TiO2-immobilized porous geopolymer composite membrane for removal of antibiotics in hospital wastewater

This experimental research proposes an environment-friendly and low-cost porous geopolymer composite membrane (PGCM) to treat antibiotics in hospital wastewater. The proposed PGCM consisted of two layers: a porous support layer and a dense coating layer. The dense coating layer was synthesized by incorporating variable TiO2 content (0, 2, 6, and 10 wt%) into the geopolymer matrix. The dense coating layer was of hierarchical mesoporous structure with 700 μm in thickness and adhered to the porous support layer. The average pore size, total pore volume, and open porosity of the dense coating layer decreased with an increase in TiO2, resulting in reduced water permeability. The PGCM was applied to remove six target antibiotics including amoxicillin, ciprofloxacin, norfloxacin, sulfamethoxazole, tetracycline, and trimethoprim in real hospital wastewater. By comparison, the PGCM with 10 wt% TiO2 achieved the highest antibiotic removal efficiencies, with the adsorption and combined adsorption/photodegradation removal efficiencies for the target antibiotics of 38-75% and 74-86%, respectively. The novelty of this research lies in the use of a tailor-made porous geopolymer composite membrane incorporated with TiO2 photooxidation as a single-step treatment of recalcitrant antibiotics contained in hospital wastewater.