n the present paper, photocatalytic degradation of paraquat using N-TiO2/SiO2 with different molar ratio of titanium: nitrogen (Ti:N) under visible light was investigated. The catalyst was prepared via immersed SiO2 in N-TiO2. N-TiO2 was synthesized by sol-gel method. | Vietnam Journal of Science and Technology 55 (4C) (2017) 277-283 PHOTOCATALYTIC DEGRADATION OF PARAQUAT USING N-TiO2/SiO2 UNDER VISIBLE LIGHT Nguyen Thi Phuong Mai1, Nguyen Manh Nghia2, Nguyen Thi Hue1 1 Department of Environmental Quality Analysis, Institute of Environmental Technology, VAST, 18 Hoang Quoc Viet, Ha Noi 2 Faculty of Physics, Hanoi National University of Education, 136 Xuan Thuy, Cau Giay, Ha Noi * Email: nthue2003@; npmai82@ Received: 1 August 2017; Accepted for publication: 17 October 2017 ABSTRACT In the present paper, photocatalytic degradation of paraquat using N-TiO2/SiO2 with different molar ratio of titanium: nitrogen (Ti:N) under visible light was investigated. The catalyst was prepared via immersed SiO2 in N-TiO2. N-TiO2 was synthesized by sol-gel method. The N-TiO2/SiO2 catalyst was characterized using X-ray diffraction, UV diffuse reflectance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy. The results from characterizations indicated that N-doped anatase TiO2 had a 20-25 nm size. Degradation of paraquat, at an initial concentration of 10 mg/L was determined by UV-Vis. Chemical oxygen demand (COD) was used for process performance. Based on the COD tests, the COD values in residual paraquat was lower than that in initial paraquat concentration after 8 hours illumination of visible light. Moreover, the experiment’s results indicated that 80% of paraquat was degraded within 8 h of illumination time. These results showed that N-TiO2/SiO2 with molar Ti:N=2:1 gives the highest degradation efficiency of paraquat under visible light. This catalyst was stable and reusable suggesting it can be applied to treat organic pollutant in water. Keywords: TiO2, photocatalyst, N dopping , paraquat. 1. INTRODUCTION Paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride ) is one of the most popular herbicide which has been used widely in the productions agriculture for control broad leaf weeds in .
