Synthesis and Characterization of a Powdered Activated Carbon/Loofah Sponge Hybrid Composite for Enhanced Trimethoprim Removal: Comparative Equilibrium, Kinetic, and Thermodynamic Modeling

The discharge of pharmaceutical micropollutants into aquatic environments is a global challenge due to their persistence and contribution to antimicrobial resistance. In this study, a novel hybrid adsorbent composed of powdered activated carbon and loofah sponge powder (PAC@LSP) was synthesized via calcium–alginate immobilization and evaluated for the removal of trimethoprim (TMP) from aqueous solutions. Characterization results confirmed the successful incorporation of PAC within the lignocellulosic framework, achieving an embedding efficiency of ۹۷.۰% while preserving the carbon’s internal microporous structure. The PAC@LSP composite exhibited an exceptional BET (Brunauer–Emmett–Teller) surface area of ۱,۲۱۸ m² g⁻¹, total pore volume of ۰.۷۴ cm³ g⁻¹, iodine number of ۱,۴۸۱.۲ mg g⁻¹, and a uniform mean particle size of ۲۵۰.۰۰ µm. Batch experiments revealed strong pH dependence, with optimum TMP removal occurring at pH ۷.۰–۸.۵. Equilibrium was attained within ۶۰–۹۰ minutes and was accurately described by the pseudo-second-order (PSO) kinetic model (R² ≥ ۰.۹۹۷۶), indicating that chemisorption governed the rate-limiting step. Equilibrium data closely followed the Langmuir isotherm model (R² = ۰.۹۹۶۸), yielding a maximum monolayer adsorption capacity of ۲۱۴.۳۵ mg g⁻¹. This performance preserved ۹۰% of the ultra-high capacity of pure PAC (۲۳۸.۱۰ mg g⁻¹) while vastly outperforming raw loofah biomass (۳۶.۴۵ mg g⁻¹). Thermodynamic analysis demonstrated that adsorption was spontaneous (ΔG° < ۰), endothermic (ΔH° = +۱۸.۴۲ kJ mol⁻¹), and entropy-driven (ΔS° = +۷۷.۲۵ J mol⁻¹ K⁻¹). The synergistic integration of activated carbon and loofah biomass successfully produces a highly efficient, sustainable, and easily filterable adsorbent that circumvents the hydraulic separation limitations of standalone fine carbons.

کلیدواژه ها:

Trimethoprim antibiotic ، Hybrid composite material ، Calcium&ndash ، alginate immobilization ، Chemisorption kinetics ، thermodynamic parameters ، Wastewater remediation