Insights into the photocatalytic degradation of triclosan over amorphous Nb2O5 catalysts

Photocatalytic degradation of triclosan is one of the most promising way to eliminate triclosan pollution in water, yet it presents profound challenges to develop efficient photocatalysts to meet the demand of application. Herein, we demonstrate a facile hydrothermal-precipitation method to prepare amorphous Nb2O5 catalysts by using niobium(V) oxalate hydrate and ammonium carbonate. A series of amorphous Nb2O5 catalysts were obtained and analyzed by detail characterizations (XRD, XPS, BET and SEM). By optimizing synthesis conditions, it was found that 180/12-Nb2O5-(1:5) catalyst exhibited the optimal photocatalytic activity for triclosan degradation. Furthermore, the pseudo-first-order kinetic equations for triclosan degradation over 180/12-Nb2O5-(1:5) catalyst were investigated under conditions with different pH value. Among them, the triclosan degradation rate over 180/12-Nb2O5-(1:5) catalyst gave the highest reaction constant k (0.5 min(-1)) and shortest half-period (t(1/2) = 0.17 min(-1)) at pH of 8. The presence of ionic state triclosan in base condition should be responsible for the improved degradation rate from acid to base reaction condition. Compared with molecular triclosan, ionic state triclosan exhibits very high reaction rate with radicals due to its strong electrophilic property. The high photocatalytic activity of 180/12-Nb2O5-(1:5) catalyst should be related to the presence of amorphous structure compared with calcined 180/12-Nb2O5-(1:5) catalyst with highly crystalline structure. The existence of N species doping and nano-sheet structure in catalyst is also thought to promote the catalytic reaction.