Recycling of arsenic-containing biohydrometallurgy waste to produce a binder for cemented paste backfill: Mix proportion optimization

Arsenic-containing biohydrometallurgy waste (BW) is used to prepare a cementitious material, on the one hand, to solve the problem of lack of cheaper and greener binder for cemented paste backfill (CPB), on the other hand, to alleviate the arsenic pollution caused by BW. The binders were prepared by mixing blast furnace slag (BFS), BW, and ordinary Portland cement (OPC). The influence of mix proportions on the binder properties was investigated, including reaction kinetics, strength development, phase assembles of hydration products and arsenic (As) immobilization effects. Isothermal calorimeter analysis suggests that the binder reaction kinetics were highly determined by the mix proportions, and more BW addition decreased the reaction rate according to the Krstulovic-Dabic model. The optimal mix proportion of binder is 65–30-5, i.e., 65 wt% blast furnace slag, 30 wt% BW, and 5 wt% OPC. The compressive strength of this sample after curing for 3 days and 60 days is about 9.25 MPa and 40.88 MPa, respectively, and the hydration products mainly consist of ettringite and calcium silicate aluminate hydrate (C-(A)-S-H). Additionally, arsenic can be effectively immobilized in the binder, resulting from the denser structure (physical encapsulation) and ion exchange between arsenate and sulfate in ettringite.