Enhanced Adsorption of GSM and 2-MIB via Surface-Amplified Powdered Activated Carbon: Adsorption Performance and Mechanism

Odorous metabolites produced by algae in source water pose severe threats to drinking water safety. Compared with conventional powdered activated carbon (PAC), in situ surface-amplified PAC exhibits superior adsorption capacity and favorable anti-interference performance in simplified aqueous systems containing selected inorganic ions for the removal of 2-methylisoborneol (2-MIB) and geosmin (GSM). This study systematically investigated the influences of PAC dosage, initial contaminant concentration, air exposure duration, inorganic anion and cation concentration, pH, and temperature on the adsorption behavior of 2-MIB and GSM onto surface-amplified PAC. Kinetic analyses reveal that the adsorption process follows the pseudo-second-order kinetic model (R2 ≥ 0.98): the rate-limiting step is governed by liquid film diffusion at low concentrations, while intraparticle diffusion dominates adsorption under high-concentration conditions. Satisfactory fitting results of the Freundlich isotherm model (R2 > 0.99) indicate heterogeneous energy distribution of surface active sites, demonstrating that heterogeneous adsorption characteristics serves as the main adsorption pathway. The relatively high adsorption energy (E) obtained from the Dubinin–Radushkevich (D-R) model suggests a possible contribution of micropore-related adsorption for both pollutants. Thermodynamic results prove that the adsorption is spontaneous (ΔG < 0) with a possible endothermic tendency (ΔH > 0). Active adsorption sites are distributed across both internal pore channels and external surfaces of PAC. This work provides a solid theoretical basis and experimental data for odor pollution remediation by the structural optimization of PAC.