Sustainable one-part geopolymeric hybrid composite derived from glauconite, talc, and olive seed waste–based activated carbon for Congo red adsorption

This study details the synthesis and application of a novel one-part geopolymeric hybrid composite (OP-GPHC) derived from glauconite, talc, and olive seed waste-based activated carbon for the efficient sequestration of Congo red (CR) dye from contaminated water. The hybrid binder was synthesized by impregnating activated carbon-based biogenic waste into a thermally treated glauconite/talc matrix, followed by alkali-activation with NaOH. Comprehensive characterization via XRD, FTIR, BET, TG/DTG, FESEM/EDX, and elemental mapping confirmed the material's exceptional adsorptive properties. A Box-Behnken design (BBD) optimization established the optimal operational conditions: pH 2.0, adsorbent dosage 0.07 g/ 25 ml, contact time 77.5 min, initial CR concentration 150 mg/L, and temperature 328 K, achieving a removal efficiency of 99.2%. Equilibrium data were best described by the Langmuir isotherm, yielding a maximum adsorption capacity of 367 mg/g at 328 K, while kinetic data followed the pseudo-first-order (PFO) model. Advanced statistical physics modeling revealed a multimolecular adsorption mechanism with a vertical orientation of CR molecules at the active sites, independent of temperature, and binding energies in the range of 19.25-21.46 kJ/mol, consistent with physisorption dominated by hydrogen bonding, π-π interactions, and electrostatic forces. Thermodynamic parameters confirmed the endothermic and spontaneous nature of the process. The OP-GPHC adsorbent exhibited excellent reusability (87.8% after five cycles) and a low production cost of $0.032/g. Based on batch-derived data, treatment of 100 L of CR-contaminated water (50 mg/L) is projected to cost approximately $1.68, highlighting its strong potential for industrial-scale tertiary treatment applications.