Ultrasound-Enhanced O3-Goethite Process for Simultaneous Removal of Iron and Organic Impurities from Zinc Sulfate Solutions

Removing iron and organic matter (OM) is a major challenge in zinc hydrometallurgical purification; conventional sequential removal is inefficient and the process is complex. In this study, we propose a novel ultrasound-enhanced ozonation-goethite synergistic system (US-O3-goethite) to simultaneously remove OM during iron precipitation. Under the optimal conditions (60 W US, pH 4.5, 70°C, O3 flow rate 24 L·h-1, reaction time 90 min), the iron removal rate reached 99.44%, and the total organic carbon (TOC) removal rate reached 97.3%. Kinetic and electrochemical analyses showed that the process conformed to the Avrami model with a low apparent activation energy (21.4 kJ·mol-1) and was mainly limited by the diffusion step. In addition, the US cavitation effect activated O3 to generate active free radicals, accelerated the oxidation rate of Fe2+, and promoted the mineralization of some OM. Most OM was removed mainly by complexation and coprecipitation with iron; at the same time, the micro-jet effect cleaned the precipitate surface, alleviated crystal poisoning, improved crystallinity, and reduced the loss of valuable metallic zinc by 2.52wt%. This study provides a theoretical basis and technical support for simplifying the hydrometallurgical purification process, and future work should focus on the technical evaluation of real solutions.