Removal Efficiency Of Cu Research Articles

A Yokenella regensburgei strain effectively removes Cu(II), Pb(II), and Cd(II) through a combination of absorption and mineralization modes

Microbial-based heavy metal removal from wastewater is a widely embraced and environmentally friendly method. Nevertheless, its sustainability and efficacy necessitate further improvement. In this study, the strain Yokenella regensburgei GXAS49-I was isolated and characterized for its bioremediation potential. The strain exhibited remarkable resistance to heavy metals, demonstrating a high removal efficiency of 85 % and 90 % for Cu(II) and Pb(II), respectively. The extracellular polymeric substance of GXAS49-I, rich in CO and CO groups, facilitated heavy metal adsorption and played a role in the removal of heavy metal ions. Additionally, GXAS49-I produced hydrogen sulfide, transforming heavy metals into sulfide sediments. Immobilizing GXAS49-I on aerobic granular sludge ensured consistently high removal efficiency for Cu(II) and Pb(II) over four consecutive cycles. The unique dual modes of absorption and mineralization of heavy metals by GXAS49-I, in conjunction with aerobic granular sludge immobilization, position it as an excellent candidate for the sustainable and effective removal of hazardous metals.

Modeling Cu removal from aqueous solution using sawdust based on response surface methodology.

Copper (Cu), as one of the heavy metals widely used in industrial and agricultural activities, has a fundamental role in the pollution of water resources. Therefore, removing Cu from the aqueous solutions is considered an important challenge in the purification of water resources. Thus, in this study, sawdust with a diameter of 260-600 μm was used to remove Cu from the aqueous solutions. At first, sawdust was washed using distilled water and dried at laboratory temperature. Cu absorption experiments in closed conditions were performed based on the central composite design (CCD) model and with a range of initial Cu concentrations equal to 1-25 mgl-1. The amount of changes for other variables, including pH, time, and amount of sawdust, was equal to 2-10, 5-185 (min), and 5-25 (gl-1), respectively. After the completion of each test, the remaining Cu concentration in the solution was measured using atomic absorption, and the percentage of Cu removed was determined from the difference between the initial and final concentrations. The results showed that the CCD model has a favorable ability to predict Cu removal from the aqueous solutions (R2=0.90 and RSME=3.34%). Based on the Pareto analysis, contact time, the amount of sawdust, pH, and the Cu concentration had the most significant effect on removing Cu from the solution. Contact time, amount of sawdust, and pH were directly related, and the amount of dissolved Cu was proportional to the removal of Cu from the solution. Therefore, sawdust is desirable as a natural adsorbent, and the removal efficiency of Cu from solutions with low Cu concentration is very high (94%). In this regard, it is advised to use sawdust in the process of targeting Cu and heavy metals due to its low cost and availability.

Effects of Cu (II) on the Growth of Chlorella vulgaris and Its Removal Efficiency of Pollutants in Synthetic Piggery Digestate.

C. vulgaris has a positive effect on the removal of nutrients from pig farm biogas slurry. However, swine wastewater often contains heavy metal ions, such as Cu (II), which may have impacts on the nutrient removal performance of C. vulgaris. Additionally, the heavy metal ions in wastewater can be adsorbed by microalgae. In this study, the stress effect of Cu (II) on the growth of Chlorella vulgaris, the Cu (II) removal by microalgae, and the effect of different concentrations of Cu (II) on the nutrient removal efficiency of C. vulgaris in biogas slurries were explored. The results showed that the microalgae biomass of microalgae on the sixth day of the experiment was the highest in the treatment with a Cu (II) concentration of 0.5 mg/L, which was 30.1% higher than that of the 2.5 mg/L group. C. vulgaris had higher removal efficiencies of Cu (II) at a Cu (II) concentration of 0.1~1.5 mg/L. The-OH, C=O, -COOH, and C-O groups on the surface of the algal cells play a significant role in the removal of Cu (II). The removal rates of COD, NH3-N, TN, and TP by C. vulgaris at a Cu (II) concentration of 0.5 mg/L were the highest, which were 89.0%, 53.7%, 69.6%, and 47.3%, respectively.

Removing copper ion from wastewater by surface precipitation using novel hierarchical hydrated magnesium carbonate crystal

It is significant to develop a low-cost, easy-to-separate and efficient adsorbent to remove heavy metals from wastewater. Therefore, the hierarchical hydrated magnesium carbonate (HMC) crystal is prepared. The performances of HMC crystal at different adsorption conditions are studied. The surfaces of HMC crystal before and after Cu2+ adsorption are characterized by XRD, FTIR, XPS, SEM and EDS mapping. The removal efficiency of Cu2+ reaches 99 % under the conditions of an initial concentration of 300 mg/L, HMC dosage of 0.5 g/L, pH value of 4.5 and adsorption time of 180 min. The adsorption kinetic and isotherm can be described by the pseudo-second-order model and Langmuir adsorption model, respectively. The maximum adsorption capacity of Cu2+ is 1406 mg/g. The hierarchical structure provides HMC crystal with sufficient hydroxide ions for Cu2+ surface precipitation and large particle size (40–100 μm) for subsequent solid–liquid separation, presenting a promising application prospect in the future.

Preparation of landscape gardening soil using undersized fraction from aged MSW by EDTA or citric acid coupled with humic acid: Effect assessment, properties, and optimization

ABSTRACT Undersized fraction from aged municipal solid waste (UFAMSW), as a kind of soil-like material, has been proved effective in providing a large amount of organic matter and nutrients for soil and plants. The characteristics and effectiveness of heavy metal pollution removal in UFAMSW attracted tremendous research interest from scientists recently. In this study, the heavy metal removal efficiencies and bioavailability of washing on contaminated UFAMSW were evaluated with three washing reagents including ethylene diamine tetra acetic acid (EDTA), citric acid (CA), and humic acid (HA). The effects of chelating agent concentration, pH, and washing time on metal removal were investigated and response surface methodology (RSM) was employed to optimize the washing conditions. The results indicated that the removal efficiencies of Cu, Zn, and Mn could be 53.68%, 52.12%, and 30.63% by EDTA/HA washing and 42.36%, 39.67% and 28.49% by CA/HA washing, respectively. The European Community Bureau of Reference (BCR) sequential extraction was applied to analyze the fraction change of heavy metals in UFAMSW before and after washing, and it was found that chelating agent combined with HA could contribute to the removal of the exchangeable fraction. Physical and chemical properties of UFAMSW were improved to some extent after washing with mixed HA and chelating agent and could achieve the quality standard of landscape gardening soil. Accordingly, the mixture of HA and other chelating agents could be a promising washing process for preparation of landscape gardening soil using UFAMSW. Implications: Our manuscript studies the removal of heavy metals from the contaminated undersized fraction from aged municipal solid waste (UFAMSW). UFAMSW, as a kind of soil-like material, has been proved effective in providing a large amount of organic matter and nutrients for soil and plants however often limited by heavy metal pollution. The UFAMSW used in this experiment was collected after the excavation and screening-sorting of aged refuse from Changshankou Domestic Waste Sanitary Landfill in Wuhan City, Hubei Province, Southern China. This study investigated the effects of EDTA, CA, HA, mixed EDTA/HA, and mixed CA/HA washing on heavy metal removal (Cu, Zn, and Mn), bioavailability of residual heavy metal and properties. The effects of chelating agent concentration, pH, and washing time on metal removal were investigated and then response surface methodology was employed to optimize the washing conditions. The results showed that washing by CA/HA and EDTA/HA, had a higher removal efficiency of heavy metals (Cu, Zn, and Mn) in UFAMSW compared to single HA. Meanwhile, HA has a higher removal for exchangeable fraction of heavy metals, the exchangeable concentration of Cu, Zn, and Mn in CA/HA and EDTA/HA washed UFAMSW were lower compared with UFAMSW washed by single CA and EDTA. Thus, mixing HA with EDTA or CA makes a less risk to environmental and the removal efficiency is acceptable. Additionally, CA/HA and EDTA/HA washing tend to improve soil physicochemical properties and soil fertility. Thus, mixing HA with different washing agent are potential methods for preparation of landscape gardening soil using UFAMSW.

Study on Cu- and Pb-contaminated loess remediation using electrokinetic technology coupled with biological permeable reactive barrier

Although the electrokinetic (EK) remediation has drawn great attention because of its good maneuverability, the focusing phenomenon near the cathode and low removal efficiency remain to be addressed. In this study, a novel EK reactor was proposed to remediate Cu and Pb contaminated loess where a biological permeable reactive barrier (bio-PRB) was deployed to the middle of the EK reactor. For comparison, three test configurations, namely, CG, TG-1, and TG-2, were available. CG considered the multiple enzyme-induced carbonate precipitation (EICP) treatments, while TG-1 considered both the multiple EICP treatments and pH regulation. TG-2 further considered NH4+ recovery based on TG-1. CG not only improved Cu and Pb removals by the bio-PRB but also depressed the focusing phenomenon. TG-1 causes more Cu2+ and Pb2+ to migrate toward the bio-PRB and aggravates Cu and Pb removals by the bio-PRB, depressing the focusing phenomenon. TG-2 depressed the focusing phenomenon the most because Cu2+ and Pb2+ can combine with not only CO32− but PO43−. The removal efficiency of Cu and Pb is 34% and 36%, respectively. A NH4+ recovery of about 100% is attained.

The utilization of cost-effective natural sorbents for the eradication of heavy metal contaminants from the real world-based adsorbate system

In India, Industrial growth has resulted towards the release of numerous contaminated heavy metals into the environment, Various industries directly discharged the effluents containing harmful pollutants such as toxic heavy metals into the aqueous medium. There are numbers of treatment methods available to remove toxic elements from effluents before disposal. Several research investigations have been conducted to determine the capacity of unconventional absorbents to remove various wastewater impurities. Bio-sorption technique uses agricultural and natural left-over materials as adsorbents since they remain considerably less expensive, supportable, and available than traditional effluent treatment technologies. This study concentrates removal efficiency of orange peels (OP), rice husk (RH) and sugarcane bagasse (SCB) from the industrial effluents. Adsorption studies have been conducted for OP, RH and SCB with differing dose, pH, and contact duration, determined to be appropriate and leading to the highest levels of removal effectiveness. At 1.00 gm dosage, the maximum % removal efficiency of Cu, Cr, Ni, Cd and Zn removal for OP, RH and SCB were 84.90%, 90.45%, 86.21%, 98.00% and 74.11% respectively by using OP, RH and SCB the max. percentage removal efficiency of Cu, Cr, Ni, Cd and Zn for OP, RH were 82.81%, 76.80%, 76.16%, 78.46%, 78.59% at a pH value of 5, 6, 5, 7 and 7 respectively. The max. percentage removal efficiency of Cu, Cr, Ni, Cd and Zn using OP, RH and SCB were 93.45%, 93.05%,77.66%, 94.62%, 85.10% at the contact time of 120, 60, 120, 60 and 80 minutes respectively.

Nano-impregnation on metakaolin backbone for enhanced removal of Cu(II) and Mn(II) ions in a binary system using fixed bed column

This paper presents a comprehensive study on the synthesis and characterization of a novel composite material composed of metakaolin (MK), cellulose nanofibers (CNF), graphene oxide (GO), and zinc oxide (ZnO) for the efficient removal of heavy metals from wastewater. The main objective of this research was to enhance the removal efficiency of Cu(II) and Mn(II) ions in a binary system using a fixed bed column adsorption technique while investigating the effect of impregnating the nanomaterials. The synthesized samples were subjected to a thorough characterization using various techniques. These analyses provided insights into the structural properties and morphology of the composite material. The adsorption performance of the MK/CNF/GO/ZnO composite was evaluated through breakthrough curve analysis and kinetic modeling. The MDR model provided good fits with R2 values of 0.962 and 0.967 for Cu(II) and Mn(II) respectively. Based on the experimental breakthrough curve data, the saturation and breakthrough capacities of the composite material were calculated to be 5.97 mg/g and 4.84 mg/g for Cu(II) and Mn(II) respectively, achieved after a saturation time of 102 min for Cu(II) and 128 min for Mn(II). The results demonstrated a synergistic effect between GO and CNF, resulting in enhanced adsorption efficiency. The incorporation of ZnO nanoparticles further improved the adsorption capacity due to their high surface area, providing additional active sites for adsorption. The results showed that combining CNF, GO, and ZnO in a composite resulted in extended breakthrough and exhaustion times compared to the combination of CNF and GO alone.

Synergistic effect and mechanism of zero-valent iron activated persulfate on Cu(II)–EDTA decomplexation enhanced with weak magnetic field

Herein, a weak magnetic field (WMF) was applied to improve the catalytic degradation of the copper-ethylene diamine tetraacetic acid complex (Cu(II)–EDTA) and recovery of Cu using zero-valent iron/peroxomonsulfate (ZVI/PS). The removal rates of Cu(II)–EDTA in the WMF/ZVI/PS system were 7.92 and 1.33 times those in the ZVI and ZVI/PS systems, respectively. The recovery rates of Cu in the WMF/ZVI/PS system were 4.78 and 1.25 times more than those in ZVI and ZVI/PS systems, respectively. Scavenger quenching experiments and electron spin resonance (ESR) results showed that more active radicals (SO4•− and •OH) were produced and both SO4•− and •OH played the important role in Cu(II)–EDTA degradation in the WMF/ZVI/PS system. The ZVI and PS dosages and initial solution pH considerably affected the removal efficiency of Cu(II)–EDTA. X-ray energy-dispersive spectroscopy (EDS) results showed that WMFs could accelerate the enrichment of paramagnetic Cu2+ on the ZVI surface. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results showed that Cu2+ ions were first adsorbed on the corroded ZVI and then reduced to Cu0 with time. A possible Cu(II)–EDTA decomposition and Cu reduction mechanism was also proposed. This study provides a promising and ecofriendly technique for treating industrial wastewater containing organic complexed metals.

Antibiotic and Heavy Metal Co-Resistant Strain Isolated from Enrichment Culture of Marine Sediments, with Potential for Environmental Bioremediation Applications.

Antibiotics and heavy metals have caused serious contamination of the environment and even resulted in public health concerns. It has therefore become even more urgent to adopt a sustainable approach to combating these polluted environments. In this paper, we investigated the microbial community of marine sediment samples after 255 days of enrichment culture under Cu (II) and lincomycin stress and ZC255 was the most resistant strain obtained. The 16S rRNA gene sequence confirmed that it belonged to the genus Rossellomorea. Strain ZC255 was resistant to 12 kinds of antibiotics, and had a superior tolerance to Cu (II), Pb (II), Ni (II), Zn (II), Cr (III), and Cd (II). Moreover, it exhibits strong bioremoval ability of Cu and lincomycin. The removal efficiency of Cu (II) and lincomycin can achieve 651 mg/g biomass and 32.5 mg/g biomass, respectively. Strain ZC255 was a promising isolate for pollution bioremediation applications.

Evaluation of efficiency of Wheat straw nanocellulose as nanoadsorbent for the removal of divalent copper, lead and zinc from aqueous solution

Novel nanocellulose (cellulosic carbohydrate polymer) embedded with Wheat straw was synthesized, characterized and examined as nanoadsorbent for the removal of copper, lead and zinc metals from aqueous solution through batch mode. The effects of pH, dose, contact time, temperature and synchronous cations on the amount of Cu (II), Pb (II) and Zn (II) adsorbed have been probed. The desirable pH was 8 and nanoadsorbent dose was 0.6 g/50 mL in the adsorption study. The removal efficiencies of Cu (II), Pb (II) and Zn (II) were 88.75%, 81.18%, 86.84% respectively. Adsorption kinetic study was employed to analyze experimental data and adsorption process followed pseudo second order kinetic model. Langmuir, Freundlich, Temkin and Redlich-Peterson isotherm models were used to indicate the adsorption of Cu (II), Pb (II) and Zn (II) on WSN and thermodynamic study affirmed that adsorption process was endothermic and spontaneous. AFM indicated size and morphology and attachment of functional groups on WSN were examined by FTIR. The results confided that adsorption is economically competent method for removing Cu (II), Pb (II) and Zn (II) and WSN is anticipative owing to its ease and low cost of regeneration

Non-negligibly negative role of e-waste-derived pyrogenic carbon in the soil washing of copper and polybrominated diphenyl ethers

The open incineration of electrical and electronic waste (e-waste) results in the accumulation of pyrogenic carbon in the soil. However, the effect of the e-waste-derived pyrogenic carbon (E-PyC) on the performance of soil washing at e-waste incineration sites remains unclear. In this study, the effectiveness of a citrate-surfactant mixed solution in removing copper (Cu) and decabromodiphenyl ether (BDE209) at two e-waste incineration sites was evaluated. The removal efficiencies of Cu (24.6–51.3%) and BDE209 (13.0–27.9%) were low in both soils and were not significantly improved by ultrasonic. Soil organic matter analysis, hydrogen peroxide and thermal pretreatment experiments, and microscale soil particle characterization demonstrated that the poor removal of soil Cu and BDE209 was due to steric effects of E-PyC on the release of the solid fraction of pollutants and the competitive sorption of the labile fraction of pollutants by E-PyC. Weathering of soil Cu weakened the influence of E-PyC but strengthened the negative impact of natural organic matter (NOM) on soil Cu removal by promoting complexation between NOM and Cu2+ ions. This study demonstrates that the negative effect of E-PyC on Cu and BDE209 removal by soil washing is non-negligible, which has implications for decontaminating e-waste incineration sites by soil washing.

Performance of biochar mixed cement paste for removal of Cu, Pb and Zn from stormwater

Using biochar as a partial replacement of Portland cement in cementitious materials is a promising solution to mitigate negative environmental impacts. However, current studies in available literature primarily focus on the mechanical properties of composites made with cementitious materials and biochar. Therefore, this paper reports the effects of the type of biochar, the percentage of biochar addition, and the particle size of the biochar on the removal efficiency of Cu, Pb, and Zn, as well as the effect of contact time on the removal efficiency of Cu, Pb, and Zn, along with the compressive strength. The peak intensities of OH−, CO32− and Calcium Silicate Hydrate (Ca–Si–H) peaks increase with increasing biochar addition levels, reflecting increased hydration product formation. The reduction of particle size of biochar causes the polymerization of the Ca–Si–H gel. However, no significant changes were observed in heavy metal removal, irrespective of the percentage of biochar addition, the particle size of biochar, or the type of biochar added to the cement paste. Adsorption capacities above 19 mg/g, 11 mg/g and 19 mg/g for Cu, Pb and Zn were recorded in all composites at an initial pH of 6.0. The Pseudo second order model best described the kinetics of the Cu, Pb, and Zn removal. The rate of adsorptive removal increases with the decrease in the density of the adsorbents. Over 40% of Cu and Zn were removed as carbonates and hydroxides through precipitation, whereas over 80% of Pb removal was via adsorption. Heavy metals bonded with OH−, CO32− and Ca–Si–H functional groups. The results demonstrate that biochar can be used as a cement replacement without negatively impacting heavy metal removal. However, neutralization of the high pH is needed before safe discharge.

Triggered heavy metals and chlorine simultaneous removal from hazardous waste incineration fly ash

To date, heavy metals and chlorine removal from hazardous waste incineration fly ash (HWI FA) by thermal treatment was scarcely reported. High content of calcium in HWI FA might affect heavy metals chlorination volatilization. The aim of this study was to realize heavy metals and chlorine simultaneous removal from HWI FA triggered by fluidized-bed municipal solid waste incineration fly ash (FBMSWI FA) during sintering. Results showed that the dilemma of low heavy metals removal efficiency was due to the dense structure and the difficulty of transformation of the stable phases including Cu2S, CuSiO3, and Zn2SiO4. By co-sintering with FBMSWI FA at the ratio of 1:1, the removal efficiency of Cu, Zn, Pb, Cd, and Cl reached as high as 84.4%, 92.0%, 99.9%, 99.5%, and 99.7%, respectively. Compared with the control, chlorination volatilization efficiency of Cu and Zn was significantly increased by 210.5% and 89.2%. The favourable promotion could be mainly attributed to Si/Al matrix in FBMSWI FA triggered the following reaction: i) Ca-bearing compounds in HWI FA were activated to destroy the dense structure, which facilitated the transformation of Cu2S to CuO; and ii) the conversion of NaCl and KCl to gaseous chlorine was promoted, which the formation of metal chlorides was accelerated.

Facile synthesis of chitosan-tartaric acid biosorbents for removal of Cu(II) and Cd(II) from water and tea beverages

Consumption of water and tea beverages leads to the intake of heavy metals by humans. Development of technology for decontamination greatly reduces the risks of the heavy metal exposure. In this study, environment-friendly chitosan-tartaric acid biosorbents (CTBs) were synthesized by a facile one-step cross-linking strategy to mitigate the Cu(II) and Cd(II) contamination in water and tea beverages. The cross linkage of tartaric acid and chitosan endowed CTBs with excellent properties in aspects of surface roughness, mechanical strength, and acid resistance. Adsorption performance and mechanism of CTBs were studied, and the Langmuir isotherm model and pseudo-second-order kinetic model were adhered during adsorption. Up to 90 % removal efficiencies of Cu(II) and Cd(II) from water and tea beverages by CTBs were achieved. Moreover, the adsorption showed only a slight reduction in the quality of tea beverages. This study offers a new insight for reduction of heavy metals-pollution in beverages.

Removal of mixed contaminants from landfill leachate-contaminated soil by flushing with bio-surfactant: laboratory column tests.

Landfill leachate-contaminated soil is widespread all over the world. In order to study the removal of mixed contaminants from landfill leachate-contaminated soil by flushing with bio-surfactant, soil column test was conducted to select an optimum concentration of bio-surfactant saponin (SAP) at first. Then, the removal efficiencies of organic contaminants, ammonia nitrogen, and heavy metals from landfill leachate-contaminated soil by flushing with SAP were studied. At last, the toxicity of contaminated soil before and after flushing was estimated by sequential extraction of heavy metals and plant growth test. The test results showed that the SAP solution with the concentration of 2.5 CMC could effectively remove the mixed contaminants from soil and would not introduce excessive pollutants of SAP in soil. Specifically, the removal efficiencies of organic contaminant and ammonia nitrogen were 47.01% and 90.42%, respectively. And the removal efficiencies of Cu, Zn, and Cd were 29.42%, 22.55%, and 17.68%, respectively. During flushing, hydrophobic organic compounds as well as physisorption and ion-exchange ammonia nitrogen in soil were removed by the solubilization effect of SAP, and heavy metals were removed by the chelation of SAP. After flushing with SAP, the reduced partition index (IR) value of Cu and Cd increased, and the mobility index (MF) value of Cu decreased. In addition, flushing with SAP reduced the plant toxicity of contaminated soil, and the residual SAP in soil promoted the plant growth. Therefore, flushing with SAP offered great potentials in remediating the landfill leachate-contaminated soil.

Enhanced copper cyanide complex precipitation using polymer-surfactant aggregates

Precipitation of metal cyanide complexes using quaternary ammonium salts has been used in cyanidation solutions after gold leaching. Due to the high residual load of metal cyanide complexes and ammonium salts, this method does not apply to effluents containing moderate or low cyanide concentrations. To overcome these limitations, in this study, we introduce poly(sodium 4-styrenesulfonate) (PSS) into a solution containing cetyltrimethylammonium bromide Sinpharm (CTAB), to form polymer-surfactant aggregates (PSAs) and enhance the removal efficiency of Cu and TCN. 93.8% and 97.0% of Cu and TCN, respectively, were removed from the synthetic solution (Cu 0.5 mM and CN 1.5 mM) under optimum dosage of 150 ppm PSS and 0.8 mM CTAB, resulting in 92.2% of substrate usage. The addition of 3.0 mM CTAB without PSS resulted in only 46.3% of substrate usage, even though the removals of Cu and TCN were 92.2 and 93.6%, respectively. The presence of thiocyanate ions significantly reduced the removal efficiency due to the competitive interaction with PSAs, whereas the pH of the solution and the temperature did not have any noticeable impact. Tests performed with an industrial effluent corroborated the results obtained with synthetic solutions: PSAs react with copper cyanide to form a precipitate that can be separated from the solution.

Optimizing the parameters of microbial fuel cells using response surface methodology to increase Cr(VI) removal efficiency and power production

Cr(VI) is present naturally as Cr2O72- and its negative charge repels electrons (e-), preventing direct reduction to Cr(III). The Cr(VI) reduction process consumes H+ , suggesting that conventional Cr(VI) reduction techniques a strictly require a low pH, increasing their cost. Therefore, the development of a process that enables Cr(VI) reduction at neutral pH conditions is of interest. In this work, Cu(II) was used as an electron shuttle medium in a microbial fuel cell (MFC). The effects of MFC operating conditions, such as Cu(II)/Cr(VI) ratio, substrate (sodium acetate) concentration and external resistance on the power density (PD) and Cr(VI) removal efficiency were investigated using the response surface methodology (RSM). The maximum Cr(VI) removal efficiency (73%) and power production capacity (30.57 mW/m2) were achieved under pH-neutral conditions with a Cu(II)/Cr(VI) ratio of 1.65, a substrate concentration of 1.36 g/L, and an external resistance of 1360 Ω. The Cr(VI) removal efficiency of the MFC system without added Cu(II) was only 43%, and the power production capacity (15.85 mW/m2) was only half of that under optimal conditions. The removal efficiency of Cu(II) was 100% after seven days. Chromium and copper deposits were observed on the cathode surface, indicating that Cu(II) was deposited on the cathode surface following Cr(VI) removal, eliminating the secondary contamination that is caused by the addition of excess Cu(II). An RSM-optimized MFC system exhibits improved chemical oxygen demand removal, Coulombic efficiency and normalized energy recovery (NER). Its NER is at least 1.5 times higher than that of an unoptimized MFC system, indicating that the MFC most efficiently converts substrates into electrons when the operating conditions are optimized. This work demonstrates that Cu(II) plays a critical role as an electron-shuttle mediator in the removal of Cr(VI). The electron transfer function of Cu(II) increases the efficiency of the reduction that involves Cr(VI), electrons and H+, and eliminates the cost of adding acidic agents, as required in the conventional method in wastewater treatment. The obtained Cu(II)/Cr(VI) ratio is used to determine the maximum amount of Cr(VI) that can be removed by a scaled-up MFC system.

Cu(II) and Cr(VI) Removal in Tandem with Electricity Generation via Dual-Chamber Microbial Fuel Cells

Microbial fuel cells (MFCs) have shown great advantages in electricity production, heavy metal removal, and energy recovery. However, the impact and mechanism of conflicting effects of numerous electron acceptors on heavy metal removal remain unknown. The effects of different initial heavy metal concentrations, cathodic dissolved oxygen, and electrode materials on the electricity generation and heavy metal removal efficiencies of Cu(II) and Cr(VI) were investigated in this study. When the initial concentration of Cr(VI) increased from 10 mg/L to 150 mg/L, the maximum voltage, coulomb efficiency, and maximum power density declined from 99 to 44 mV, 28.63% to 18.97%, and 14.29 to 0.62 mW/m2, and the removal efficiencies of Cu(II) and Cr(VI) decreased dramatically from 98.34% and 99.92% to 67.09% and 37.06%, respectively. Under anaerobic cathodic conditions, the removal efficiency and removal rate of Cu(II) and Cr(VI) were lower than those under aerobic conditions. When the cathode electrode was titanium sheet and graphite plate, the coulomb efficiency and maximum power density increased to 38.18%, 50.71%, 33.95 mW/m2, and 62.23 mW/m2. The removal efficiency and removal rates of Cu(II) and Cr(VI) were significantly increased to 98.09%, 86.13%, and 0.47, 0.50 mg/(L h) with a graphite plate, respectively. The pH of the cathode varied considerably greater as the MFC current increased. Cu(II) and Cr(VI) were removed and reduced to elemental Cu, Cu2O, and its oxides as well as Cr(OH)3 and Cr2O3 precipitates on the cathode electrode by cathodic bioelectrochemical reduction.

Simultaneous removal of multiple heavy metals using single chamber microbial electrolysis cells with biocathode in the micro-aerobic environment

The simultaneous and efficient removal of various heavy metals from wastewater to satisfy the requirements of zero discharge has been a research hotspot and difficult point. In the laboratory scale (0.5 L), the biocathode microbial electrolytic cells (BCMECs) were constructed with the pre-screened heavy metal-tolerant electroactive bacterial, mainly of the Sphingomonas, Azospira and Cupriavidus. The BCMECs system showed a more satisfactory removal effect for multiple heavy metals and organic pollutants. At the auxiliary voltage of 0.9 V and initial concentration of 20 mg L−1, the removal efficiency of Cu, Pb, Zn, Cd and COD were 98.76 ± 0.32%, 98.01 ± 0.76%, 73.58 ± 4.83%, 84.39 ± 5.95%, 77.55 ± 1.51%, respectively. It was found by various characterization techniques (CV, EIS, XPS et al.) that the constructed biocathode has the function of electrocatalytic reduction of heavy metal ions in a micro-aerobic, film-free environment. The positive shift (0.030–0.229 V) of the initial potential for heavy metal reduction and the absence of a significant increase (＜ 10 Ω) in the interfacial resistance indicated a reduction in the total free energy of the reduction reaction, which promotes the reaction and improves the efficiency of heavy metal removal. Bacterial community analysis revealed that the Proteobacteria has been dominant in different heavy metal environments. With the increase of heavy metal concentration, Sphingomonas, Azospira and Cupriavidus showed stronger tolerance and became the dominant genus. This study emphasized the important performance of biocathodes and the effective treatment of heavy metal wastewaters by BCMECs and provided a reasonable way for industrial and mining enterprises to innovate the water treatment process.