Application of alkali-activated cementitious materials: Cyanide tailings solidification, bio-ceramsite preparation and thiocyanate wastewater treatment

Cyanide tailings are typical hazardous wastes produced during gold cyanidation processes, and their low harmless treatment efficiency leads to a resource utilization rate below 10%. To achieve safe solidification and high-value resource recycling of such tailings, this study adopted cement, slag powder and fly ash to prepare alkali-activated ternary cementitious binders, and fabricated non-fired bio-ceramsite using cyanide tailings as the main matrix. Under the optimal formulation conditions with 45% composite binder, 55% cyanide tailings and 5% hydrogen peroxide, qualified bio-ceramsite with stable physical properties was obtained. Serving as high-performance biofilm carriers, the as-prepared ceramsites exhibited excellent purification performance toward thiocyanate-containing mine wastewater. After stable biofilm domestication and operation under fixed hydraulic retention time, pH and ambient temperature, the thiocyanate concentration in practical mine wastewater decreased from 98.96–216.35 mg/L to 0.79–3.42 mg/L, fully meeting the corresponding wastewater discharge limits. This work provides a feasible technical route for promoting large-scale resource utilization of cyanide tailings and boosting green sustainable development of mining industry.