Experimental study on the adsorption of Pb²⁺ by multifunctional grafted sisal fibers and verification in tailings cemented paste backfill

： Lead–zinc tailings (LZT), which pose a toxic element pollution risk, represent a significant environmental challenge in mining areas. This study proposes a novel strategy to enhance the Pb2+- fixation capacity of LZT by utilizing natural sisal fiber (SF). The key premise of this approach is to improve the Pb²⁺ adsorption capacity of SF to ensure effective performance in engineering applications. We prepared a graft-modified SF (GMSF) with multifunctional groups and investigated its adsorption capacity in Pb²⁺ containing wastewater. The modified fiber achieved an impressive Pb²⁺ adsorption efficiency of 99.60% within just 10 min, with an adsorption capacity of 138.26 mg/g. A segmented model was established for the adsorption curve. During the first 10 min, the adsorption followed a pseudo-first-order kinetic model, indicating that physical adsorption predominated. After this initial period, the desorption process conformed to the ExpAssoc model. Analysis revealed that the desorption phenomenon was due to the excessively high initial concentration of Pb²⁺, in which electrostatic repulsion between the chemically and physically adsorbed Pb²⁺ caused some of the ions to return to the solution. After 2 h, the nitrogen and oxygen atoms in GMSF formed stable metal complexes with Pb²⁺ through their vacant orbitals and electronegativity, effectively fixing the Pb²⁺. Promising results were observed in subsequent cemented paste backfilling experiments, in which the sample strength improved, and most of the Pb²⁺ was effectively immobilized.