Experimental Study on Erosion Resistance of EICP-Solidified Iron Tailings Sand Assisted by Sodium Citrate

To address environmental risks, slope erosion, and potential dam-failure hazards associated with stockpiled iron tailings sand, this study proposes a sodium citrate (SC)-assisted enzyme-induced calcium carbonate precipitation (EICP) method for the stabilization of iron tailings sand. The solidification performance of this method was systematically investigated through miniature penetration tests, one-dimensional infiltration tests, rainfall scouring tests, calcium carbonate content (CCC) measurements, and microstructural observations. Its environmental effects were further evaluated based on heavy metal leaching tests. The results show that SC can regulate the EICP reaction rate and the CaCO₃ precipitation process. Considering the overall solidification effect, anti-infiltration performance, and environmental impact, the preferable treatment parameters under the present experimental conditions were determined as an EICP solution spraying dosage of 3 L/m², four spraying cycles, and an SC concentration of 7.5 g/L. Compared with conventional EICP treatment, the surface strength and CCC of iron tailings sand increased by 23.4% and 11.9%, respectively, while the cumulative infiltration amount decreased by 14.71% and the infiltration duration was prolonged to 1.5 times. After 60 min of rainfall scouring, the SC–EICP-treated slope exhibited only slight sheet erosion, and the cumulative mass loss was reduced by 82.64% compared with that before SC incorporation. Meanwhile, the leachate pH remained stable at approximately 8.13, and the immobilization efficiencies of Pb²⁺ and Cd²⁺ reached 79.5% and 68.8%, respectively. SC promotes the ordered aggregation of CaCO₃ through Ca²⁺ complexation and regulates the formation of flower-like aragonite aggregates, which, together with dispersed CaCO₃, fill micro- and macropores, thereby enhancing interparticle bonding strength and structural stability. This study may provide a new approach for the stabilization and erosion protection of iron tailings sand stockpile slopes.