Factorial design for process optimization and generation of kinetic data for yttrium and europium leaching

Abstract

Factorial design has been implemented to develop regression equations for leaching of Y and Eu from phosphor coating of spent fluorescent lamps (FLs). On the basis of leaching extent, H2SO4 was the most suitable lixiviant. Parameter chosen for 23 full factorial design were temperature, H2SO4 concentration and pulp density. Leaching extent obtained at design conditions were fed to Minitab and regression equations for time intervals namely 1, 2, 3 and 4 h were generated. Experiments were carried out to validate equations and results were within �5% w/w of calculated values. These equations were solved for 99.9�100% leaching and obtained conditions have been represented as response surfaces. More than 99% of Y and Eu can be leached with H2SO4 of concentration 6�9.3% v/v at temperature 70�95�C and pulp density 5�20% w/v in 3 h.Leaching extents required for kinetic studies were also determined from regression equations. � 2018 Institute of Materials, Minerals and Mining and The AusIMM Published by Taylor & Francis on behalf of the Institute and The AusIMM.