metal recovery

Silver is an element with the highest thermal and electrical conductivity, making it ideal for electrical applications. One of the most commonly consumed electronic wastes containing silver is Printed Circuit Boards (PCBs). To reduce the amount of PCB waste and increase the availability of silver, an environmentally friendly solvent called Deep Eutectic Solvent (DES) is proposed to extract silver from PCB waste. This study aims to synthesize DES-glyceline and investigate the behavior and effectiveness of silver extraction using this DES glyceline. The optimum mole ratio of choline chloride and glycerol to synthesize DES was 1:2. The density of DES-glyceline was measured by a pycnometer, about 1.1378 g/L. The FT-IR spectra showed a broadening peak of the O-H band and its shifting from 3273 cm-1 in glycerol to 3124 cm-1 in DES-glyceline. The NMR characterization demonstrated the deshielding effect of O-H proton in glycerol, from 3.44 ppm to 4.63 ppm and 5.19 ppm. Both results indicate the formation of hydrogen bonds attributed to DES formation. The success of silver extraction by DES-glyceline was proven by cyclic voltammetry, resulting in an anodic peak at 0.132 V and a cathodic peak at -0.037 V. XRF characterization showed that the silver concentration contained in the initial PCB sample was 178.59 ppm. The recovery optimum condition for silver from PCB extraction was at the temperature of 120°C and at the time of 16 hours with a leaching percentage of almost 85%. This environmentally friendly, low-cost, low toxicity, and high biodegradability DES-glyceline shows tremendous promise for efficiently recovering silver from PCB e-waste.

Photo-electro-catalysis process has received major attention in the past decade as a substitutional wastewater treatment technology. Photo-electro-catalysis process is widely employed for removing different pollutants (organic, and inorganic (cationic and anionic)) from wastewater. It has been recently developed by modifying the photo-reactor system, the experimental parameters, and the structure of photo-anodes during preparation to enhance the pollutants removal from wastewater, reduce their adverse health risk resulting from environmental accumulation, and give a chance to reuse the treated wastewater for a variety of applications. This review aims to summarize recent studies (especially in the last five years) that developed the photo-electro-catalytic degradation system of organic, heavy metal, and mixed pollutants under UV light, visible light, and sunlight. This review demonstrates the effect of experimental variables, photo-reactor arrangements, mass transfer, phase, length, and diameter of nanoparticles or tubes on the anode, type of deposition on the anode, and cathode characteristics (type and dimensions) on the photo-electro-catalytic technologies. The drawbacks of photo-catalysts, affecting the photo-electro-catalytic properties, are also discussed and solved. Finally, the review focuses on the photo-electro-catalysis enhancements by combining this process with other proven treatment processes. This review can provide perspectives on the important factors that evolve photo-electro-catalysis for the complete purification of polluted wastewater in the future.