Study On The Comprehensive Utilization Of Hazardous Wastes Containing Aluminium Compounds From A Chemical Factory

In light of the characteristics of high aluminium compounds content, the alkali extraction and acid precipitation were applied to reduce and recycle the hazardous waste. Then the extract was characterized by X-ray Fluorescence (XRF)and Infrared Spectra. The wastewater from the hazardous waste extraction was treated by the Fenton reagent method and the ferriccarbon micro-electrolysis method respectively. The COD was the indicator. At last the two processes were compared by treatment effect and economic feasibility in order to determine a suiTable method.Firstly, the alkali extraction and acid precipitation method were applied to dispose hazardous waste. The optimum condition was determined through single factor analysis. The experimental results was found that the extraction rate was up to 44.67% and the hazardous waste was obviously reduced in half when sodium hydroxide dosage was 100mL, hydrochloric acid dilution was four times, the reaction time of hydrochloric acid was 90min and filtering mode was medium speed filtering.The XRF and infrared tests were conducted on hazardous waste and extract, the extraction of Al was 91.19%.Secondly, raffinate was conducted by the Fenton reagent method. It was indicated that the COD was reduced to 574.37 mg/L, and the efficiency was up to 69.37%under the optimal condition as follows:the initial pH was 3.50, hydrogen peroxide dosage was 60mmol/L, the Fe2+ dosage was 12mmol/L, and the reaction time was 25min. In the meantime, the target as pH and NH3-N were reduced to 7.01 and 50.86mg/L respectively. Further more, the reaction mechanism and kinetics on treatment of raffinate was discussed. The kinetic research revealed that the remove of COD was in accordance with the first-order kinetic model, and the reaction rate constant was 0.0279min-1.Thirdly, raffinate was disposed by the ferriccarbon micro-electrolysis. The optimization condition was studied by orthogonal experiment and single factor analysis when the initial pH was 3.00, the iron-carbon ratio was 2.0:1, the dosage of ferrum was 0.70g, correspondingly the dosage of carbon was 0.35g, and the reaction time was 55min, the removal efficiency of COD was as high as 65.07%. Meanwhile, the indexs like pH and NH3-N were reduced to 6.95 and 56.41mg/L respectively. By comparison, this operating cost is higher than Fenton reagent method. The Fenton reagent method was applied to engineering practice. The total economic benefits was 237.07 yuan/t.