Study On The Degradation Product And Process Of An Anthraquinone Dye By TiO₂Photocatalytic Degradation

Anthraquinone dye was widely used as the second largest category of dyes, with itsbright color, stable, and complex structure. Traditional method to degradation anthraquinonedye is not satisfied. Photocatalytic degradation is one of the effective methods amongadvanced oxidation process （AOP）, for its characteristics of that complete degradation oforganic compounds, difficult to make a toxic intermediate product and secondary pollution.The targets of this thesis are to promote the application in dyeing wastewater byphotocatalytic oxidation. In this work, photocatalytic degradation of an anthraquinone dye,C.I.Acid Green25（AG25）, under UV light irradiation using TiO2nanoparticles was studied.This thesis investigated the changes of molecular structure, degradation kinetics, generationof intermediate products, speculates degradation process, and the biodegradability is alsoanalyzed.The main parts of this thesis are as follows:（1） Two ion chromatography （IC） methods for simultaneous determination of anionic(formic acid, acetic acid, lactic acid, oxalic acid, malic acid, Cl^-, SO₄^2-, NO₂^-, NO₃^-) andsimultaneous determination of inorganic cations （Na⁺, NH₄⁺） are established. Calibrationcurves for the nine anions and two cations were well correlated （r2>0.99）. The methodexhibits good reproducibility. The set-up methods were used to analyze the organic acids,inorganic anions and cations produced from the degradation of the C.I.Acid Green25by TiO2photocatalytic oxidation.（2） Experimental results showed when reaction time was30minutes, the decolorizationrate reaches almost100%, and absorption peaks between400nm and800nm almostdisappear. While the degradation rate reaches almost100%when reaction time was45minutes, and absorption peaks around200nm was greatly attenuated. This indicates themacromolecule conjugated structure of AG25degraded faster than anthraquinone andbenzodiazepines materials.（3） The degradation process-lnAt/A0and t followed the first kinetic equation.Photocatalytic mineralization of AG25was monitored by total organic carbon （TOC）,inorganic anions and cations. After60min’s photocatalytic degradation, the TOC removalrate group to81%. According to the results of IC, that the sulfonic acid group of AG25was mostly oxidate into SO₄^2-, and–N was mostly degradate into NH₄⁺after reaction.（4） The varies of the possible intermediates during degradation process were monitored withLC-MS and GC-MS. Combined analysis of total organic carbon （TOC）, UV-vis spectrum and ionchromatography in degradation processes, a possible degradation pathway for the photocatalyticoxidation of Acid Green25has been proposed.（5） The biodegradability, evaluated by ratio of BOD5and COD. The BOD5/COD valueincreases from0.07before the treatment to0.5, the biodegradability increases remarkably.