A kinetic study of indium, aluminum, arsenic, and strontium extraction from LCDs using biometabolites produced by Aspergillus niger

Abstract

Waste liquid crystal displays (LCDs) contain significant quantities of both valuable and hazardous metal(loid)s, presenting potential environmental risks alongside valuable opportunities for resource recovery. Biohydrometallurgy holds great promise as a technology widely applicable for dissolving metals from both ores and secondary resources. While recognized for its eco-friendliness and cost-effectiveness, bioleaching faces a challenge in terms of slow kinetics, potentially affecting process efficiency and speed. This study, for the first time, presented a comparative kinetic analysis of metal's bioleaching from end-of-life LCDs by Aspergillus niger, utilizing various rate models. Kinetic evaluation revealed different rate-determining mechanisms for each metal extraction during different time periods, indicating an overall mixed control mechanism between chemical reactivity and diffusion. The reaction rate constants and relevant calculated activation energies showed that the degree of accessibility for element's bioleaching was as follows: As > Al > In > Sr. Thermodynamic variables like activation enthalpy and entropy values determined from the Arrhenius plots at varied temperatures and the results showed that the bioleaching reactions of Al, As, In, and Sr from waste LCDs were endergonic, reactant-favored, non-spontaneous with positive Gibbs free energy values. RSM was used to optimize the interactive effects of parameters that affect the element's extraction rates. The optimal bioleaching parameters were a temperature of 70 °C, and a leaching time of 29 h, which led to the highest extraction of 81.4 % Al, 69.1 % As, 60.0 % In, and 33.3 % Sr from LCD waste under solid/liquid ratio of 10 g/L and shaking speed of 160 rpm. The findings and insights presented in this paper have the potential to advance the field and provide practical guidance for environmentally friendly and economically viable recycling of LCDs.