Optimization of pyrite cinder strengthening continuous acid decomposition of ilmenite by response surface methodology

Pyrite cinder could release more heat to improve he acid decomposition reaction of ilmenite, lower concentrations of sulfuric acid, increase the amount of TiO₂ waste acid reused, reduce titanium gypsum emissions, and promote the green and sustainable development of TiO₂. Using pyrite cinder as strengthening activator, the continuous acid decomposition conditions for ilmenite were optimized by using response surface methodology based on Box-Behnken design method. The acid decomposition conditions such as acid ilmenite ratio, acid concentration and pyrite cinder dosage mainly affected the reaction temperature, reaction equilibrium, reaction velocity, volatilization degree of water and sulfuric acid, ultimately affecting the solidification degree of the products and reaction yields. Pyrite cinder could improve the exothermic behavior, raise the reaction temperature and obtain higher acid decomposition yield. The prediction model for the acid decomposition parameters was with good fitting result and could be used to predict the reaction yields or optimize the reaction parameter values. The prediction model was significant and reliable with actual correlation coefficient R² of 0.9989. The synergistic interaction was very obvious, and the interaction between acid ilmenite ratio and acid concentration was larger than the other two interactive factors. Verification experiments confirmed the predicted yields could be achieved above 98.26% under the optimal conditions, proving the model had a high level of significance, confirming the reliability of the experimental operation. The continuous acid decomposition process had lower raw material consumption, higher TiO₂ yield, fully reusing of 65.35% titanium dioxide waste acid, and comprehensive utilization of pyrite cinder, making it cleaner and more environmentally friendly.