Removal Of Trivalent Chromium Research Articles

Trivalent chromium ion removal from synthetic wastewater using graphene oxide nanocollector by various flotation mechanisms

ABSTRACT The scarcity of freshwater resources for industrial applications poses a significant global concern. Therefore, wastewater treatment is vital for industrial reuse and decreases environmental damage. Chromium, commonly encountered in industrial wastewater, is regarded as a highly toxic metal and a significant environmental pollutant. In this study, the ion removal of trivalent chromium was investigated by graphene oxide (GO) and sodium dodecyl sulfate (SDS) as collectors using various flotation methods including foam fractionation, ion flotation, and precipitation flotation. The effective parameters of the collector type and pH were studied to assess the chromium ion removal, water recovery during the process, and flotation mechanisms. Experimental results indicated that the highest ion removals, achieved with SDS and GO collectors, were 88.86% and 86.07%, respectively, at a pH of 6.3 using the ion flotation method. Notably, GO reduced water recovery by approximately 15% compared to optimal conditions using SDS. The results indicated the remarkably high efficacy of GO as a nanocollector in the ion flotation process for efficiently removing chromium ions with significantly lower collector consumption.

A promising approach for the removal of hexavalent and trivalent chromium from aqueous solution using low-cost biomaterial.

Heavy metal pollution is an enduring environmental challenge that calls for sustainable and eco-friendly solutions. One promising approach is to harness discarded plant biomass as a highly efficient environmental friendly adsorbents. In this context, a noteworthy study has spotlighted the employment of Euryale ferox Salisbury seed coat (E.feroxSC) for the exclusion of trivalent and hexavalent chromium ions. This study aims to transform discarded plant residue into a novel, environmentally friendly, and cost-effective alternative adsorbent, offering a compelling alternative to more expensive adsorption methods. By repurposing natural materials, we can contribute to mitigating heavy-metal pollution while promoting sustainable and economically viable solutions in environmental remediation. The effect of different parameters, i.e., chromium ions' initial concentration (5-25mg L-1), solution pH (2-7), adsorbent dosage (0.2-2.4g L-1), contact time (20-240min), and temperature (298-313K), were investigated. E.feroxSC proved highly effective, achieving 96.5% removal of Cr(III) ions at pH 6 and 97.7% removal of Cr(VI) ions at pH 2, with a maximum biosorption capacity of 18.33mg/g for Cr(III) and 13.64mg/g for Cr(VI), making it a promising, eco-friendly adsorbent for tackling heavy-metal pollution. The adsorption process followed the pseudo-second-order kinetic model, aligning well with the Langmuir isotherm, exhibited favorable thermodynamics, and was characterized as feasible, spontaneous, and endothermic with physisorption mechanisms. The investigation revealed that E.feroxSC effectively adsorbed Cr(VI) which could be rejuvenated in a basic solution with minimal depletion in its adsorption capacity. Conversely, E.feroxSC's adsorption of Cr(III) demanded rejuvenation in an acidic milieu, exhibiting comparatively less efficient restoration.

Removal of trivalent and hexavalent chromium from aqueous solution using fiber of Agave americana plant and its modified forms

Chromium contamination due to industrial effluents has been recognized as one of the major problems since chromium compounds affect human health leading to adverse health effects of humans. Among many adsorbents that have been experimented with, cellulose fibers have been identified to be very effective for chromium removal. Agave americana, a plant native to Central America, is rich in cellulose fibers, which consist of esters, ethers of alcohol derivatives of cellulose showing coordinating ability toward heavy metal ions. This study is aimed at optimization of solution parameters, such as shaking time, settling time, solution pH and adsorbent dosage, while varying one parameter at a time throughout a broad range keeping others constant, for most efficient adsorption of Cr(III) species, followed by investigation of equilibrium and kinetics aspects under optimized conditions. Adsorption of Cr(III) from solutions of different concentrations on untreated AAF fulfills the requirements of the Langmuir adsorption isotherm at equilibrium which is probably due to the fine fibrous nature of the biosorbent. Moreover, the extent of Cr(III) on Agave americana fiber (AAF), investigated during the early stages of adsorption, leads to the validity of the pseudo first-order kinetics with a relatively high regression coefficient. Although untreated AAF shows a strong affinity toward Cr(III), its adsorption ability toward Cr(VI) is undetectable, suggesting that surface modification of AAF be performed. In this context, EDTA-treated AAF demonstrates a significant improvement on Cr(VI) removal, indicating the possibility of extending the present investigation for removal of chromium species under industrial setting.

A mechanistic evaluation for total removal of toxic hexavalent and trivalent chromium from water by oxygen vacancy-engineered nanocomposite

Oxygen vacancy-engineered nanocomposites are emerging materials in adsorption and photocatalysis research. This study evaluated total toxic Chromium removal by a nanocomposite of core-shell zeolite A@oxygen-vacant ZnO1−X (ZA@ZnO1−X) from water using its coexisting dual characteristics. ZA@ZnO1−X has removed 98.3% of total Cr, achieving a discharge limit of 0.05 ppm of Cr(VI) after the photoreduction and adsorption simultaneously. The detailed structural and physicochemical properties of synthesized ZA@ZnO1−X nanocomposite show higher BET surface area, oxygen-vacant percentage, and visible light photoactivity than the sole ZnO1−X nanosheet. The photocatalytic reduction efficiency (PRE) effect is systematically studied on varying operational variables like pH, citric acid (CA), Cr(VI) concentration, catalyst load, presence of anions, and radical scavengers. ZA@ZnO1−X removed Cr(VI) and Cr(III) simultaneously by 98.5% PRE with a catalyst load of 4 g/l, CA= 5 mM, pH= 5.06 under halogen light irradiation (300 W, 240 V) for 50 mins. This experimental study evaluates the prominent role of oxygen vacancy of ZA@ZnO1−X for photocatalytic reduction of Cr(VI) and enhanced adsorption of Cr(III). The kinetic study reveals adsorption of both Cr(VI) and Cr(III) follows pseudo-second-order kinetics, whereas photoreduction of Cr(VI) follows pseudo-first-order kinetics. A possible mechanism of total Cr removal is sketched, supporting enhanced adsorption due to unsaturated Zn atoms and unpaired e- at the oxygen defect site, followed by photoreduction by photogenerated e- and CO2-• radical. The ZA@ZnO1−X performance is reduced by only 2.5% after five consecutive runs without deformation. The easy regeneration process makes it suitable for toxic total Cr removal, avoiding any secondary pollution.

Removal of trivalent chromium from aqueous solutions by natural clays: Valorization of saturated adsorbents as raw materials in ceramic manufacturing

Kaolinite/illite (KUb) and sepiolite (SEP) clays were used to study Cr(III) adsorption removal from aqueous solutions so that they could be utilized after saturation for ceramic manufacturing. SEP had a larger specific surface area and a higher PZC than KUb. The removal of Cr(III) was evaluated using a batch equilibration procedure at pHi = 4 and pHi = 6. Fast removal kinetics were observed for both clays. Maximum removal capacity was determined by changing the concentration of Cr(III) while keeping the concentration of clay constant and by altering the amount of clay while keeping the concentration of Cr(III) constant. In all situations, SEP had greater capacity than KUb, and capacity was greater for both clays at higher pHi. Not only did the pHi impact the removal capacity and efficiency, but so did the pH during adsorption and the initial concentration of Cr(III). Because of the higher PZC, the pHf for SEP was higher for the same pHi. The higher the pH and Cr(III) concentration, the higher the probability of Cr(OH)3 precipitation and the higher the removal capacity.Dried saturated clays were uniaxially pressed and sintered at 1000 °C for 2 h. The densities of the sintered materials were nearly identical to those of pure clay-based materials, but the compressive strengths were higher, which is significant for the use of saturated clays as raw materials in ceramic manufacturing. Leaching of Cr from SEP-based material was significantly higher than from KUb-based material probably due to the presence of CaCO3 in the SEP.

Trivalent chromium removal from tannery wastewater with low cost bare magnetic Fe3O4 nanoparticles

In this work, a new method is proposed to remove Cr (III) in tanning wastewater with low cost bare magnetic Fe3O4 nanoparticles. It has achieved ultra-high chromium capture capacity under high selectivity. The maximum capture capacity of magnetic Fe3O4 nanoparticles for Cr (III) in chromium containing tanning wastewater is 456.20 mg/g at optimal pH 8. In a pilot scale apparatus running continuously at 18 L/h for 8 h, the chromium removal efficiency could be stabilized above 98.5% with chromium concentration reduced from 1065 mg/L to about 15 mg/L at the primary treatment. After secondary treatment, the outlet chromium concentration drops to 0.2 mg/L (lower than 0.5 mg/L, the maximum allowable concentration of Cr total in tanning wastewater determined by China), and the chromium removal efficiency is steadily above 97.8%. The results revealed that the method could be used economically as an efficient technique for removal of Cr (III) in chromium containing leather tanning wastewater and has great potential in heavy metal wastewater treatment.

Rationally designed Shewanella oneidensis Biofilm Toilored Graphene-Magnetite Hybrid Nanobiocomposite as Reusable Living Functional Nanomaterial for Effective Removal of Trivalent Chromium.

Sustainable treatment of wastewater containing trivalent chromium (Cr3+) remains a significant challenge owing to the several limitations of the existing methodologies. Herein, combination of biosynthesis and Response Surface Methodology (RSM) for the fabrication and optimization of Shewanella oneidensis biofilm functionalized graphene-magnetite (GrM) nanobiocomposite was adopted as a 'living functional nanomaterial' (viz. S-GrM) for effective removal of Cr3+ ions from aqueous solution. In the biosynthetic process, S.oneidensis cells reduced the GO-akaganeite complex and adhered on the as-synthesized GrM nanocomposite to form S-GrM hybrid-nanobiocomposite. The process parameters for fabrication of S-GrM hybrid-nanobiocomposite was optimized by RSM based on four responses of easy magnetic separation, biofilm formation along with protein, and carbohydrate contents in extracellular polymeric substances (EPS). The morphology and chemical composition of S-GrM hybrid-nanobiocomposite were investigated using various spectroscopic and microscopic analyses and subsequently explored for removal of Cr3+ ions. The hybrid-nanobiocomposite effectively removed 304.64±14.02mg/g of Cr3+ at pH 7.0 and 30°C, which is found to be very high compared to the previously reported values. The high surface area of graphene, biofilm biomass of S.oneidensis and plenty of functional groups provided a unique structure to the S-GrM hybrid-nanobiocomposite for efficient removal of Cr3+ through synergistic interaction. The FTIR and zeta potential studies confirmed that electrostatic and chelation/complexation reaction played key roles in the adsorption process. The fabrication of S-GrM nanobiocomposite thus creates a novel hybrid 'living functional nanomaterial' for low cost, recyclable, and sustainable removal of Cr3+ from wastewater.

Enhanced removal of trivalent chromium from leather wastewater using engineered bacteria immobilized on magnetic pellets

Leather wastewater contains various toxic contaminants, with trivalent chromium (Cr(III)) having high concentration and adversely affecting wastewater treatment. In this study, a Cr(III) adsorption protein (MerP) was displayed on the cell surface of Escherichia coli and then coupled with a magnetic pellet system to facilitate Cr(III) adsorption. The results showed the engineered strain M-BL21 achieved an in vitro Cr(III) adsorption capacity of 2.38 mmol/g. Next, the magnetic pellets were prepared as component ratios of sodium alginate (2.5%), polyvinyl alcohol (8%), Fe3O4 nanoparticles (3.5%), and M-BL21 at 3 g/L. The optimized system was capable of Cr(III) adsorption at an efficiency of 91.29%, which was substantially higher than that of the magnetic carrier alone (67%). Results of scanning electron microscopy with energy-dispersive X-ray analysis proved that Cr(III) was absorbed on the magnetic pellet. The recyclable performance of magnetic property (13.34185 emu/g) and high Cr(III) adsorption efficiency (68.75%) remained after five cycles of Cr(III) absorption. In the medium-scale experiment, 25 L of leather wastewater were treated with magnetic pellet and the Cr(III) removal efficiency reached 88.2%. Thus, our results present an advanced, fully operational, and eco-friendly method for in situ removal of Cr(III) from contaminated wastewater.

Removal of trivalent chromium from tannery wastewater using solid wastes

The leather tanning industry is one of the important industrial activities in Egypt. However, this industry produces large amounts of wastewater containing trivalent chromium Cr (III) residues that are considered, if not treated, a significant risk to the environment. Although Cr (III) is not as toxic as Cr (VI), there is a high possibility that Cr (III) residues can be oxidized to Cr (VI). Due to this risk, chromium removal from tannery wastewater becomes a vital process. The current study demonstrates the ability of the use of different solid waste materials in the removal of trivalent chromium from tannery wastewater. Four agricultural waste materials and two industrial solid waste materials were tested. The agricultural solid waste materials include rice husk, rice straw, sugarcane bagasse and sawdust; while the industrial waste materials include cement kiln bypass dust and marble powder. The results showed that the cement kiln dust and marble powder can provide the highest removal of chromium from aqueous solution. The results also showed that cement kiln dust can remove more than 99% of the trivalent chromium when the pH of the solution is raised above 8.75.

Simultaneous Removal of Trivalent Chromium and Hexavalent Chromium from Soil Using a Modified Bipolar Membrane Electrodialysis System.

In this study, a modified bipolar membrane electrodialysis system equipped with a "back-to-back" soil compartment was fabricated for simultaneous removal of trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)) from contaminated soils. The results showed that the soil solution pH had a significant effect on the Cr(III) and Cr(VI) desorption, and the desorption data fit well with the Elovich kinetic model. Current density had an obvious effect on Cr(III) and Cr(VI) removal, cell voltage, soil pH, current efficiency, and specific energy consumption, and the optimal current density was 2.0 mA/cm2. The removal efficiencies of Cr(III) and Cr(VI) were both 99.8%, while Cr(III) and Cr(VI) recoveries were somewhat lower at 87 and 90%, respectively, because some Cr(III) and Cr(VI) were adsorbed by the membranes. An energy consumption analysis indicates that the back-to-back soil compartment equipped system increased the current efficiency and decreased the specific energy consumption. When a system equipped with two back-to-back soil compartments was used to remove chromium from soil, the current efficiency increased to 28.8% and the specific energy consumption decreased to 0.048 kWh/g. The experimental results indicate that the proposed process has the potential to be an effective technique for the treatment of soil contaminated with heavy metals.

Eggshell adsorption process coupled with electrocoagulation for improvement of chromium removal from tanning wastewater

ABSTRACTThe present work deals with the removal of trivalent chromium from chrome tanning effluent in a batch stirred electrocoagulation cell with aluminium alloy coupled with biosorption using Eggshell (ES). Effects of operating time, current density and adsorbent dose have been investigated. Compared to a simple electrocoagulation (EC), the concentration of chromium using a coupled or combined EC/ES process has been successfully reduced to environmentally acceptable levels even with a concentrated tanning effluent (3.21 g/L). The maximum uptake of chromium ions was obtained at lower current densities of 200 A/m2, at operating time of 110 min and with the eggshell dose of 12 g/L. The energy consumption during the coupled electrocoagulation/adsorption process was also reduced comparatively to the simple electrocoagulation. A pseudo-second-order chemical sorption model satisfactorily described kinetic data. The water treated by this technique respects the strengths Moroccan standards and the method was found to be highly efficient and relatively fast compared to existing conventional techniques.

The Physiological Responses of Water Hyacinth (Eichhornia crassipes (Mart). Solms) and Water Lettuce (Pistia stratiotes L.) as Trivalent Chromium Bioaccumulator

Chromium is one of the heavy metals used in industrial fields, i.e., metallurgical industry, chemical industry, heat-retardant, and leather tanning industry. Untreated wastewater from these industries can pollute rivers and threaten the aquatic ecosystem. Some aquatic plants such as water hyacinth ( Eic hhornia crassipes ) and water lettuce ( Pistia stratiotes ) have been known as metal hyperaccumulators and can be used as phytoremediator for polluted water. This study aims to determine the physiological and morphological responses of water hyacinth and water lettuce plants treated by different concentrations of trivalent chromium and to study which plant is effective for trivalent chromium removal. The experiment was conducted for 2 week at screen house. After two weeks, the plants were harvested and the weight was measured. The samples were separated into shoot and root and were analyzed for Cr content, chlorophyll, proline and CAT enzyme activity. The results of this study indicated that the levels of water hyacinth chromium in roots and leaves are lower (863.988 mg/Kg, 899.126 mg/Kg, 685.877 mg/Kg for treatment 40 ppm, 80 ppm, and 120 ppm respectively) than the levels of chromium in water lettuce (1584.264 mg/Kg, 1660 mg/Kg, 1413 mg/Kg for treatment 40 ppm, 80 ppm, and 120 ppm respectively). Physiological parameter, i.e., chlorophyll and proline levels in water hyacinth and water lettuce from all concentration treatment did not differ significantly (P> 0.05). The activity of the catalase enzyme in water hyacinth and water lettuce decreased with increasing chromium levels. The highest catalase enzyme activity was observed in control treatment of water lettuce (1.61 unit/mg) and 40 ppm treatment of water hyacinth (1.006 unit/mg). The highest biomass dry weight of both plants was found in plants with control treatment (15.38 gr and 8.48 gr for water hyacinth and water lettuce respectively). Therefore, we concluded that water lettuce is better for trivalent chromium removal than water hyacinth.

Feasibility and mechanism of microbial-phosphorus minerals-alginate immobilized particles in bioreduction of hexavalent chromium and synchronous removal of trivalent chromium

Chromium(VI) contaminated groundwater has become an increasingly prominent problem due to its extensive application in industry. Based on the easy-loss defect of microbial in practical application and previous research on the coupling enhancement of Cr(VI) bioreduction by phosphorus minerals, Microbial-Phosphorus minerals-Alginate (MPA) immobilized particles were proposed and investigated in this study. The feasibility of MPA immobilized particles were proved, with the higher reduction efficiency, lower phosphorus surplus, significant 94% of total Cr reduction and 85% of intragranular fixation. These superiorities were also obtained at different pH and initial Cr(VI) concentration conditions. Furthermore, the mechanisms of the enhancement of MPA were investigated from microbial level (microbial biomass, antioxidase, gene expression and microbial community analysis) and physics level (adsorption kinetic and isotherm), where the speculation that the reduction mainly took place outside the particles was proposed. This research provides a new approach for the practical application of Cr(VI)-contaminated groundwater in-situ bioremediation.

Nitrilotriacetic acid modified bamboo charcoal (NTA-MBC): An effective adsorbent for the removal of Cr (III) and Cr (VI) from aqueous solution

In the present study, nitrilotriacetic acid (NTA) was used as a chelating agent for surface modification of bamboo charcoal (BC). Nitrilotriacetic acid modified bamboo charcoal (NTA-MBC) was applied as an adsorbent for the removal of trivalent and hexavalent chromium from aqueous solution. Batch mode adsorption studies were performed using various parameters such as pH, contact time, adsorbent dose, initial metal ion concentration and temperature. The adsorption data were analyzed using Langmuir, Freundlich and Temkin isotherms. Maximum adsorption capacity of NTA-MBC obtained from Langmuir isotherm was found to be 1000 mg/g for Cr (III) at pH 3 with adsorbent dose of 1 g/l and 270 mg/g for Cr (VI) at pH 3 with adsorbent dose of 2 g/l. Thermodynamic studies of adsorption of both Cr (III) and Cr (VI) indicated that the nature of adsorption process was spontaneous and endothermic in nature. Enhanced adsorption capacity of NTA-MBC can be attributed to the formation of 1:1 or 1:2 complexes by NTA present on the surface of bamboo charcoal with Cr (III) and Cr (VI) in aqueous solution. The adsorption phenomenon was observed to follow pseudo second order kinetics model. The surface characteristics of NTA-MBC were examined using SEM, BET and FT-IR. The NTA-MBC was also examined for its application in purification of water through the column studies and observed to be a promising material for packing of columns in water treatment plants.

Synthetically modified nano-cellulose for the removal of chromium: a green nanotech perspective.

Existing processes for the decontamination of heavy metals from water are found to be cost-prohibitive and energy-intensive which is totally against the sustainable concept of development. Green nanotechnology for water purification for ecosystem management, agricultural and industry is an emerging as leading global priority and occupies better position over the current state of water purification. Herein, the diafunctionalised polyaniline modified nanocellulose composite sorbent (PANI-NCC) has been used to introduce amine and imine functionalities for the removal of trivalent and hexavalent chromium from water bodies. The fabricated nanobiomaterial has been authenticated by modern spectroscopic, microscopic techniques. The modified PANI-NCC is rod-like in shape, ~60 nm in size. The roughness and crystallinity index is also quantified and found to be 49.67 nm and 84.18%, respectively. The optimised experimental finding provides the efficient removal of trivalent [Cr(III)] (47.06 mg/g; 94.12%) and hexavalent [Cr(VI)] (48.92 mg/g; 97.84%) chromium from synthetic waste water. The fabricated nano biosorbent is deemed to be a potent biosorbent for technological development to remove the toxic metals in the real environmental water samples.

Removal of trivalent chromium from aqueous solution using aluminum oxide hydroxide.

Water is second most essential for human being. Contamination of water makes it unsuitable for human consumption. Chromium ion is released to water bodies from various industries having high toxicity which affects the biota life in these waters. In this study aluminum oxide hydroxide was tested for its efficiency to remove trivalent chromium from aqueous solutions through batch mode experiments. Chromium concentrations in aqueous solutions and tannery waste water before and after adsorption experiments were determined using flame atomic absorption spectrometry. The effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(III) were studied. The study revealed that more than 99 % removal of Cr(III) was achieved over wide range of initial pH (3–10). The optimum conditions for the removal of Cr(III) were found to be at pH 4–6 with 40 g/L adsorbent dose at 60 min of contact time. The adsorption capacity was assessed using Langmuir and Freundlich isotherms. The equilibrium data at varying adsorbent dose obeyed the two isotherms. The adsorbent was found to be efficient for the removal of Cr(III) from tannery waste effluent.

Amino-functionalized mesoporous MCM-41: an efficient adsorbent for the removal of chromium (III) ions from aqueous solution

Amino-functionalized mesoporous MCM-41 (NH 2 -MCM-41) has been synthesized and explored as sorbent for removal of trivalent chromium, from aqueous media. The chemical and morphological structures of NH 2 -MCM-41 were investigated by scanning electron microscopy, energy-dispersive x-ray, and x-ray diffraction techniques. The best performance of NH 2 -MCM-41 as sorbent for removal of trivalent chromium was observed at optimized conditions: pH 3, adsorbent dose (1 g/L), contact time (2 hrs) and temperature (40 °C). Langmuir isotherm model was best fitted to the experimental data with high value of regression coefficient compared to Freundlich and Temkin models indicating monolayer adsorption of the chromium ions on the surface of NH 2 -MCM-41 with the maximum Langmuir adsorption capacity of 83.33 mg/g. The adsorption mechanism can be explained by the combined effects of strong chemical interaction of chromium (III) ions with the surface amino group and some un-reacted silicate groups of NH 2 -MCM-41. Adsorption kinetics was best described by pseudo-second-order kinetics model as compared to pseudo-first-order and followed by both diffusion as well as intra-particle pore diffusion mechanism. Thermodynamic analysis revealed that the adsorption was highly favorable, spontaneous and endothermic in nature which allows application of amino-functionalized MCM-41 as a promising adsorbent for the treatment of industrial effluents and other environmental samples.

Marine macro-alga Sargassum cymosum as electron donor for hexavalent chromium reduction to trivalent state in aqueous solutions

In this study, the brown macro-alga Sargassum cymosum was used as an electron donor for the reduction of hexavalent chromium to its trivalent form, through the oxidation of the biomass, and as a natural cation exchanger for the subsequent trivalent chromium sequestration from aqueous solutions. The reaction kinetics for hexavalent chromium reduction in aqueous solutions was evaluated as a function of the pH and initial concentrations of Cr(VI) and biomass. Hexavalent chromium reduction was found to be highly dependent on the pH of the solution, since protons are involved in the reduction mechanism. The concentration of organic compounds per unit of biomass able to reduce the hexavalent chromium was 3.0mmol/g, i.e., 1g of biomass was able to reduce 3mmol of Cr(VI). FTIR and potentiometric titration techniques showed that trivalent chromium removal was mainly associated with weak acidic carboxylic groups present at the surface of the biomass. The oxidation of the biomass during Cr(VI) reduction generated new binding sites responsible for trivalent chromium removal. A kinetic model based on a pseudo-first-order reaction successfully fitted the hexavalent chromium concentration profiles. Trivalent chromium concentration was predicted based on a mass balance of the total chromium in solution, considering the instantaneous binding of trivalent chromium to the negatively charged functional groups present at the surface of the biomass.

An Efficient and Fast Process for the Removal of Trivalent and Hexavalent Chromium from Contaminated Water Using Zinc Peroxide Nanomaterial

Higher concentration of trivalent and hexavalent chromium (percent to mg L-1) can be effectively removed from water by adsorption or precipitation process, but difficult to remove lower concentration (< 0.25 mg L-1) upto prescribed limits of World Health Organization (WHO) and United State-Environment Protection Agency (US-EPA). The lower concentration of chromium can be effectively removed using reverse osmosis system. In the proposed study we have successfully removed higher to lower concentration (20 to 0.1 mg L-1) of trivalent and hexavalent chromium using alone polyvinylpyrrolidone (PVP) functionalized zinc peroxide (ZnO2) nanomaterial below detection limit (0.001mgL-1) of Flame Atomic Absorption Spectrophotometer instrument (FAAS) within 15 minutes. The utilized nanomaterial alone act as oxidizing as well adsorbing agent, and purify water upto safe potability limits. The adsorption capacity of functionalized ZnO2 nanomaterial for total chromium was found to be 4.98 mg g-1 which is much better than the several other materials reported in the literature for chromium removal. A process patent for the synthesis of varying sizes functionalized ZnO2 nanomaterials has been granted in United State of America (Patent number 8,715,612; May 2014), South Africa, Bangladesh and India.

Removal of Cr 3+ by electrocoagulation from simulated wastewater

Trivalent chromium (Cr3+) removal from aqueous solution by electrocoagulation using iron electrodes material was investigated in this paper. Effects of current density, initial concentration of Cr 3+, operating time, pH, electrode distance, and operating cost have been investigated. At higher current density and solution pH, remarkable removal of Cr3+ was observed. Experiments have been show that the maximum removal percentage of the Cr3+ 99.89 % was at initial concentration 1000mg/L, current density 9.34mA/cm2 and reaction time 1 hours. Energy consumption was calculated for Cr3+ removal at different time. The method is observed to be very effective in the removal Cr3+ ion from aqueous solution. Electrocoagulation process need simple equipment, designable any size, use any chemical substances and low operating cost.DOI: http://doi.dx.org/10.5564/mjc.v15i0.330 Mongolian Journal of Chemistry 15 (41), 2014, p89-93