Copper slag assisted coke reduction of phosphogypsum for sulphur dioxide preparation

• Copper slag (CS) as a novel additive significantly enhances phosphogypsum (PG) decomposition, increasing PG decomposition rate from 83.38% to 99.35% and SO2 yield from 78.62% to 96.81% at a CS/PG mass ratio of 1. • The addition of CS lowers the PG decomposition temperature from 992.4 °C to 949.6 °C, improving energy efficiency and process economics. • Optimal reaction conditions are CS/PG mass ratio of 1, Coke/PG mass ratio of 0.06, at 1100 °C for 20 minutes, achieving near-complete PG conversion. • This approach utilizes solid waste copper slag, reducing costs and environmental impact, offering a sustainable pathway for PG valorization and SO2 production.