Experimental and simulation studies of metal sulfide precipitates separation in copper smelting waste acid using a gravitation field-flow fractionation method

Abstract

Sulfide precipitation method has been widely used in the removal of arsenic and heavy metals from copper smelting waste acid. Nevertheless, tiny metal sulfide particles are generated during the process, making it difficult to achieve solid-liquid separation as well as solid-solid separation. This study designed an innovative gravitational field-flow fractionation (GFFF) tank to effectively separate fine sulfide precipitate particles of different heavy metals, relying on the difference in particle sizes. To achieve better tank performance, the effects of process conditions on the size variation of precipitate particles produced in metal sulfide precipitation process (Cu(Ⅱ), Zn(Ⅱ), or As(Ⅲ)) were firstly investigated. The results show that supersaturation level, sulfide to metal molar ratio, and pH have significant effects on the precipitate particle size, while reaction time affects slightly. The optimum conditions were identified to achieve the greatest possible differences in particle sizes of the three metal sulfide precipitates. To further analyze its performance, a 3D model of the GFFF tank was built, with the fluid flow field and precipitate particle movement simulated under the optimum conditions. The simulation results demonstrate that the designed GFFF tank can realize efficient separation of fine metal sulfide precipitates for the recovery of valuable metals.