Treatment Of Chromium-containing Wastewater Research Articles

Study on the adsorption performance of fly ash loaded on nano-FeS for chromium-containing wastewater treatment

In view of the problems caused by chromium-containing wastewater, such as environmental pollution, biological toxicity, and human health risks. Based on fly ash adsorption and nano-FeS reduction characteristics, fly ash loaded nano-FeS composite (nFeS-FA) was synthesized using mineral supported modification technology and ultrasonic precipitation method. The effect of adsorbent dosage, initial pH, contact time, and initial concentration of the solution on the adsorption of Cr(VI) and total Cr by nFeS-FA was investigated. The characteristics of Cr(VI) and total Cr adsorption by nFeS-FA were studied using adsorption isotherms, adsorption kinetics principles, as well as XRD, TEM, SEM-EDS, and BET analysis. The results demonstrated that under the conditions of nFeS-FA of 8 g/L, initial pH of 4, contact time of 150 min, and initial concentration of the solution at 100 mg/L, nFeS-FA achieved removal efficiency of 87.85 % for Cr(VI) and 71.77 % for total Cr. The adsorption of Cr(VI) and total Cr by nFeS-FA followed the Langmuir model and pseudo-second-order kinetic model, indicating monolayer adsorption with chemical adsorption as the dominant mechanism. XRD, TEM, SEM-EDS, and BET revealed that the flaky nano-FeS was uniformly distributed on the surface of fly ash, exhibiting good dispersion and thereby increasing the specific surface area. During the adsorption experiments, nFeS-FA reacted with Cr(VI), and the generated Fe3+ mainly existed as FeOOH precipitation, while S2− reacted with Cr(III) to produce Cr2S3 precipitation. Therefore, nFeS-FA exhibited excellent adsorption performance towards Cr(VI) and total Cr. It can serve as a technological reference for the remediation of heavy metal chromium pollution in the field of water treatment.

The hyper-crosslinked aniline polymer@MOFs hybrid materials reinforced with active ionic sites for efficient and fast Cr(VI) removal

The adsorption of toxic metal ions by composite materials of metal–organic frameworks (MOFs) has attracted significant attention in recent years. In this work, a series of hybrid materials HPAN@M−x consisting of protonated hyper-crosslinked aniline polymer (HPAN) and MOFs were synthesized via the Friedel-Crafts reaction between aniline and dimethoxymethane in the presence of MIL-101(Cr), followed by protonation with hydrogen bromide. These hybrid materials exhibited enhanced adsorption rate and capacity for Cr(VI) ions compared to both individual MIL-101(Cr) and HPAN. The effects of the ratio of aniline to MIL-101(Cr), solution pH, adsorption temperature, impurity ions on the removal of Cr(VI) ions were systematically investigated. Notably, HPAN@M−b not only achieved an adsorption capacity up to 290.9 mg·g−1 in 7 min but also exhibited excellent cycling stability by maintaining a high Cr(VI) removal efficiency of 95.6 % after five cycles. The enhanced adsorption performance is attributed to the synergistic effect between MIL-101(Cr) and HPAN. Mechanism studies indicated that the removal for Cr(VI) ions involved a combination of ion exchange and electrostatic adsorption processes. Additionally, the desorbed Cr(VI) ions were transformed into added-value barium chromate (BaCrO4) precipitates, allowing for resource utilization of Cr(VI) ions. This study represents a significant advancement towards developing MOFs-based hybrid materials for practical treatment of chromium-containing wastewater.

Integrated treatment of chromium-containing wastewater with application of the improved ferritization method

Integrated treatment of chromium-containing wastewater with application of the improved ferritization method

Reparation of nano-FeS by ultrasonic precipitation for treatment of acidic chromium-containing wastewater

Nano-FeS is prone to agglomeration in the treatment of chromium-containing wastewater, and ultrasonic precipitation was used to synthesize nano-FeS to increase its dispersion. The optimization of the preparation method was carried out by single factor method (reaction temperature, Fe/S molar ratio and FeSO4 dropping flow rate) and response surface methodology. Dynamic experiments were constructed to investigate the long-term remediation effect and water column changes of nano-FeS and its solid particles. The changes of the remediation materials before and after the reaction were observed by SEM, and the mechanism of the remediation of chromium-containing wastewater by nano-FeS prepared by ultrasonication was revealed by XRD. The results showed that the reaction temperature of 12 °C, Fe/S molar ratio of 3.5 and FeSO4 dropping flow rate of 0.5 mL/s were the best parameters for the preparation of nano-FeS. The nano-FeS has efficient dispersion and well-defined mesoporous structure in the form of needles and whiskers of 40–80 nm. The dynamic experiments showed that the average removal of Cr(VI) and total chromium by nano-FeS and its immobilized particles were 94.97% and 63.51%, 94.93% and 45.76%, respectively. Fe2+ and S2− ionized by the FeS nanoparticles rapidly reduced Cr(VI) to Cr(III). Part of S2− may reduce Fe3+ to Fe2+, forming a small iron cycle that gradually decreases with the ion concentration. Cr(III) and Fe2+ form Cr(OH)3 and FeOOH, respectively, with the change of aqueous environment. Another part of S2− reacts with Cr(III) to form Cr2S3 precipitate or is oxidized to singlet sulfur. The FeS nanoparticles change from short rod-shaped to spherical shape. Compared with the conventional chemical precipitation method, the method used in this study is simple, low cost, small particle size and high removal rate per unit.

Nitric Acid-Treated Blue Coke-Based Activated Carbon's Structural Characteristics and Its Application in Hexavalent Chromium-Containing Wastewater Treatment.

This study primarily focused on the efficient transformation of low-priced blue coke powder into a high-capacity adsorbent and aimed to address the pollution issue of hexavalent chromium (Cr (VI))-laden wastewater and to facilitate the effective utilization of blue coke powder. A two-step method was utilized to fabricate a blue coke-based nitric acid-modified material (LCN), and the impact of nitric acid modification on the material's structure and its efficacy in treating Cr (VI)-contaminated wastewater was evaluated. Our experimental results illustrated that, under identical conditions, LCN exhibited superior performance for Cr (VI) treatment compared to the method employing only potassium hydroxide (LCK). The specific surface area and pore volume of LCN were 1.39 and 1.36 times greater than those of LCK, respectively. Further chemical composition analysis revealed that the functional group structure on the LCN surface was more conducive to Cr (VI) adsorption. The highest amount of Cr (VI) that LCN could bind was measured at 181.962 mg/g at 318 K. This was mostly due to chemisorption, which is dominated by redox reactions. The Cr (VI) removal process by LCN was identified to be a spontaneous, exothermic, and entropy-increasing process. Several tests on recycling and reuse showed that LCN is a stable and effective chromium-containing wastewater adsorbent, showing that it could be used in many situations.

Biochar derived from coffee grounds with molybdenum disulfide composites for Cr (VI) removal from wastewater

Discharging pollutants containing toxic metal ions has become a global problem, and improper disposal of coffee grounds can also cause environmental pollution. In this work, 1T-MoS2@STC (Solvothermal Carbonization, STC) was prepared from coffee grounds and molybdenum disulfide by a one-step solvothermal method that is simple in operation, low in energy consumption and low in cost, which possesses efficient adsorption of Cr (VI) in wastewater. The 1T-MoS2@STC was characterized by SEM, TEM, XRD, XPS, Zeta potential, FTIR, and BET analyses. The results showed that MoS2 was successfully loaded on coffee grounds. According to the pseudo-second order (R2 = 0.99) kinetics model, chemisorption was the main cause of adsorption. The adsorption process followed the Langmuir (R2 = 0.99) isothermal model, and the maximum adsorption capacity was 795.17 mg/g. The adsorption mechanism can be attributed to electrostatic interaction, redox reaction between Cr (VI) and active sites, and chelation between Cr (III) and hydroxyl. When 1T-MoS2@STC was applied to the treatment of actual water samples, the removal rate was also maintained at a high level (90%). In addition, 1T-MoS2@STC can maintain long-term stability (90 days) and low leaching of molybdenum (<3 mg/L) in wastewater. Therefore, in the treatment of chromium-containing wastewater, the 1T-MoS2@STC composite material simultaneously exhibited significant adsorption capacity, high interference resistance, stability and low leaching rate. This study provides a new efficient and stable Cr (VI) adsorbent and promotes the practical application of MoS2 biomass derivatives composites in water purification.

Construction of Core-shell Sb2 s3 @Cds Nanorod with Enhanced Heterointerface Interaction for Chromium-Containing Wastewater Treatment.

How to collaboratively reduce Cr(VI) and break Cr(III) complexes is a technical challenge to solve chromium-containing wastewater (CCW) pollution. Solar photovoltaic (SPV) technology based on semiconductor materials is a potential strategy to solve this issue. Sb2 S3 is a typical semiconductor material with total visible-light harvesting capacity, but its large-sized structure highly aggravates disordered photoexciton migration, accelerating the recombination kinetics and resulting low-efficient photon utilization. Herein, the uniform mesoporous CdS shell is in situ formed on the surface of Sb2 S3 nanorods (NRs) to construct the core-shell Sb2 S3 @CdS heterojunction with high BET surface area and excellent near-infrared light harvesting capacity via a surface cationic displacement strategy, and density functional theory thermodynamically explains the breaking of SbS bonds and formation of CdS bonds according to the bond energy calculation. The SbSCd bonding interaction and van der Waals force significantly enhance the stability and synergy of Sb2 S3 /CdS heterointerface throughout the entire surface of Sb2 S3 NRs, promoting the Sb2 S3 -to-CdS electron transfer due to the formation of built-in electric field. Therefore, the optimized Sb2 S3 @CdS catalyst achieves highly enhanced simulated sunlight-driven Cr(VI) reduction (0.154 min-1 ) and decomplexation of complexed Cr(III) in weakly acidic condition, resulting effective CCW treatment under co-action of photoexcited electrons and active radicals. This study provides a high-performance heterostructured catalyst for effective CCW treatment by SPV technology.

Simultaneous treatment of chromium-containing wastewater and electricity generation using a plant cathode-sediment microbial fuel cell: investigation of associated mechanism and influencing factors.

A novel plant cathode-sediment microbial fuel cell (P-SMFC) was constructed to treat Cr-containing wastewater, and the effects of the plants used, initial concentrations of Cr(VI) employed, and the external resistance on the treatment of wastewater and generation of electricity were investigated. The results showed that the system achieved the best performance when Acorus calamus was the cathode plant, the external resistance was 2000 Ω, and the initial Cr (VI) concentration of the overlying water of is 230mg/L. A maximum power density of 40.16 mW/m2 was reached, and Cr (VI) and COD removal efficiencies in the overlying water were 99.94% and 98.21%, respectively. The closed-circuit installation promoted the attachment of many microorganisms to the cathode, anode and sediment, increased species abundance, and reduced species diversity. The P-SMFC is inexpensive to construct, it consumes no energy, and it can generate bioelectricity; it thus has great application development value as a chromium-containing wastewater treatment method.

Effective removal of hexavalent chromium from aqueous system by biochar-supported titanium dioxide (TiO

Environmental context Photocatalytic TiO2 materials are good prospects in water quality treatment due to their stable chemical properties and limited secondary pollution. TiO2 photocatalytic material prepared with biochar as a carrier can greatly improve the photocatalytic efficiency of CrVI, and the removal rate of CrVI can reach 84.4%. This study shows that biochar-supported TiO2 photocatalytic composites are feasible for the green and efficient removal of CrVI from an aqueous phase. Rationale TiO2 has great application prospects in the treatment of chromium-containing wastewater due to its photochemical stability and low toxicity. Loading TiO2 on solid adsorption materials can improve the photocatalytic efficiency and solve the problem of difficult separation and recovery of TiO2. Methodology In this study, biochar-supported TiO2 (BC-TiO2) and acid-washed biochar-supported TiO2 (HBC-TiO2) were prepared by a sol–gel method using biochar (BC) and acid-washed biochar (HBC) as adsorption carriers. The effects of various experimental parameters such as ultraviolet irradiation conditions, catalyst dose and pH on the removal efficiency of CrVI by BC, HBC, BC-TiO2 and HBC-TiO2 were investigated. The structure and morphology of the four materials were characterised. Results The results indicated that under the optimal reaction conditions (pH = 6, dosage of biochar materials/photocatalytic composites = 5 g/6 g), the removal percentage of CrVI changed as BC-TiO2 (Light) (84.43%) &gt; HBC-TiO2 (Light) (80.19%) &gt; BC-TiO2 (Dark) (57.9%) &gt; HBC-TiO2 (Dark) (52.94%) &gt; HBC (30.06%) &gt; BC (14.66%). Loading TiO2 on biochar materials improved the specific surface area and increased the reaction sites when compared with BC and HBC. Discussion This study shows that BC-TiO2 is more suitable to remove CrVI from an aqueous system because of its high removal efficiency. The enrichment of CrVI on the biochars and the close contact between the biochar and TiO2 through the Ti–O–C dense heterojunction promote the interfacial transfer of CrVI, which is the key to the removal of CrVI. This study has great significance for the treatment of chromium-containing wastewater by photocatalytic composites.

Chromium-containing wastewater reclamation via forward osmosis with sewage sludge ash temperature-sensitive hydrogel as draw agent

A temperature-sensitive hydrogel modified with sewage sludge ash (SSA) was used as an advanced draw agent for forward osmosis (FO) application in treating chromium-containing wastewater. The performance of the modified hydrogel (SSA-TSH) was measured in terms of the swelling and deswelling properties, as well as adsorption and desorption effects on Cr(VI), chemical oxygen demand (COD), total phosphorous (TP) and ammonium (NH4+-N) in chromium-containing wastewater. Furthermore, the efficiencies of wastewater treatment, water flux, and the reusability of the SSA-TSH as draw agent in the FO process (FO-SSA-TSH) using a commercially available thin-film composite membrane (Sterlitech) were also investigated. The results indicated that FO-SSA-TSH achieved high removal rates of pollutants (Cr(VI): 96.9 %–97.4 %, COD: 97.1 %–97.4 %, TP: 97.7 %–99.6 %, and NH4+-N: 76.8 %–77.9 %) in various Cr(VI) concentrations (0– 40 mg/L) due to the high rejection rate of FO membrane and notable adsorption capacity of the hydrogel. Moreover, the average water flux of FO-SSA-TSH (1.95– 2.02 LMH) was nearly twice as much as that of the FO with pure temperature-sensitive hydrogel as draw agent (FO-TSH, 1.33– 1.42 LMH) in 24 h chromium-containing wastewater treatment. In addition, SSA-TSH with excellent deswelling property exhibited high water recovery performance and good reusability in low cost and energy consumption after the FO permeation process for wastewater treatment.

Sodium alginate encapsulated nano zero valent iron loaded in aminated magnesium hydroxide for effective removal of chromium

Chromium-containing wastewater is one of the major pollutants affecting water safety. The adsorption-reduction property of nano zero-valent iron particles (nZVI) is an effective way to counter chromium pollution. However, nZVI is affected by surface passivation as well as agglomeration in the process of use. To overcome this limitation and to strengthen its performance in the treatment of chromium-containing wastewater, we proposed a new approach by sodium alginate (SA) encapsulated nZVI loaded in the pores of aminated spherical magnesium hydroxide (MH-NH2). The prepared ternary composite (nZVI@SA/MH-NH2) exhibited better stability, dispersibility, larger specific surface area, and more active sites. We found that nZVI@SA/MH-NH2–1 could remove 97.92% of Cr(VI) from the solution within 5 min at pH = 3 without oxygen. Adsorption capacity of nZVI@SA/MH-NH2–1 could reach 134.00 mg/g. Moreover, the acidic environment could achieve the slow release of OH− at the expense of MH-NH2 carriers to increase the pH of the solution, enabling the generated Cr(III) to form Cr(OH)3 and precipitate out of the solution. nZVI@SA/MH-NH2 could achieve the removal of total chromium from the solution in one step. This strategy contributed to the cheap and efficient separation of Cr(VI) together with Cr(III) from the wastewater.

Synchronous reduction and removal of hexavalent chromium from wastewater by modified magnetic chitosan beads

As one of the highly toxic heavy metal contaminants, hexavalent chromium (Cr(VI)) poses a serious hazard to the environment and public health due to its excellent solubility in aqueous environment. To synchronously reduce and remove Cr(VI) from wastewater efficiently, a class of functionalized magnetic chitosan (CS) beads (MCB-ECH-SH/SO3H) was synthesized with CS as the substrate material and in situ assembling Fe3O4 nanoparticles as the incorporated magnetic material, followed by epichlorohydrin (ECH) cross-linking and l-cysteine grafting. Results showed that Cr(VI) in aqueous solution could be rapidly adsorbed onto MCB-ECH-SH/SO3H via electrostatic attraction, meanwhile -SH groups introduced by l-cysteine grafting could not only significantly facilitate the reduction of Cr(VI) to less toxic trivalent chromium (Cr(III)), but also promote the resultant Cr(III) chelating onto adsorbent due to the proton consumption caused by Cr(VI) reduction, resulting in the synergistic enhancement of Cr(VI) detoxification and total chromium (Cr(Total)) removal. The batch adsorption experiments revealed that the well designed MCB-ECH-SH/SO3H could be applied over a wide pH range (initial pH of 1.0–7.0), and showed much higher remove efficiency (99.6 ± 0.2 %) of Cr(VI) than MCB and MCB-ECH at initial pH 5.0 (60 °C) due to the improvement of stability and reducing capacity. The Cr(Total) sorption behaviors were well according with the pseudo-second-order kinetic and Langmuir models, indicating a single-layer, exothermal, and chemical sorption process, while the maximum Cr(Total) removal capacity of MCB-ECH-SH/SO3H was estimated to be 293.46 mg∙g−1, exceeding most of previously reported related adsorbents. Moreover, MCB-ECH-SH/SO3H could still maintained strong adsorption performance after five cycles and exhibited excellent ability to remove 95 % Cr(VI) within 1 h for low concentration Cr(VI)-containing wastewater. The combination of synchronous reduction and adsorption property, high removal capacity, convenient magnetic separation and good recycling performance makes MCB-ECH-SH/SO3H an ideal candidate for chromium-containing wastewater treatment.

Fe doped g-C3N4 composited ZnIn2S4 promoting Cr(VI) photoreduction

30% FeCN/ZIS (30% Fe doped g-C3N4 composited ZnIn2S4) was synthesized by a simple water bath method, via in-situ growth of abundant well-dispersed ZnIn2S4 nanosheets on the Fe doped g-C3N4 surface. Experimental results showed the optimized 30% FeCN/ZIS achieved the best photoreduction of Cr(VI) performance within a wide pH range, which was 9.5 times and 700 times higher than that of pure ZnIn2S4 and 30% FeCN (Fe doped g-C3N4). This is due to the intense synergy between the Fe-Nx bond and close interface contact produces a high-speed charge transfer channel, thus significantly improving the efficiency of optical carrier separation and migration. Meanwhile, UV-vis diffuse reflection spectra and photoluminescence spectroscopy showed that iron doping significantly narrowed the bandgap of g-C3N4, preventing electron-hole pair recombination. Further, the microstructures and charge separation properties were analyzed by scanning electron microscope, Photoluminescence Spectroscopy and time-resolved photoluminescence, which revealed the structure-activity relationship of composite structure and the synergistic mechanism of each functional component. This research should provide a viable technique for creating composites with high photocatalytic activity for the treatment of chromium-containing wastewater.

Efficient Removal of Cr(VI) by TiO2 Based Micro-Nano Reactor via the Synergy of Adsorption and Photocatalysis.

The low-toxicity treatment of chromium-containing wastewater represents an important way of addressing key environmental problems. In this study, a core-shell structural ZIF-8@TiO2 photocatalyst was synthesized by a simple one-step hydrothermal method. The obtained composite photocatalyst possessed improved photocatalytic activity compared with TiO2. The results indicated that the optimized ZIF-8@TiO2 composite exhibited the highest removal efficiency with 93.1% of Cr(VI) after 120 min under UV-vis irradiation. The removal curves and XPS results indicated that the adsorbed Cr(VI) on the ZIF-8 during the dark process was preferentially reduced. The superior removal efficiency of ZIF-8@TiO2 is attributed to the combination of both high adsorption of ZIF-8, which attracted Cr(VI) on the composite surface, and the high separation efficiency of photo-induced electron-hole pairs. For the mixture of wastewater that contained methyl orange and Cr(VI), 97.1% of MO and 99.7% of Cr(VI) were removed after 5 min and 60 min light irradiation, respectively. The high removal efficiency of multiple pollutants provides promising applications in the field of Cr(VI) contaminated industrial wastewater treatment.

微波改性凹凸棒处理含铬废水的研究

微波改性凹凸棒处理含铬废水的研究

Recycling and modeling of chromium from sludge produced from magnetic flocculation treatment of chromium-containing wastewater

In this paper, an effective and sustainable treatment method for recycling chromium from sludge produced by magnetic flocculation was established. Chromium was extracted from sludge with hydrogen peroxide and sodium hypochlorite, and then, superparamagnetic ferroferric oxide nanoparticles (MPs) were recovered by magnetic separation. The recovery percentage of chromium with sodium hypochlorite was higher than that with hydrogen peroxide, and the maximum was 99.12%. With increasing MPs use times, the adsorption percentage of chromium decreased, but there was no significant change in the recovery percentage of chromium in sludge. The purity of the recovered sodium chromate crystals was 96.28%. The back-propagation algorithm was used to model chromium recovery. The correlation coefficient between the model prediction data and experimental data was 0.9990, and the average absolute error was 0.51. The maximum recovery percentage of chromium obtained from model prediction was 99.27%, and the corresponding optimal conditions were consistent with those of experiments.

Design of BiOBr0.25I0.75 for synergy photoreduction Cr(VI) and capture Cr(III) over wide pH range

Conversion of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) is an effective way to reduce its environmental risk, especially via photoreduction process. However, over a wide range of pH values, it is still a great challenge to achieve a high removal rate, and the disposal of produced Cr(III) should be concerned. In this work, we implemented a high removal rate at 98% for Cr(VI) and total chromium (Cr(T)) over a wide pH range (4–10) through the synergistic effect of adsorption, photoreduction and immobilization on the surface of BiOBr0.25I0.75. The substitution of bromine by iodine reduced the adsorption energy of Cr(VI) on BiOBr0.25I0.75, promoting the adsorption of Cr(VI). Meanwhile, the introduced iodine upshifted the conduction band (CB), enhancing the reduction ability for Cr(VI) to Cr(III). The negative surface of BiOBr0.25I0.75 can capture Cr(III), achieving a high removal rate for Cr(T). The pH-independent feature for Cr(VI) and Cr(III) removal make BiOBr0.25I0.75 a potential material for chromium-containing wastewater treatment. This work provides an effective strategy for removing chromium over a wide pH range.

Efficient treatment of wastewater from galvanic plants

The article discusses a promising method for the purification of chromium-containing wastewater from galvanic plants. A review and comparative analysis of existing methods and technologies for treatment of industrial waste from various organochromium compounds, such as reagent-based, biological, ion-exchange and others, are presented. The advantages of using the combined method of chromium-containing wastewater treatment based on electroflotation with preliminary electrocoagulation are shown. The effectiveness of the proposed combined method is evaluated and the design of electroflotocoagulator is developed.

Gold-silver nanoparticles modified electrochemical sensor array for simultaneous determination of chromium(III) and chromium(VI) in wastewater samples

The oxidation state of ions is a crucial aspect that often has been overlooked when determining the toxicity of chromium (Cr) species in environmental samples. In this study, a novel electrochemical sensor array based on gold-silver nanoparticles modified electrodes was developed for simultaneous determination of the two main chromium species (Cr(III) and (VI)). Specifically, the working electrodes of screen-printed carbon electrodes (SPCEs) were modified with silver-gold bimetallic nanoparticles through electrochemical deposition for detection of Cr(VI). The silver-gold bimetallic nanoparticles were further oxidized to form stable silver-gold bimetallic oxide nanoparticles for the detection of Cr(III). The results showed that the addition of silver with a theoretical value of 1% of gold could contribute to the formation and stabilization of oxides on the surface of gold nanoparticles. After characterization, the two kinds of electrodes were integrated as an electrochemical sensor array for selective and sensitive detection of Cr(VI) and Cr(III). The linear range and limit of detection (LOD, identified by three times of signal-to-noise ratio) were found to be 0.05–5 ppm and 0.1 ppb for Cr(VI), and 0.05–1 ppm and 0.1 ppb for Cr(III), respectively. Finally, the electrochemical sensor array was proven for successful detection of Cr(VI) and Cr(III) in tap water, artificial saliva and artificial sweat samples, and monitoring of Cr(VI) and Cr(III) in chromium-containing wastewater treatment process. Combined with a handheld dual-channel electrochemical device, the simultaneous determination of Cr(VI), Cr(III) and total chromium contents can be easily achieved for various samples.

A novel approach to Chromium rejection from sewage wastewater by pervaporation

Pervaporation is an effective method, especially in the separation of azeotropic mixtures or in the recovery of some components from the mixtures. Although various methods have been used for the treatment of chromium-containing wastewater that has become a matter of concern for the health of aquatic ecosystems, the pervaporation has never been used before in the literature. In this study, Cr/water (Cr (III), Cr (VI)) mixtures were separated by a pervaporation using polyvinyl alcohol (PVA) and sodium Y (NaY) zeolite membranes. Study results indicated that increasing the zeolite percentage, the membrane thickness, the amount of Cr in the feed solution and, the pH all increased rejection and decreased flux. In contrast, an increase in temperature caused rejection to decrease and flux to increase. The best rejection obtained for Cr (VI) was 144.4%. For Cr (VI) removal from sewage wastewater, the maximum rejection under optimum conditions was 160% and the flux was 0.12 kg/m2h. Also, Cr (VI) was not detected in any permeates. The permeate concentration was calculated to be 97.1% in experiments with a Cr (III)/water mixture. PVA/NaY membrane showed selective permeability for Cr (VI), while it does not show selective permeability for the useful Cr (III) component.