Photocatalytic degradation of bisphenol A over Rh/TiO2 suspensions in different water matrices

A series of noble metal-promoted Me/TiO2 (P25) photocatalysts (Me: Pt, Ru, Pd, Rh) of the same metal loading (0.5 wt.%) were synthesized by the wet impregnation method and their photocatalytic activity was tested for the degradation of bisphenol A (BPA) under simulated solar irradiation. Results of H-2 chemisorption, XRD, BET and UV-vis DRS experiments showed that dispersion of small metal crystallites on the TiO2 surface did not affect appreciably the phase composition (similar to 85% anatase), specific surface area (47-49 m(2)/g) and optical band gap (3.2 eV) of the semiconductor. Pt/TiO2 catalyst exhibited the higher efficiency under solar irradiation. In contrast to other Me/P25 catalysts investigated, the Rh/P25 catalyst exhibited increased activity for the title reaction in the presence of 20 mg/L humic acid (HA), which was about 2.5 times higher than that obtained in ultrapure water (UPW). The apparent rate constant for the degradation of BPA in UPW + HA was found to increase proportionately with an increase of catalyst concentration in the range 50-400 mg/L. The rate was not affected appreciably by the presence of inorganic ions contained in bottled water but decreased substantially in a secondary treated wastewater matrix. Results of liquid chromatography-time-of-flight-mass spectrometry (LC-TOF-MS) showed that degradation of BPA proceeds via two main pathways, which involve (i) hydroxylation, and (ii) cleavage of isopropylidene group with subsequent formation of para-substituted phenol derivatives.(C) 2016 Elsevier B.V. All rights reserved.