Regenerative HMFI@Zeolite fixed-bed column for the treatment of petroleum-produced water: An examination of operational conditions and quantum chemical interaction mechanisms

A key challenge in fixed-bed adsorption systems is balancing high contaminant removal with long-term stability and a mechanistic understanding at the molecular level. This work demonstrates that a hierarchical MFI-type zeolite (HMFI@Z), when used in a regenerative fixed-bed column, efficiently removes cyclohexane carboxylic acid (ACHC) from petroleum-produced water under realistic conditions. Operational optimization revealed that higher feed concentrations and flow rates accelerated breakthrough and column exhaustion, with a maximum uptake of 3.44 mg g ⁻¹ under 35 mg L ⁻¹ and 10 mL min ⁻¹. Validation with real effluent yielded a removal efficiency of 58.15 %, breakthrough at 10 min, and complete saturation at 80 min. Dynamic models showed excellent agreement with experimental data, supporting the scalability of the process. The adsorbent maintained over 80 % adsorption capacity across 17 recycles, underscoring its long-term reusability. High performance was attributed to the material's surface acidity, hierarchical porosity, and stable electronic features. Quantum chemical calculations revealed that deprotonated HMFI@Z surfaces — particularly O ⁻ sites — act as the most reactive centers for ACHC binding. Key electronic descriptors corroborated the experimentally observed interactions and regeneration behavior. Two main interaction pathways were identified: (i) hydrogen bonding and electrostatic interactions dominating initial adsorption, and (ii) electron donor–acceptor mechanisms contributing to retention and stability. These results advance fundamental understanding of interaction mechanisms in zeolitic adsorption systems and highlight HMFI@Z as a recyclable, robust material for treating petroleum-derived effluents.