Improving the catalytic performance of TiO2 by its surface deposition on CNT buckypapers for use in the removal of wastewater pollutants

Buckypapers (BPs) consist of carbon nanotube (CNT) membranes with good mechanical, thermal and electrical properties. We report the modification of CNT buckypapers by the surface deposition of a thin layer of titanium dioxide and their subsequent photocatalytic use for the removal of three wastewater pollutants: diclofenac (DF), carbofuran (CB) and methylene blue (MB). The results show the following decreases (RE) in the initial concentrations of these pollutants, REDF=99.5%, REMB=96% and RECB=90% after 90 min of exposure to UV-Vis radiation using ～0.6 mg of photocatalyst. Experiments also showed that the degradation rate of diclofenac (k = 0.1028 min−1) is respectively 3.5 and 6 times faster than the values for CB (k = 0.0298 min−1) and MB (k = 0.0174 min−1), probably due to the easier bond cleavage in DF. UV-Vis irradiated solutions of these pollutants were then analyzed by mass spectrometry to identify the species formed during photocatalysis and suggest possible degradation paths for MB, DF, and CB. Data showed that the degradation of DF involves the formation of a photocyclization product through loss of HCl molecule, clearly consuming less energy than that needed for the opening of the central aromatic ring in MB or the loss of the N-meth l amide functional rou for CB.