Copper Removal Efficiency Research Articles

Microalgal and cyanobacterial strains used for the bio sorption of copper ions from soil and wastewater and their relative study

Heavy metals and other organic pollutants are the hazardous materials causing soil and water pollution, hence, bioremediation of these components is a matter of concern for environmental biotechnologists. Twenty one microalgal and cyanobacterial strains were evaluated for removal of copper from aqueous solutions and soil containing 10 ppm copper. 5 out of 21 strains have shown comparatively higher tolerance to copper stress. The biosorption capabilities of all the five strains were assessed using techniques like ultraviolet (UV) spectrophotometers, scanning electron microscope (SEM), inductively coupled plasma mass spectrometry (ICP-MS), and confocal Microscopy. It was found that the five selected strains could grow normally upon incubating with 20 ppm of Cu. Copper removal efficiencies of these microalgae (S. obliquus, A. braunii, C. fusca, L. JSC-1 and C. saccharophila in water were 99.9, 99.3, 97, 96.7, and 96%, while for soil was 73, 75, 71, 70, 68%, respectively. A minor leakage of nucleic acid and protein were detected with time. Furthermore, no any visible morphological changes were observed after six days of treatment, while minor changes were noticed after 12 days in water, and severe morphological deformations occurred after 24 days of bioremediation in soil. Our findings reveal that the selected microalgal strains have high potential for Cu bioremediation at certain concentration for 12 days exposure from water and 24 from soil.

Copper and Zinc Removal Efficiency of Two Reactive Filter Media Treating Motorway Runoff—Model for Service Life Estimation

The predominant techniques used for road runoff treatment are sedimentation and filtration. In filtration systems, the ability of the media to adsorb the contaminants is a finite process. Consequently, construction, operation and maintenance managers of such systems should know in advance the service life, i.e., when the used medium should be replaced, and associated costs of operation and maintenance. A batch experiment followed by a packed bed reactor (PBR) experiment addressed the kinetics of the studied media argon oxygen decarburization slag (AOD) and Polonite, followed by the development of a 1D-model to describe the change of concentration of Cu and Zn within time. The batch test results showed that Cu and Zn adsorption followed the Freundlich isotherms for AOD and Polonite. Those results coupled with the linear driving force model and the developed model resulted in good agreement between the PBR results and the simulation. The model was capable to predict (i), the service life at the hydraulic load of 0.18 m/h for AOD (Cu: 395 d; Zn: 479 d) and Polonite (Cu: 445 d; Zn: 910 d), to show (ii) the profile concentration in the PBR within time and the gradient of the concentration along the height of the reactor.

Treatment of acid rock drainage using a sulphate-reducing bioreactor with a limestone precolumn

ABSTRACT Sulphate reducing bacteria (SRB) offer promise for the treatment of mine waste due to their effectiveness removing toxic heavy metals as highly insoluble metal sulphides and their ability to generate alkalinity. The main objective of this study was to develop a treatment composed of a sulphate-reducing bioreactor with a limestone precolumn for the removal of Cu(II) from a synthetic ARD. The purpose of the limestone column was to increase the pH values and decrease the level of Cu in the effluent to prevent SRB inhibition. The system was fed with a pH-2.7 synthetic ARD containing Cu(II) (10–40 mg/L), sulphate (2000 mg/L) and acetate (2.5 g COD/L) for 150 days. Copper removal efficiencies in the two-stage system were very high (95–99%), with a final concentration of 0.53 mg/L Cu, and almost complete removal occurred in the limestone precolumn. In the same manner, the acidity of the synthetic ARD was effectively reduced in the limestone precolumn to 7.3 and the pH was raised in the bioreactor (7.3–8.0). COD consumption by methanogens was predominant from day 0–118, but SRB dominated at the end of the experiment (day 150) when the average COD removal and sulphide production were 74.8% and 61.7%, respectively. Study of the microbial taxonomic composition in the bioreactor revealed that Methanosarcina and Methanosaeta were the most prevalent methanogens while the genera Desulfotomaculum and Syntrophobacter were the dominant SRB. Among the SRB identified Desulfotomaculum intricatum (99% identity) and Desulfotomaculum acetoxidans (96%) were the most abundant sequences of bacteria capable of using acetate.

Biosorption of copper ions through microalgae from piggery digestate: Optimization, kinetic, isotherm and mechanism

The remediation of heavy metal contaminated wastewater using microalgae has attracted more and more attention. In this study, the removal of copper (II) from piggery digestate by Desmodesmus sp. CHX1 was investigated. Results showed that the optimal conditions for copper (II) removal by Desmodesmus sp. CHX1 were pH of 6.00, microalgae inoculation concentration of 0.41 g/L and treatment time of 4 d, with the copper removal efficiency of 88.35%. The biosorption process of copper (II) by Desmodesmus sp. CHX1 under optimal conditions well followed the pseudo second order model, with the rate constant and the theoretical and experimental biosorption capacity of 0.15 mg/(L·h) and 0.85 mg/L, respectively. The isotherms adsorption of copper was described well by the Langmuir model, biosorption maybe dominated the adsorption process. The affinity of Cu2+ by functional groups in the microalgal cell walls was the main mechanism for copper removal by Desmodesmus sp. CHX1.

Copper and Lead Ions Removal by Electrocoagulation: Process Performance and Implications for Energy Consumption

Electroplating wastewater contains high amount of heavy metals that can cause serious problems to humans and the environment. Therefore, it is necessary to remove heavy metals from electroplating wastewater. The aim of this research was to examine the electrocoagulation (EC) process for removing the copper (Cu) and lead (Pb) ions from wastewater using aluminum electrodes. It also analyzes the removal efficiency and energy requirement rate of the EC method for heavy metals removal from wastewater. Regarding this matter, the operational parameters of the EC process were varied, including time (20−40 min), current density (40−80 A/m2), pH (3−11), and initial concentration of heavy metals. The concentration of heavy metals ions was analyzed using the atomic absorption spectroscopy (AAS) method. The results showed that the concentration of lead and copper ions decreased with the increase in EC time. The current density was observed as a notable parameter. High current density has an effect on increasing energy consumption. On the other hand, the performance of the electrocoagulation process decreased at low pH. The higher initial concentration of heavy metals resulted in higher removal efficiency than the lower concentration. The removal efficiency of copper and lead ions was 89.88% and 98.76%, respectively, at 40 min with electrocoagulation treatment of 80 A/m2 current density and pH 9. At this condition, the specific amounts of dissolved electrodes were 0.2201 kg/m3, and the energy consumption was 21.6 kWh/m3. The kinetic study showed that the removal of the ions follows the first-order model.

Copper and nickel removal from plating wastewater in the electrodialysis process using a channeled stack

Electrodialysis (ED) is an advanced separation process used to treat industrial wastewater using potential differences. In this study, flow rates within the stack were increased by creating a flow channel to increase the limiting current density (LCD). Increasing the flow rate within the stack increases the diffusion flux, which leads to an increase in LCDs. Experiments show that the applied voltage of the flow-accelerated stack was improved by 12.2% compared to the stack without a flow channel, but the LCD decreased by 3.6%. The removal efficiency of both copper and nickel between the two stacks was greater than 95.6%, with no significant difference. However, the concentration rate of ions was superior in the stack without a flow channel. This may be attributed to the fact that the applied voltage increases when the channel is attached, resulting in differences in the separation rate and the resulting concentration polarization. In terms of the current efficiency, the channel-less stack was found to be 42.5% better than the channeled stack. It would be desirable to apply voltages below the LCDs as those exceeding LCDs at the same membrane flow rate would significantly reduce the economic feasibility.

Insights into enhanced electrokinetic remediation of copper-contaminated soil using a novel conductive membrane based on nanoparticles.

Electrokinetic remediation is a process in which a direct electric current is applied across a section of contaminated soil to remove metals. To improve the electrokinetic remediation in this study, a conductive membrane was fabricated via in situ chemical polymerization employing pyrrole and copper oxide nanoparticles. The fabricated membrane was placed in an electric field as part of the electrode structure. A physical model was constructed and filled with copper-contaminated kaolinite in the concentration of 200mg/kg. To control the pH, 0.1M citric acid and 0.01M potassium chloride were used as the electrolyte solutions. Experimental parameters such as voltage, current, pH, EC, drained flow, and copper concentration were measured. The results showed that the minimum surface resistivity of the fabricated membrane under a maximum pressure of 8.2kPa was 2.55 kΩ/m2. The experimental results demonstrated that the use of citric acid as an electrolyte was more useful to desorb the copper due to the formation of the copper-citrate complex. When employing the fabricated membrane, the copper removal increased from 13% (in CT-2) to 63% (in GM-2), while the removal of copper using potassium chloride electrolyte increased from 42% (in CT-1) to 52% (in GM-1). The highest power consumption was obtained in experiments using citric acid. Due to the higher removal efficiency of copper in GM-2, the energy utilization efficiency (β) increased and reached 29.9 near β value of GM-1 with the lowest power consumption.

New strategy to enhance heavy metal ions removal from synthetic wastewater by mercapto-functionalized hydrous manganese oxide via adsorption and membrane separation.

The development of efficient materials and methods for the elimination of heavy metals contamination from water bodies is increasingly demanded as these toxic cations can acute diseases to humans or make serious threat to the environment. The aim of this research is to evaluate the effectiveness of the organosilane coupling agent for the modification of hydrous manganese oxide and the application of the functionalized nanoadsorbent for the removal of nickel and copper ions from synthetic wastewater samples. The synthesized thiol-functionalized hydrous manganese oxide was characterized in terms of their morphology, surface area, functional groups, surface elemental compositions, and the structural properties. In the adsorption process of Ni(II) and Cu(II), the effective parameters including the initial metal cation concentration (20-150 mg/L), operation temperature (298-318 K), and the contact time at the optimum pH were investigated. The uptake of Ni(II) and Cu(II) ions on the prepared adsorbents followed by the Freundlich isotherm model reveals the heterogeneous adsorption, with the adsorption capacities of 24.96 mg/g and 31.2 mg/g for the modified adsorbent and 23.92 mg/g and 29.6 mg/g for the virgin adsorbent, respectively. Based on the results, both the virgin and the functionalized adsorbents exhibited high affinity to copper ions than nickel in the single-component system. Kinetic experiments of both metal ions clarified that the experimental data was well predicted by pseudo-second-order model and the equilibrium was achieved after 10 min of contact time. Additionally, the incorporation of the as-prepared adsorbents in the electrospun nanofibers membrane matrix showed the promising potential for the removal of metal cations. The nickel and copper removal efficiency by the membranes containing 1.5 wt% of the modified adsorbent was 80% and 89%, respectively which implying that the modified adsorbent could be employed more efficiently in other treatment techniques for the removal of metallic pollutants. The modification of hydrous manganese oxide by the functional mercaptosilane increases the adsorption sites for trapping the metal ions and improves the adsorption capacity, making high capability for the removal of metal ions from the effluent.

Green synthesis of bio-functionalized nano-particles for the application of copper removal – characterization and modeling studies

Green technology for the synthesis of nanoparticles has gained momentum due to its cost-effectiveness and eco-friendly nature. In this research study, silver nanoparticles (AgNps) were synthesized using an eco-friendly biological method involving the use of marine algae, Halimeda gracilis. The surface properties of the synthesized silver nanoparticles were studied using UV–visible spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy methods. During the synthesis of nano particles, the parameters namely temperature (30 °C to 90 °C), pH (6–10), silver nitrate (AgNO3) concentration (1–3 mg/ml) and quantity of algal extract (1–3 ml) were optimized to improve the production of AgNPs. The application of the synthesized silver nanoparticles for the adsorptive removal of copper from aqueous and industrial wastewater was investigated. Intra-particle diffusion mechanism was identified to be controlling step in metal removal. Regeneration of sorbent was carried out using 2.0 M HCl and the reusability was verified for 6 cycles. A removal efficiency of copper (64.8%) from electroplating wastewater demonstrated the industrial application potential of the synthesized silver nanoparticles.

Removal of Heavy Metals from Industrial Wastewater by Chemical Precipitation: Mechanisms and Sludge Characterization

Chemical precipitation using lime (Ca(OH)2), caustic soda (NaOH) and soda ash (Na2CO3) for the removal of simultaneous heavy metals (Cu(II) and Zn(II)) from industrial wastewater of the cable industry was carried out in laboratory by jar tests. For each reagent used, an improvement in copper and zinc removal efficiency was obtained by increasing the precipitating reagent dose (10–400 mg/L). Efficiencies of over 90% can be achieved. Chemical precipitation efficiency is related to the pH of the treatment. At a high final pH level (8 < pH < 10), the removal efficiency of copper for each precipitating agent is slightly higher than that of zinc and the residual metal contents were in conformity with industrial discharge standards. In sludge product, zinc and copper were precipitated as amorphous hydroxides including Zn(OH)2 and Cu(OH)2. Based on XRD analysis, the presence of an amount of other additional phases was noticed for copper. SEM images show that sludges produced are not large in size and are compact in structure. Corresponding EDX (energy-dispersive X-ray spectroscopy) shows that the amount of copper is higher than the amount of zinc in all recovered sludge. Wastewater treatment with soda ash resulted in a lower volume and a large product size of sludge. As a result, drying steps can be less expensive. This is a significant advantage comparably with the other precipitating agents. Soda ash may be considered as cost-effective precipitating agent for Cu(II) and Zn(II) in the industrial wastewater of the cable industry.

Adsorptive-photocatalytic performance and mechanism of Me (Mn,Fe)-N co-doped TiO2/SiO2 in cyanide wastewater

In this study, Me (Mn, Fe)-N co-doping is used to improve the treatment efficiency of TiO2/SiO2 on cyanide wastewater, and to explore the reasons for the change in the catalytic performance of the material. The characteristics of the materials are studied by field emission scanning electron microscopy (FESEM)/ energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Brunner−Emmet−Teller (BET), Thermal gravimetric analyzer (TGA) and UV–vis spectrometer, which indicate that TiO2 is anatase type with a particle size of 10–11 nm; Doping elements (Fe, N, and Mn) are well dispersed in the material; Fe or Mn doping can increase the specific surface area of TiO2, while N doping has the opposite effect. Further, the comparison of the treatment effects of cyanide wastewater by TiO2/SiO2 doped with single (N, Fe, Mn) and co-doped with Me (Mn, Fe)-N demonstrates that the materials co-doped with Mn-N possesses the most efficient photocatalytic performance. The degradation efficiency of cyanide reaches 97.09% and the adsorption removal efficiencies of copper and zinc ions reach 88.54% and 100% under light irradiation within 2 h. The mechanism of Mn-N co-doped synergistic catalysis has been studied by combining X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). This indicates that the reason for the significant improvement of the photocatalytic performance of the material is that co-doping produced a new electronic states that overlaps the valence band of TiO2, which promotes the transfer of photogenerated carriers and reduces the electron-hole recombination. This work can efficiently and cleanly decompose cyanide while adsorbing and removing heavy metals, which may be of great significance to the development of the gold industry.

Electro-Kinetic Removal (EKR) of Heavy Metals from Contaminated Soil using Palm Fibers and Organic Material

The heavy metals that are contaminating the soil considered a global problem and especially in Iraq. One of the latest techniques is EKR that can hand a senior promise to clean the contaminated soil with heavy metals. Iraq is the top country in terms of the number of palm trees and the dates that are produced each year, which eliminates thousands of tons of waste are eliminated. This study involves, firstly, mediating an EKR off-site pilot study of impact assessment of the organic material in the soil at a pH of 3. Regent HNO3 and diluted NaOH were chosen to set the samples of distilled water, reaching the desired pH value. Secondly, test the capacity of date palm fibers (DPF) as a low cost, obtainable, and eco-friendly invert osmosis blocker. In this pH 3, organic removal of copper is more active than without the organic material of the same ph; 50 %, 47%, on the way. However, it was concluded that in Iraq, the utilization of organic materials and fibers of the palm are available at low cost, and materials of eco-friendly have succeeded to improve the removal of copper method in the EKR Reactor; via raising the efficiency of copper (%R) removal to be around 50%.

Optimization of process conditions to improve copper adsorption capacity of raw and treated Algerian bentonite: Characterization, kinetics and equilibrium study

Raw bentonite (RB) locally available in Mostaganem (Algeria) deposit has been treated in the presence of NaOH (B-NaOH), MgCl2 (B-MgCl2) and H2SO4 (B-H2SO4) to improve its adsorption ability for the removal of copper ions from aqueous solutions. Characterization of all adsorbents supported montmorillonite, illite and kaolinite as major clay minerals identified for the raw and treated bentonites and proved the aluminosilicate structure of the clays. In synthetic solutions, the adsorption equilibrium of copper onto RB, B-MgCl2 and B-H2SO4 is reached in 30 min. while, equilibrium is reached after 4 hours when using B-NaOH. The adsorption kinetics are well described by the pseudo-second-order model. The adsorption of copper is pH-dependent. The Langmuir, Freundlich and Dubinin-Radushkevich isotherms indicate a suitable fit between the experimental data and models. The corresponding parameters indicate that the sorption mechanism might be physical in nature. The maximum adsorption capacities of Langmuir that are obtained are in the following order 25.1 mg/g (RB) < 28.03 mg/g (B-H2SO4) < 39.89 mg/g (B-MgCl2) < 72.80 mg/g (B-NaOH). The removal efficiency of copper in industrial wastewater was 45.75 %, 55.22 %, 63.27 % and 70.39 % using RB, B-MgCl2, B-H2SO4 and B-NaOH, respectively. The B-NaOH exhibit a higher adsorption capacity of copper with the other tested bentonites.

Optimization of copper removal from wastewater by fly ash using central composite design of Response surface methodology

This study aimed to investigate the possibility of utilizing a locally available fly ash as a low-cost adsorbent material for the removal of copper from aqueous solution. Though copper is an essential element, it can be poisonous to human beings at higher concentrations. The removal efficiency of copper is studied under the different initial concentrations of copper (20–50 mg/L), pH (2–6), and fly ash dosage (20–80 g/L). A second-order polynomial model is proposed to study the interactive effects of the parameters. The result of the analysis of variance (ANOVA) confirms the quadratic model is very significant. The optimization of the process variables is carried out by using a full factorial rotatable Central Composite Design (CCD) in Response Surface Methodology (RSM) by Design-Expert Software (Version 6.0.8, State Ease, USA). The maximum removal of copper is achieved at an initial copper concentration of 43 mg/L, pH 6, and fly ash dosage 63 g/L. The value of the determination coefficient (R2) is found to be 0.9945. The value of Prob > F of the developed model is < 0.0001, indicating the applicability of the model. The fly ash has been analyzed by XRD, DTA, FTIR, and SEM/EDS techniques. The results of this study indicate that this fly ash can be used as a low-cost adsorbent to treat acidic wastewater generated from industries like electroplating, fertilizer, copper smelting, acid mine drainage, etc.

Performance Evaluation of Emulsion Liquid Membrane for Simultaneous Copper and Cadmium Removal: Dispersion Tool Comparison

The content of heavy metal ions in industrial wastewater could be a great threat to the environment and humans’ health. Owing to this issue, the emulsion liquid membrane (ELM) is proposed as an effective technique to remove heavy metal from aqueous solution. The current work intended to compare the performance of ELM extraction using two dispersion tools; conventional stirrer and Taylor-Couette Column (TCC). The effect of stirring speed and extraction time of both devices on the removal efficiency of copper and cadmium will be looked at. Results obtained demonstrated a huge reduction in extraction time to simultaneously remove the two types of heavy metals. The maximum extraction efficiency in conventional stirrer for both copper and cadmium were found at 400 rpm in 20 mins (99.52%) and 10 mins (95.47%), respectively. Meanwhile, the highest efficiency in TCC for copper was found to be slightly lower although it offers shorter time for the performance to peak. 200 rpm of outer cylinder is required to achieve 96.38% while 600 rpm is required to remove as high as 81.59% of cadmium. The extraction time required to obtain the maximum removal in TCC is 5 mins and 3 mins for copper and cadmium, respectively.

Phytoremediation of Copper-Contaminated Water with Pistia stratiotes in Surface and Distilled Water

Copper contamination of industrial waste streams is increasingly common with copper used in an array of industrial processes. Phytoremediation of copper-contaminated water with Pistia stratiotes presents a cost-effective, efficient and uncomplicated alternative for copper removal from industrial wastewater. This study examines the ability of Pistia stratiotes to remove copper from distilled water representing a highly nutrient-deficient medium and natural surface water containing plant nutrients inherently. Control and experimental sets were set up with growth solutions of distilled water and natural surface water spiked with 5 g/mL, 10 g/mL, 15 g/mL, 20 g/mL and 25 g/mL copper. The control sets were devoid of Pistia stratiotes while the experimental sets contained Pistia stratiotes. Copper concentration and pH of the solutions were tracked over 10 days. This study revealed the ability of Pistia stratiotes to remove copper in both types of growth solution with contamination level ranging from 5 to 25 mg/L and pointed to its ability to phytoremediate higher level of copper contamination. Pistia stratiotes also raised the pH of the growth solutions. Copper removal from both types of growth solution demonstrated a predominantly first-order elimination kinetics except for copper concentrations above 15 mg/L in distilled water where the zero-order elimination kinetics predominated. Copper removal efficiency decreased with increasing copper concentrations in both types of growth solution with removal efficiency in natural surface water growth solutions consistently higher. It highlights the ability of Pistia stratiotes to phytoremediate highly nutrient-deficient and natural surface water media.

Coaction of bio-sorption and bio-filtration for the remediation of domestic and agricultural wastewater contaminated with heavy metal

Most heavy metals are well known for their toxicity and carcinogenic properties and when disposed-off through wastewater from anthropological activities poses a serious threat to the human population and other living organisms of the receiving body. The presence of heavy metals also hampers biodegrading potential for microorganism to remediate wastewater due to theirs toxic-inhibition. In this study we combine the coaction of bio-sorption and bio-filtration with aim to improve the remediation efficiency of the Copper (Cu2+) contaminated domestic and agricultural wastewater samples in Nakhon Pathom Province, Thailand. Rice husk, agricultural waste from rice farming abundant in the area, was used as natural bio-sorbent material and tested to identify its optimum adsorption conditions. The adsorbed wastewater after sorption was fed through bio-filtration tank (sand-filled and bio-augmented with Pseudomonas stutzeri DMST 28410) and underwent bio-filtration regimes to complete the coaction remediation. Results from the present study showed rice husk grounded to the size of 106μm powder at optimal sorption conditions (pH 7, dosage 10g/L, mixing rate 150rpm., sorption time 90min., initial Cu2+ concentration 12mg/L) was effective and removed more than 40% of the metal concentration from the wastewater samples. For domestic wastewater, coaction with bio-filtration further improved the copper removal efficiency up to 96% when treated for 180min. Poultry farm wastewater yielded similar copper removal results, with sorption accounted for about 36% and coaction with bio-filtration totalling up to 97% copper removal. Wastewater parameter, Chemical Oxygen Demand (COD) from both sources after bio-sorption exhibited rises in concentration. This poses the need to further explore other pre-treatment methods for rice husk for it to fully be utilized as bio-sorbent in the removal of copper and other heavy metals from wastewater.

Comparative studies on removal of heavy metals from electroplating wastewater through soil aquifer treatment (SAT) in conjunction with adsorbents.

The study demonstrates the efficiency of the soil aquifer treatment (SAT) towards removal of heavy metals within electroplating wastewater thereby rendering it suitable for ground water discharge. The unique proposition of this research is to use a combination of soil and adsorbent properties to enhance the remediation of heavy metals such as nickel, copper and zinc. A comparative study through statistical analysis is employed to illustrate the effectiveness of the various SAT systems build using various combinations of SM and SC soil types along with bioadsorbents such as eucalyptus leaves, sawdust and Mosambi peel. Further, the mass balance analysis of heavy metals is carried out to comprehend the course of expulsion. The study, through a statistical approach, endorses that the SAT in conjunction with adsorbent gives much better removal efficiency than the SAT without adsorbent. Additional removal efficiency of 14% to 30% can be achieved with introduction of adsorbents within the SAT system. The optimal removal efficiency of nickel, copper and zinc was observed to be at 87, 98 and 93% respectively when passed through the combination of SM soil with sawdust.

Use of cement kiln dust to remove copper from simulated wastewater using the Response surface methodology

Copper removal from simulated wastewater was achieved using Cement Kiln Dust (CKD) as adsorbent. The effects of contact time, pH, initial copper ion concentration, rotational speed, and Cement Kiln Dust (CKD) amount were studied. The best operating conditions were determined by applying a Response Surface Methodology (RSM). The results showed that the copper concentration has the main effect on the efficiency of copper removal followed by time, shaking rate, dosage of cement kiln dust, and pH. The best operating conditions were found to have a pH value of 8, contact time 90 minutes, shaking rate of 300 rpm, copper ion concentration 20 ppm, and a quantity of CKD equivalent to 35 g / l. Based on this optimum condition, 99 % of the efficiency of copper removal was achieved.

Applicability of weathered coal waste as a reactive material to prevent the spread of inorganic contaminants in groundwater.

It is necessary to determine an environmentally friendly method of reusing the vast amount of coal waste that is generated during coal preparation. This study evaluates the applicability of using weathered coal waste in a permeable reactive barrier to prevent groundwater contamination. Coal waste, with different weathering degrees, was obtained from two coal mining sites in South Jeolla Province, Korea. The reactivities of the coal waste with inorganic contaminants, such as copper, cadmium, and arsenic, were examined in batch and column experiments. The batch experiment results indicate that the coal waste removal efficiencies of copper (99.8%) and cadmium (95.4%) were higher than those of arsenic (71.0%). The maximum adsorption capacities of coal waste for copper, cadmium, and arsenic calculated from the Langmuir isotherm model were 4.440 mg/g, 3.660 mg/g, and 0.718 mg/g, respectively. The equilibrium of adsorption was attained within 8 h. The column experiment results reveal that the coal waste effectively removed inorganic contaminants under flow-through conditions. Faster breakthrough times were observed in single solute system (As(V) = 19.3 PV, Cu(II) = 47.6 PV) compared with binary solute system (As(V) = 27.8 PV, Cu(II) = 65.4 PV). To confirm the applicability of using coal waste in a groundwater environment, its decontamination ability was analyzed at low concentrations and under various pH conditions. To examine the potential ecological risks in the subsurface environment, a test to determine acute toxicity to Daphnia magna and a toxic characteristic leaching procedure (TCLP) test were conducted. The coal waste was found to satisfy appropriate standards. The acute toxicity test also confirmed the ecological safety of using coal waste in a groundwater environment. The acceptably high capacity and fast kinetics of inorganic contaminant sorption by the coal waste indicate it could potentially be employed as a reactive material. The recycling and application of this abundant waste material will contribute to solving both coal waste disposal and water pollution problems.