Environmental disposal of sulphide-rich and desulfurized tailings: Thickening, rheological, mechanical, and leaching...

The surface disposal of sulphide-rich tailings (compared to ordinary tailings, it contains many sulphides) will cause environmental and groundwater pollution, and it is an eco-friendly method to prepare cemented paste backfill (CPB) from sulphide-rich tailings and backfill it into underground goafs. However, the thickening performance of sulphide-rich and desulfurized tailings is unclear, the sulphide-rich CPB strength cannot meet the standard. Therefore, a comprehensive study was conducted on its thickening performance through settling columns and dynamic thickening experiments, mechanics, and leaching tests were also conducted. The optimal flocculant conditions with different sulphide contents were obtained through settling column experiments. Meanwhile, it was found that turbidity and initial settling rate (ISR) were linearly related to tailings feeding concentration. Due to the higher specific gravity of sulphide-rich tailings, under different flocculation conditions, the higher the sulphide content, the higher the concentration, and there is a linear correlation between sulphide content and concentration. The results of dynamic thickening show that rake-shearing can improve the concentration and the shear yield stress, both of which increase rapidly at first and then slowly with the extension of shearing time. A logarithmic model of concentration based on shear yield stress was established. The unconfined compressive stress of the CPB prepared from tailings desulfurized to 20.7 wt%-S (S20.7) is much higher than that of 30.7 wt%-S sulphide content tailings (S30.7), which can meet the backfilling requirements. The concentration of metal ions in the soaking solution of S20.7 CPB is higher, and the environmental impact is small. Finally, it is recommended to choose S20.7 for backfilling. The study is significant for revealing the thickening and mechanical performance evolution of sulphide-rich tailings and environmental protection disposal.