Microwave Accelerating Chromium Slag Processing Of Simulated Azo Dye Wastewater

Azo dyes waste water is not only high chromatic, strong noxious, but also difficult to degrade and easy decompose to carcinogenic aromatic amine under deoxidization condition. So, azo dyes waste water must be treated urgently. In this paper, methyl orange which has azo dyes structure was studied for research the conditions and mechanism of decomposing process about the solution of methyl orange. The influence about decoloring effect of solution, removal effect of TOC, decomposing degree of methyl orange, the residue concentration of methyl orange and chromium(VI) in the solution was researched by five factors which were dosage of chromium slag, additive mass of H₂O₂, pH value of aqua solution, power of microwave and time of microwave process. The feasibility about two methods was studied for determining the concentration of methyl orange and chromium (VI) simultaneous in the solution. They are polarography and ultraviolet and visible spectrophotometry using two wavelengths.The veracity of result was bad when utilize ultraviolet and visible spectrophotometry by two wavelengths determining the concentration of methyl orange and chromium (VI) in the aqua solution.becuse of enshrouding process by methyl orange. In this thesis, polarography was studied for determining two compositions simultaneous. The detection limit of chromium (VI) and methyl orange were 9.46×10^-8 g/L and 1.86×10^-6 g/L respectively, and the relative standard deviations were 2.18% and 4.98% respectively. This method simple and convenient, shortcut, good veracity, high precision, and could determine the concentration of methyl orange and chromium (VI) simultaneous in the aqua solution. This method applied successfully to simultaneous determination of chromium and methyl orange in practice waste water.Microwave irradiation could enhance the temperature of solution, strengthen the thermic movement of molecule, and improve the rate of equation, accelerate decomposing process of methyl orange. The residue concentration of methyl orange can be reducing by microwave irradiation. The residue concentration of methyl orange was lesser when the power of microwave was bigger. Enhancing the power was propitious to decompose methyl orange. The more power the more removal rate. The removal rate was gradually augmenting when the power was from 180W to 360W and the rate ascending current become relaxedly when the power was exceed 360W. In addition, the concentration of methyl orange and chromium (VI) was also influenced by the power of microwave. The concentration of chromium (VI) in the solution was lowest, all the concentration of methyl orange which were in the solution and in the solid residue were lower, the removal rate of methyl orange was high, when the power of microwave was 540W.The study which using difference dosage of H₂O₂ indicate that the influence about removal of methyl orange was very observably by H₂O₂, the solution was decolor when we add a letter of H₂O₂ in solution, but the removal rate of organic compound was immovabile. The removal rate of TOC was zooming when we add more dose of H₂O₂. Diversifications current become slowly, solution was decoloring completely when the dose exceeds 0.5mL. The result indicate that—N=N—bond which in the structure of methyl orange has been destroyed and it has been decomposed absolutely.Acerbic or alkaline solution mostly influences the decomposing process of methyl orange. Methyl orange can gain good decomposing effect under pH 2-12. Treatment effect was worst under the strong acerbic condition and better under the strong alkaline condition, especially, it was best under pH 4⁶. The structure of methyl orange was quinone style in acerbic solution and azo style in alkaline solution.The research which adding difference dosage chromium slag the influence about removal of methyl orange was also very observably by chromium slag. The colour of solution changing was not obvious and removal of TOC was only 0.5% when we don't add slag into solution. The removal of TOC was zooming, and the more slag the more removal rate when we add it. It indicated that chromium slag was very important in this equation. The removal changing become slowly when the dose reaches 1.0g later. And adding slag couldn't enhance removal of TOC.To research UV-VIS spectrum and fluorescence spectrum, we have conjectured the decomposing mechanism about methyl orange. Decomposing process was likely to this under the condition which make up of microwave, chromium slag, H₂O₂ and weak acerbic aqueous solution. First, in the structure the N—N bond was destroyed, creating N, N-dimethyl-4-aminobenzene and 4-amino-benzenesulphonate, 4-amino-benzenesulphonate deamino creating benzenesulphonate. Later, the benzenesulphonate become to benzene and finally become to CO₂ and H₂O etc. N, N-dimethyl-4-aminobenzene diamine creating, N, N-dimethylbenzene, secondly, becoming to benzene, finally, organic compound was decomposed becoming to CO₂ and H₂O etc.