Interpenetrating carboxymethyl cellulose-hydroxyethyl cellulose hydrogel for graphite tailings solidification:...

This study focused on graphite tailings (GTs) storage and addressed problems such as heavy-metal migration and high carbon emissions resulting from the use of traditional cement-based solidifying agents. A bio-based interpenetrating network hydrogel was prepared via graft crosslinking of carboxymethyl cellulose and hydroxyethyl cellulose for GTs solidification. Systematic evaluations were conducted through mechanical testing, water erosion resistance assessment, heavy-metal leaching analysis, microstructural characterization, and molecular dynamics (MD) simulations. Compared with GTs obtained using single-component systems, GTs solidified using the prepared hydrogel exhibited 54% and 77% higher unconfined compressive strength and splitting tensile strength, respectively. At a hydrogel dosage of 5%, the immobilization efficiencies of Cu, Ni, and Mn exceeded 70%, with the mass retention rate maintained at 97% after five water erosion cycles. Microstructural characterization indicated the formation of a rigid-flexible coupled network that enabled pore filling and particle encapsulation. Under clearly defined model assumptions, MD simulations revealed an adsorption-assisted pore-sealing process, in which the water-accessible free-volume fraction decreased from ∼62% to ∼19% with increasing simulation time and subsequently stabilized, indicating restricted water transport pathways consistent with improved erosion resistance. Overall, the prepared hydrogel enables low-carbon and efficient GTs solidification, demonstrating the comprehensive advantages of bio-based hydrogel binders.