Sodium hexametaphosphate-mediated electrostatic-hydration coupling: interfacial complexation and in situ...

Bentonite-based hydraulic barriers are prone to performance degradation under high-concentration contaminant attack. Research on solid-waste-based barrier materials with high bentonite contents remains limited. To achieve low carbon footprint, high strength, and low permeability, this study proposes an in situ gel-growth strategy: under sodium hexametaphosphate (SHMP)-mediated electrostatic-hydration coupling, a montmorillonite-C-(A)-S-H intergrown framework is constructed within a high-loading (72 wt%: bentonite accounts for 72 % of the total dry powder raw materials.) Ca-bentonite/industrial solid-waste composite (BM@GF). Multivariate optimization and response surface analysis show that BM@GF attains a minimum permeability coefficient (PC) of 7.03 × 10^-12 m·s^-1 and an unconfined compressive strength (UCS) of 4.22 MPa, corresponding to 438-fold and 19-fold improvements, respectively, over a conventional soil-bentonite (S-B) barrier. During rapid setting (24 h) under aggressive media (strong acids/alkalis; 10-100 mmol·L^-1 Pb²⁺ and Cr³⁺), the chemical-compatibility (CC) retention exceeds 95 %. Life-cycle assessment indicates a 75.3 % reduction in carbon footprint and a 25 % decrease in production cost relative to Portland-cement-based materials, while leaching tests verify immobilization of hazardous metals below regulatory thresholds. SHMP-mediated construction of the montmorillonite-C-(A)-S-H intergrown architecture provides a new pathway for the sustainable valorization of industrial solid wastes in barrier applications.