Integrated adsorption-containment performance of a PAC-modified bentonite-biochar composite for phenol remediation

To address the environmental challenges posed by phenol emissions in coal chemical wastewater, this study developed a polyanionic cellulose (PAC)-modified calcium bentonite-biochar composite (PB4%-C8%) with integrated adsorption-cutoff functionality. The composite was synthesized using calcium bentonite (CaB), PAC (4 wt %), and corn stalk biochar (8 wt %), and characterized via XRD, SEM-BET, and FTIR. PB4%-C8% exhibited a 188.3% increase in specific surface area (56.712 m2/g) compared to CaB (19.674 m2/g). Under phenol concentrations of 100–400 mg/L, PB4%-C8% demonstrated low permeability (1.0 × 10−12–1.0 × 10−10 m/s), meeting cutoff wall standards (<1 × 10−9 m/s). At pH 8 and a dosage of 5.0 g/L, it achieved beyond 70% phenol removal from 100 mg/L solutions, with adsorption behavior well-described by the Langmuir isotherm (R2 = 0.9975) and pseudo-second-order kinetics (R2 = 0.9921), yielding a maximum adsorption capacity of 15.48 mg/g. After four regeneration cycles, the removal efficiency remained at 56.5%, confirming structural stability. The synergistic effects of PAC (enhancing swelling and chemical resistance) and biochar (providing adsorption sites) endowed PB4%-C8% with dual adsorption-cutoff capabilities, offering a sustainable solution for phenol wastewater treatment and contaminated site remediation.