Color-Mixing Effects In The Visible Light/H₂O₂ System

"Color-mixing effect"refers to the phenomenon that several single-color substance solutions such as red,yellow and blue,which cannot be degraded in the visible light/H₂O₂system,can be degraded after they are mixed into brown coloration.In this thesis,the causes of"color-mixing effect"in the field of water treatment were discussed.The yields of hydrated electrons,singlet oxygen,superoxide anion radicals and hydroxyl radicals in single-color and mixed-color solutions under visible light irradiation were measured and compared.The results show that there was no significant difference in the yields of hydrated electrons and singlet oxygen in the single-color solutions and the mixed-color solutions.However,the yields of superoxide anion radicals in mixed brown solutions were significantly higher than that in other single-color solutions,indicating that the reason of"color-mixing effect"was the increase of superoxide anion radicals’yields improve.Superoxide anion radicals can catalyze H₂O₂ to produce more hydroxyl radicals,which can degrade the mixed-color solution in visible light/H₂O₂ system.The"color-mixing effect"is explained mainly by higher hydroxyl radicals generation from increased superoxide anion radicals production.The theory of"color-mixing effect"has guiding significance for the actual wastewater treatment.The result show that the COD removal rate of brown-black Liaohe Oilfield wastewater in visible light/Fenton system was better than that in UV/Fenton system after 180minutes of illumination.In this thesis,the causes of this phenomenon were analyzed in depth.There are a lot of benzene compounds in Liaohe Oilfield wastewater and another colored organic wastewater.A red-brown intermediate product formed by the polymerization of p-benzoquinone and oxygen was produced during the degradation of benzene compounds.And the red-brown color can be considered as a mixed-color,with good photosensitivity,and can make better use of visible light.Benzene compounds widely exist in wastewater and are the most representative organic pollutants in wastewater.Hence the"color-mixing effect"has a wide range of universal value in the actual water treatment.In order to study the"color-mixing effect",a new method for the detection of superoxide anion radicals in water system was established.In this method,hydroxylamine hydrochloride was used as the probe,Fe³⁺was used as the auxiliary metal ion.Hydroxylamine hydrochloride was oxidized by superoxide anion radicals and consumed,and the remaining hydroxylamine hydrochloride in solution reduced from Fe³⁺to Fe²⁺.Then the reduction of absorbance value of([Fe（phen）₃]²⁺)complex at 510 nm was measured to indirectly indicate the generation of superoxide anion radicals.The method was simple and feasible and could be used for the stable measurement of superoxide anion radicals produced by chromophoric dissolved organic matters under acidic conditions in visible light systems.