Recovery of Cerium from Spent Autocatalyst by Sulfatizing-Leaching-Precipitation Process

A new approach to recover and purify cerium oxide from the spent autocatalyst after cordierite substrate dissolution and catalytic metals separation has been investigated. Cerium oxide was converted to Ce(IV) sulfate by baking with concentrated H2SO4 at 250 degrees C, and similar to 95% product could be subsequently dissolved in 1.0 M H2SO4 solution at 75 degrees C and 5% pulp density in 180 min. At the optimal conditions (molar ratio of cerium/oxalic acid of 1:15 at 25 degrees C and 120 min), similar to 98% Ce(IV) in the obtained solution was eK e precipitated as Ce(III) oxalate deca-hydrate, which was calcined at 550 degrees C to produce cerium oxide of high purity (similar to 99.9%). The transformation of cerium oxide during the recovery process using acid baking, oxalate precipitation, and calcination was examined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis, which provided necessary information on different phases and oxidation states of cerium. The recovery of cerium oxide is the last stage of the zero-waste process based on the substrate dissolution by which it is possible to recycle all the valuable components from the spent autocatalyst.