Photocatalytic Degradation of an Odorous Pollutant: 2-Mercaptobenzothiazole in Aqueous Suspension Using Nd3+-TiO2 Catalysts

Photocatalytic degradation of an odorous chemical, 2-mercaptobenzothiazole (MBT), in aqueous suspension was investigated using pure TiO2 and neodymium ion doped TiO2 (Nd3+-TiO2) catalysts. The photocatalytic activity of Nd3+-TiO2 was evaluated in the photocatalytic degradation of MBT in aqueous solution. The experimental results showed that the overall kinetic constant (k) of MBT degradation using Nd3+-TiO2 was significantly higher than that using TiO2 and an optimal content of neodymium ion doping was found to be 1.2% (molar ratio). The main intermediates during the MBT degradation were identified by LC/MS-MS, and the final products including sulfate ion, ammonium ion, and nitrate ion were also determined by ion chromatography. Only three main intermediates including benzothiazole, 2-hydroxybenzothiazole, and benzothiazole-2-sulfite were found during the MBT degradation using the TiO2 catalyst, while five main intermediates including benzothiazole, 2-hydroxybenzothiazole, benzothiazole-2-sulfonate, benzothiazole-2sulfite, and anilinesulfonic acid were found during the MBT degradation using 1.2% Nd3+-TiO2. On the basis of analytical results, a possible pathway of MBT degradation in such a photocatalytic oxidation reaction was proposed and illustrated. It was concluded that the photodegradation of MBT and its intermediates can be enhanced owing to the neodymium ion doping.