溶气浮选法处理重金属离子废水的研究

【作者】 高莹；

【导师】 王晖；

【作者基本信息】 中南大学 ， 化学工艺， 2010， 硕士

【摘要】 本文以低浓度重金属Cr6+和Pb2+离子模拟废水为研究对象,在溶气浮选装置中分别考察了离子浮选法和沉淀浮选法对重金属离子的去除效果,研究了表面活性剂种类及用量、絮凝剂种类及用量、pH值、浮选时间及次数、溶气压力等因素对两种重金属离子废水溶气浮选行为的影响,并进行了相关的宏观动力学分析,获得了符合国家排放标准的重金属离子废水溶气浮选处理方案。单一重金属离子废水的实验结果表明,离子浮选法对两种重金属离子废水的处理效果均不理想,无论是Cr6+还是Pb2+离子,重金属离子的去除率仅能达到40%左右。沉淀浮选法的处理效果明显优于离子浮选法：当Cr6+初始浓度为10mg／L、pH值为9、表面活性剂十二烷基苯磺酸钠浓度为15mg/L、絮凝剂硫酸亚铁用量为nFe2+：nCr6+=5：1、浮选时间35min、溶气压力0.38MPa时,Cr6+的去除率可以达到93.13%；当Pb2+初始浓度为20mg/L、pH值为8.5、表面活性剂十二烷基硫酸钠浓度为15mg／L、絮凝剂硫酸铝用量为nAl3+：nPb2+=2：1、溶气压力0.37MPa时,Pb2+去除率达到97.73%。二元组分混合重金属离子废水的沉淀浮选结果研究表明：当十二烷基硫酸钠浓度为15mg/L、pH值为9、硫酸亚铁加入量为摩尔比5：1、溶气压力为0.38MPa时,混合重金属离子废水中Cr6+和Pb2+的去除率分别可以达到96.59%和95.34%,此时废水中残留的Cr6+和Pb2+的浓度分别为0.34mg/L和0.87mg/L,低于国家相关排放标准(Cr6+≤0.5mg/L,总铅≤1.0mg／L)。论文的正交实验研究结果表明了Pb2+离子废水溶气浮选(沉淀浮选法)时,铝铅摩尔比是很重要的影响因素,各因素对去除率的显著性水平顺序是铝铅摩尔比>溶气压力>表面活性剂浓度>pH。论文对溶气浮选处理废水中Pb2+离子的宏观动力学进行了研究,得出在最佳操作条件下,处理Pb2+可等效为一级化学反应,等效速率方程为：VA=0.190CA,速率常数k=0.190min-1。通过对浮选柱中物料流动状态的研究,得出平均停留时间tm=11.68min,方差σθ2=0.528,给出了停留时间分布密度函数方程。更多还原

【Abstract】 In this paper, trace of heavy metal ion Cr6+ and Pb2+ in the simulation wastewater was removed using ion flotation and precipitate flotation by especially designed dissolve-gas flotation column in a laboratory. The influence of factors such as the kinds and concentration of surfactant, pH value, flotation time, the pressure of solute gas, the kinds and mol concentration of coagulase on flotation behaviors of heavy metal ion were investigated. And then at the optimized flotation conditions, the correlative analysis of macroscopical dynamies of Pb2+ ion was discussed. The processing method of dissolved-gas flotation of heavy metal ion which can meet the national discharge standard was obtained.Results of research on flotation of single metal ion showed that:the removal of effect wasn’t satisfied to two metal ions by ues of ion flotation, which was only 40% about to Cr6+ and Pb2+. The effiency of precipitate flotation was significantly better than that of the ion flotation. When the concentration of Cr6+ion was 10mg/L, pH value was 9, the concentration of Sodiumdodecyl benzene sulfonate was 15mg/L, the mol concentration of Ferroussulfate heptahydrate was nFe2+:nCr6+=5:1,flotation time was 35min, the pressure of solute gas was 0.38MPa, the removal efficiency of Cr6+was 93.13%. When the concentration of Pb2+ ion was 20mg/L, pH value was 8.5,the concentration of Sodiumdodecyl sulfate was 15mg/L, the mol concentration of Aluminum sulfate was nAl3+:nPb2+=2:1,the pressure of solute gas was 0.37MPa, the removal efficiency of Pb reached 97.73%.Results of research on flotation behavior of the mixed metal ions indicated that:when the concentration of Sodiumdodecyl sulfate was 15mg/L, pH value was 9, the mol concentration of Ferroussulfate heptahydrate was 5:1,the pressure of solute gas was 0.38MPa, the removal efficiency of Cr6+and Pb2+ was 96.59% and 95.34%, respectively.And the concentration of Cr6+ and Pb2+ in residual solution was 0.34mg/L and 0.87mg/L, so that they can meet the national discharge standard (Cr6+≤0.5mg/L, total Pb2+≤1.0mg/L).In the paper the orthogonal experiment of Pb precipitate flotation demonstrated that:the range the mol concentration of Aluminum sulfate was the most important factor. The sequence of significance level of all factors was nAl3+:nPb>the pressure of solute gas>the concentration of surfactant>pH value. The analysis of macroscopical dynamies of Pb2+ flotation was investigated. The result proved that the process of foam separation could be regarded as first order reaction at the optimized flotation conditions, and the equivalent speed equation was vA=0.190cA and equivalent speed constant was k=0.190min-1.By measuring and analyzing the distribution of residence time and the fluid flowing in flotation column, the average residence time was tm=11.68min, variance wasσθ2=0.528.The distribution density function of residence time was confirmed combined with the relevant experiments.更多还原