Abstract-Water pollution caused by organic and inorganic contaminants represents an important ecological and health hazard. In this study the photocatalytic reduction of Cr(VI) and degradation of salicylic acid (SA) in aqueous suspensions using commercial TiO2 was investigated. The effect of operating parameters such as photocatalyst loading, initial pollutant concentration and pH were optimized in aqueous solution containing salicylic acid alone and hexavalent chromium alone. The performance of the photocatalyst reactor was evaluated on the basis of salicylic acid removal and metal ion reduction. The rate of salicylic degradation for the ternary salicylic acid /Cr(VI)/TiO2 system were generally lower than that for the respective binary salicylic acid/TiO2 systems. This could be attributed to partial catalyst deactivation to some extent..

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A nanocomposite photocatalyst consisting of titanium dioxide (TiO2) supported on multiwalled carbon nanotubes (MWCNTs) has been successfully prepared and used for the treatment of wastewater contaminated with tetracycline (TC), a recalcitrant antibiotic pollutant. The TiO2/MCNT composites were prepared by a simple evaporation-drying method. The properties of MWCNT/TiO2 were optimized by dispersing different amounts of TiO2 onto MWCNT. The structural and optical characteristics of the nano-engineered photocatalyst composite were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) techniques. Photocatalytic degradation of TC was conducted in a quartz glass reactor. Different kinetic models were used to demonstrate the governing mechanisms. The findings revealed that the TiO2/MWCNT composite had enhanced photocatalytic activity (95% TC removal) compared to TiO2 (86% removal). The photocatalyst nanocomposite exhibited overall pseudo-second-order reaction kinetics and favored the Langmuir adsorption isotherm. Although up to 95% degradation of TC was achieved, only 75% of it was mineralized as a result of the formation of stable refractory intermediates.