Multifunctional imine-boronate double network hydrogels for acidic wastewater pretreatment, featuring crosslinking...

Acidic mine drainage (AMD) requires efficient and controllable pH pretreatment to ensure the stability of subsequent remediation processes. Herein, a fully polysaccharide-based imine-boronate double-network hydrogel (PVA/QCMC/DSA/BA) was developed as a multifunctional pH-regulating material, in which the crosslinking degree could be precisely tuned. The hydrogel exhibited bidirectional and mild pH regulation, neutralizing acidic solutions (pH 3.0) to approximately 8.0 and moderating alkaline solutions (pH 11.0) to ∼9.5 without abrupt pH overshooting. Moreover, a CaCO₃-loaded hydrogel variant was developed to further enhance sustained neutralization performance under highly acidic conditions. By adjusting the crosslinking degree, the swelling ratio of the hydrogel could reach up to 4110.3 %, while the pH adjustment rate varied by up to 50 %, demonstrating a controllable structure-function relationship. In addition, the hydrogel exhibited an elongation at break exceeding 1000 %, excellent self-healing efficiency (72-100 %), and strong antibacterial activity with inhibition efficiencies above 99 %. A dose-response model based on consumed protons (Δn(H⁺)) was established to predict pH regulation performance under AMD conditions, highlighting the potential of this hydrogel system as a practical pretreatment material for acidic wastewater.