Statistical modelling and kinetics of copper loss to printed circuit board (PCB) fibreglass during PCB ammine leaching

Abstract

ABSTRACT PCB dust leach feed contains fibreglass particles responsible for incomplete copper recovery observed during PCB dust leaching. Interaction of fibreglass particles with ammine leach solution was studied by varying contact time, operating temperature and pulp density at different initial concentrations. Box Behnken RSM design was utilised to design the experimental tests. The 3D plots, ANOVA, Pearson correlation and multiple regression analysis show the initial copper concentration impacts the response QCu most. Of the five non-linear adsorption kinetic models employed, Elovich and Avrami's kinetic model best fitted the experimental data with R2 of 0.9632 and 0.9435, respectively. The pHpzc analysis of fibreglass particles shows the material possesses a neutral surface charge at pH = 7.1. Evaluation of the kinetic models and pHpzc analysis of copper losses to PCB fibreglass particles supports dual mechanisms of physisorption and ion exchange co-occurring in the solid–liquid systems. At 1 g fibreglass particles in 100 mL of 50 mg/L copper ammine leach solution, maximum loss of about 1.5 mg/L copper was obtained in 12 h. This clearly indicates limitation to maximum target metal recovery. Copper loss to fibreglass particles occurs during PCB leaching up to an amount which depends on the mass fraction of the glass fiber particles in the pulp, leach solution concentration and time.