The Activity And Mechanism Of Photocatalytic Degradation Of Alizarin Green By Cerium Ions

The printing and dyeing wastewater takes a large proportion of industry wastewater inChina, and because of its characteristics, such as large water volume, high concentrationorganic pollutant, deep chromaticity, high alkalinity, changeable water quality and complexingredient, it is difficulty to treat, and the decolorization and mineralization is a majorproblem in the printing and dyeing wastewater. In recent years, due to the development of thetextile industry, printing and dyeing wastewater treatment is gradually increasing urgent.Meanwhile, in order to relieve the pressure of water environment caused by printing anddyeing wastewater, state and local governments have also established more strict emissionstandard. It is essential to search for a high-performance physico-chemical treatment methodfor dyeing wastewater.In this paper, according to the achievements we made, the simple cerium salt Ce（NO3）3was used as the photocatalyst to degrade organic pollutants such as alizarin green, reactiveblue P-3R, methylene blue, methyl orange II, rhodamine B, acid orangeⅡ andp-nitrophenolunder UV irritation, and we studied the degradation activity and reaction mechanisms of Ce³⁺to anthraquinone dye AG under UV irradiation. First, the effects of operating factors, such aspH, Ce³⁺, AG concentrations and negative ions were studied respectively, and we got the mainoperating parameters under optimum treatment condition; Then, the degradation of the systemto other dyes and p-nitrophenol was researched. Eventually, the reaction mechanism andintermediate products were also discussed in detail.Results were showed as below:（1） cerium nitrate could degrade AG by UV irradiation effectively. The initial reaction rateincreased linearly with the inverse value of AG concentration andconcentration increasing.Decreased first and then increased with the initial pH of the solution increasing. TOC removalrate was high under acidic conditions. The degradation effect of the system to other types ofdyes and p-nitrophenol was also good.（2） The main operating parameters under optimum treatment condition is: pH2.05，AG0.16mM, Ce³⁺0.2mM,25℃.（3） The fluorescent experiments showed that there was OH radical at the beginning of thereaction, and OH was the main active species.（4） After analysising of the intermediate product at different reaction times bydirect-infusion electrospray ionization mass spectrometry （ESI-MS）, the degradation processis as follows: First, an initial successive hydroxyl radical attacks on the dye molecules tobreak of-NH-group. Then subsequent oxidation of these products results in hydroxylationand the SO3-group is lost. Finally, the carboxylic acids are formed from the ring opening, andthey are further oxidized to carboxylic acids and CO2.This paper researches the active and mechanism of dye degradation by UV/Ce³⁺system. As per the literature, it is the first attempt made to show that the homogeneous Ce3+ions canbe used as a photocatalyst for remediation of pollutants, and the new basis technical supportfor further engineering application of advanced oxidation technology is provided.