“…Among these processes, hydrometallurgic processes offer high metal selectivity and recovery with a flexible mode of operation and suitability for small scale applications, making it an attractive alternative for the treatment of WPCBs. In previous studies, different lixiviant systems, including sulfuric acid, hydrochloric acid, nitric acid, iodide, ammonia, cyanide, thiourea, thiosulphate and microbes, were examined (Huang et al, 2014;Li et al, 2012;Oishi et al, 2007;Hu et al, 2006;Yang et al, 2011). In most cases, an oxidant, usually hydrogen peroxide (H 2 O 2 ) and ferric (Fe 3+ ) due to their high reduction potentials of 1.78 V and 0.77 V, was involved given that metals in WPCBs are found in native and/or alloy form (Birloaga et al, 2013).…”