Treatment technique for wastewater from bauxite flotation and an application for its reuse

Abstract

During bauxite flotation, flotation indexes decrease with increasing water circulation time, resulting in the discharge of bauxite flotation wastewater as well as a waste of resources and great environmental safety risks. To determine how to return the wastewater back to the flotation process, this study aimed to identify the main components affecting the flotation indexes of flotation wastewater, and coagulation, biological and combined biological-coagulation methods were used to remove the components that affected the production index of wastewater. The results revealed that the accumulation of hydrolyzed polyacrylamide (HPAM) in circulating water reduced the flotation indexes. The combined biological-coagulation method was efficient and consisted of two steps: two-stage biological pretreatment to reduce the stability of HPAM in wastewater followed by coagulation treatment to remove HPAM. At an initial pH of 8, the biological coagulation treatment system stabilized after 4 days of continuous operation, and the treated water was subjected to a flotation test and attained good indexes: the proportion of alumina recovered increased from 62.80% to 68.52%, and the mass ratio of Al2O3 to SiO2 in the tailings decreased from 1.73 to 1.36. These indexes proved the feasibility of reusing the treated water for bauxite flotation. Microbial diversity analysis showed that Labrenzia played an important role in the biological pretreatment, and Gemmobacter, Stappia, Exiguobacterium, Pseudofulvimonas, and Acetoanaerobium played supporting roles. Based on the research results, a prototype reuse technology based on bauxite flotation wastewater treatment was established, and an industrial engineering application was developed through engineering design.