Activated nickel tailings for remediation of arsenic-contaminated soils: Tailings activation, leaching toxicity and passivation mechanisms

Abstract

Soil arsenic contamination caused by industries such as metallurgy is multifaceted in its harm, affecting both soil ecosystems and directly threatening human health. This study proposes a method that uses activated nickel tailings as an alkaline activator to solidify arsenic-contaminated soil. The results show that mechanical activation is a better method for activating nickel tailings than thermal activation. Before the consolidation of contaminated soil, the slurry mixing time is close to 90 s and the mixing rate is close to 135 rpm, which can effectively ensure the solidification efficiency of As (more than 90 %). The leaching toxicity of As and Ni ions is lower than 0.1 mg/L and 0.02 mg/L, respectively, which is lower than the national standard requirements. Mechanism analysis showed that most of the pollutants are encapsulated within the solidified body by the network structure formed by alkali activated nickel tailings, thus achieving stabilization. In addition, transition metals (Fe, Ni, Co, etc.) in nickel tailings will oxidize As(III) to As(V) with poor fluidity, further improving solidification efficiency on the basis of solidification/stabilization. This study provides an economic, environmentally friendly, and effective approach for both the resource utilization of tailings and the remediation of contaminated soils.