Photosensitised Degradation of Phenol by Visible Light and a Riboflavin-derivative adsorbed on the Surface of TiO2

DAVID POSSETTO; JOSE NATERA; GARCIA NORMAN; MASSAD WALTER

Congreso; XIII ELAFOT; 2017

Contamination of surface water due to poor agricultural practices and excessive use of pesticides is a growing problem in our country. Recently CASAFE (Chamber of Pesticides in Argentina) reported that the consumption of pesticides increased 858% in the last 22 years [1]. Among the alternatives for the treatment of toxic organic pollutants in the water or effluents, called advanced oxidation processes (POAs) are one of the most attractive, most of them are characterized by hydroxyl radicals (OH●) in quantity sufficient to oxidize most of the organic compounds. The treatment of water by heterogeneous photocatalysis using titanium dioxide as a catalyst is one of the most interesting POAs among the scientific community [2] since it is inert and highly chemically stable. However, photodegradation processes using TiO2 requires light with wavelength less to 370 nm, which represents less than 5% of the solar radiation that reaches the earth. In this sense, the sensitization processes resulting from the photoexcitation of dye molecules (sensitizers) have succeeded in increasing the degradation efficiency of TiO2 with sunlight. Photosensitization is a convenient method to extend the photoresist of semiconductor materials to the visible region. Typically, the dye is adsorbed on the surface of the semiconductor and absorbing visible light reaches excited state(s) which are capable of injecting electrons into the conducting band of the semiconductor.This paper reports the characterization of films based on TiO2 and Rf-PO4 synthesized by two different methodologies. Procedure 1: The dye was adsorbed on the surface of TiO2 by immersion of the film in a Rf-PO4 solution after sintering the TiO2 for 30 minutes at 500°C. Procedure 2: The dye was incorporated to the TiO2 previously to the sintering process at 180ºC to prevent the Rf-PO4 thermal degradation.To test the photocatalytic efficiency of the developed system, phenol was chosen as the model pollutant. The discharge of phenolic compounds from industrial sources such as synthetic resins, petroleum refineries and coke oven processes, even at low concentrations, poses a major threat to aquatic organisms [3]. For the sensitized photodegradation process of phenol, a solution was irradiated in the presence of the different films synthesized. Also, different sources of radiation (simulated solar light and blue LEDs) were used for photodegradation. Comparative studies were carried out between the different films to evaluate the degradation efficiency of phenol.Material used for photodegradation% Degradation of phenol with 40 min of irradiationSimulated solarLEDs lightProcedure 11010Procedure 22520film of TiO2 alone50Identification of the photoproducts was made by HPLC. In all cases, the majority photoproducts coincided with the products generated by Phenol photodegradation by a TiO2 suspension [4].In conclusion, the better degradation performance was obtained using the film synthesized by the procedure 2. In addition, the union of the Rf-PO4 on the TiO2 allowed extending the photoresponse of the film to the visible region, obtaining a greater efficiency for the degradation of the Phenol.