Electrochemical Recovery of Gold from Waste Electric and Electronic Equipment Using Circulating Particulate Bed Reactor (CPBE)

29th Symposium of Malaysian Chemical Engineers 2016

Ravinder, T.^1 ; Ali, U.F.M.^1 ; Ridwan, F.M.^1 ; Ibrahim, N.^1 ; Azmi, N.H.^1

School of Environmental Engineering, Universiti Malaysia Perlis, Kompleks Pusat Pengajian Jejawi 3, Perlis, Arau

02600, Malaysia^1

关键词: Capital and operating costs;    Electrical energy consumption;    Electrochemical process;    Electrochemical reactor;    Electrochemical recovery;    Mass transport control;    Reactant concentrations;    Waste electric and electronic equipments;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/206/1/012093/pdf
DOI  :  10.1088/1757-899X/206/1/012093

来源: IOP

【 摘 要 】

The utilization of electrochemical process recovery involving low reactant concentrations of metal requires electrodes with high mass transport rates and specific surface areas. This is essential to increase cross-sectional current densities whilst optimizing the capital and operating costs. Experimental results demonstrated that Circulating Particulate Bed Reactor (CPBE) is suitable for the recovery of low concentrations of gold from aqueous chloride solution containing AuCl4-and AuCl2-of less than 0.5 mol m-3(2g m-3). Elemental gold was successfully obtained on 0.5-1 mm gr particles in an electrochemical reactor incorporating a cation-permeable membrane and operated in bath recycle mode. Depletion to concentration -3mol m-3(-3) appeared to be mass transport controlled at an applied potential of +0.20 V (SCE), specific electrical energy consumption (SEEC) of ca. 800-1300 kWh h (tonne Au)-1for cell voltages (U) of 2.0-3.0 V, and fractional current efficiencies of ca. 0.95. However, atomic absorption and UV spectrophotometry established that as the ([AuCl4-+ [AuCl2-]) concentration decayed, the [AuCl4-]:[ AuCl2-] molar ratio changed. A multistep mechanism for reduction of AuCl4-ions explained this behavior in terms of changing overpotentials for AuCl4-and AuCl2-reduction as total dissolved gold concentration decreased. In addition, SEM images confirmed that adherent and coherent Au deposits were achieved with CPBE for Au deposition under mass transport control at 0.20 V (SCE).