| Arsenic is an extremely toxic element,and arsenic compounds are a kind of very toxic and hazardous substance.Most of the arsenic pollution comes from the discharge of industrial waste water,which mainly comes from the acidic wastewater after acid cleaning by exhaust gas in the process of non-ferrous metal smelting,the main features of this acidic waste water are large acidity,complex composition,etc.Studies at home and abroad have found that pentavalent arsenic is not only much less toxic than trivalent arsenic,but also easier to handle.This paper mainly completes the related research of extraction and separation technology to separate arsenic from acidic aqueous solution.A single-stage extraction experiment was used to compare the extractability of solutions containing As(III)and As(V)with TBP and TBP+N235 extraction systems,the results of the study found that the extraction effect of trivalent arsenic in pure TBP systems is much lower than that of pentavalent arsenic,in the experiment of acidity of As(III)and As(V)in pure TBP system,the highest extraction rate of trivalent arsenic was 5.77%,while the highest extraction rate of pentavalent arsenic reached 21.97%;the difference in the extraction rates between the two was significant.Through the study of pentavalent arsenic extraction experiment with TBP + N235 system,it has been found that the extraction of pentavalent arsenic by TBP+N235 is more effective than the extraction of pentavalent arsenic by pure TBP,in the comparison of the experimental results of acidity and arsenic concentrations in the two systems,the highest extraction rate of TBP+N235 system was 7.15% and 8.97% higher than that of the pure TBP system.Through orthogonal test,the optimal extraction conditions for the TBP+N235 extraction system determined by single-stage extraction experiments were: 50% TBP+20% N235+30% sulfonated kerosene,extraction time was 4 min,and extraction ratio was 1.5:1.The acidity of the prepared wastewater simulation solution is 20%,the initial concentration of sodium arsenate is 3g/L,and the As(V)concentration was 559.0mg/L,the single-stage extraction was used as a superior condition,after five countercurrent extraction experiments,the final pentavalent arsenic extraction rate was 88.3%.The stripping organic phase was extracted with water as the stripping agent,the stripping ratio was 1:1,the stripping time was 4 min,and the final stripping rate was 92.10% after twostage countercurrent stripping.The above study found that using TBP+N235+sulfonated kerosene as the extraction system,a five-stage countercurrent extraction under suitable extraction conditions can provide good extraction results,the pentavalent arsenic with a concentration of 559.0 mg/L was reduced to 66.9 mg/L after extracted,and the arsenic concentration was greatly reduced,however,compared with the national arsenic emission standards,there is still a certain gap,and the raffinate can be returned to the beginning of the EDI+ ultrasonic coupled advanced arsenic oxide treatment process mentioned in this paper.For the loaded organic phase,using water as the back-extractant under two-stage back extraction with appropriate conditions,the pentavalent arsenic in the organic phase was reduced to 7.90%,the organic phase after back extraction can be returned to the extraction process to realize the recycling of resources,the high concentration of arsenic in the aqueous phase after back-extraction can be processed to produce elemental arsenic,which not only reduces pollution,but also has certain economic benefits.This article selected an extraction ratio of 1.5:1,which is much lower compared to the previous arsenic extraction study,this not only reduces the amount of extracted organic matter,but also reduces the phase separation time of the extraction process and improves the extraction production efficiency.The countercurrent extraction method was applied to the arsenic extraction process with TBP+N235,and good results were obtained. |
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