Treatment Of Hexavalent Chromium Research Articles

In situ stannous reagent generator (SRG): An alternative hexavalent chromium treatment technology in drinking water industry

Access to safe drinking water is a basic necessity for human health. Rock and soil are rich sources of chromium, a metal that is present naturally. Chromium commonly exists in two oxidation states: trivalent chromium (chromium-3, Cr (III), Cr3+) and hexavalent chromium (chromium-6, Cr (VI), Cr6+), in the natural environment, as well as in the water treatment and distribution systems. While Cr (III) is an essential nutrient for humans, Cr (VI) is a dangerous pollutant that can build up in both the environment and the tissues of living things. The Cr (VI) treatment traditionally uses techniques such as electrodialysis reversal, ion exchange, electrochemical, reduction, coagulation, oxidation and filtration systems. Chemical costs, secondary waste production, and unintentional regeneration of Cr (VI) after treatment are difficulties with standard Cr (VI) treatment. In order to remediate Cr (VI) in raw water, this study looks into the in-situ stannous reagent generator (SRG) package as a potential disruptive green technology. SRG was able to reduce roughly 40 parts per billion (ppb) of Cr (VI) to below 1.0 ppb after being installed on a raw water source site for a 10-day trial period. The In Situ SRG technology provides an efficient and safe method for treating Cr (VI) in drinking water, reduces the health risks associated with Cr (VI) exposure by converting it to a less toxic form and reduces chemical handling risks. Reductive Cr (VI) treatment technologies based on the use of stannous tin hold tremendous promise in the future to overcome green-house gas (GHG) emissions and other anthropogenic environmental change, in addition to effectively reducing Cr (VI) in drinking water to the permissible limits and high energy cost challenges. In Situ Stannous Reagent Generator (SRG) technology is designed to convert Cr (VI) to its less toxic trivalent form, Cr (III), which is less harmful and easier to remove from water.

Improvements in the reduction coagulation filtration process for hexavalent chromium treatment

AbstractReduction coagulation filtration using ferrous iron (Fe(II)‐RCF), or reduction filtration using stannous tin (Sn(II)‐RF), for the removal of hexavalent chromium (Cr(VI)) from drinking water represent attractive alternatives to ion exchange or reverse osmosis. With a new maximum contaminant level for Cr(VI) anticipated in California, this study sought to expand on previous research by applying Fe(II)‐RCF and Sn(II)‐RF to multiple groundwaters under a variety of reductant dose and reduction time scenarios. Four different granular filter media were also tested for removal of total chromium (Cr(T)) following Cr(VI) reduction to trivalent chromium (Cr(III)). Sodium hypochlorite, instead of aeration, was used to oxidize excess Fe(II) to Fe(III) prior to filtration, with minimal Cr(III) to Cr(VI) reoxidation. Sn(II)‐RF was also able to achieve Cr(T) and Cr(VI) treatment goals without dedicated reduction time prior to filtration. Results of this study were used to develop more up‐to‐date, feasibility‐level, 20‐year annualized cost estimates.

Modeling of Hexavalent Chromium Removal with Hydrophobically Modified Cellulose Nanofibers.

Cellulose nanofibers (CNF) are sustainable nanomaterials, obtained by the mechanical disintegration of cellulose, whose properties make them an interesting adsorbent material due to their high specific area and active groups. CNF are easily functionalized to optimize the performance for different uses. The hypothesis of this work is that hydrophobization can be used to improve their ability as adsorbents. Therefore, hydrophobic CNF was applied to adsorb hexavalent chromium from wastewater. CNF was synthetized by TEMPO-mediated oxidation, followed by mechanical disintegration. Hydrophobization was performed using methyl trimetoxysilane (MTMS) as a hydrophobic coating agent. The adsorption treatment of hexavalent chromium with hydrophobic CNF was optimized by studying the influence of contact time, MTMS dosage (0–3 mmol·g−1 CNF), initial pH of the wastewater (3–9), initial chromium concentration (0.10–50 mg·L−1), and adsorbent dosage (250–1000 mg CNF·L−1). Furthermore, the corresponding adsorption mechanism was identified. Complete adsorption of hexavalent chromium was achieved with CNF hydrophobized with 1.5 mmol MTMS·g−1 CNF with the faster adsorption kinetic, which proved the initial hypothesis that hydrophobic CNF improves the adsorption capacity of hydrophilic CNF. The optimal adsorption conditions were pH 3 and the adsorbent dosage was over 500 mg·L−1. The maximum removal was found for the initial concentrations of hexavalent chromium below 1 mg·L−1 and a maximum adsorption capacity of 70.38 mg·g−1 was achieved. The kinetic study revealed that pseudo-second order kinetics was the best fitting model at a low concentration while the intraparticle diffusion model fit better for higher concentrations, describing a multi-step mechanism of hexavalent chromium onto the adsorbent surface. The Freundlich isotherm was the best adjustment model.

Economic and performance evaluation of electrocoagulation unit for the treatment of hexavalent chromium using Taguchi method

Economic and performance evaluation of electrocoagulation unit for the treatment of hexavalent chromium using Taguchi method

Chitosan-based composite microspheres for treatment of hexavalent chromium and EBBR from aqueous solution

Hexavalent chromium is widely used in industrial fields, but its pollution has posed a great threat to the environment due to its high toxicity. We created a chitosan-based microsphere biosorbent (CP) by combining polyethyleneimine with chitosan adopting inverse emulsion polymerization method. Under the optimal conditions (pH = 3), the maximum adsorption capacity of composite microspheres can reach 299.89 mg g−1, which is much higher than that of chitosan microspheres (168.91 mg g−1). When the amount of CP is 0.25 g L−1, the removal rate of 50 mg L−1 Cr(VI) and 50 mg L−1 Eriochrome blue-black R (EBBR) can reach 95% and 99%, respectively. The time required for CP to reach adsorption equilibrium (180 min) was significantly shorter than that of chitosan microspheres (540 min), and the adsorption rate was significantly improved. Langmuir isotherm model, pseudo-second-order kinetic model and thermodynamic calculation results penetrated an endothermic spontaneous, monolayer, and chemical adsorption process. Biomass composite microspheres CP has obvious selectivity and the adsorption capacity retention rate of CP was still 71.32% after four adsorption cycles. This work proposed an easily prepared and biomass-based microspheres for the effective removal of Cr(VI) in printing and dyeing wastewater pollution through adsorption.

Killing Two Birds with One Stone: Biomineralized Bacteria Tolerate Adverse Environments and Absorb Hexavalent Chromium.

Heavy metal ions in contaminated water, such as hexavalent chromium, are harmful to humans. Bacterial biosorption is an ideal method for the treatment of hexavalent chromium. However, hexavalent chromium in solution causes bacteria to produce reactive oxygen species, which leads to bacterial death and affects biosorption. We developed a microfluidics-based biomimetic mineralization method to encapsulate bacteria (e.g., Escherichia coli and Bacillus subtilis) with zeolitic imidazolate framework-8 (ZIF-8), thus allowing the bacteria to form a continuous and homogeneous shell. The artificial shells endowed bacteria with the ability to tolerate harsh environments, which was significant during the treatment of contaminated water. The adsorption of hexavalent chromium was a two-step process: first the fast physical adsorption of ZIF-8 and biosorption by bacteria (up to 30–50% adsorption in 1 day), followed by secondary biosorption after decomposition of the system. The maximum adsorption of hexavalent chromium by the encapsulated bacteria reached 90%. The microfluidic device developed in this study provides a simple method to encapsulate bacteria mildly and enable cell survival in extreme environments, offering the possibility of future microbial applications in environmental and other fields.

Ethylenediamine‐Modified Hollow Porous Nanospheres for Effective Removal of Chromium (VI)

AbstractThe synthesis of recyclable adsorbents with satisfactory adsorption properties is more beneficial to their value in environment‐related applications. Organic porous polymer has become a potential adsorption material because of its convenient and effective modifiability and relatively high specific surface area. Here, we report for the first time a novel synthesis of ethylenediamine‐modified hollow porous nanospheres (HPNs‐NH2) via hyper‐crosslinking mediated self‐assembly strategy using polylactide‐b‐polystyrene‐b‐polyglycidyl methacrylate (PLA‐b‐PS‐b‐PGM) triblock copolymers as precursors, followed by further ring‐opening of epoxy groups with ethylenediamine (EDA). Owing to the special multistage pore structure, high surface area and a large number of amino active sites, the obtained solid adsorbent HPNs‐NH2 showed high adsorption capacity (493 mg/g) for Cr(VI), and its adsorption performance can still be maintained at a high level after eight cycles. These obvious advantages indicated that HPNs‐NH2 is expected to play an important role in the treatment of hexavalent chromium in sewage.

Use of sulfuric acid-carbonization materials from grape pulp for the removal of hexavalent chromium (Cr(VI)): mechanism and characterization

This study investigated the reduction of hexavalent chromium (Cr(VI)) with sulfur dioxide (SO2) and adsorption of Cr(VI) onto dried grape pulp carbonized with sulfuric acid. Cr(VI) reduction capacities of SO2 were determined. The filtrate was titrated with NaOH solution after shaking and filtering the carbonized material to retain unreacted sulfuric acid (H2SO4). Simple washing recovered 25–38% of the experimental acid at low concentrations. The carbonized material was washed twice with distilled water and then dried at 105 °C and weighed. The carbonized material had a yield of 56.6% (grape pulp/sulfuric acid ratios of 1:2), and the lower the H2SO4 content, the better the yield, suggesting that the higher the acid content, the lower the Cr(VI) content per unit grape pulp. Cr(VI) reduction capacities were 219.5, 195.3, and 190.9 mg Cr(VI)/g-H2SO4 for the grape pulp/sulfuric acid ratios of 1:1, 1:2, and 1:3, respectively. Novelty statement: A carbonaceous material was obtained from grape pulp by carbonizing with concentrated sulfuric acid. The main objective of this study was to evaluate gas, liquid, and solid products or co-products obtained during carbonization process for hexavalent chromium treatment in aqueous solutions. In this context, (a) hexavalent chromium reduction capability of the gas evolved during carbonization was determined, (b) characterization of unreacted acid recovered by washing the carbonized product left after carbonization step was done, (c) carbonaceous adsorbent obtained was characterized and (d) hexavalent chromium adsorption characteristics of carbonaceous material obtained was determined. HIGHLIGHTS Reduction and adsorption mechanisms of hexavalent chromium were investigated. A waste recycling method was proposed. The effects of sulfuric acid on carbonization were assessed. The structures and chemical compositions of a carbonized material were evaluated. The carbonized material is a cost-effective porous adsorbent for a clean environment.

AWWA Water Science Author Spotlight

<i>AWWA Water Science</i> Author Spotlight

Performance of lab-scale microbial fuel cell coupled with unplanted constructed wetland for hexavalent chromium removal and electricity production.

The microbial fuel cell coupled constructed wetland (CW-MFC) was used for treatment sewage and simultaneously generating electricity. The main aim of this study was to explore the optimal conditions for the treatment of hexavalent chromium (Cr (VI)) wastewater by the CW-MFC system. The performance of CW-MFC in removing Cr (VI) and chemical oxygen demands (COD) contained in wastewater and its electricity generation were studied. Electrode spacing, Cr (VI) and COD concentration, and hydraulic retention time (HRT) had certain effects on the performance of CW-MFC. For the electrode spacing of 10cm, the highest power density of 458.2mW/m3 could be obtained with the influent concentration of Cr (VI) (60mg/L) and COD (500mg/L). The highest Cr (VI) and COD removal rate were obtained with the HRT of 3days. Compared with CW system, the electrical energy generated in CW-MFC was beneficial to improving the removal efficiency of COD and Cr (VI). Thus, the results confirmed that CW-MFC is a promising technology to remove Cr (VI) from wastewater and achieve bioelectricity production simultaneously.

Treatment of simulated chromium-contaminated wastewater using polyethylenimine-modified zero-valent iron nanoparticles

Abstract The treatment of hexavalent chromium (Cr(VI)) contaminated water is considered the highest priority in the environmental field. Cr(VI) is a known carcinogen and is toxic even at parts per billion levels. In recent years, zero-valent iron nanoparticles (nZVI) have been regarded the best candidate for the decontamination of heavy metals such as chromium (Cr) in contaminated groundwater. Surface modification of nZVI has proven to enhance its stability and mobility in groundwater. In this work, the decontamination of a Cr-contaminant (Cr(VI)) through reductive reaction with polyethylenimine (PEI) coated nZVI (PEI–nZVI) was studied. Characterization was conducted using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and X-ray absorption near edge structure (XANES). The XRD patterns indicated that the nZVI product after Cr-contaminated water treatment corresponds to Fe3O4. Interestingly, the XANES and XPS analyses revealed the reduction of toxic Cr(VI) to less toxic Cr(III) with concurrent oxidization of nZVI to form Fe2O3, Fe3O4, or FeO. A Cr(VI) degradation efficiency of over 99.9% was observed within 10 min for the Cr concentration range 150–300 ppm. Cr(VI) was significantly adsorbed onto the surface of the nZVI nanoparticles; this could represent a cost-effective process for the in-situ remediation of Cr-contaminated groundwater. Owing to its excellent performance for the removal of Cr(VI), the environmentally friendly PEI–nZVI core-shell nanoparticle signifies an effective method for Cr(VI) decontamination.

Study of the properties and mechanism of deep reduction and efficient adsorption of Cr(VI) by low-cost Fe3O4-modified ceramsite

To efficiently treat low-concentration chromium wastewater at low cost, adsorbent iron-modified ceramsite (FCM) was successfully prepared. The adsorbent was characterized by SEM, XRD, FT-IR, XPS, ζ potential and VSM. From the experimental results, the optimum adsorption pH, adsorbent dosage and adsorption time were 4, 1g/L and 120min, respectively. The percentage removal of Cr(VI) was 93% and the reduction efficiency of Cr(VI) was 74.3% when the concentration was 2mg/L. After 5cycles, using 0.1mol/L NaOH as the regeneration agent, the removal rate of Cr(VI) did not decrease significantly. Furthermore, the mechanism of deep reduction and adsorption, the process of regeneration, the kinetics and adsorption isotherms were also explored. This paper can provide theoretical and technical support for reducing the toxicity and the advanced treatment of hexavalent chromium.

Nanocomposites based on 3D macroporous biomass carbon with SnS2 nanosheets hierarchical structure for efficient removal of hexavalent chromium

In this study, a novel nanocomposite, carbon/SnS2 with 3D hierarchical macroporous (MCS), was successfully prepared for rapid photocatalytic treatment of hexavalent chromium (Cr(VI)). The 3D macroporous carbon (MC) can be obtained through a simple carbonization process of loofah. Since the MCS has a large specific surface area, it can provide numerous photocatalytic active sites and has excellent adsorption properties for the Cr(VI). In addition, the excellent electrical conductivity and unique hierarchical nanoarchitecture of macroporous biomass carbon could rapidly absorb the Cr(VI) from wastewater and provide electron transport tunnel for rapid charge separation/transport to suppress hole electron recombination. It is confirmed that such three dimensional photocatalytic material can quickly purify Cr(VI)-containing wastewater under mild visible light irradiation, with a efficiency of 63.2% Cr(VI) reduction within 120 mins. Besides the high visible light-driven photocatalytic activity, MCS also exhibits excellent cycling stability. In addition, the SEM images of MCS before and after photocatalytic removal of Cr(VI) indicate that the morphology of composite was perfectly maintained and no peeling-off of SnS2 was observed. More importantly, this study demonstrated that MCS can be used for practical applications due to its stability and economic availability.

Treatment of Hexavalent Chromium Contaminated Wastewater Using Activated Carbon Derived from Coconut Shell Loaded by Silver Nanoparticles: Batch Experiment

Chromium (Cr(VI)) causes serious impacts on the environment and human. In this study, the commercial activated carbon-loaded silver nanoparticle (AgNPs-AC) was used as a new adsorbent to remove Cr(VI) from the aqueous solution. Batch adsorption experiments were conducted to evaluate the effects of pH, the initial concentration of Cr(VI), contact time, and dose of AgNPs-AC upon removal of Cr(VI) from the aqueous solution. The results showed that at pH of 4, the contact time of 150 min, 40 mg/L of initial Cr(VI), and dosage of 20 mg AgNPs-AC/25 mL were the most suitable condition for absorption of Cr(VI) onto AgNPs-AC from the aqueous solution. The maximum adsorption capacity achieved at abovementioned conditions was 27.70 mg/g. Meanwhile, the adsorption capacity of commercial activated carbon from a coconut shell obtained only 7.61 mg/g in the case where the initial Cr(VI) concentration is 10 mg/L and the contact time is 60 min. The adsorption kinetic data were found to fit best to the pseudo-second-order model with a high correlation coefficient (R2 = 0.9597). The adsorption process was controlled by chemisorption due to the appearance of new chemical species on the adsorbent surface. The positively charged functional groups rapidly reduced Cr(VI) to Cr(III), and Cr(III) was subsequently adsorbed by the carboxyl group on the adsorbent’s surface. From this study, it can be concluded that AgNPs-AC is a fully promising, low-cost adsorbent in the removal of Cr(VI) from the aqueous solution.

Preparation of quaternary amine-grafted organosolv lignin biosorbent and its application in the treatment of hexavalent chromium polluted water

A novel cationic biosorbent was synthesized by grafting organosolv lignin with GT (also named (2-hydrazinyl-2-oxoethyl)-trimethylazanium chloride, abbreviated as GT) and formaldehyde in an aqueous solution by an eco-friendly way (named QA-g-OL). QA-g-OL was employed as biosorbent to remediate hexavalent chromium polluted water. Research found Cr(VI) removal is a pH-dependence process. It was also found that part of the Cr(VI) was reduced to Cr(III) during the process of adsorption in the range of pH was 2.0 to 7.0. Furthermore, QA-g-OL possess strong absorbability for Cr (VI) in a broad concentration range (from 10 to 100 mg/L). The removal efficiencies of Cr (VI) were 93.40%, 96.70%, 98.78% and 97.84% when initial concentration was 10, 20, 50, 80 and 100 mg/L under optimum pH, respectively. On the other side, the adsorption process exhibited swift equilibrium characteristics, the adsorption equilibrium can be achieved within 10 min. The mechanism of hexavalent chromium removed by QA-g-OL were also discussed, results can be benefit for the application of biomass-based adsorbents in the treatment of hexavalent chromium polluted wastewater.

Citizen Science

Encouraging the public to care more about our water systems and services is the responsibility of every water professional, and it seems like an easy sell given that water directly affects public health and underpins the livelihoods and lifestyles that define our communities. One way to expand opportunities for community engagement beyond a community-wide event or issue is through citizen science. Citizen science—scientific research that is conducted in whole or in part by amateur scientists—is an opportunity for water professionals to connect with community members who are issue-focused and to influence and engage those whose interests lie elsewhere. Citizen science projects can be relatively low cost because they typically involve volunteers who are motivated by civic duty or community activism. Of course, these projects require time, resources, and oversight, including promotion/recruitment, training, and ongoing data collection and validation. If weighted more toward promotion, citizen science at a minimum allows a wide range of age and interest groups to better understand issues by fostering interactions with experts to investigate and track pertinent data such as water quality and supply parameters. The water industry could benefit from data points provided by citizen scientists, such as linking locational water quality measurements through online applications like GPS, GIS, mapping platforms, and social networks. As our analytical capabilities improve, it will be interesting to see if more concerned citizens become involved, and who knows what sensors may ultimately be included as simple smartphone applications in the future. Of course, for crowd-sourced data to be usable, there need to be quality assurances and data validation, and ongoing training and oversight could support at least some level of useful information collection. Across North America there are local, regional, and national efforts underway to encourage citizen science projects involving water, and looking forward, citizen science could ultimately be leveraged into the modern paradigm of safe water. For example, a well-distributed base of volunteers with sensors making measurements in a watershed can be coupled with localized, real-time monitoring and analysis so that utility managers can make more immediate source water protection decisions and adjust long-term strategies. The contributions of citizen scientists could be considered another layer of protection within the multi-barrier approach that typifies modern potable water systems. In the end, citizen science can promote engagement, contribute to social identity, and hopefully inspire curiosity in the next generations. Although this month's Journal AWWA doesn't include any contributions from citizen scientists, it does have several excellent peer-reviewed original research articles from academic and government investigators. Topics cover halide removal from drinking waters using silver-amended coagulation (page 13), stripping trihalomethanes using tray aeration (page 26), hexavalent chromium treatment using ion exchange (page 27), asbestos–cement pipe deterioration (page 28), and water main failures (page 29). Feature articles include topics such as partnerships for source water protection (page 30), advanced metering infrastructure (page 36), innovative financing (page 42), and sustainability (page 50). Please consider submitting your original research and practical perspectives for publication in Journal AWWA to better connect the water industry.

Nanofiltration to Improve Process Efficiency of Hexavalent Chromium Treatment Using Ion Exchange

Managing waste brine from strong base anion exchange processes used for hexavalent chromium removal is an important operational, environmental, and economic consideration. This study investigates the use of nanofiltration to recover excess regenerant salt and reduce the waste volume using brine collected from full‐ and pilot‐scale installations. Using a 2 N sodium chloride regeneration solution, divalent anions (i.e., sulfate and chromate) exhibited high rejections (&gt;0.97), and monovalent anions (i.e., chloride and nitrate) exhibited low to negative rejections (−0.2 to 0.05), allowing preferential passage of excess regenerant salt. A batch concentration model was developed for a case study. Waste can be concentrated to 0.6 bed volume and a significant fraction of the regenerant salt can be recovered. This process would require about 20 m2 of membrane area per 1,000 L of resin to treat waste in 8 h, which could be implemented in a mobile treatment unit serving multiple decentralized systems.

Optimization of strong-base anion exchange O&M costs for hexavalent chromium treatment

Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being considered for regulation in other locations. While strong-base anion exchange (SBA-IX) can efficiently remove Cr(VI) to low-levels that may be required to comply with future MCLs, operational and maintenance (O&M) costs can be considerable if the spent brine is disposed of as hazardous waste. Through bench- and pilot-scale experiments and full-scale demonstrations, this study examined the ability of emerging and established brine treatment and reuse techniques as well as recently developed resins to decrease O&M costs.When profiling anion elution during regeneration with nanofiltration treated and untreated spent brine, it appeared that at least 1 and 3 reuse cycles were feasible, respectively. Stannous- and ferrous-based reductants were more efficient than sulfur-based reductants when treating spent brine. Bed volumes to 8 μg/L chromium breakthrough with 7 resins varied by as much as a factor of 2 and correlated (R2 = 0.84) with resin total exchange capacities. Spent brine reuse, segmented regeneration (an optimized brine reuse method), ferrous reduction, and nanofiltration of spent brine were estimated to decrease O&M costs by 30, 70, 63, and 61%, respectively. Selection of high performing resins was the most simple way to decrease O&M costs (up to 70% savings).The sum of nitrate and sulfate raw water equivalent concentrations was found to be the principal water quality parameter that influenced the performance of 4 resins in 7 different groundwaters because nitrate and sulfate concentrations were orders of magnitude greater than chromium concentrations. Resins with higher chromium capacities eluted more co-contaminants including arsenic, selenium, uranium, and vanadium because they likely had higher co-contaminant capacities. Co-contaminant elution was found to be complex because associations can form between regenerant and co-eluting anions. Sodium chloride was the most efficient regenerant, though other regenerants provided benefits such as enhanced uranium elution most likely by complexing with uranium to inhibit its precipitation. Nitrate peaking was found to be limited even when reusing untreated and nanofiltration treated spent brine.

Removal of Cr(VI) from groundwater by Fe(0)

This research was conducted to investigate the treatment of hexavalent chromium (Cr(VI)) by iron powder (Fe(0)) columns of simulated permeable reactive barriers with and without calcium carbonate (CaCO3). Two columns filled with Fe(0) were used as Cr(VI) removal equipment running at a flow velocity of 10 ml/min at room temperature. After 200 days running of the two columns, the results showed that Fe(0) was an effective material for Cr(VI) reduction with an average removal rate of above 84.6%. The performance of Column 2 with CaCO3 was better than Column 1 without CaCO3 in terms of average Cr(VI) removal rate. The presence of CaCO3 buffered the increasing pH caused by Fe(0) corrosion in Column 2 and enhanced the removal rate of Column 2. Scanning Electron Microscopy (SEM) images of Fe(0) in the three stages of running of the two columns illustrated that the coat layer of Column 1 was a little thicker than that of Column 2. Energy-dispersive spectrometry (EDS) results showed that the surface of Fe(0) of Column 2 contained more chromium elements. Raman spectroscopy found that all iron oxide was generated on the Fe(0) surface of Column 1 and Column 2 and chromium class objects were only detected on Fe(0) surface in Column 2.

Floatable, macroporous structured alginate sphere supporting iron nanoparticles used for emergent Cr(VI) spill treatment

Treatment of hexavalent chromium (Cr(VI)) spill accident is a great challenge due to its high toxicity, sudden and extensiveness. In this study, we designed and fabricated a hierarchical, ordered and macroporous structured alginate sphere to support in-situ synthesized zero-valent iron nanoparticle (the alginate-nZVI sphere). Field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDS) images showed well dispersion of nZVI on the composite. This alginate-nZVI sphere exhibited good separability in effective removal of Cr(VI). The result from Cr(VI) removal experiment demonstrated a Cr(VI) removal efficiency of 98.2% at equilibrium time, which can be ascribed to the well dispersion of the nZVI. In addition, the alginate-nZVI sphere was effective in Cr(VI) removal in a wide range of pH from 3.0 to 11.0, by the merit of alginate substrate. Hence, the alginate-nZVI sphere might be a promising agent for an emergent Cr(VI) spill treatment by enhancing the dispersion, stabilization and separation properties of nZVI.