Reaction kinetics modeling for lithium and cobalt recovery from spent lithium-ion batteries using acetic acid

Lithium and cobalt recovery from spent lithium-ion batteries(LIBs) is a major focus because of their increased production and usage. The conventional method for recycling spent LIBs using inorganic acids produces harmful byproducts. In this work, the leaching agent was substituted with a less expensive and more environmentally friendly alternative—acetic acid—and a mathematical model was developed to describe the kinetics of the recovery process. The variables used were the pH value, temperature, H_2O_2 concentration, and the solid-to-liquid(S/L) ratio. The mathematical model used was the shrinking core model, which was modified to accommodate an equilibrium reaction. The experimental results show that the rate of recovery of Li and Co over time was only affected by temperature. The leaching behaviors of Li and Co were found to oppose each other. An increase in temperature resulted in increased recovery of Li but decreased recovery of Co because of the product-favoring endothermic reaction of Li and the reactant-favoring exothermic reaction of Co. The product of Li has a lower entropy value than the reactant as a free-moving ion, whereas the product of Co leaching has a higher entropy value as a stiff crystal complex. Thus, temperature conditioning is a pivotal factor in the leaching of spent LIBs.

Sequential alkaline-organic acid leaching process to enhance the recovery of rare earth elements from Indonesian coal fly ash

In this decade,coal fly ash(CFA)is considered a potential secondary source of rare earth elements(REEs).However,most REEs in coal fly ash are encapsulated in aluminosilicate glass,making it challenging to recover them through acid leaching.In this study,a sequential alkaline-organic acid leaching was developed for the recovery of REEs from CFA.The effect of alkaline leaching using NaOH solution on the destructive ability of aluminosilicate glass,as well as the mineralogy and morphology changes of the resulting coal fly ash,was first studied.Furthermore,the effectiveness of alkaline leaching on the recovery ability of REEs through organic acid leaching was evaluated.The results show that the maximum leaching efficiency for Si and Al,which was obtained at the optimum alkaline leaching conditions,namely NaOH concentration of 10 mol/L,reaction temperature of 65℃,liquid/solid(L/S)ratio of 10 mL/g,and reaction time of 90 min,is 28%and 32%,respectively.The digestion reaction with NaOH lixiviants also causes coal fly ash to become more porous,making it advantageous in the organic acid-leaching process at the REEs recovery stage.The utilization of the desilicated residue produced from the digestion process in acid leaching effectively increases the overall REEs recovery from 32.2%to 77.6%.