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Fe(II)-modifi ed ZEOSAND packed column; Cr(VI), 500 μg/L; NaCl, 15 g/L; ■: breakthrough curve; ▲: pH of the effl uent
Source publication
Three different types of Fe(II)-modified natural zeolites were tested as supports in continuous-flow columns for the treatment of Cr(VI) contaminated water. The natural zeolites chosen as support were commercially available Zeosand (80% clinoptilolite), ATZ (79% phillipsite/chabazite), and ZS-55RW (90% Chabazite). All the examined modified zeolites...
Similar publications
Presence of hexavalent chromium, Cr(VI), in water is an important environmental and human health problem. Natural zeolites are widely accepted as non-expensive adsorbents for sustainable remediation, however they are not effective in removing metals in anionic form. The paper presents study on use of silver (Ag) modified natural clinoptilolite to i...
Citations
... Some of the most common methods to control Cr(VI) levels in water are ion exchange, precipitation, flocculation, reverse osmosis, electrocoagulation, electrodialysis, membrane filtration, solvent extraction, and adsorption [3,5,10,14,15]. Each of these methods has advantages and drawbacks. For instance, ion exchange, electrocoagulation, reverse osmosis, electrodialysis, and membrane filtration require a high amount of energy and regular maintenance [3,6,10]. ...
The potential of pretreated sugarcane bagasse (SCB) as a low-cost and renewable source to yield activated carbon (AC) for chromate CrO42− removal from an aqueous solution has been investigated. Raw sugarcane bagasse was pretreated with H2SO4, H3PO4, HCl, HNO3, KOH, NaOH, or ZnCl2 before carbonization at 700 °C. Only pretreatments with H2SO4 and KOH yield clean AC powders, while the other powders still contain non-carbonaceous components. The point of zero charge for ACs obtained from SCB pretreated with H2SO4 and KOH is 7.71 and 2.62, respectively. Batch equilibrium studies show that the most effective conditions for chromate removal are a low pH (i.e., below 3) where >96% of the chromate is removed from the aqueous solution.
... The modified zeolite can be used more efficiently in the fields of catalysis [5][6][7][8][9][10][11][12], the preparation of new materials [13,14], and adsorption [15][16][17][18][19][20][21]. In the field of adsorption, modified zeolite is used to adsorb fluoride [22], sulfur [23], phosphate [24], bacteria [25], basic blue 41 [26] and Cd 6? [27], Ru 3? [28], As 5? [29], Pb 2? [30], Zn 2? [24,31], Cr 3? [31] and other heavy metal ions. However, in the process of adsorption and separation of zeolite, especially for complex industrial wastewater systems, saturated zeolite is difficult to separate from the action system, which is a major problem in practical applications. ...
Zeolite has many advantages such as outstanding ion exchange performance, large specific surface area and uniform pores in the field of wastewater treatment. However, zeolites are difficult to separate from complex industrial wastewater systems. Magnetically modified zeolite (MMZ) composites with both magnetic and adsorption properties were synthesized by attaching Fe3O4 to the surface of Na-zeolite by chemical co-precipitation. MMZ can be better adsorbed from wastewater by permanent magnets for reuse. The structure, morphology and magnetic properties of MMZ were characterized. Compared with Na-zeolite, the structure of MMZ has no obvious change, Fe3O4 is evenly coated on the surface of the zeolite matrix, the specific surface area is greatly increased, and the magnetism is sufficient to attract the permanent magnet. The adsorption efficiency of MMZ for Pb²⁺, Cd²⁺, and Cu²⁺ in simulated wastewater was largely dependent on pH. According to the Langmuir and Freundlich isotherms to fit the equilibrium data, the maximum monolayer saturated adsorption capacities of the three ions are 83.20 mg/g, 30.58 mg/g and 16.16 mg/g, respectively, which are greatly improved compared with the samples before modification. Therefore, MMZ is an adsorbent with good adsorption performance and easy to be recycled and reused.
... Various materials were utilized for the remediation of toxic Cr 6+ from water such as bio-sorbents [18], charcoal [19], zeolites [20], layered double hydroxides [21], carbon nanotubes [22], clay-based materials [23], polymeric based adsorbents [24], biochar [25], graphene-based adsorbents [26], and ACs [27]. In the recent decades, raw AC and AC composites gained more attention in water treatment fields compared to other adsorbents due to their high efficacy, large surface area, facile regeneration, and variety of surface functional groups [28]. ...
Hexavalent chromium (Cr⁶⁺) is a carcinogenic pollutant found in different wastewater streams. The current study investigates the potential removal of Cr⁶⁺ from aqueous solutions by nitrogen-doped coconut granulated activated carbon (N-GAC). The raw GAC was chemically and thermally treated with urea (1:1 ratio) in an ethanol medium and calcined under nitrogen atmosphere at temperatures 400 °C and 600 °C. The optimized sample (N-GAC 400 °C) possessed a remarkable surface area (474.62 m²/g) while the chemical composition analysis revealed successful doping of nitrogen with no significant changes on the mesoporous morphology of the raw GAC. The adsorption studies revealed that Cr⁶⁺ adsorption capacity was higher for N-GAC 400 °C. The removal efficiency was significantly decreased with increasing the initial solution pH (optimum pH 2.2). The temperature has no significant effect on the adsorption capacity. The equilibrium experimental results were best fitted with Sips and Redlich-Peterson isotherm models with R² ≥ 0.987 with a maximum adsorption capacity of 15.15 mg/g. The kinetic data agreed with the pseudo 2nd order model (R² > 0.997). The isotherm and kinetic studies revealed that physisorption and chemisorption processes are involved in the removal process. The adsorption mechanism was mainly controlled by electrostatic interactions, ion exchange and reduction of Cr⁶⁺ to trivalent chromium mechanisms. Accordingly, the N-GAC can be considered a promising material for the adsorptive removal of heavy metals from water.
... Using minerals as a support for the Fe(II) ions instead of using the dissolved salt is more satisfactory in reducing Cr(VI), as it consumes smaller amounts of Fe(II) salts and does not require the addition of acids to obtain acidic conditions (Brigatti et al. 2000). Although some studies have tested minerals modified with Fe(II) to reduce Cr(VI) (Kiser and Manning 2010;Lv et al. 2014;Lofù et al. 2016;Ahn and Do 2016;Kwak et al. 2018), the mechanisms involved in this process are not well detailed. Therefore, the present study assessed the main mechanisms involved in the removal of Cr(VI) from solution by redox using zeolite and vermiculite modified with Fe(II). ...
Mechanisms of Cr(VI) reduction by Fe(II) modifed zeolite (clinoptilolite/mordenite) and vermiculite were evaluated.
Adsorbents were treated with Fe(SO4)·7H2O to saturate their exchange sites with Fe(II). However, this treatment decreased
their CEC and pHPZC, probably due to the dealumination process. Vermiculite (V-Fe) adsorbed more Fe(II) (21.8 mg g−1)
than zeolite (Z-Fe) (15.1 mg g−1). Z-Fe and V-Fe were used to remove Cr(VI) from solution in a batch test to evaluate
the efect of contact time and the initial concentration of Cr(VI). The Cr(VI) was 100% reduced to Cr(III) by Z-Fe and
V-Fe in solution at 18 mg L−1 Cr(VI) after 1 min. Considering that 3 mol of Fe(II) are required to reduce 1 mol of Cr(VI)
(3Fe+2+ Cr+6→ 3Fe+3+ Cr+3), the iron content released from Z-Fe and V-Fe was sufcient to reduce 100% of the Cr(VI)
in solutions up to 46.8 mg L−1 Cr(VI) and about 90% (V-Fe) and 95% (Z-Fe) at 95.3 mg L−1 Cr(VI). The Fe(II), Cr(III),
Cr(VI), and K+ contents of the adsorbents and solutions after the batch tests indicated that the K+ ions from the K2Cr2O7
solution were the main cation adsorbed by Z-Fe, while vermiculite did not absorb any of these cations. The H+ of the acidic
solution (pH around 5) may have been adsorbed by V-Fe. The release of Fe(II) from Z-Fe and V-Fe involved cation exchange
between K+ and H+ ions from solution, respectively. The reduction of Cr(VI) by Fe(II) resulted in the precipitation of Cr(III)
and Fe(III) and a decrease in the pH of the solution to<5. As acidity limits the precipitation of Cr(III) ions, they remained
in solution and were not adsorbed by either adsorbent (since they prefer to adsorb K+ and H+). To avoid oxidation, Cr(III)
can be removed by precipitation or the adsorption by untreated minerals.
... However, the adsorption seems to be the most efficient techniques in separation, concentration and removal of chromium. Several adsorbents have been studied for chromium removal from aqueous solutions, including activated carbon [15,16], activated alumina [17], metal oxide [18][19][20], bimetallic nanocomposites [21], Layered double hydroxide [22], zeolite [23], biomass [24][25][26][27][28][29], chitosane [30,31], silica gel [32,33], and ions exchanger resins [34][35][36][37][38]. Recently, a new adsorbent constitute of a polymer matrix and an active material, microsphere or microcapsule, gained a great interest in the research of removal of chromium ions [39][40][41][42][43][44][45][46][47][48][49][50]. Microspheres can be presented as an alternative technology as a new class of adsorbent which can be prepared with a wide range of polymers and various technique. ...
PVC microspheres included with Aliquat-336 as extractant were prepared by phase inversion method. Theirs morphology and structure was determined by scanning electronic microscopy (SEM) and BET analysis. SEM images show an asymmetric structure and different morphologies, obtained by varying the concentration of the polymer. The prepared microspheres were used as adsorbent to the removal of Cr(VI) from an aqueous solution. Various parameters were studied like, the extractant dosage, the microspheres dosage, the agitation speed and the aqueous solution pH. The prepared microspheres were able to remove chromium from aqueous solution and had a maximum adsorption capacity qm more than 35mg/g.
... • The Cr metabolism ability of the chrAB engineered strain is stronger than the chrA engineered strain. • Cr-resistance in chrA and chrAB genes may involve several mechanisms, such as sulfate ion channel and respiratory chain electron transfer Cr(VI) contamination in groundwater systems is conventionally treated using the pump-andtreat methods which involve the extraction of contaminated water from the aquifer, treatment above ground, and injection of the treated water back into the aquifer [65,66]. Even though a number of successful reports are available on the success of using the pump-and-treat technique to remediate Cr-contaminated groundwater, the issue in removing residual Cr persists until present day [67]. ...
... Therefore, the chemical processes are viewed as costly and environmentally intrusive. Alternative biological treatment methods using aquatic biomass and/or Cr(VI) reducing bacteria have long been investigated and proposed by a number of researchers [65,69]. These methods may be applied ex situ [71] or in situ in biological barriers [72]. ...
Purpose of Review
Hexavalent chromium, Cr(VI), and trivalent chromium, Cr(III), are two chromium compounds with practical importance due to their high occurrence and solubility in the environment. Current Cr(VI) treatment techniques involve chemical reduction of Cr(VI) to Cr(III), which posed serious threat to workers and environment notably from long exposure and toxic fumes.
Recent Findings
Numerous reports have demonstrated the feasibility of using biological processes for the treatment of Cr(VI) industrial effluents by either pure culture or a consortium of Cr(VI)-reducing bacteria, with various degrees of success. Among issues to be considered include high cost of nutrient for the bacteria, low Cr resistant-reducing ability of environmental isolates, difficulty in scaling up finding in the laboratory to pilot scale and on-site application as well as the understanding on the dynamic underlying mechanisms for bacterial Cr(VI) reduction.
Summary
This review highlights cytotoxicity and genotoxicity properties of Cr(VI), which form the biggest motivation for continuous development in the field of Cr(VI) treatment technologies, latest finding in aerobic and anaerobic bacterial reduction of Cr(VI), operational challenges for bacterial Cr(VI) reduction, and some examples for laboratory-scale and pilot-scale evaluation of free and immobilized (biofilm) cells of Cr(VI) resistant-reducing bacteria.
... Lee et al. (2006) used Fe-loaded zeolite and was found to removed Cr(VI) to below the detection limit at a reasonably rapid rate within 20 h, under slightly acid to around neutral pH. Lofu et al. (2016) adopted a comparable method and showed Cr(VI) removal rate of 90 mg kg − 1 of zeolite but experienced a considerable loss of iron leaching. NaY Zeolite, a kind of alkali silicon aluminate, was also studied for Cr(VI) removal. ...
Chromium (Cr) is a trace element critical to human health and well-being. In the last few decades, its contamination, especially hexavalent chromium [Cr(VI)] form in both terrestrial and aquatic ecosystems, has amplified as a result of various anthropogenic activities. Chromium pollution is a significant environmental threat, severely impacting our environment and natural resources, especially water and soil. Excessive exposure could lead to higher levels of accumulation in human and animal tissues, leading to toxic and detrimental health effects. Several studies have shown that chromium is a toxic element that negatively affects plant metabolic activities, hampering crop growth and yield and reducing vegetable and grain quality. Thus, it must be monitored in water, soil, and crop production system. Various useful and practical remediation technologies have been emerging in regulating chromium in water, soil, and other resources. A sustainable remediation approach must be adopted to balance the environment and nature.
... It was established that the Zeorites lowered the concentration of Cr(VI) below the European level. Furthermore, Zeosand with a broader pH range of stability provided the best Fe(II) uptake (0.54 wt%) and a 90 mg Cr/kg zeolite removal of Cr(VI) (Lofù et al., 2016). Also, a reduction of Cr(VI) concentration to less 0.01 mg/L which is well below the United States Environmental Protection Agency (USEPA) and the North Carolina Department of Environment and Natural Resources (NCDENR) levels was observed in the groundwater samples after an injection of sodium dithionite was put to test . ...
Despite the importance of chromium (Cr) in most anthropogenic activities, the subsequent environmental adulteration is now a source of major concern. Cr occurs in numerous oxidation states, with the furthermost stable and frequently occur states being Cr(0), Cr(III) and Cr(VI). Cr(0) and Cr(III) are vital trace elements while Cr(VI) is dispensable and noxious to living organisms. Predominantly in plants, Cr at low concentrations of about 0.05-1 mg/L assist to boost growth as well as increase productivity. However, accumulation of Cr could represent a potential threat to living organisms. Cr absorption, displacement and accretion depend on its speciation, which also determines its toxicity which is often diverse. Indications of its toxicity include; reduction of seed germination, retardation of growth, reduction of yield, inhibition of enzymatic activities, weakening of photosynthesis, nutrient, oxidative disparities and genetic mutation in plants as well as several injurious diseases in animals and humans. In this study, we have presented a comprehensive review as well as an informative account of the influence of Cr on the environment drawn from researches carried out over the years following an analytical approach. Uniquely, this work presents a review of the effects and remediation of Cr from soil and wastewater drawn from several evidence and meta-data-based articles and other publications. Accordingly, the write-up is intended to appeal to the consciousness of the general public that the significance of Cr notwithstanding , its environmental toxicity should not be taken for granted.
... For that natural zeolite must be modified to capable for adsorption anion. There are many researchers to improve capacity and selective adsorption of natural zeolite to remove Cr(VI) such as modification natural zeolite with surfactant [9], magnetic oxide ion [30], polyhexamethylene-guanidine-modified natural zeolitic [10]. Modification natural zeolite with polymer compound as a particular class of organo-modified natural zeolites, which are mechanically and chemically stable in various aqueous environments [11]. ...
A Cr(VI)-imprinted-poly(4-VP-co-EGDMA) (IIP) was proposed to be used in the process of selective extraction of low concentration of Cr(VI) ion from aqueous solution. The polymer was synthesized by using Cr(VI) ion as a template, 4-vinylphiridine (4-VP) as complexion agent and monomer, ethylene glycol dimethyl acrylate (EGDMA) as cross-linker, benzoyl peroxide (BPO) as initiator and ethanol/acetone as a porogen. Non ion-imprinted-poly(4-VP-co-EGDMA) (NIP) as a control polymer was prepared too. The synthesis was conducted by using precipitation polymerization method. The prepared of IIP unleached, IIP leached and NIP were characterized by XRD, FTIR, SEM-EDX and BET-BJH instrument. Based on the characterization data, it can be found that all of this imprinting material have a micro and mesopore structures. The effect of sorbent dosage, pH, contact time and temperature on Cr(VI) adsorption from aqueous solution were investigated. The result shows that the adsorption of Cr(VI) ion was highest at pH 2 with 30 min contact time at 313 K with an initial concentration of Cr(VI) 14 mg/L. The selective studies shows that the IIP material was a very selective to adsorp Cr(VI) even in water was found interfering ion such as Ni(II) and Cr(III) respectively. Kinetic and isotherm modeling were also studied by using 5 models in each. The result of modeling kinetic shows that Cr(VI) adsorption fit with the Pseudo-second-order model while modeling isotherm followed the Freundlich model. The application of this material to adsorb Cr(VI) from electroplating industrial waste which reaches 96% and the reusability testing also shows that this adsorbent has good stability even though it was used 10 times repeatedly.
... It is well known that bottom sediments can be used as valuable indicators of the impact of human activity on the water bodies' quality, being they capable of accumulating both organic and inorganic pollutants over time. Several studies have considered the role of sediments in determining the fate of metals and organic compounds in seawater (Chapman, 1996;Tomadin, 2000;Spagnoli et al., 2010;Mugnai et al., 2010;Lofù et al., 2016;Chapman et al., 2013;Mali et al., 2016). Moreover, the impact of hydrodynamic processes on the spatial distribution of pollutants in coastal areas has been addressed (Malcangio et al., 2017;Valentini et al., 2017;Mali et al., 2017aMali et al., , 2017bMali et al., , 2018. ...
Data generated by long-term monitoring programs for coastal areas are intricate and require advanced tools able to identify the factors, natural or anthropogenic, responsible for the observed quality status. In the present study, data stemming from a 5-year monitoring programme of the Apulian coast were utilized for validating a speedy and comprehensive approach to assess the environmental quality of the marine-coastal area. Selecting 12 indicator contaminants controlling the pollution degree of the bottom sediments and attributing to each of them a weighted relevance according to their hazard potential, two multimetric indexes were calculated, helping to establish how and to what extent the selected contaminants could affect the achievement of good chemical and ecological status of coastal area. The relationships between calculated hazard degree values and the main natural factors loading on the study area were addressed through multivariate analyses. The variability of hazard degree values over time was explained by means of combined use of multivariate analyses and multimetric indexes, affording a handy method that allows to differentiate the role of natural factors, such as hydrodynamic and morphological features of the coastal track versus that of anthropogenic pressures. The combined approach adopted supports a reliable hazard assessment at long-term period and at a large spatial scale.
