Enhanced tetracycline degradation using UV/Fenton/titanium dioxide (TiO2) hybrid process

Abstract

TiO 2 was synthesized using neem leaf extract as soft bio template and Titanium (IV) isopropoxide (C 12 H 28 O 4 Ti) as a precursor. Morphological properties revealed well crystalline anatase phase of 19.8 nm size for the biotemplated TiO 2 (B-TiO 2 ) compared to 24.2 nm of the non-templated TiO 2 (N-TiO 2 ). TEM revealed a nano sheet-like structure for the B-TiO 2 and it exhibited a larger S BET surface area (35.45 m 2 /g) and average pore diameter (5.74 nm) compared to the N-TiO 2 (19.72 m 2 /g) and (2.028 nm) respectively. XPS results showed carbon peaks indicating small bio-carbon doping on the lattice of the TiO 2 , which can promote charge transfer upon light excitation during photocatalyst reactions. The results of the photoluminescence study indicate reduced PL intensity of the B-TiO 2 which signifies the suppression of recombination of charge carriers or electron-hole pairs in the B-TiO 2 . The photocatalytic activity was assessed by the photodegradation of tetracycline (TC: 50 mg/L) under UV irradiation and the B-TiO 2 was employed as a photocatalyst. In the absence of UV light, B-TiO 2 catalyst slightly removed TC due to limited active species. However, the degradation of TC increases significantly due to the synergetic effect of the UV/Fenton/B-TiO 2 hybrid system. Moreover, the biotemplate exposes the surface of the B-TiO 2 which permits improved utilization of all surface-active sites. Quenching experiments were also performed via scavengers, results confirmed that hydroxyl radicals, superoxide radicals and electrons are the key reactive species in the TC degradation. The effects of influential parameters such as B-TiO 2 dosage, TC concentration, pH, and Fe 2+ to H 2 O 2 molar ratio were also investigated, in addition, the catalyst is stable, as it achieved > 80% TC degradation efficiency after five reuse cycles.