Ultrasound-assisted Fenton-like reagent to leach precious metals from spent automotive catalysts: process optimization and kinetic modeling

Ultrasound-assisted Fenton-like was utilized to leaching precious metals from spent automobile catalysts. The effect of different factors including solid to liquid (S/L) ratio, H2O2 percentage and initial Fe2+ concentration was done. Response surface methodology (RSM) was used to optimize the effective factors in the leaching of Al and Ce from the spent automobile catalyst. The optimum conditions for three effective factors were 0.01% (w/v) S/L ratio, 10.3% (v/v) H2O2 and 12.6% (w/v) Fe2+. The recovery efficiencies of Al and Ce in the optimum conditions were 81.7 and 47.2% in 4 h, respectively. In the absence of ultrasound, Al and Ce recoveries decreased to 69.5 and 13.4%, respectively. The residue after leaching was applied for Pt and Pd recovery using aqua regia, which results to 100% recovery. The modified shrinking core modeling results suggested that chemical reaction was the rate controlling step. The characterization methods including scanning electron microscopy (SEM) and X-ray diffraction (XRD) before and after bioleaching were performed.