Aspirin adsorption onto activated carbon derived from spent tea leaves: statistical optimization and regeneration study

Abstract

Contamination of water sources by contaminants of emerging concerns, including pharmaceutical compounds, threatens the well-being of human who relies on the water sources. Development of cost-effective adsorbents for maximum removal of these contaminants is important to ensure clean and safe water access. This study demonstrates the reusability of activated carbon synthesized from spent tea leaves (STL-AC) for aspirin adsorption at optimized conditions. The maximum aspirin removal was 98.97% after optimization of process conditions using Response Surface Methodology. The adsorbent can be reused up to five cycles via solvent elution, with aspirin removal percentage above 85%. The repeated adsorption–desorption cycles affected the adsorbent textural properties, however the adsorbent surface chemistry was not affected by the regeneration. The aspirin adsorption proceeds via pore filling together with hydrogen bonding and π–π interaction between the aspirin molecules, however electrostatic repulsion between the deprotonated aspirin molecules and negatively charged STL-AC resulted in reduced removal percentage at high solution pH. This study signifies the superior property of STL-AC in adsorptive removal of aspirin, therefore the potential of such adsorbent in treatment of municipal wastewater, as well as hospital and pharmaceutical manufacturing effluents will be investigated.