Effects Of Tetracycline Degradation Behavior On Ag/BiVO₄

This study selected tetracycline antibiotics as the research object, and Ag/BiVO4 as the photocatalyst, studying the behavior of tetracycline degradation under the ultraviolet, visible light. Taking into account the main factors in the actual wastewater treatment photodegradation, focusing on the pH, Ca2+, Mg2+ on Ag/BiVO4 photocatalytic degradation of tetracycline, and conducted a mechanism analysis. To achieve better degradation effect, the way that in combination of Ag/BiVO4 and hydrogen peroxide for the degradation of tetracycline hydrochloride.At the same time, because of the Ag/BiVO4 has the potential ability to using visible light, so studying the degradation of tetracycline under visible light may provide a theoretical basis on Ag/BiVO4 photocatalyst catalytic application in the actual production. According to the research, we can concluded that,(1)Scanning the UV-vis spectra we can obtained that the main absorption wavelength of Bi VO4 is 445 nm, and the main absorption wavelength Ag/BiVO4 is540 nm.Compared with BiVO4, Ag/BiVO4 can make better use of visible light.(2)Under visible light irradiation conditions, because BiVO4 loaded Ag can absorbed the visible light better, so the effect of degradation of tetracycline hydrochloride is better. Comparing the impact of different amounts of silver to the photocatalytic degradation efficiency, we can see that loading of 2% Ag/Bi VO4 catalyst has the best performance of the photocatalytic degradation of tetracycline hydrochloride. Under UV irradiation conditions, tetracycline hydrochloride have occurred slow oxidative degradation in BiVO4 and Ag / BiVO4 catalyzed by longer light irradiation. But because BiVO4 can make better use ultraviolet light, and thus the catalytic effect of the degradation of tetracycline hydrochloride is better than Ag/BiVO4 catalyst.(3)Photocatalytic degradation of tetracycline hydrochloride by BiVO4 and Ag/BiVO4 utilizing its unique photosensitivity as well, belonging to theheterogeneous photocatalytic degradation reactions. Processes in heterogeneous photocatalytic degradation reactions, relies mainly on a photosensitive material by absorbing light energy then exciting electron-hole pairs, generating adsorbed oxygen,water molecules on which play a role with the electron-hole pairs generated hydroxyl free radicals and other highly oxidizing free radicals then react with tetracycline hydrochloride to get degraded. Therefore, the amount of catalyst can effectively promote tetracycline hydrochloride photolysis, excess catalyst will plug electron-hole pairs, so it can not be dissolved, the role of water molecules to produce hydroxyl radicals, hindering further photocatalytic degradation, resulting in the degradation rate decreases.(4)pH play an influential role in the tetracycline hydrochloride and tetracycline photodegradation, as the performance of cationic form, anionic form, neutral ionic form related in different pH. Contains three different ionization tetracycline group,the ionization equilibrium constant pKa1, pKa2, pKa3 values in aqueous solution were 3.30,7.69,9.69. At pH 3.3 to 7.7, with tetracycline can be seen as a dimethylamino group and a phenolic hydroxyl group and the negatively charged ions(+-0), at a pH less than 3.3, can be seen as a cationic, pH greater than 7.7 can be seen as an anion. Weakly acidic and neutral environment conducive to Ag/BiVO4 catalytic degradation of tetracycline hydrochloride; alkaline environment tetracycline hydrochloride and catalyst are negatively charged, rejection, inhibits Ag/Bi VO4 catalytic activity, reduce light degradation rate of tetracycline hydrochloride.(5)Ca2 + and Mg2 + will happen to tetracycline hydrochloride chelation reaction of chelates, is not conducive to bind Ag/BiVO4 adsorption catalyst, will greatly reduce the Ag/BiVO4 catalytic degradation rate of tetracycline hydrochloride.(6)Hydrogen peroxide joint Ag / BiVO4 under UV and visible light conditions on the degradation of tetracycline hydrochloride has a duality. The right amount of hydrogen peroxide will promote the reaction, an excess of hydrogen peroxide will lead to the conversion of hydroxyl radicals, and thus interfere with the photocatalytic degradation.