【作者】 范会生；

【导师】 高从堦；

【作者基本信息】 中国海洋大学 ， 化学工程， 2009， 硕士

【摘要】 我国水资源短缺、人均占有量很低,而水污染却非常严重。随着人口的增长和国民经济的发展,水资源供需矛盾日益突出。硅胶生产属于高耗水行业,硅胶废水也是工业生产领域的一个重要污染源。本文以硅胶废水治理回用的需要为出发点,研究了膜分离技术处理硅胶废水的参数条件,为实际工程应用提供参考。本文针对硅胶废水的特点,选择混凝作为纳滤的预处理。在混凝沉淀的预处理实验中,试验考察了混凝剂种类、混凝剂投药量、pH值等对除硅效果的影响。通过一系列试验筛选出最合适的絮凝剂为氯化铝,并对影响混凝效果的各种操作条件进行了优化。预混凝处理的最佳运行条件为:氯化铝投加量为120mg/L,pH值7.5-9.5,总搅拌时间在4min左右,搅拌后静置60min。在最佳条件下,硅的去除率大于93%,出水SiO2的含量低于20mg/L。在混凝基础上,实验研究了纳滤系统的运行参数(操作压力、操作时间以及进水水温)对纳滤膜的运行状况和分离性能的影响。用溶解—扩散模型解释了操作压力对膜通量、分离性能的影响规律:随操作压力的增加,膜通量增大,系统对离子去除率先增大后减小。根据膜运行时间增加出现的膜通量下降、去除率降低的现象,揭示了运行时间对膜的影响规律。用溶解—扩散模型和Arrhenius方程就进水水温对膜的影响做了分析。在试验范围内,NFⅠ膜对硫酸钠的截留率在99%以上,产水电导率小于170μs·cm-1;NFⅡ膜对硫酸钠的截留率大于98%,产水电导率小于370μs·cm-1 ,可满足不同用水要求。针对膜过程的操作特性和污染物特点设计了几种膜清洗方法,同时借助扫描电镜分析综合考察了膜清洗效果和膜污染机制。研究发现,引起膜污染的主要原因是浓差极化,采用0.1%NaOH+1%Na2-EDTA(pH=12)溶液和0.2%盐酸(pH=2)溶液进行复合清洗,几乎使膜通量得到完全恢复。实验结果表明,混凝—纳滤系统在技术上可行,可以有效去除原水中硅、硫酸钠、硬度等。产水最好的水质能达到自来水的水质指标,可以满足一般企业的回用要求,是处理硅胶废水的一种有效方法。更多还原

【Abstract】 China is a country with water shortage, insufficient per capita water resources and serious water pollution. With population growth and economic development, the conflict between water resources supply and demand is increasingly obvious. Silica gel production is high water consumption industry and silica gel wastewater has always been a key source of pollution in the field of industrial production. In order to treat the silica gel wastewater and recycle the water, in this paper the key parameters of the process of treating silica gel wastewater with membrane was studied, which have reference to actual project.According to the characters of silica gel wastewater, coagulation was used as the pretreatment of nanofiltration. The effects of coagulant type, coagulant dosage and pH on silica removal were inspected in the coagulation experiments. With a series of tests, AlCl3 was screened out to be the best coagulant, and the operating conditions influencing coagulation effect were optimized. The optimal conditions of pre-coagulation were as follows: the dosage of AlCl3 was 120mg/L, pH value was 7.5-9.5, stirring time was 4min, standing time after being stirred was 60min. Under optimum conditions, the removal rate of silica was over 93%, Silica was lower than 20mg/L in the treated effluent.Based on the coagulation experiments, the influence of NF operation parameters(operation pressure, operation period and feed water temperature)on running status and membrane separation performance was explored in the experiments. Solution-diffusion model was used to explain the influence of operation pressure on membrane flux and separation performance: with the operating pressure increasing, the permeation flux increased and the removal rate of ions increased first and then decreased. Along with the operation period extension, the membrane permeation flux decreased and the removal rate of ions decreased, which revealed the effect of operation period to membrane. Analysis was made for the effects of feed water temperatures on membrane performance using solution-diffusion model and Arrhenius equation. In the test range, Na2SO4 rejection of NFⅠwas higher than 99%, permeate conductivity was lower than 170μs·cm-1; Na2SO4 rejection of NFⅡwas higher than 98%, permeate conductivity was lower than 370μs·cm-1, so the permeate quality can meet different requirement.According to the characteristics of the membrane process and fouling of the membrane, several kinds of cleaning strategies were applied during the experiments, and the SEM and the EDS analyses were carried out. The cleaning efficiency and the fouling mechanism were thus investigated. It was found that the reason of the nanofiltration membrane fouling was concentration polarization, and the flux was almost recovered after cleaning with 0.1%NaOH+1%Na2-EDTA and 0.2% HCl.It was shown that the Coagulation-Nanofiltration system was technically feasible, and the system can effectively remove silica, Na2SO4 and hardness. The permeate quality was close to municipal tap water, which can meet the reuse requirement of common enterprises. The Coagulation-Nanofiltration system is efficient way to treat the silica gel wastewater.更多还原