Copper Removal Efficiency Research Articles

Effect of Voltage variation on the Geotechnical Properties and Removal Efficiency of Heavy Metal Contaminants from Contaminated Soil using Electrokinetic Remediation Technique

A lot of research work has shown that despite the effectiveness of the electrokinetic remediation technology in decontaminating heavy metal contaminated soils, more work is still required to fully understand the role of voltage in the remediation process. There is need to establish the optimum voltage that would best remove heavy metals from such contaminated soil and its attendant effect on the geotechnical properties of the remediated soil. Effect of voltage variation on the removal efficiency of lead, copper and the geotechnical properties of remediated heavy metal contaminated soil using electrokinetic remediation technique was investigated in this research. The contaminated soil was remediated by applying direct current (DC) to the remediation setup at 0.5V/cm, 1.0V/cm, 1.5V/cm and 2.0V/cm. The concentration of the heavy metals after remediation were determined using the Oxford Instrument Analyzer to evaluate removal efficiency, geotechnical properties tests were also conducted on the soil specimens at each phase of remediation. The results showed that the lead removal efficiency was highest at 2.0V/cm (86%) with the shortest remediation time of 5days and lowest at 0.5V/cm (39%) at 9days. 52% of copper was removed at 2.0V/cm in 5days and 29% at 0.5V/cm after 9days of remediation. At 1.0V/cm, the lead and copper removal efficiency are 75% and 40% respectively. There was no significant change in the Specific Gravity of all the soil samples with the test results lying between 2.0 and 2.2. The soil is generally silty fine sand with not less than 40% passing the sieve no.200 (75micron). 45% passed through sieve 75micron for unremediated soil and slightly reduced to 40%, 40.4% and 40.2% for 30V, 45V and 60V respectively. The soil is non-plastic with the liquid limit of between 25.8% and 29.5% belonging to the A-4 group of soil. The maximum dry density improved across all the three compactive efforts, from 1.8390g/cm3 to 1.8480g/cm3 with WAS compactive effort and from 1.8000g/cm3 to 1.8320g/cm3 with BSL method with an average optimum moisture content of 10%. The CBR values increases with increase in voltage applied. The unsoaked CBR values averagely increased with 31%, 18% and 7% for BSH, WAS and BSL compactive efforts respectively. The durability index with resistances of 89% and 90% to loss in strength was recorded at 1.0V/cm and 1.5V/cm respectively, this, when compared to the resistance to loss in strength of 71% in unremediated soil has respectively 25.3% and 26.8% durability advantages. There was also a consistent increase in the UCS values, from 381kN/m2 to 474kN/m2 and from 351kN/m2 to 447kN/m2 when WAS and BSL methods of compaction were used. Generally, there was improvement in the geotechnical properties of the remediated soil. These improvements are maximum at 1.0V/cm and 1.5V/cm with little or no further improvement at 2.0V/cm. It is recommended that 1.0V and 1.5V are suitable for remediation purpose since it requires low energy consumption.

Polymeric Flocculation as a Sustainable Solution for Heavy Metal Removal from Leachate in Barka Landfill, Oman

Purpose: This study investigates the effectiveness of polymeric flocculation in removing heavy metals from leachate through filtration, sedimentation, and precipitation, aiming to separate and eliminate particulate matter. to separate and remove particulate matter. Method: This study investigated the use of alum and chitosan to remove heavy metals from leachate. The addition of a polymeric flocculant, chitosan, promoted the formation of stable flocs, which effectively removed heavy metals. Chitosan, a natural biopolymer, was found to be a promising alternative to synthetic polymers. Main Findings: The experimental results demonstrated that alum outperformed chitosan in terms of removing heavy metals. Under optimal conditions, an alum dosage of 6 mg/l at a pH of 6.23 resulted in copper and magnesium removal efficiencies of 84% and 92%, respectively. In contrast, the optimal chitosan dosage was 8 mg/l at a pH of 7.5, with copper and magnesium removal efficiencies of 43.1% and 91.8%, respectively. Implications: Leachate treatment reduces heavy metals and organic compounds, controls odors, and generates foam indicating the presence of gases like carbon dioxide and methane. These gases can be harnessed for clean energy production and green hydrogen development. harnessed for clean energy production and green hydrogen development. Novelty: This study is the first to scientifically analyze leachate treatment at the Barka landfill. Chitosan, a natural polymer, effectively removes suspended matter and heavy metals, reducing their concentrations. removes suspended matter and heavy metals, reducing their concentrations.

Optimized combination of zero-valent iron and oxygen-releasing biochar as cathodes of microbial fuel cells to enhance copper migration in sediment

Membrane-less single-medium sediment microbial fuel cells (single-SMFC) can remove Cu2+ from sediment through electromigration. However, the high mass transfer resistance of the sediment and amount of oxygen at the cathode of the SMFC limit its Cu2+ removal ability. Therefore, this study used an oxygen-releasing bead (ORB) for slow oxygen release to increase oxygen at the SMFC cathode and improve the mass transfer property of the sediment. Resultantly, the copper removal efficiency of SMFC increased significantly. Response surface methodology was used to optimize the nano zero-valent iron (nZVI)-modified biochar as the catalyst to enhance the ability of the modified ORB (ORBm) to remove Cu2+ and slow release of O2. The maximum Cu2+ removal (95 %) and the slowest O2 release rate (0.41 mg O2/d·g ORBm) were obtained when the CaO2 content and ratio of nZVI-modified biochar to unmodified biochar were 0.99 g and 4.95, respectively. When the optimized ORBm was placed at the single-SMFC cathode, the voltage output and copper removal increased by 4.6 and 2.1 times, respectively, compared with the system without ORBm. This shows that the ORBm can improve the migration of Cu2+ in the sediment, providing a promising remediation method for Cu-contaminated sediments.

Comparison of Acid- and Base-Modified Biochar Derived from Douglas Fir for Removal of Copper (II) from Wastewater

Copper is a non-biodegradable heavy metal, and high levels in water bodies cause serious environmental and health issues. Douglas fir biochar has a higher number of carboxylic, phenolic, and lactonic groups, which provide suitable active sites for copper removal. Douglas fir biochar (BC) was modified using 20% solutions of KOH (KOH/BC), H2SO4, (H2SO4/BC), and Na2CO3 (Na2CO3/BC). All materials were characterized using SEM, SEM-EDS, FTIR, TGA, XRD, BET, and elemental analysis. These modifications were done to compare the activations of those sites by measuring copper removal efficiencies. KOH/BC, H2SO4/BC, and Na2CO3/BC materials gave surface areas of 389.3, 326.7, and 367.9 m2 g−1, respectively, compared with pristine biochar with a surface area of 578.9 m2 g−1. The maximum Langmuir adsorption capacities for Na2CO3/BC, KOH/BC, BC, and H2SO4/BC were 24.79, 18.31, 17.38, and 9.17 mg g−1, respectively. All three modifications gave faster kinetics at 2 mg/L initial copper concentrations (pH 5) compared with pristine BC. The copper removal efficiency was demonstrated in four different spiked real water matrices. The copper removals of all four water matrices were above 90% at 2 mg/L initial concentration with a 2 g/L biochar dosage. The competitive effects of Pb2+, Zn2+, Cd2+, and Mg2+ were studied at equimolar concentrations of Cu2+ and competitive ions for all four materials.

Efficient Cu(II) removal with boronated zero-valent iron via inhibition of oxygen adsorption and enhanced electron transfer

The inhibition of electron transfer by the iron oxide passivation layer and the competition of oxygen for electrons limited the efficiency of heavy metal removal by zero-valent iron reduction. Herein we synthesized micron zero-valent iron modified with boric acid by mechanical ball milling, and demonstrated its enhanced copper ions removal performance. Compared to pristine ZVI, B-ZVI is approximately 2.6 times more efficient in the removal of copper. Interestingly, copper removal was significantly inhibited under air atmosphere for pristine ZVI. However, for B-ZVI, copper removal efficiency was almost insignificantly different between air and argon atmosphere conditions. Furthermore, the modification of ZVI with boric acid promoted the Cu(II) reduction proportion. Boronated modification effectively inhibited oxygen competition for electrons in removing heavy metals by zero-valent iron, which was conducive to the improvement of the heavy metal removal efficiency and the electron utilization of zero-valent iron. This study elucidated the importance of surface modification on the reactivity of micron-sized zero-valent iron and provided an efficient heavy metal removal strategy with zero-valent iron for environmental remediation.

Modelling and optimization of copper removal from water using carbon nanotubes with RSM and ANN

In this study, it was aimed to remove heavy metal copper from aqueous solutions by using MWCNT-OH, which is a multi-walled carbon nanotube. Modelling and optimization were performed using the Response Surface Method (RSM) and Artificial Neural Networks (ANN). Model equations were derived by both methods. ANOVA analyses were performed with RSM to determine the significance of the parameters on removal efficiency and adsorption capacity. Contour graphs showing the binary parameter interactions were obtained. Optimization was carried out to obtain the maximum removal efficiency and maximum adsorption capacity using both RSM and ANN. Using RSM and ANN, the maximum copper removal efficiencies were obtained at 45.1% and 39.1%, while the maximum adsorption capacities were found to be 16.7 mg/g and 17.12 mg/g, respectively. In addition, test experiments and modelling methods were compared, revealing that the modelling capability of ANN was superior to that of RSM.

Copper removal from aqueous solutions by white rot fungus Pleurotus ostreatus GEMB-PO1 and its potential in co-remediation of copper and organic pollutants

Addressing the environmental contamination from heavy metals and organic pollutants remains a critical challenge. This study explored the resilience and removal potential of Pleurotus ostreatus GEMB-PO1 for copper. P. ostreatus GEMB-PO1 showed significant tolerance, withstanding copper concentrations up to 2 mM. Its copper removal efficiency ranged from 64.56 % at 0.5 mM to 22.90 % at 8 mM. Transcriptomic insights into its response to copper revealed a marked upregulation in xenobiotic degradation-related enzymes, such as laccase and type II peroxidases. Building on these findings, a co-remediation system using P. ostreatus GEMB-PO1 was developed to remove both copper and organic pollutants. While this approach significantly enhanced the degradation efficiency of organic contaminants, it concurrently exhibited a diminished efficacy in copper removal within the composite system. This study underscores the potential of P. ostreatus GEMB-PO1 in environmental remediation. Nevertheless, further investigation is required to optimize the simultaneous removal of organic pollutants and copper.

Harnessing graphene oxide-enhanced composite metal-organic frameworks for efficient wastewater treatment

The issue of carwash wastewater emerges as a pressing environmental concern on a global scale, primarily due to the intricate nature of its pollutants, which makes effective treatment a formidable challenge. In the face of this complex scenario, the pursuit of an efficient treatment methodology assumes paramount importance. In response to this complex scenario, this study embarked on an exploration of a novel polymeric adsorbent material synthesized from Zeolitic Imidazolate Framework-67, Zeolitic Imidazolate Framework-8, Polyethersulfone, and graphene oxide in a fixed-bed treatment system for carwash wastewater. The investigation encompassed three distinct filter column depths, measuring 8 cm, 12 cm, and 16 cm, respectively. With an increase in filter depth from 8 cm to 16 cm, notable improvements were observed in the removal efficiencies for most contaminants. Notably, oils/grease removal showed an increasing trend with column depth, reaching 95.4%, 98.6%, and 100% for 8 cm, 12 cm, and 16 cm depths, respectively. TSS and Turbidity removal efficiencies remained consistently high at 100% across all depths, showcasing effective removal of solid particulate matter. Copper and Zinc removal efficiencies increased with deeper column depths, reaching values of 80.4%–89.9% and 79.6%–90.3%, respectively. Surfactants exhibited efficient removal, with values ranging from 90.6% to 96.6%. Total Dissolved Solids removal efficiency increased from 71.6% to 83.4% as column depth increased. Similarly, Chemical Oxygen Demand, Biochemical Oxygen Demand, total organic carbon, and phosphates removal efficiencies showed improvement with increasing column depth, reaching values of 95.4%, 98.3%, 98.8%, and 89.3%, respectively. Moreover, The composite MOF beads demonstrated significant adsorption capacities in carwash wastewater treatment, with a noteworthy 35.08 mg/g for Oils/Grease and 28.12 mg/g for Biochemical Oxygen Demand, highlighting their efficiency in removing hydrophobic contaminants and organic pollutants.The derived results highlight the potential of the composite material for carwash wastewater treatment towards advancing the field of wastewater treatment.

Removal of Copper (II) from Mining Waste Water by Adsorption onto Activated Carbons Produced from Hazelnut Shell

Mining wastewater is one of the most important environmental problems today because of the heavy metal ions they contain. Wastewaters containing heavy metal pollution are generally acidic waters with low BOI (Biochemical oxygen demand) value. Various processes such as mineral processing waste disposal, illegal mining, domestic waste disposal, and others result in the release of heavy metals into the waters. One of the heavy metals that cause problems in terms of environmental pollution is copper. Copper metal is commonly found in metal and metal plating industry wastewater. Although metal industry wastewater is low in quantity, they are toxic waste. For this reason, industrial wastewater must be treated before being discharged into the receiving environment. In this study, the amount of Cu in wastewater of the mining operation in Gümüşhane was determined. Heavy metal pollution was eliminated with an adsorbent produced from agricultural biowaste. It has been tried to determine the amount of adsorbent, contact time, and treatment efficiency of wastewater at different pHs of activated carbon produced by chemical activation. As a result, an average of 88.7% efficiency was obtained with activated carbon activated with KOH, while 22,4% copper removal efficiencies were obtained with raw material (hazelnut shell) used without activation. It was determined that the appropriate working pH was 5,0; the amount of adsorbent was 0.05 g and Qmax 121,2. As a result, in this study, very low-cost adsorbents were produced using waste hazelnut shells, and a biotechnological approach was proposed to clean copper-containing wastewater.

Adsorption removal of copper (II) and chromium (VI) from wastewater by Fe3O4-loaded granular activated carbon

Abstract Combining with the characteristics of Fe3O4 and activated carbon, magnetic granular activated carbon (GAC–Fe3O4) was prepared by chemical coprecipitation. With GAC–Fe3O4 as the adsorbent, the effects of GAC–Fe3O4 dosage, the initial pH of wastewater temperature, and the initial concentration of copper (II) and chromium (Ⅵ) on the removal performance were explored. The adsorption process of copper (II) and chromium (VI) on magnetic GAC was studied using adsorption kinetics, adsorption isotherms, scanning electron microscopy, and infrared spectroscopy. The experimental results indicate that among these influencing factors, the pH value of wastewater plays a vital role in the removal efficiency. When the pH value was 6 and 2, the initial concentration of copper (II) and chromium (VI) ions was 5 ppm, the optimum removal efficiencies of copper (II) and chromium (VI) were 99.98 and 96.39%, respectively. As to the adsorption mechanism of GAC–Fe3O4, the adsorption of copper (II) and chromium (VI) in wastewater was more consistent with the Langmuir model. The adsorption process in this study can be well explained by the pseudo-second-order kinetic model.

Rapid and effective removal of copper, nitrate and trichloromethane from aqueous media by aluminium alloys

Zero-valent iron (ZVI) has been extensively studied for its efficacy in removing heavy metals, nitrate, and chlorinated organic compounds from contaminated water. However, its limited effectiveness due to rapid passivation and poor selectivity is prompting for alternative solutions, such as the use of aluminium alloys. In this study, the efficacy of five distinct aluminium alloys, namely Al–Mg, Al–Fe, Al–Cu, and Al–Ni, each comprising 50 % Al by mass at a concentration of 10 g/L, was assessed using copper, nitrate and trichloromethane (TCM) as model contaminants. Results show that chemical pollutants reacted immediately with Al–Mg. On the contrary, the remaining three alloys exhibited a delay of 24 h before demonstrating significant reactivity. Remarkably, Al–Mg alloy reduced nitrate exclusively to ammonium, indicating minimal preference for nitrate reduction to N2. In contrast, the Al–Cu, Al–Ni, and Al–Fe alloys exhibited N2 selectivity of 3 %, 5 %, and 19 %, respectively. The removal efficiency of copper, nitrate and TCM reached 99 % within 24 h, 95 % within 48h and 48 % within 48h, respectively. Noteworthy findings included the correlation between Fe concentration within the Al–Fe alloy and an increased N2 selectivity from 9.3 % to 24.1 %. This resulted in an increase of Fe concentration from 10 % to 58 % albeit with a concurrent reduction in reactivity. Cu2+ removal by Al–Fe alloy occurred via direct electron transfer, while the removal of nitrate and TCM was facilitated by atomic hydrogen generated by the alloy's hydrolysis. Intriguingly, nitrate and TCM suppressed Cu2+ reduction, whereas Cu2+ improved nitrate reduction and TCM degradation. These findings demonstrate the great potential of Al–Mg and Al–Fe alloys as highly efficient agents for water remediation.

Influence of remediation by electrokinetic on the chemical and geotechnical properties of clayey soil contaminated by copper sulfate

The enhanced electrokinetic (EK) technique is an innovative approach and increasingly used in remediation of the fine-grained texture soils contaminated with different types of contaminant. In this study, the EK is enhanced by adding an intermediate compartment and using purging solutions at the electrode’s compartments. The natural clayey soil samples were obtained from Al-Ahadab oil field and artificially contaminated with two ratios of copper sulfate (66666.67 and 26666.67 mg/kg). The feasibility of using EK technique was evaluated by the efficiency of extracting copper from soil and the magnitude of recovery in the geotechnical properties of soil. The duration of remediation was continued for about 240-250 hours depending either on the continuity of electroosmosis flow or reach a constant rate of electrical current. The removal efficiency of copper from contaminated soil samples was ranged from 98.4% to 99.6%. The EK remediation technique proved a marginal impact on the specific gravity and Atterberg’s limits, but it has a significant effect on the shear strength parameters and compressibility of soil. Furthermore, the EK technique can be considered an efficient method for removing the low and high concentrations of copper sulfate from clayey soil of low permeability.

Optimizing copper removal from synthetic water using electrocoagulation and response surface methodology

The purification of water and wastewater requires a lot of energy and large amounts of chemicals can still be used with conventional techniques. The electrocoagulation (EC) method, an electrochemical treatment approach, has been suggested as a more cost-effective and environmentally friendly alternative. In this study, the removal of copper from synthetic water was investigated using EC technique. Box-Behnken Design (BBD) and Response Surface Methodology (RSM) were applied to optimize operating parameters such as current density, electrolysis time and initial pH. Analysis of variance (ANOVA) was used to assess the effect of factors and their interactions, and multiple regression analysis was used to fit it to a second-order polynomial equation. According to the results, current density had the greatest impact on copper removal. A current density of 7.24 mA/cm², a reaction time of 27.43 minutes, and an initial pH value of 7.56 were determined to be optimal conditions. Under these optimal conditions, the copper removal efficiency was 97.5%. Therefore, EC combines with RSM is an efficient treatment approach for copper-contaminated water.

Removing DOM from chloride modified hydrochar could improve Cu2+ adsorption capacity from aqueous solution

The behavior and composition of hydrochar-based dissolved organic matter (DOM) would affect the efficiency of copper (Cu) removal from wastewater through adsorption. In this study, the reed was hydrolyzed in the presence of feedwater with and without ZnCl2, FeCl3, and SnCl4 to produce pristine hydrochars (PHCs), which were named H2O-HC, ZnCl2-HC, FeCl3-HC, and SnCl4-HC. After removal of DOM, washed hydrochars (WHCs) were obtained, labelled as W–H2O-HC, W-ZnCl2-HC, W-FeCl3-HC, and W-SnCl4-HC. The release dynamics of DOM from PHCs were analyzed, and the adsorption behaviors of Cu2+ on both PHCs and WHCs were investigated. The results showed that chloride-modifications were beneficial for the porosity, specific surface area (SSA), and functional groups of WHCs. Meanwhile, the quantity of hydrochar-based DOM was significantly affected by chloride-modifications. In particular, the relative contents of Ar–P and Fa-L in the DOM released from hydrochars varied with time and modification. Furthermore, the Qe of Cu2+ adsorption on WHCs followed the order of W-SnCl4-HC > W-FeCl3-HC > W-ZnCl2-HC > W–H2O-HC at 15 °C. Compared to PHCs, the adsorption capacity of Cu2+ on WHCs was improved by 7.15–119.77% at the temperature of 35 °C. Simultaneously, the adsorption capacity of Cu2+ in WHCs showed a significant correlation with the SSA via physical adsorption (P < 0.05). Moreover, XPS analysis revealed that Cu2+ adsorption also occurred via complexation and chelation through newly formed Cu–O group between W-SnCl4-HC and Cu2+. Notably, the increase of Cu2+ adsorption in WHCs was significantly correlated with the release of Fa-L and Ar–P from PHCs (P < 0.05). This study found that the content and composition of hydrochar-based DOM could be a major driving factor for Cu2+ adsorption.

Effects of nitric oxide on the phytoremediation of swine wastewater by Pistia stratiotes under copper stress

Nitric oxide (NO) is widely present in wastewater. As a signaling molecule, NO influences many aspects of phytoremediation, especially in response to heavy metal stress. The current understanding of the impact of NO on the tolerance of Pistia stratiotes and other plants to Cu2+ in swine wastewater is limited. This study aimed to investigate the impact of NO on the physiological response of Pistia stratiotes and its efficacy in removing pollutants from swine wastewater under varying concentrations of Cu2+ ranging from 1~4 mg/L. The findings showed that NO treatment reduced copper stress at 2~4 mg/L Cu2+ while increasing oxidative stress at 1 mg/L Cu2+. According to an analysis of physiological parameters and copper concentrations, the results found a significant correlation between increased copper tolerance and elevated levels of antioxidants and transport coefficients. The morphology of copper and the results of the principal component analysis indicate that NO facilitated the humification process of the dissolved organic matter. The investigation found that the removal efficiencies of NH3–N, NO3–N, and total phosphorus in NO treatment were enhanced to 95.76%, 88.72%, and 91.89%, respectively. Collectively, it was determined that NO is a regulator of phytoremediation to copper in wastewater via promoting antioxidative, copper transport, DOM bound, nutrients uptake, thus adequate amount could improve the tolerance of Pistia stratiotes to Cu2+. This study is expected to provide a theoretical basis for rationally regulating NO concentration and effectively improving the removal efficiency of copper in swine wastewater.

Effect of biocomposite production factors on the development of an eco-friendly chitosan/alginate-based adsorbent with enhanced copper removal efficiency

Nowadays, wastewater treatment is a critical concern, particularly regarding the removal of heavy metals through adsorption methods. Extensive research has been conducted on obtaining high-yield and environmentally friendly adsorbents. Natural polymer adsorbents especially have shown promise in ion and organic molecule adsorption. To enhance the practical applicability of adsorbents, the combination of biopolymers to form biocomposites is a promising alternative. In this study, adsorbents based on a 1:1 wt./wt. of chitosan (CS) and alginate (SA) were prepared. The influence of the regeneration route and drying conditions on the copper adsorption capacity was investigated, along with reaction parameters such as contact time, adsorbent particle size, and pH. The highest adsorption capacity was observed in the composite material obtained through a one-pot regeneration process and freeze-dried. The CSAR3L sample exhibited a remarkable adsorption capacity of 288 mg Cu(II)/g after 360 min at 25 °C. The synergistic effect between the CS and SA precursors was confirmed by analyzing the individual precursors and their mechanical mixture. The initial adsorption rates at pH 6 followed the order: CSAR3-L > Bk-CSR3L > Bk-SAR3L + Bk-CSR3L > Bk-SAR3L. The physicochemical and morphological properties of the materials were studied by FTIR, XRD, DLS, XPS, optical microscopy, EDS-SEM, elemental chemical analysis, and TGA-DTG. The utilization of different drying methods resulted in the formation of calcium carbonate crystalline phases in the as-prepared materials, thus creating substantial adsorption active sites. After the adsorption process, hydroxylated copper sulfate phases and a significant decrease in calcium concentration were observed, indicating that an ion exchange adsorption mechanism occurred. The analysis of adsorption kinetics and the shape of the adsorption isotherms, in agreement with the characterization results, suggested the presence of multiple active sites and the formation of a chemisorption monolayer.

Electrocoagulation/flotation process for removing copper from an aqueous environment

The presence of copper in aqueous environments such as drinking water has led to several environmental effects, such as flavor and odor. The increase in Cu levels in ground and surface water has been mainly attributed to anthropogenic and natural sources. Consequently, this applied-analytical study aimed to investigate copper removal from urban drinking water through batch reactor electrocoagulation/flotation (ECF) with aluminum electrodes. The copper removal efficiency was evaluated under various operating conditions of current density (0.8–2.4 mA/cm2), initial concentration (1–100 mg/L), pH (3.5–10.5), and time (10–30 min). Cu was determined using the method outlined in the standard procedures (3500-Cu B at 4571 nm). The results indicated that increasing the current density from 0.8 to 2.4 mA/cm2 and the reaction time from 10 to 30 min improved Cu+2 removal efficiency (from 95 to 100%). In addition, the results demonstrated that Cu+2 reduction is 100% with an initial concentration of 100 mg/L, a pH of 7.5, a reaction time of 30 min, and an anode current density of 2.4 mA/cm2. The Taguchi method results for copper removal efficiency show that reaction time is the most significant variable. Furthermore, Cu removal kinetics models in an ECF reactor are second-order (R2 > 0.92). The Cu removal in the ECF reactor is due to redox and adsorption. Moreover, the operational costs of Cu treatment with Al electrode pairs are estimated to range from 8857 and 9636 Rial/kg of Cu removed. Thus, it can be concluded that the ECF process is very efficient in removing Cu from aqueous environments under optimum conditions.

Continuous single-stage elemental sulfur reduction and copper sulfide precipitation under thermoacidophilic conditions

Metal sulfide precipitation is a viable technology for high-yield metal recovery from hydrometallurgical streams, with the potential to streamline the process design. A single-stage elemental sulfur (S0)-reducing and metal sulfide precipitating process can optimize the operational and capital costs associated with this technology, boosting the competitiveness of this technology for wider industrial application. However, limited research is available on biological sulfur reduction at high temperature and low pH, frequent conditions of hydrometallurgical process waters. Here we assessed the sulfidogenic activity of an industrial granular sludge previously shown to reduce S0 under hot (60–80 °C) and acidic conditions (pH 3.6). A 4 L gas-lift reactor was operated for 206 days and fed continuously with culture medium and copper. During the reactor operation, we explored the effect of the hydraulic retention time, copper loading rates, temperature, and H2 and CO2 flow rates on the volumetric sulfide production rates (VSPR). A maximum VSPR of 274 ± 6 mg·L−1·d−1 was reached, a 3.9-fold increase of the VSPR previously reported with this inoculum in batch operation. Interestingly, the maximum VSPR was achieved at the highest copper loading rates. At the maximum copper loading rate (509 mg·L−1·d−1), a 99.96% copper removal efficiency was observed. 16 s rRNA gene amplicon sequencing revealed an increased abundance of reads assigned to Desulfurella and Thermoanaerobacterium in periods of higher sulfidogenic activity.

Structural design of SiO2/TiO2 materials and their adsorption-photocatalytic activities and mechanism of treating cyanide wastewater

Cyanide wastewater contains free cyanide and metal-cyanide complexes, which need to be treated before they are discharged. In this study, we synthesized a mesoporous SiO2/TiO2 material, and used it to treat cyanide wastewater by an adsorption-photocatalytic oxidation synergistic method. The effects of material structure and TiO2 loading method on the removal efficiencies of cyanide, copper and zinc were investigated. The experiments proved that the gel-sol method was more effective, and the kinetic and thermodynamic analysis of dark adsorption process was performed. The results indicated that the dark adsorption kinetics conformed to the pseudo second order, and the thermodynamics indicated that it was an endothermic process. The experimental data stated clearly that the degradation efficiency of total cyanide reached 95.98% and the removal efficiencies of copper and zinc reached 92.70% and 98.69% under the conditions of dark adsorption for 0.5 h and photocatalysis for 4.0 h, respectively. The cyanide was chemisorbed on the material surface. XPS, XRD analysis indicated that cyanide was finally decomposed into NO3− and CO2; copper and zinc were removed in the form of CuO, Cu2O, ZnO.

Performance of electrocoagulation process for copper removal in simulated artisanal and small-scale mining wastewater

Electrocoagulation treatment was applied in the simulated artisanal and small-scale mining wastewater for 60 minutes. Copper concentration of 625 mg.L−1 was used in the study which was based on the real artisanal and small-scale mining wastewater (conductivity = 13 mS.cm−1, initial pH = 10) collected from Paracale, Camarines Norte, Philippines. Batch experiments using a pair of iron electrodes with an interelectrode distance of 2 cm were used for this study and we have determined the optimized conditions such as conductivity, initial pH, and current density for the various electrocoagulation runs. Decreasing initial conductivity and pH of real mining wastewater while increasing current density favours higher removal efficiency. With the conductivity of 3.5 mS.cm−1, initial pH of 9, and current density of 33.5 mA.cm−2, copper removal efficiency was 93.5%. Based on these operating conditions, energy consumption was 36.82 kWhr.m−3 and electrodes consumption were 2.09 kg.m−3. This study revealed that electrocoagulation is feasible to treat higher concentrations of copper present in mining wastewater.