Application of waste acid from phosphogysum dam as an eco-friendly depressant in collophane flotation.

Dealing with waste acid generated in phosphoric acid (H 3 PO 4) production has always been a problem due to the lack of cost-effective and environment-friendly disposal technology. This study introduces a novel method of utilizing the waste acid as a depressant in collophane flotation aiming at reusing waste acid and reducing the consumption of sulfuric acid (H 2 SO 4) in flotation plants. Its effectiveness was confirmed by flotation test in lab- and industrial-scale test. The depression mechanism is investigated via solution chemistry calculation and scanning electron microscope analysis. Laboratory-scale flotation results indicate that the utilization of waste acid coupled with H 2 SO 4 can strengthen depression performance on collophane, improving recovery efficiency compared with the use of H 2 SO 4 alone as depressant. Results demonstrate that H 2 PO 4 − is the effective species in waste acid. It depresses the flotation of collophane by reacting with active Ca sites on the surface to form CaHPO 4 and Ca(H 2 PO 4) 2 , thus preventing collector adsorption and reducing collophane surface hydrophobicity. The application of waste acid in industrial test shows the flotation recovery increases by 1% accompanied with the reduced consumption of H 2 SO 4 by 30.03% (from 15.5 kg/t to 10.8 kg/t). An increased profit of 890,043 RMB in a month is achieved due to the application of waste acid. Notably, approximately 197,000 t waste acid is consumed for a month, which brings considerable environmental benefits. In summary, the application of waste acid in collophane flotation is an efficient, economical, and eco-friendly alternative for the treatment of waste acid. • Waste acid could be applied on collophane flotation as depressant without disposing. • The industrial application indicates waste acid could replace part of H 2 SO 4 steadily. • Consumption of plenty waste acid brings considerable economic environmental benefits. • Depression mechanism was studied by solution chemistry calculation and SEM analysis. [ABSTRACT FROM AUTHOR]