Treatment of manufacturing scrap TV boards by nitric acid leaching

The leachability tests for manufacturing scrap TV boards (STVB) have indicated the release of metals beyond the limit levels with potential problems for environmental pollution. Treatment of STVB is therefore requisite for its safe disposal in landfills. The nitric acid leaching of STVB for the removal/recovery of valuable metals (Cu and Ag) was studied by adopting the Box-Behnken design. Statistical analysis of data has revealed that the concentration of nitric acid is the most influential parameter affecting the leaching process. Effects of solids ratio and temperature on the rate and extent of the extraction of copper were also proved to be statistically significant. However, the interaction effects of these parameters were found to be insignificant. The leaching kinetics were consistent with the shrinking particle model under chemical control with an activation energy of 38.6 kJ/mol. High concentrations of nitric acid (2-5 M HNO3) were required to achieve high copper extractions (88.5-99.9%) at a pulp density of 6% w/v. The extraction of silver was enhanced from 14% to 68% with increasing the concentration of nitric acid from 1 to 5 M. These findings also demonstrate that copper may well be selectively extracted from STVB by adjusting the concentration of nitric acid.