Sustainable Multifunctional Hydrogel Based on SA/GEL/PVA/GL for the Synergistic Inhibition of Coal Spontaneous...

To improve the prevention of coal spontaneous combustion (CSC) and overcome the poor durability of traditional inhibitors, a novel double-network (DN) biomass hydrogel, termed SGPGc, was developed. It was synthesized from sodium alginate (SA), gelatin (GEL), poly-(vinyl alcohol) (PVA), and glycerol (GL) via a CaCl₂-borax dual cross-linking system. The Ca²⁺-SA ionic network constituted a rigid skeleton, whereas the dynamic borate bonds between B-(OH)₄ ^- and PVA provided toughness and self-healing capability. This synergy endowed SGPGc with a high tensile strength of 16.25 MPa and a fracture elongation of 286.07%, ensuring tolerance to harsh underground mining environments. The hydrogel also exhibited excellent thermal stability and water retention, showing only 38.6% water loss at 90 °C, coupled with a high rehydration capacity of 37.73 g/g (dry weight basis) for the dried film, which enabled dynamic cooling and functional regeneration. Structural analysis revealed that SGPGc significantly reduced the total pore volume and specific surface area of coal by 47.23 and 50.25%, respectively, effectively blocking oxygen diffusion channels. Furthermore, its water retention capability enabled sustained cooling, while its high rehydration capacity facilitated secondary sealing. In comparison with raw coal, the SGPGc-treated samples showed significantly reduced CO generation and production rate, along with substantially increased crossing point temperatures (CPT, up by 33.7 and 29.0 °C). The demonstrated inhibition efficacy surpassed that of conventional calcium chloride, confirming the operational closed-loop synergistic mechanism of "barrier-cooling-functional regeneration" in effectively inhibiting CSC.