EVALUATION OF ACTIVATED CARBONS OBTAINED FROM COLOMBIAN MINERAL COALS FOR ADSORPTION OF CAFFEINE

Abstract

Caffeine is a natural alkaloid used as a key ingredient in craft and industrially produced beverages. The caffeine concentration in water bodies worldwide is increasing to the point of being classified as an emerging contaminant with potentially harmful effects on aquatic ecosystems. Given the importance of both, coffee and carbon production in Colombia, activated carbons prepared from local mineral coals have been considered a cost-effective alternative for the treatment of wastewater from coffee plantations. In this study, activated carbons from the Colombian regions of Cundinamarca and Santander were evaluated as matrices for caffeine adsorption in an aqueous solution. The prepared activated carbons were characterized and subjected to adsorption tests and kinetic studies. The caffeine concentration (adsorbate) and the activated carbon (adsorbent) to liquid ratio were considered as the experimental factors in the evaluation of removal capacity. The results showed that the mineral coal from the Cundinamarca region has better physicochemical (low ash and volatile matter contents and high iodine number) and better adsorption capacity, reaching specific caffeine retention of 882.1 mg/g. The adsorption process corresponds with Freundlich’s adsorption model suggesting heterogeneous adsorption, while pseudo-second-order kinetics indicated the dominance of a chemical adsorption mechanism.