Studies On The Reactions And Catalysys For Catalytic Wet Peroxide Oxidation Of Sodium Anthraquinone-2-Sulphonate

Sodium anthraquinone-2-sulphonate(SAS), an important intermediate of anthraquinone dyes, is the main raw material for the synthesis of anthraquinone acid dyes, which can be used in the synthesis of reactive dyestuff, vat dye and disperse dye. This kind of dye wastewater is typical organic wastewater with high concentration, high chroma, thigh acidity and high salinity. Using the conventional processes directly, such as biological and physicochemical methods for treatment is inefficient. Catalytic wet peroxide oxidation technology as an advanced oxidation process has been used in degradation of refractory organic wastewater. Compared with the wet air oxidation technology, catalytic wet peroxide oxidation technology(CWPO) gains more attention because it could decrease reaction conditions, shorten reaction time and raise oxidation efficiency. The purpose of this paper is to select a kind of catalyst with higher dispersion of active component, better activity and stability. The appropriate conditions of reaction for catalytic wet peroxide oxidation and catalyst preparation were preliminarily proved, which would provide basis theory for practical engineering application.In this paper, a kind of composite catalyst containing the main activated component Cu, the second activated component Mn and rare-earth element Ce has been prepared. It is the composite catalyst suitable for treating highly concentrated organic wastewater of sodium anthraquinone-2-sulphonate by catalytic wet peroxide oxidation technology. The technical parameters such as concentration of the impregnation solution, impregnation temperature, impregnation time, calcination temperature, calcination time, etc were investigated, and the optimum parameters were determined as follows:the concentration of Cu2+is6%; the concentration of Mn2+and Ce3+is2%; the impregnation temperature is25℃; the impregnation time is12h, the calcination temperature is500℃; the calcination time is4h.Easily dissolution of the active component in high temperature conditions has seriously affected the popularization and application of copper series catalyst in practical engineering. The way of active component dissolution is divided into two parts, the reactive dissolution and the acidic leaching. Wherein the reactive dissolution is the main dissolution. Changing the influent pH, calcination temperature and doping auxiliaries can improve the situation of Cu2+leaching. Doping Ce can effectively improve the stability of the catalyst and decrease the dissolution of Cu+, which is the main of active component. The dissolved quantity of Cu2+was decreased from25.4mg·L-1to2.7mg·L-1.Catalyst prepared by the method mentioned above is applied to CWPO for SAS(5g·L-1) simulated wastewater treatment and the processing conditions, such as reaction temperature, velocity of stir, dosage of the catalyst, dosage of perhydrol solution and influent pH, is optimized. The optimized conditions were determined as follows:the reaction temperature is190℃; the velocity of stir is500r·min-1; the dosage of the catalyst is4g·L-1; the dosage of30%perhydrol solution is55mL·L-1and the influent pH is9. In these conditions, COD removal of simulated wastewater is the best and COD removal can reach95.33%after100minutes reaction.LC-MS was used to analyze the metabolites of SAS in the degradation process by CWPO technology, and the degradation pathway has been inferred. Sodium anthraquinone-2-sulphonate(SAS) was firstly oxidized into2-(4-hydroxybenzoyl)-benzoic acid, then2-(4-hydroxybenzoyl)-benzoic acid was degraded into o-phthalic acid and hydroquinone, and then o-phthalic was oxidized into catechol and o-quinone. Then o-quinone was oxidized into2,4-hexadienedioicacid.1,4-Benzoquinone as the metabolites of hydroquinone and2,4-hexadienedioicacid degraded into maleic acid, and maleic acid was decomposedinto oxalic acid. At last partial organics were mineralized to CO2and H2O.