【作者】 黄满满；

【导师】 张浩勤； 张翔；

【作者基本信息】 郑州大学 ， 化学工程， 2013， 硕士

【摘要】 随着社会的不断发展,环境污染问题日益严重。重金属废水以其特有的危害方式已严重地威胁着人类健康和生态平衡。二硫代氨基甲酸盐(dithiocarbamate, DTC)作为—类重金属捕集剂,对重金属有良好的捕集效果,但在酸性条件下效果并不理想。论文旨在开发一种新型DTC类重金属捕集剂,希望能够用于处理酸性重金属废水。主要研究内容和结果如下：(1)论文以尿素(urea)、二硫化碳为原料,合成了一种DTC类重金属捕集剂,命名为DTC-U。考察了原料用量、反应时间、反应温度等对DTC-U产率的影响,优化的合成条件为：尿素、氢氧化钠、二硫化碳的摩尔比为n(尿素)：n(氢氧化钠)：n(二硫化碳)=1：2.2：2.2；二硫化碳、乙醇的体积比为V(二硫化碳)：V(乙醇)=1：1.5；反应温度为35℃；反应时间为3h。红外光谱特征表明DTC-U分子中具有二硫代氨基甲酸基团；该重金属捕集剂易溶于水、不溶于乙醇、丙酮等常见有机溶剂；毛细管法测定熔点为108℃。(2)论文将DTC-U分别用于处理含Pb2+、Cd2+、Cu2+废水,考察了投加量、废水pH值、反应时间、絮凝剂等因素对处理效果的影响。实验结果表明,对于含量为10mg/L的重金属废水,在pH=5,室温反应时间8～12min,絮凝剂PAC和PAM用量分别为100mg/L和5mg/L的条件下,对含Pb2+、Cd2+、Cu2+废水的投加量分别为20、40、45mg/L时,三种废水均可以达到国家排放标准(GB25466-2010)的要求。(3)论文研究了DTC-U对多种重金属离子共存的捕集能力。实验结果表明,对于含Pb2+、Cd2+、Cu2+、Zn2+的废水,DTC-U对不同重金属离子的螯合能力不同,其螯合能力顺序为Cu2+>Pb2+>Cd2+>Zn2+。DTC-U能使废水中四种金属离子全部达到国家排放标准,而一般所用碱中和法是无法做到的；且此时DTC-U投加量小于单独处理四种废水所需的投加量之和。(4)论文对DTC-U和常用的DTC-1和DTC-2进行了比较,其中DTC-1以乙二胺为原料进行合成,DTC-2以三乙烯四胺为原料进行合成。比较结果表明：①对于中性废水,DTC-2处理含Pb2+废水效果较好；DTC-U处理含Cd2+废水效果较好；DTC-1处理含Cu2+废水效果较好；三种重金属捕集剂的处理效果均优于硫化钠。②对于酸性废水(pH<6),DTC-U的处理效果要优于DTC-1和DTC-2,且避免了硫化钠在酸性条件下使用会产生硫化氢气体的缺陷。综上所述,重金属捕集剂DTC-U合成方法简单,原料廉价易得且低毒,捕集重金属能力强,可捕获多种重金属离子,pH值适用范围宽,水溶性好,在酸性条件下使用不会产生硫化氢气体,无二次污染。具有良好的应用前景和市场价值。更多还原

【Abstract】 As society progresses, the environment pollution is increasing. Human health and ecological balance are threatened by heavy metal wastewater due to its special hazards. Dithiocarbamate (DTC) as a kind of heavy metal capturing agent, has good capture effect to heavy metals, but the capture effect is poor when used in acidic conditions. The paper aims to research and develop a new type of DTC metal capturing agent, and expect to use it in treatment of heavy metal wastewater in acidic environment. The main research contents are as follows:(1) In this study, a new heavy metal capturing agent containing DTC is synthesized by using urea and carbon disulfide, which is named DTC-U. The effects of raw materials consumption, reaction time, temperature on productivity are investigated. The optimum synthetic conditions are obtained as follows:molar ratio of urea to carbon disulfide to sodium hydroxide is1:2.2:2.2, volume ratio of carbon disulfide to ethanol equals1:1.5, reaction temperature is35℃, and reaction time3hours. DTC-U is characterized by infra-red spectrum, the result confirm that the DTC group is formed in the molecule. The solubility experiment show that DTC-U is highly soluble in water and insoluble in common organic solvents such as ethanol and acetone. The melting point determined by verification regulation of melting-point-measuring instruments with capillary method is108℃.(2) DTC-U is used to treat the wastewater containing Pb2+, Cd2+, Cu2+separately. The effects of dosage, pH, reaction time, flocculating agent on removal rate are investigated. The results show that the three types of wastewater can meet the request of the criterion (GB25466-2010) under the experiment conditions of pH=5, room temperature, dosage of DTC-U about20mg/L,40mg/L,45mg/L separately, dosage of PAC and PAM used as flocculating agent about100mg/L and5mg/L respectively, reaction time8to12minutes.(3) The capture ability of DTC-U to different heavy metal ions when they coexisted in wastewater is also studied in this paper. The results show that the capture ability of DTC-U to Pb2+, Cd2+, Cu2+and Zn2+ions in wastewater following the sequence of Cu2+>Pb2+>Cd2+>Zn2+, and the residual concentration of the four kinds of heavy metal ions can meet the national discharge standards, the dosage of DTC-U is less than that when the four ions present alone separately in wastewater, while they can not achieve the same result when treated by alkali precipitation.(4) The capture ability to heavy metal ions of DTC-1and DTC-2synthesized by ethanediamine and triethylenetetramine respectively is compared with that of DTC-U in this paper. For neutral wastewater, DTC-U takes on better removal effect for Cd2+, while DTC-1and DTC-2have better removal for Cu2+and Pb2+respectively. Three of them are show better removal effect for the three kinds of ions than that of sodium sulfide. But for acid wastewater (pH<6) containing Cd2+, Pb2+and Cu2+, the removal effect of the three ions treated by DTC-U are better than that of DTC-1, DTC-2and sodium sulfide. Furthermore, the formation of hydrogen sulfide can be avoided when sodium sulfide used in acidic environment.In conclusion, DTC-U is synthesized with simple method. Its raw materials are low cost, less toxic and widely available. DTC-U also shows better treatment effect in treating various kinds of heavy metal wastewater at wide pH ranges. It can be dissolved in water easily and can not cause secondary pollution of hydrogen sulfide when used in acidic environment. It has great application foreground and market value prospects.更多还原