# Microwave Pre-Treatment for Efficient Zinc Recovery via Acid Leaching

## TL;DR

This paper introduces a microwave pre-treatment method to significantly improve zinc recovery from refractory clinker using acid leaching.

## Contribution

The novel use of microwave thermal treatment to convert ZnS to ZnO and enhance leaching efficiency in zinc recovery.

## Key findings

- Microwave treatment increases zinc extraction from 39.1% to 92.5% under optimized acid leaching conditions.
- Microwave-induced phase transformation of ZnS to ZnO and microcrack formation improve clinker porosity and reactivity.
- Thermodynamic analysis confirms the enhanced reactivity of ZnO due to favorable Gibbs free energy and exothermic reactions.

## Abstract

This study presents an innovative approach to processing refractory zinc-bearing clinker using microwave thermal treatment followed by acid leaching. Microwave irradiation induces phase transformations, converting sphalerite (ZnS) to zincite (ZnO), and generates microcracks that enhance clinker porosity and reactivity. These changes significantly improve zinc dissolution during sulfuric acid leaching. Key parameters—acid concentration, temperature, solid-to-liquid ratio, and leaching time—were optimized, achieving a zinc extraction of 92.5% under optimal conditions (40 g/L H2SO4, solid-to-liquid ratio 1:4, 600 °C, 5–7 min) compared to 39.1% without pre-treatment. Thermodynamic analysis confirms the higher reactivity of ZnO, driven by favorable Gibbs free energy and exothermic reaction characteristics. These findings demonstrate the potential of microwave processing to intensify hydrometallurgical processes, offering energy efficiency and environmental benefits for industrial zinc recovery.