Oxytetracycline removal by biological/chemical activated mesoporous carbon

Abstract

The presence of emerging pollutants in water matrices is an increasing concern; therefore, the development of sustainable technologies that enable the removal of these pollutants is required. The goal of the present study was to propose a methodology to prepare a sustainable catalyst using functionalized mesoporous activated carbon and an enzyme for the removal of oxytetracycline. Four strategies of laccase immobilization were evaluated using a 32 experimental design to evaluate the enzyme immobilization efficiency. The activated carbon was functionalized with hydrochloric acid, glutaraldehyde, or carbodiimide, resulting in four different enzyme immobilization carriers. The response variables evaluated were the protein-specific load capacity and specific activity of immobilized laccase. All developed carriers successfully immobilized the enzyme; among these, the carriers treated with hydrochloric acid and glutaraldehyde had significant protein-specific capacities with yields of 90%, while the carbodiimide carrier had a yield below 40%. In addition, the hydrochloric acid-treated carrier achieved the highest specific activity (168 ± 52 U/g) and specific protein load (13.48 ± 0.90 mg/g). The antibiotic removal assays that employed this catalyst showed better performance (100%) than the free enzyme, which was used as a reference. However, the apparent antibiotic removal mechanism was found to be pollutant adsorption instead of degradation, which was ascribed to the high affinity of the hydrochloric acid-treated carrier for the studied pollutant.