Mechanism of combination membrane and electro-winning process on treatment and remediation of Cu2+ polluted water body.
Mechanism of treatment and remediation of synthetic Cu2+ polluted water body by membrane and electro-winning combination process was investigated. The influences of electrolysis voltage, pH, and electrolysis time on the metal recovery efficiencies were studied. Relationship between trans-membrane pressure drop (DeltaP), additions ratio, initial Cu2+ concentration on operating efficiency, stability of membrane and the possibility of water reuse were also investigated. The morphology of membrane and electrodes were observed using scanning electron microscopy (SEM), the composition of surface deposits was ascertained using combined energy dispersive X-ray spectroscopy (EDX) and atomic absorption spectrophotometer. The results showed that using low pressure reverse osmosis (LPRO), Cu2+ concentration could increase from 20 to 100 mg/L or even higher in concentrated solutions and permeate water conductivity could be less than 20 microS/cm. The addition of sodium dodecy/sulfate sodium dodecyl sulfate improved Cu2+ removal efficiency, while EDTA had little side influence. In electro-reduction process, using plante electrode cell, Cu2+ concentration could be further reduced to 5 mg/L, and the average current efficiency ranged from 9% to 40%. Using 3D electrolysis treatment, Cu2+ concentration could be reduced to 0.5 mg/L with a current efficiency range 60%-70%.
Recovery of copper and chelating agents from sludge extracting solutions
Removal of extraction solution containing chelated copper from printed circuit board industry sludge by cementation on powdered iron was studied. This work applied the recovery and extraction of ethylene diamine tetraacetate (EDTA) and diethylene triamine pentaacetate (DTPA) as remediation agents and metal precipitated from printed circuit board sludge extracting solutions. The recovery of copper by cementation process using powdered iron was dependent on the Fe:Cu molar ratio. Results of the experiments showed that recovery efficiencies were typical of those of a Fe:Cu molar ratio as high as 8:1 for each sludge sample. The differences of recovery efficiencies may be due to competition for active sites on the surface of the powdered iron. Copper deposits on the surface almost always occur in the form of the copper metal that are well distributed, with purified copper powder being observed in characterization with scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The recycled extract containing EDTA or DTPA was used to chelate supplementary fresh copper-containing sludge. Extraction efficiencies of copper by using Fe-precipitated EDTA or DTPA from previous cementation were higher than sequential application of the Fe-EDTA or Fe-DTPA solution. Similar copper extraction efficiencies using both pristine and reused extract containing chelants validates the enduring chelating capability of EDTA and DTPA and suggests further opportunities to employ recycled chelant to reduce its usage. This work confirmed the feasibility of copper removal from sludge chelated wastewater by cementation and subsequent recycling of chelant extraction.
Notes. Trace element content of northern Ontario peat
Peat samples were collected at 0-20- and 20-40-cm depths from several peatland ecosystems located in northern Ontario, Canada. Analysis was made for the trace metals Zn, Pb, Cu, Cr, Cd, and Hg. Concentration values in general were in the low ppm range and did not significantly differ in terms of peatland type or depth except for Pb. This element was signficantly higher in surface peats in bogs and fens. Concentration of metals in peats found in the study were equivalent to those in US coals, suggesting caution during combustion in terms of potential atmospheric input of metals.