Nano-electrokinetics coupled approach for enhanced solidification and stabilization of antimony-laden soil

The urgent necessity to address antimony (Sb) contamination in soil, a threat to groundwater and drinking water safety, underscores the significance of developing effective remediation strategies. This study innovatively integrated nano-electrokinetic (nano-EK) technology with geopolymerization to remediate laboratory-spiked, heavily Sb-contaminated soils (10000 mg Sb kg⁻¹). The nano-EK system synergistically enhanced alkali-activated geopolymerization kinetics, stabilizing Sb pollutants within the soil matrix. Orthogonal optimisation (25 runs) revealed that increasing EK duration from 60 to 480 min, voltage from 5 to 25 V, and adopting a 40 % soil–18 % fly ash–36 % GBFS–6 % water–glass recipe reduced Sb leaching from 85.6 mg L⁻¹ (untreated) to 6.8 mg L⁻¹ and raised compressive strength from 18.6 ± 1.2 MPa to 38.4 ± 0.9 MPa (p < 0.001). The introduction of 1.25 % nano-hydroxyapatite (NHAP) further cut leaching by 69 % and improved strength to 38.4 MPa, demonstrating exceptional solidification/stabilisation (S/S) efficacy. Electrolysis-generated OH⁻ ions reacted with Sb ions at the cathode, forming insoluble Sb oxide precipitates (Sb₂O₃ or Sb₂(OH)₃), which were further adsorbed by NHAP and encapsulated by geopolymers. This altered Sb speciation in the soil matrix, promoting the formation of composite mineral structures that immobilized Sb within the mineral lattice, greatly enhancing material stability and environmental durability. This integrated approach offers a breakthrough in Sb-contaminated soil remediation, combining the strength of nano-EK and geopolymerization for environmental safety and public health protection. This study not only serves as a technical benchmark for addressing severely contaminated soils but also establishes a precedent for the combined utilization of diverse remediation techniques.