A preliminary study to investigate the beneficiation of low-grade phosphate sludge using reverse flotation: Modeling and optimization through Box-Behnken design and response surface methodology.

Abstract

This preliminary study explored a novel approach to enriching unexploited low-grade phosphate washing sludge (PS) using a combination of attrition scrubbing, desliming, and reverse flotation. By employing a Box-Behnken experimental design (BBD) and response surface methodology (RSM), the study optimized flotation parameters (pH of the pulp, Flotation time, Ester, and Amine dosage), to achieve significantly higher P2O5 grade and recovery. Key findings include the effective upgrading of P2O5 grade from 15.84% to 19.6% in the fraction +20 μm through attrition scrubbing and desliming, demonstrating the efficacy of pre-treatment. Additionally, BBD and ANOVA analysis revealed that flotation time, pulp pH, and ester dosage significantly influenced P2O5 grade and recovery, while amine dosage had a less pronounced effect. RSM optimization yielded optimum flotation conditions of 10 minutes flotation time, 481.81 g/T ester dosage, 400 g/T amine dosage, and 4.58 pulp pH. Under these optimized conditions, a P2O5 grade of 28.61% and a recovery of 71.5% were achieved, with deviations from predicted values of less than 2%, demonstrating the effectiveness of the RSM-based approach. These preliminary findings enhance the way for future studies aimed at validating the effectiveness of this treatment methodology under industrial conditions and assessing its long-term economic and environmental viability.