| Though the raw materials structure of the sulpHuric acid production in our country has been adjusted greatly in the past ten years, pyrite will be still the main material in a short time. The wastewater produced by the sulpHuric acid production is sour and contains many kinds of harmful substances, among them the content of arsenic and fluorine are very high, which is the main characteristic of this kind of wastewater.This kind of wastewater will pollute water and soil seriously if it is discharged directly with not treatment, it will enter the human body through food chain or the surface water or groundwater finally to danger humans health. So, it is urgent to treat the acid arsenic wastewater effectively and it has great social , economic and environmental meanings to study and develop high-efficient and economy arsenic wastewater treatment technology. When the water meets the water-pollution-control-standards, harmful substances such as arsenic are mostly transfered to the mud . This is not an ideal final result.It will cause the secondary pollution to pile up or landfill the arsenic waste residue simplely. So, it is a new great subject that we face how to realize the safe treatment for arsenic waste residue.The arsenic wastewater as the research object comes from Daye non-ferrous metals smeltery company. The original dirty acid treatment craft has some problems, such as the content of arsenic in the discharged water exceeds standard and the amount of mud is large.The subject has researched the process conditions and treatment results of several technologies, such as lime neutralization, sulpHurate, lime neutralization- aluminium salt coprecipitation, lime neutralization- ferric salt coprecipitation and lime neutralization- oxidize- ferric salt coprecipitation. The results of the test show that it is optimum to adopt lime neutralization- oxidize- ferric salt coprecipitation to deal with the wastewater. The discharged water can meets the national sewage emission standard, the concentration of arsenic is lower than 0.5 mg/L. Including the previous gypsum recycle craft, the new craft still adopts three sections to treat the wastewater. It have only improved the original process conditions, so it can totally utilized existing facilities , and reduce investment. It has been analysed in the article that pH value plays importantly role in the course of getting rid of the arsenic, and discussed the mechanism of oxidization and ferric salt coprecipitation for getting rid of arsenic.The theory and experimental results show that it is very essential to add aeration to original craft, it is the key to improve the efficience of getting rid of rate of arsenic. It has been carried on stabilization / solidification for arsenic waste residue. In the experimental, the way of arsenic waste residue pretreatment, batching system, the ratio of water and dust, the kind of additives, the way of grinding and the maintain conditions all affect the results of stabilization / solidification for arsenic waste residue, which have been researched. It is found that calcining arsenic waste residue under high temperature in advance can improve the intensity of solidification body largely, and the discharge rate of arsenic is reduced. But considered that it costs much to calcine, so this part is only regarded as the theoretical research, don't apply to reality. In this essay, the mechanism of action for arsenic in solidification body is analysed, the mechanism of portland cement hydration reaction and fly ash activation is discussed, and apply theory to make rational explanation for the result of test.The techniques in this subject is economical and effective, they can really realize the finally safely handling of dangerous solid waste such as arsenic waste. The subject can offer reliable basises and guidances for the industrialization of these techniques, it can offer references for Daye Company to improve the original craft. |
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