Extraction and recovery of nitric acid and copper from leach liquor of waste PCBs

Abstract

The disposal of large quantities of electronic scrap world wide is causing an enormous harm to environment as well as to mankind. Therefore, efforts have been made to develop a suitable hydrometallurgical process for the extraction of metals from electronic scraps.The leach liquor of waste PCBs was generated containing 18.78g/LCu, 0.38g/LFe, 0.13g/LNi, 1.34g/L Pb and 6.3 M HNO3. Initially, HNO3 was extracted from the leach liquor using TBP as an extractant. Various process parameters such as time, concentration of extractant, O/A ratio etc were studied for the extraction of HNO3. It was observed that the extraction of HNO3 increased from 8.1–39.6% with increase in TBP concentration from 10 to 100%. The plot of log D vs. log[TBP] gives a straight line with slope ~ 1indicated that the 1 mole of TBP used for the extraction of 1mole of HNO3. The McCabe – Thiele Plot was drawn to investigate the stage required for maximum acid extraction. After extraction of HNO3 from leach liquor, extraction of copper was investigated using LIX84IC. Various parameters such as effect of pH, phaseratio, strippingetc. Were studied to investigate the optimum experimental condition for the extraction of copper. The extraction of Cu increased from 37 to 88% with the increase in the Ph range from 0.7 to 2.0. The optimum equilibrium pH for Cu extraction was found to be ~2.0. The McCabe– Thiele Plot for Cu extraction indicated that 2 counter current stages is enough for its complete removal from acid free leach liquor at O/A=1.2/1 maintaining equilibrium pH~2.0. The present study reports removal of acid and Cu from the leach liquor of waste PCBs in an eco-friendly manner.