Photocatalytic improvement of Y 3+ modified TiO 2 prepared by a ball milling method and application in shrimp wastewater treatment.

Semiconductor photocatalysis is an advanced oxidation process driven by solar energy which has widespread applications in the treatment of organic pollutants in liquid and gas phases. In this work, titanium dioxide nanoparticles modified with yttrium ions (Y 3+ ) were prepared by a ball milling method. The effects of Y 3+ mole fraction, ball-to-powder weight ratio, milling time and milling rate on the photocatalytic activities were evaluated by the degradation of methylene blue (MB) under UV light. Then Y 3+ /TiO 2 photocatalysts prepared at the optimized ball milling conditions were applied to treat shrimp wastewater under UV and visible light. Chemical oxygen demand (COD Cr ), 3D fluorescence spectroscopy and total organic carbon (TOC) were used to detect the water samples taken from the photocatalytic experiments. Experimental results showed that when the mole fraction was 2%, the ball-to-powder weight ratio was 4 : 1, milling time was 4 h and milling rate was 500 rpm, the reaction rate constant of MB degradation can reach up to 0.1112 min -1 which was 4.2 times as fast as pure TiO 2 . All Y 3+ /TiO 2 samples showed a red shift of absorption compared to pure TiO 2 and it led to a visible light absorption response. The content of surface oxygen vacancies has significantly increased and the BET specific area increased to 104 m 2 g -1 . The COD Cr removal rates of shrimp wastewater were 43.8% and 37.5% for 2% Y 3+ /TiO 2 under UV and visible light, respectively. Besides, the TOC removal rates were 67.5% and 38.8%, respectively. Humic-like substances and fulvic-like substances in shrimp wastewater can be mineralized after 90 minutes irradiation.