Rapid recovery of dilute copper from a simulated Cu-SDS solution with low-cost steel wool cathode reactor

Electronucleation mechanism of copper in wastewater by controlled electrodeposition analysis

In order to improve the efficiency of copper deposition in wastewater containing the surfactant polyvinylpyrrolidone (PVP) and reveal the mechanism of copper crystals, a controlled electrodeposition process was developed using a low-cost stainless steel cathode and investigated using chronoamperometry (CA), electrochemical impedance spectroscopy (EIS) and infrared spectroscopy (IR). The theoretical analysis was verified by fitting them to experimental curves and calculating the kinetic parameters of the deposition process. The experimental results showed that Cu(PVP)2 was formed by the reaction between the C[double bond, length as m-dash]O bond of PVP and Cu2+. When powdered, reduction of Cu2+ in the Cu(PVP)2 structure was promoted, a positively-charged PVP-coating layer was formed on the surface of the copper crystal nuclei to inhibit the growth of the copper powder. At a potential of -0.2 V, the electrodeposition crystallization curve of copper changed from progressive nucleation to instantaneous nucleation. The kinetic parameters of the deposition process were calculated by fitting the experimental curves to verify the correctness of the theoretical analysis. The EIS tests showed that removing the powder reduced the resistance of the organic solvent (PVP) film on the electrode surface and the charge transfer resistance during copper deposition. According to particle size analysis, removing the powder could reduce the growth energy of copper powder on the electrode surface, increase the area of the active part on the electrode surface, increase the current efficiency of copper powder to 84.2%, and control dust. The size of copper powder reached up to around 900 nm.

Recovery of copper and water from copper-electroplating wastewater by the combination process of electrolysis and electrodialysis

In this paper, a laboratory-scale process which combined electrolysis (EL) and electrodialysis (ED) was developed to treat copper-containing wastewater. The feasibility of such process for copper recovery as well as water reuse was determined. Effects of three operating parameters, voltage, initial Cu(2+) concentration and water flux on the recovery of copper and water were investigated and optimized. The results showed that about 82% of copper could be recovered from high concentration wastewater (HCW, >400mg/L) by EL, at the optimal conditions of voltage 2.5 V/cm and water flux 4 L/h; while 50% of diluted water could be recycled from low concentration wastewater (LCW, <200mg/L) by ED, at the optimal conditions of voltage 40 V and water flux 4 L/h. However, because of the limitation of energy consumption (EC), LCW for EL and HCW for ED could not be treated effectively, and the effluent water of EL and concentrated water of ED should be further treated before discharged. Therefore, the combination process of EL and ED was developed to realize the recovery of copper and water simultaneously from both HCW and LCW. The results of the EL-ED process showed that almost 99.5% of copper and 100% of water could be recovered, with the energy consumption of EL ≈ 3 kW h/kg and ED ≈ 2 kW h/m(3). According to SEM and EDX analysis, the purity of recovered copper was as high as 97.9%.

Micellar-enhanced ultrafiltration of cadmium and methylene blue in synthetic wastewater using SDS

Single and simultaneous removal of Cd(2+) and methylene blue (MB) with sodium dodecyl sulfate (SDS) by micellar-enhanced ultrafiltration under different experimental conditions was investigated. In single removal process, with initial SDS concentration increasing, the removal efficiency of Cd(2+) and MB kept increasing and then decreased. When the initial concentrations of SDS and Cd(2+) were 1.0 cmc and 50 mg L(-1), respectively, the maximum removal efficiency of Cd(2+) was obtained as 99.2%. Removal efficiency of MB could achieve more than 99.9% with initial SDS concentration below 2.0 cmc. As compared with single Cd(2+) removal, the removal efficiency of Cd(2+) in the presence of MB was slightly higher with initial SDS concentration below 1.0 cmc, while decreased with the SDS concentration above 1.0 cmc. The maximum removal efficiency of Cd(2+) was 98.8% when initial concentrations of SDS and MB were 1.0 cmc and 4 mg L(-1), respectively. The removal efficiency of MB in the presence of Cd(2+) could achieve higher than 96.5%, which was only 3.4% less than the optimum result of the single removal. Meanwhile, effect of pH on removal efficiency of Cd(2+) was more significant than that of MB.