【作者】 曲云欢；

【导师】 曾光明； 刘鸿亮；

【作者基本信息】 湖南大学 ， 环境工程， 2009， 博士

【摘要】 本论文针对泡沫分离法处理胶团强化超滤渗透液的机理及应用基础进行研究。采用十二烷基硫酸钠(SDS)为表面活性剂,系统地研究了泡沫分离过程主要参数的影响规律,优化了分离过程条件,考察了混合金属离子泡沫分离的选择性,研究了组合工艺对分离效果的影响,并通过考察SDS表面化学性质及泡沫性能,气泡尺寸分布,泡沫分离动力学过程,分析了泡沫分离过程的作用机制。首先综述重金属污染现状及危害,介绍胶团强化超滤和泡沫分离技术在环境保护中的应用前景及存在问题,提出研究目的和内容;其次进行了SDS表面化学性质、胶团特性及泡沫性能的研究。25℃时纯水中SDS临界胶团浓度为7.8×10-3mol/L。SDS表面吸附分子横截面积为0.46nm2,表面活性剂分子呈单分子层垂直排列。用Langmuir经验吸附方程回归分析得到饱和吸附量Γm为3.6×10-10mol/cm2。温度、重金属离子浓度、pH值、电解质、乙醇对SDS的CMC有明显影响。SDS胶团化过程为自发进行的熵驱动过程。SDS浓度,pH值,温度,电解质,乙醇,重金属离子浓度对泡沫性能影响显著,振荡和通气两种方法评价SDS泡沫性能的变化规律基本一致;接着考察了在不同空气流量、SDS浓度,离子强度条件下泡沫分离设备的气泡特性,通过图像识别软件IPP6.0研究气泡大小及分布,气泡大小最直接的影响因素是分离装置孔径的大小,泡沫分离过程中操作参数对气泡直径也有影响。在实验条件下产生的气泡平均直径均在2mm以下;采用泡沫分离技术处理胶团强化超滤渗透液,取得良好的效果,处理后金属Cd2+离子浓度小于0.1mg/L,出水水质达到国家污水综合排放标准。泡沫分离Cd2+动力学研究符合一级动力学方程,空气流量、温度、pH值、表面活性剂SDS浓度对分离速率常数k有明显的影响;对混合金属离子废水进行泡沫分离,研究发现表面活性剂SDS对三种金属离子有一定的选择性;最后对胶团强化超滤与泡沫分离组合工艺进行研究,组合工艺明显降低表面活性剂SDS用量,相比于单一MEUF,工艺联用后,大大降低了出水中SDS浓度,提高重金属离子分离效率。本论文采用图像分析法考察了气泡尺寸分布,研究了泡沫分离过程的动力学及混合金属离子的选择性,初步探讨了泡沫分离过程的机理。同时对泡沫分离过程参数控制、工艺优化等问题进行研究。结果表明,运用泡沫分离技术处理胶团强化超滤渗透液,处理后金属Cd2+可以达标排放;将MEUF-FF联用能明显降低SDS用量,降低SDS出水浓度,提高重金属离子分离效率。组合工艺能使各种处理技术综合应用,扬长避短,为重金属废水净化提供广阔的发展前景和应用价值。更多还原

【Abstract】 This study focuses on mechanisms and application of the permeate in Micellar-Enhanced Ultrafiltration (MEUF) by using Foam Fractionation (FF). Sodium Dodecyl Sulfate (SDS) was applied as the surfactant. Effects of operation parameters on foam fractionation process were investigated systemically. The conditions of separation process were optimized. The selectivity of the foam fractionation of mixture ions was investigated. The effect of combined technique on separations was studied. In addition, mechanisms of foam fractionation were analyzed by surface chemistry nature and foam performance of SDS, dynamics process of foam fractionation and distribution of air bubble size.Firstly, the present situation and harm of heavy metal pollution were summarized, the application prospect and existence question of the technique of MEUF and FF in the environmental protection were introduced, and the purpose and content of the research were also proposed. Next, the surface chemistry nature, the micelle characteristic and foam performance of SDS were investigated. The Critical Micelle Concentration (CMC) of SDS is 7.8×10-3mol/L in the pure water at 25℃. The area Am of SDS was 0.46nm2, and the surfactant was exactly erect in the foam surface. The saturated adsorptive capacityΓm is 3.6×10-10mol/cm2 by using Langmuir adsorption equation. The temperature, the pH value, and the concentration of heavy metal ions and NaCl, had the obvious influence on CMC. The process of SDS micelles was the entropy-driven process which was carried on spontaneously. The SDS concentration, the pH value, the temperature, the ethanol concentration, the NaCl concentration, and the concentration of heavy metal ions, had the influence on the foam performance of SDS markedly. The transformation rule of vibrate and ventilate to estimate foam performance of SDS was consistent basically. The effects of conditions of air flow rate, SDS concentration, and ionic strength on air bubble characteristic of separation equipment were investigated. The size and distribution of air bubble were studied by using image recognition software IPP6.0. The direct influencing factor of air bubble diameter was the aperture size of separation equipment, and the operating parameters of foam fractionation were also influential. The mean diameter of air bubble was below 2mm under the experimental condition. By using foam fractionation to treat the permeate in MEUF, the Cd2+ concentration in the effluent was lower than 0.1 mg/L which could meet the integrated wastewater discharge standard (the first grade of national discharge standards in China). The Cd2+ dynamics research of foam fractionation conformed to the first-order kinetic equation. The air flow rate, the temperature, the pH value, and the concentration of SDS had the obvious influence on separation rate constant k. We use foam fractionation to treat wastewater containing mixed metal ions. Results showed that the SDS had the good selectivity to three metal ions. Finally, the study was to adopt the combined technique of MEUF-FF to treat the wastewater. Compared with the single MEUF, the combined technique of MEUF-FF could reduce the amount of SDS consumption significantly. After using combined technique it enhanced the separation efficiency of heavy metal ions markedly and decreased the concentration of SDS in the effluent.The method of image analysis was applied to review the size and distribution of air bubble in the paper. To study the dynamics process of foam fractionation and the selectivity of the mixture of metal ions, mechanism of foam fractionation process was primarily discussed. Effects of operation parameters on foam fractionation process and optimization of craft were investigated simultaneously. The result indicated that the Cd2+ concentration in the effluent could meet the integrated wastewater discharge standard by using foam fractionation to treat the permeate in MEUF. The combined technique of MEUF-FF could enhance the separation efficiency of metal ions markedly and decrease the concentration of SDS in the effluent. The study provides value for application and the broad prospects for heavy metal-containing wastewater treatment by combined technique of MEUF-FF.更多还原