott for calculating organic phase activity coefficients. The three methods employed provide the same result: that the dominating zinc complex in the organic phase is ZnR2(RH). Some analytical improvements have been carried out, such as purification of D2EHPA, a purity determination method for D2EHPA, an analytical method for the determination of D2EHPA concentration in aqueous solutions. Fr-IR has also been used to illustrate the role of water in the formation of the organic metal complexes. While in the extraction of nickel an appreciable amount of water is co-extracted, the extraction of zinc does not show the same behaviour.
Extraction of uranium from fertiliser-grade phosphoric acid with a novel synergistic mixture of di-nonyl phenyl phosphoric acid (DNPPA) and tri-n-butyl phosphate (TBP) is reported in this paper. The effects of varying the concentrations of phosphoric acid, DNPPA and TBP on the distribution ratio of uranium have been studied. Batch counter-current extraction tests have been carried out. The extracted uranium in the organic phase was efficiently stripped at 65 °C using concentrated phosphoric acid containing ferrous iron. The stability of the solvent was investigated by extended contact testing as well as cyclic extraction and stripping tests. The data on the effect of temperature on the extraction showed that the enthalpy change is −24 kJ/mol when DNPPA-TBP is used as the extractant, more than double when DNPPA alone was used. Uranium extracted by DNPPA-TBP is further subjected to a second cycle of extraction using D2EHPA-TBP and scrubbing impurities. The uranium is finally converted to a high purity UO3 product using precipitation with hydrogen peroxide and heat treatment at 200 °C.
The development of a solvent extraction process for the recovery of high-grade lanthanum oxide from a light rare earth (RE) (La, Pr, Nd) chloride solution is described. In a preliminary stage, process parameters and experimental conditions were explored in bench-scale experiments. The effect of variables such as nature and concentration of the extractants (di-2-ethylhexylphosphoric acid [DEHPA] and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester [HEH(EHP)]), contact time, acidity and rare earth concentration in the extraction stage as well as the effect of the hydrochloric acid concentration in the stripping stage were investigated. The continuous counter-current experiments were carried out in a mini-battery unit of mixer-settlers. The final set-up was comprised of 22 stages: 8 for extraction, 8 for scrubbing and 6 for stripping. A high-grade oxide (>99.9% La2O3) was obtained with a yield superior to 99.9%.
To review the pharmacogenetics of bipolar disorders, the authors searched databases for genetic association and linkage studies involving response to long-term prophylactic lithium treatment, as well as treatment with antidepressants or clozapine. Significant ethnic variations in the metabolism and efficacy of antidepressants, as well as clozapine, have been reported by several groups. Systematic studies suggest that that genetic factors affect the response to prophylactic lithium treatment. Numerous associations between the three traits of interest and candidate gene polymorphisms have been proposed. Among these, an association between the serotonin transporter gene and response to serotonin reuptake inhibitors appears robust. Considerable interest has also focused on serotonergic gene polymorphisms and response to clozapine. Response to pharmacotherapy in bipolar disorders may be mediated by genetic factors, but the role played by heritability is unknown.
Minas Gerais state normative legislation by 16
COPAM, no. 10, Minas Gerais state normative legislation by 16/12/1986,
Brazil.
Handbook of Solvent Extraction
- T C Lo
T.C. Lo, M.H.I. Baird, C. Hanson (Eds.), Handbook of Solvent Extraction,
John Wiley & Sons, 1983.