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Over the past few years, heavy metals have been proved as one of the most important contaminants in industrial wastewater. Chromium is one of these heavy metals, which is being utilized in several industries such as textile, finishing and leather industries. Since hexavalent chromium is highly toxic to human health, removal of it from the wastewate...
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... formation mechanism of polyaniline in the aquatic environment is presented in Figure 1. Aniline in an acidic solution exists as an anilinium cation, and an aniline radical cation is supposed to be the first product of an oxidation pro- cess (pattern A). ...
Context 2
... changes lead to the product changing color, turning to green. This state of poly- aniline is called protonated emeraldine, which is shown in pattern C in Figure 1. Furthermore, if it is applied to a stron- ger oxidation agent, polyaniline will turn to protonated pernigraniline, which is blue (pattern D), and if it was washed by a base, it would turn to the form of basic emeral- dine that is also blue (pattern E). ...
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Purpose
It is essential to track the development of resource and pollution intensive industries such as textile, leather, pharmaceutical, etc., under burgeoning pressure of environmental compliance. Therefore, the purpose of this paper is to analyze the progress of Indian leather industry in terms of individual factors and total factor productivity...
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... The EDX elements of MMT/HA/PVA and MMT/HA/PVA@PANI were analyzed, and the results are shown in Fig. 2f, g. It is found that carbone (C), nitrogen (N), oxygen (O), aluminum (Al), silicon (Si) and magnesium (Mg) are the main elements of MMT/HA/PVA, while MMT/HA/ PVA@ PANI adds chlorine (Cl) element, which comes from the Cl doping of PANI [31]. EDX confirmed the successful compounding of PANI and MMT/HA/PVA. Figure 2h shows the infrared spectrum analysis results of PANI, MMT/HA/PVA and MMT/HA/PVA @PANI. ...
... In contrast, in aqueous solution with pH > 6, CrO 4 2− becomes the dominant The increase of solution pH results in the decrease of positive charge on the surface of adsorbent due to deprotonation of amino group, and the electrostatic repulsion between Cr(VI) anion and adsorbent increases, thus limiting the adsorption of Cr(VI). Furthermore, OH − in solution may compete with CrO 4 2− for adsorption sites, which will further reduce the adsorption capacity of materials [31]. ...
It is still challenging to avoid polyaniline agglomeration and fabricate polyaniline-based adsorbents with stable structure, excellent adsorption performance. Herein, we synthesized montmorillonite/humic acid/polyvinyl alcohol@polyaniline (MMT/HA/PVA@PANI) composite porous hydrogel adsorbent by Pickering emulsion template-in situ chemical oxidative polymerization, and the enhancement effect of this design idea on the adsorption performance of PANI was studied with heavy metal ion hexavalent chromium Cr(VI) as the target adsorbate. The in-situ polymerization of aniline at the Pickering emulsion interface and the unique three-dimensional network structure of the hydrogel act as an effective “confinement” for the growth of the polyaniline. The porous structure of hydrogel can be used as water channel, which can accelerate the combination of adsorbate and adsorption site, and significantly improve the adsorption capacity and adsorption rate. Compared with the pure PANI (43.48 mg g⁻¹ PANI), MMT/HA/PVA@PANI (1753.60 mg g⁻¹ PANI) obviously had significantly higher removal efficiency, which increased the removal efficiency of Cr(VI) by about 40 times. Adsorption experiments suggest that solution pH, adsorbent dosage, contact time and initial concentration all have certain effects on adsorption performance. According to the FESEM, EDX, FTIR and XPS analysis of the materials before and after adsorption, the removal of Cr(VI) is mainly enhanced by ion exchange, electrostatic attraction and chemical reduction. In conclusion, MMT/HA/PVA@PANI adsorbent has novel design, good adsorption performance and strong stability, and it has great development prospects in removing heavy metal ions from wastewater.
... PVA-based hydrogel as carrier can provide a uniform system for aniline polymerization, effectively improve the problem of easy agglomeration of aniline polymerization, and improve its mechanical strength and processability. Composite hydrogel is an excellent adsorbent for removing Cr (VI), which has the dual advantages of hydrogel and conductive polymer (Riahi Samani et al. 2016). Emulsion polymerization is one of the ideal strategies to obtain porous hydrogels, but the traditional surfactant-stabilized emulsion often has the disadvantages of foaming, high toxicity, and high cost (Yuan et al. 2020). ...
Hexavalent chromium Cr(VI) is a typical harmful pollutant, which is carcinogenic or mutagenic to aquatic animals and humans. In this study, sepiolite/humic acid/polyvinyl alcohol@ polyaniline (SC/HA/PVA@PANI) composite porous hydrogel adsorbent was synthesized by Pickering emulsion template in situ chemical oxidative polymerization for adsorption of Cr(VI) from aqueous solution. The in situ polymerization of aniline at the Pickering emulsion interface and the unique three-dimensional network structure of the hydrogel act as an effective “confinement” for the growth of the polymer. The porous structure of the material acts as a water channel, which effectively accelerates the binding of the adsorbate to the adsorption sites, and significantly improves the adsorption rate and adsorption capacity. The adsorption capacity of PANI for Cr(VI) confined in three-dimensional network of composite porous SC/HA/PVA@PANI hydrogel reached 1180.97 mg/g-PANI, which increased about 27-fold compared the adsorption capacity of pure PANI (43.48 mg/g). It is shown that the experimental design effectively avoids the agglomeration of PANI and improves its potential adsorption performance. In addition, the analysis of FESEM-EDX, FT-IR, and XPS spectra before and after adsorption confirmed that the main adsorption mechanisms of Cr(VI) on SC/HA/PVA@PANI included ion exchange, electrostatic attraction, and redox reaction. In conclusion, SC/HA/PVA@PANI has good stability and excellent adsorption performance, which is a new type of Cr(VI) ion adsorbent with great potential.
... In recent years, PVA-based hydrogels have attracted considerable attention in the eld of adsorption because of their non-toxicity, low cost, simple preparation, directional adjustment function and fast adsorption rate(Chen et al., 2020;Gulyuz &Arslan, 2021;Sun et al., 2015). PVA-based hydrogel as carrier can provide a uniform system for aniline polymerization, effectively improve the problem of easy agglomeration of aniline polymerization, and improve its mechanical strength and processability.Composite hydrogel is an excellent adsorbent for removing Cr (VI), which has the dual advantages of hydrogel and conductive polymer(RiahiSamani et al., 2016). Emulsion polymerization is one of the ideal strategies to obtain porous hydrogels, but the traditional surfactant-stabilized emulsion often has the disadvantages of foaming, high toxicity and high cost(Yuan et al., 2020). ...
Hexavalent chromium Cr(VI) is a typical harmful pollutant, which is carcinogenic or mutagenic to aquatic animals and humans. In this study, sepiolite/humic acid/polyvinyl alcohol@ polyaniline (SC/HA/PVA@PANI) composite porous hydrogel adsorbent was synthesized by Pickering emulsion template-in situ chemical oxidative polymerization for adsorption of Cr(VI) from aqueous solution. The in-situ polymerization of aniline at the Pickering emulsion interface and the unique three-dimensional network structure of the hydrogel act as an effective "confinement" for the growth of the polymer. The porous structure of the material acts as a water channel, which effectively accelerates the binding of the adsorbate to the adsorption sites, and significantly improves the adsorption rate and adsorption capacity.The adsorption capacity of PANI for Cr(VI) confined in three-dimensional network of composite porous SC/HA/PVA@PANI hydrogel reached 1180.97 mg/g-PANI, which increased about 27-fold compared the adsorption capacity of pure PANI (43.48 mg/g). It is shown that the experimental design effectively avoids the agglomeration of PANI and improves its potential adsorption performance. In addition, the analysis of FESEM-EDX, FT-IR and XPS spectra before and after adsorption confirmed that the main adsorption mechanisms of Cr(VI) on SC/HA/PVA@PANI included ion exchange, electrostatic attraction and redox reaction. In conclusion, SC/HA/PVA@PANI has good stability and excellent adsorption performance, which is a new type of Cr(VI) ion adsorbent with great potential.
... The Langmuir isotherm assumes a homogeneous, monolayer adsorption mechanism (Riahi Samani et al., 2016). It was then assumed that once a Cr (VI) or a phenolate ion attaches on a site, no further attachment can take place on the occupied area. ...
Several industrial effluents contain Cr (VI) and phenol in varying concentrations. These compounds are highly toxic even at low concentrations. In this study, Exfoliated Graphite (EG) was investigated as an adsorbent towards the removal of these contaminants. This was motivated by its availability, ease of synthesis and high surface area. The exfoliation process resulted in graphite that had a worm-like accordion structure and an increased surface area from 2.4 to 22.4 m²g⁻¹. The optimum loading for both pollutants was 30 g/L and equilibrium was attained in a 48 hours period. Maximum Cr (VI) removal (89.8%) occurred under acidic conditions (pH 2) while phenol was preferentially removed (62.3%) under basic environments (pH 12). Three non-linear adsorption models, namely Redlich-Peterson, Freundlich and Langmuir were evaluated. The Redlich-Peterson isotherm, with an exponential constant, β°=°0.8982 best described the equilibrium data for Cr (VI) with a regression coefficient of R2°=°0.9965 while the Langmuir isotherm accurately described the phenol adsorption with a regression coefficient of R2°=°0.9975. The pseudo-second order rate equation adequately represented the experimental data for phenol and Cr (VI) with regression coefficients greater than 0.99. Adsorption thermodynamic studies revealed that the attachment of phenol and Cr (VI) onto EG was a feasible, endothermic and spontaneous process.
... PANI-PVA film have been used for applications such as, sensors [11], membrane [12], optical recording material [13,14], pulsed photoconductivity [15], ion-exchange ability, metal recovery [16][17][18], supercapacitor [19,20], etc. Generally, polyaniline with polyvinyl alcohol blends/composites have been synthesized by (i) in-situ polymerization of aniline with PVA [11,[21][22][23][24], (ii) incorporation of polyaniline into PVA [20,[25][26][27] and (iii) preparation of PVA film and coating of polyaniline on PVA film [19]. ...
This work aims to make environmentally friendly coating consists of an aqueous dispersion of conducting polyaniline (PANI) salt containing H2SO4 and PVA dopants in polyvinyl alcohol (PVA) for electrostatic discharge, sensor and corrosion applications. Aniline is oxidized by ammonium persulfate to PANI-sulfate salt (PANI-SA) without using any protic acids, wherein, sulfuric acid generated from ammonium persulfate during the oxidation of aniline gets doped on to PANI system. The results of PANI-SA are compared with (i) PANI-H2SO4 salt prepared in presence of sulfuric acid in the aniline polymerization and (ii) PANI salt containing dopants of H2SO4 and PVA, (PANI-SA-PVA), prepared with polymeric alcohol, PVA, instead of hazardous sulfuric acid, in the polymerization of aniline. Yield, conductivity, density, diffraction pattern, morphology and thermal properties of PANI-SA are more or less similar to that of the PANI-SA-PVA system. However, yield and conductivity of PANI-H2SO4 are higher than that of PANI-SA-PVA due to the increase of oxidizing efficiency by H2SO4. These three salts, PANI-SA, PANI-H2SO4 and PANI-SA-PVA are dissolved in aqueous PVA. These dispersions are coated on (i) glass slide to find the hydrophilic nature (ii) transparent polyethylene terephthalate film for ESD application, (iii) ceramic tube for sensing ammonia gas, and (iv) stainless steel plate for corrosion study. Among the three PANI salts, PANI-SA-PVA dispersed in PVA shows better performance.
... The new researches show that synthesis of polyaniline attended by some other polymers increase polyaniline capacity for heavy metals removal. For example Removal of heavy metals from aqueous solution using polyaniline and polyaniline/ ferricyanide [58], polyaniline/graphene oxide [59], polyaniline/silica gel [60], polyaniline/polyvinyl alcohol [61,62], polyaniline/polystyrene [63,64], polyaniline-poly ethylene glycol [65] have been reported and all have mentioned a significant improvement of removal efficiency. The chemically synthesized polyaniline naturally exists in powder shape and is unable to be used in column system. ...
Polyaniline/ Sawdust /Poly Ethylene Glycol/ (PANi/SD/PEG) composite synthesized chemically is used as an adsorbent to remove hexavalent chromium from water. Adsorption experiments have been done in batch and continuous (column) mode. Some parameter such as pH, contact time, PANi/SD/PEG dose, isotherms in batch mode and pH, column bed depth and fluid flow rate in column mode were investigated. Result shows that PANi/SD/PEG has a good performance to remove hexavalent chromium ion from aqueous media. By presence of PEG, prepared composite has been homogenized and further absorption has been occurred. The best adsorption occurs under pH 2 and optimum contact time for removal of hexavalent chromium ion in batch experiment was about 30 min. Adsorption of Cr (VI) by PANi/SD/PEG fitted well in Langmuir isotherms. Maximum adsorption of hexavalent chromium was calculated 3.2 (mg/g). In column experiments, pH and column bed depth were found to be more prominent than fluid flow rate. Though, about 22% of Cr (VI) can be recovered using 0.1 M NaOH in the batch system, the recovered Cr (VI) in column system was less than 7.9%.
... Over the past few years, several techniques have been proposed to remove mercury from water. Some of these methods are precipitation, membrane separation, ion exchange, and adsorption (Phothitontimongkol et al. 2009;Samani et al. 2016). Among these techniques, adsorption is suggested to be one of the most reliable techniques and a great interest has been devoted to develop a new type of adsorbents in the form of polymers to adsorb mercury from an aqueous solution. ...
... Moreover, by employing a stronger oxidation agent, protonated pernigraniline will be formed and the color of the product will change into blue (pattern D). Besides, the washing of it with base will form a basic emeraldine in a blue color (pattern E). (Samani et al. 2016) Considering the high affinity of PANi to adsorb various heavy metals and the powerful capability of it to chemical synthesize with other materials, in this study, the removal of mercury in an aquatic environment using composites of polyaniline and synthesis of polyaniline with various additive materials such as polyvinyl alcohol (PVA) and polyethylene glycol (PEG) was investigated. To this end, they were tested under various pH values, contact time, and initial mercury concentrations. ...
In this study, polyaniline (PANi) was chemically synthesized with polyvinyl alcohol (PVA) to form PANi/PVA composites. Then, the composite was employed for adsorption of mercury from aqueous environment and a thorough comparison of PANi/PVA and PANi composites was made by conducting various experiments in different pH values, initial mercury concentrations, and contact time. The adsorption isotherms were also provided, and the effect of various water constituents was investigated. The results showed that both composites are considerably effective on removing mercury from aqueous environment. PANi and PANi/PVA removed around 92.7 and 90% of mercury at pH of 6. The solution pH also played an important role on adsorption efficiency, the optimum pH for the adsorption of mercury by PANi and PANi/PVA was determined as 5.5 and 6, respectively. Besides, the optimum contact time for both composites was calculated as 30 min and the efficiency of mercury removal was increased with a reduction in initial mercury concentration.
... In January 1991, a massive oil spill in Kuwait attracted the attention of many people around the world. About 92 percent of the producing oil wells were detonated and ignited, causing severe environmental and engineering impacts (Mukhopadhyay et al., 2008;Samani et al., 2016). In addition to the environmental threats, the geotechnical properties of the contaminated soil were altered and caused enormous damage to the existing structures. ...
Various materials have conventionally been utilized to improve geotechnical properties of soils. Recently, utilization of microorganisms to this end has attracted lots of attention because of its high capabilities. Various oil degrading bacteria have proven to be effective on degrading crude oil pollution from the soil. However, their effect on geotechnical properties of the soil has not been thoroughly investigated. In this research, various oil-degrading bacteria were employed to degrade crude oil contamination from crude oil contaminated sandy soil. Then, alterations on geotechnical properties of bio-treated sand were ascertained. The results showed that by employing these microorganisms, more than 50% and 80% of the crude oil was degraded after 10 and 30 days of bio-treatment, respectively. Moreover, the bio-treated samples, which are slightly crude oil contaminated, acquire larger values of maximum dry density and cohesion in comparison to untreated contaminated samples. As treatment time increases, the value of internal friction angle remains almost constant and unconfined compression strength slightly increases. Generally, the bio-treatment alters geotechnical properties of the contaminated soil and the application of bio-treated soil as a road basement in road construction and erosion controller is suggested.
... One drawback of this approach is the large-scale acidification of water sources containing high levels of Cr(VI) to below pH 5. And, once chromate has been removed with the aid of GAC, the acidic water requires neutralization prior to release into waterways or community use. Reports of polymers containing alcohols, anilines, and catechols (1,2-dihydroxybenzene) have been described as Cr(VI)-removing agents [19][20][21][22] by either complexation or serving as reducing agents to furnish Cr(III). As part of a strategy to remove Cr(VI) from source water, we sought to identify small organic molecules containing bidentate alcohol or amine functional groups that could form complexes with aqueous chromate ions at pH 7. The newly formed neutral organic-Cr(VI) compounds would, by virtue of superior physicochemical properties, be better suited for absorption onto GAC. ...
Hexavalent chromium, Cr(VI), in the form of chromate (CrO4²⁻) or dichromate (Cr2O7²⁻) is a well-described carcinogen found in the drinking water in many parts of the country at levels deemed unsafe by the U.S. Environmental Protection Agency and the World Health Organization. We report on the ability of bidentate organic molecules containing diols or diamines to capture chromate ions from aqueous sources by forming cyclic organic-Cr(VI) carbonates or ureas. After their formation, the cyclic organic-Cr(VI) molecules are readily absorbed onto granulated activated charcoal to facilitate Cr(VI) removal. Using density functional theory, E0 values for the reactions of diols and diamines with chromate were calculated and correlated with the experimental findings of Cr(VI) removal.
