Recovery of copper and recycling of acid from the leach liquor of discarded Printed Circuit Boards (PCBs)

Abstract

Present work is focused on the recovery of metal and recycling of acid from the leach liquor of discarded Printed Circuit Boards (PCBs) using solvent extraction technique. The waste PCBs are segregated and processed for leaching under the optimized condition developed by our group at CSIR-NML. Further, the systematic basic studies were carried out to recover nitric acid (HNO3) and copper (Cu) from the leach liquor of PCBs using tri-butyl phosphate (TBP) and 2-hydroxy-5-nonylacetophenone oxime (LIX 84IC), respectively. The leach liquor mainly contains Cu (22.97 g/L) and nitric acid (6.3 mol/L). Various process parameters viz. effect of pH, extractant concentration, time, phase ratio, loading capacity, etc. were studied and optimized. Complete extraction of HNO3 was achieved using TBP in three stages at phase ratio (O/A) 3/1 in mixing time of 15 min. The acid free leach liquor obtained was further used for selective extraction of Cu using LIX 84IC. Mc-Cabe Thiele plot indicates 99.99% Cu can be extracted in two stages using 30% LIX 84IC at an equilibrium pH 2, O/A ratio 1/1 in contact time of 15 min. Complete stripping of Cu from loaded organic was achieved with 10% sulfuric acid (H2SO4) in 5 contacts at a phase ratio (O/A) of 1/1. From the pure copper solution metal or salt could be produced by evaporation, precipitation, electrowinning, crystallization, etc.