Antituberculosis drugs degradation by UV-based advanced oxidation processes

Abstract

Several advanced oxidation processes (AOPs) were investigated for the degradation of isoniazid (INH) and rifampicin (RIF) in aqueous solution: TiO2 and ZnO heterogeneous photocatalysis and homogeneous and heterogeneous UV-A photo-Fenton processes. Under optimized conditions (pH 6.0 and 500mgL−1 of photocatalyst) the UV-A TiO2-photocatalysis removed approximately 90% of INH and 60% of RIF at 60min. Under similar experimental conditions, the degradation efficiency of ZnO was significantly lower to INH. The low-cost UV-A homogeneous photo-Fenton process removed 70% of INH and 80% of RIF at 60min. Photo-Fenton process using iron-immobilized in chitosan beads showed lower degradation efficiency (7% to INH and 50% to RIF) probably due to low iron availability in the catalyst surface. A radical scavenging assay was performed to investigate the effect of free radicals (hydroxyl radical (OH), electron vacancy (hole, h+), superoxide radical anions (O2−), and singlet oxygen (1O2)) on INH and RIF degradation during TiO2/UV-A photocatalysis. The two drugs have distinct degradation mechanisms, while RIF is degraded by h+, INH suffers influence of various active species. The TiO2/UV-A photocatalysis was employed to degrade INH/RIF residue.