Comparative Study on Enhanced Photocatalytic Activity of Visible Light-Active Nanostructures for Degradation of Oxytetracycline and COD Removal of Licorice Extraction Plant Wastewater

This study evaluates the effects of carbon, nitrogen, and sulfur dopants on photocatalytic activity TiO2 for degradation oxytetracycline (OTC) chemical oxygen demand (COD) removal from licorice extraction plant wastewater (LEPW). Three novel visible-light-responsive nanostructures, including L-Histidine-TiO2, L-Methionine-TiO2 L-Asparagine-TiO2, were successfully synthesized. The results showed that modification with these three amino acids made catalyst active in visible light region reduced recombination rate e?/h+ pairs according to PL analysis. photodegradation efficiency L-Histidine (2 wt.%)-TiO2 was 100% 94% OTC COD, respectively. It highest under illumination, compared L-Methionine (1.5 L-Asparagine wt.%)-TiO2. Synthesized composites characterized SEM, XRD, FTIR, DRS, analyses. biological COD (BOD5/COD) ratio treated LEPW determined be 0.5–0.6, confirming enhanced biodegradability effluent. effect independent variables, namely, initial concentration dosage, irradiation time, pH solution, intensity, process evaluated by Response Surface Methodology (RSM), optimum value each parameter maximum determined. radical trapping experiment performed various scavengers order propose a mechanism, showing hydroxyl radicals main species. stable reusable structure even after four cycles following optimal conditions [COD]: 300 mg/L, [catalyst]: 1 g/L, intensity: 25 W/cm2 at = 4 180 min irradiation.