Effect of process variables on leaching behavior and kinetics of silver element from waste photovoltaic modules

In order to achieve efficient leaching of silver, in waste photovoltaic panels, the leaching process using nitric acid was investigated. The effects of nitric acid concentration, leaching time, solid–liquid ratio, and leaching temperature on the silver leaching rate were examined. The response surface method was used to establish an experimental model for analyzing and optimizing the leaching experiment. The results showed that the nitric acid concentration had the most significant effect on the leaching rate. The leaching rate of 98.02% was achieved under the following optimal leaching conditions: a nitric acid concentration of 18%, a leaching time of 32 min, a solid–liquid ratio of 1:30, and a leaching temperature of 60 °C. According to the shrinkage nuclear model, the leaching kinetics of silver using nitric acid followed a chemical reaction-controlled process with an apparent activation energy of 42.26 kJ/mol. Scanning electron microscopy–energy-dispersive x-ray spectrometry results of minerals before and after leaching confirmed the efficient recovery of silver in waste photovoltaic cells.