Solar-driven remediation of antibiotics in synthetic and real reverse osmosis brine: Addressing lattice oxygen demand and electron transfer for improved purification

This study investigated the significance of integrated advanced oxidation process with reverse osmosis (RO) to ensure the purification and elimination of micropollutants, primarily pharmaceuticals prior to the discharge of brine to the environment. To envisage this, TiO₂ based solar driven photocatalysis was employed, highlighting the crucial role of oxygen vacancy formation in the lattice of TiO₂ for enhancing the purification of antibiotic contaminants from RO brine. The study elucidated how variations in oxygen environments such as oxygen rich yellow TiO₂ (Y-TiO₂) and oxygen vacancy black TiO₂ (B-TiO₂) influence photodegradation reaction kinetics taking ofloxacin (OFX) and tetracycline (TC) as model pollutants. The B-TiO₂ exhibited 8.5 times higher photodegradation for OFX compared to Y-TiO₂, proving significance in tuning of oxygen environment in lattice. The photodegradation efficiency plot showcases B-TiO₂′s efficacy, demonstrating 99.8 % and 99.4 % for OFX and TC, respectively. Additionally, the study investigated the photocatalytic degradation mechanism, identifying predominant charge carriers and reactive species involved, while also assessing the durability of photodegradation processes. The impact of pH on the photocatalytic performance of B-TiO₂ in degrading antibiotics explored, spanning pH levels from 2.5 to 10.5. An exploration on band alignment formation in B-TiO₂ explains the effectiveness of it over Y-TiO₂. Lastly, efficacy of B-TiO₂ in degrading antibiotics in real RO brine with high level of salinity (60,200 ppm TDS) is demonstrated, which resulted with photodegradation efficiency of 31.25 % for OFX and 67.8 % for TC, proving applicability of integrated system as a sustainable purification approach. Moreover, the blockage of chloride ions quenching demonstrated improvements in photodegradation emphasizing the influence of chloride ions in high saline conditions.