Photocatalytic improvement of Y3+ modified TiO2 prepared by a ball milling method and application in shrimp wastewater treatment

Abstract

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 (Y³⁺) were prepared by a ball milling method. The effects of Y³⁺ 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 Y³⁺/TiO₂ 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 TiO₂. All Y³⁺/TiO₂ samples showed a red shift of absorption compared to pure TiO₂ 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 m² g⁻¹. The COD_Cr removal rates of shrimp wastewater were 43.8% and 37.5% for 2% Y³⁺/TiO₂ 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.