Comparison of titanium dioxide based catalysts preparation methods in the mineralization and nutrients removal from greywater by solar photocatalysis

The present study investigated the solar photocatalytic treatment of greywater using modified TiO2 catalysts, viz., M-TiO2, U-TiO2, NP-TiO2, and NT-TiO2 synthesized through ultrasonication, microwave, and sol-gel method with/without doping respectively. X-ray dispersive spectroscopy (XRD) results indicated a negligible change in the crystallinity of the modified catalysts compared to commercial TiO2 catalyst, Degussa P-25 (P-25). Scanning electron microscopy (SEM) analysis depicted the lowest particle size of 88.89 nm for U-TiO2. The calculated band gap energy for P-25, U-TiO2, M-TiO2, NP-TiO2, and NT-TiO2 were 3.65, 3.1, 3.5, 3.35, and 2.7 eV, respectively. The mineralization efficiency was in the order of NT-TiO2>U-TiO2>NP-TiO2-M-TiO2>P-25, with the highest mineralization efficiency of about 75% within 3 h using NT-TiO2. The nitrate removal was in the order of NT-TiO2>U-TiO2-NP-TiO2>M-TiO2>P-25, with the nitrate removal of 92.5%. Simultaneous oxidation of organic matter and reduction of ammonia were observed during the solar photocatalytic treatment of greywater. The comparison of sunlight NT-TiO2-system with other photocatalytic treatment employed for greywater reveals that the NT-TiO2 system was highly energy efficient (-31.86 kWh (kgCOD)(-1)) compared to other systems. (C) 2019 Elsevier Ltd. All rights reserved.