【作者】 王刚；

【导师】 常青；

【作者基本信息】 兰州交通大学 ， 环境工程， 2013， 博士

【摘要】 重金属废水大量排放已造成环境严重污染，寻求重金属废水新的处理方法成为当前研究热点，而开发一种高效、廉价、实用的重金属废水处理剂将具有重要的意义。本论文采用现有的高分子絮凝剂聚乙烯亚胺作为母体，通过化学合成方法将重金属离子的强配位基团二硫代羧基引入到其分子结构中，制备出具有捕集重金属和去除浊度双重功能的新型高分子絮凝剂聚乙烯亚胺基黄原酸钠（PEX）。采用该新型絮凝剂，可直接利用传统化学沉淀法的处理设施，同时去除重金属离子和降低浊度，从而可减少后续处理单元，简化处理工艺，使重金属废水的治理变得简单易行。本文以聚乙烯亚胺（PEI）、二硫化碳（CS2）、氢氧化钠（NaOH）为原料，采用正交实验法确定了PEX最佳制备条件，获得三种不同分子量的PEX（PEX–1、PEX–6、PEX–60）；并借助元素分析、紫外分析、红外分析等方法对PEX进行了表征。以PEX为研究对象，通过絮凝实验法考察了PEX除浊性能、捕集重金属性能以及处理实际重金属废水性能；并对PEX的溶液特性、PEX存放稳定性、螯合絮体形态特征、螯合絮体的稳定性能以及重金属回收性能进行了探讨。主要研究结果如下：影响PEX制备条件的主要因素为PEI的分子量、CS2的用量、反应温度和反应时间。分子量不同的PEI制备PEX最佳条件不尽相同，PEX–1最佳制备条件为：PEI、CS2、NaOH投加比例1:2:2，预反应温度35℃，预反应时间30min，主反应温度40℃，主反应时间150min；PEX–6最佳制备条件为：PEI、CS2、NaOH投加比例1:3:3，预反应温度20℃，预反应时间30min，主反应温度40℃，主反应时间60min；PEX–60最佳制备条件为：PEI、CS2、NaOH投加比例1:1:2，预反应温度25℃，预反应时间30min，主反应温度60℃，主反应时间60min。PEX为两性高分子絮凝剂，在等电点时，PEX溶液Zeta电位为零，体系出现浑浊且浊度达到最高。PEX–1、PEX–6、PEX–60溶液的等电点pHiep分别为4.6、5.0、8.4（蒸馏水体系）以及3.8、5.0、8.7（自来水体系）。PEX的除浊性能优于母体PEI的除浊性能，且在PEX等电点时浊度的去除率最大；体系中共存的重金属离子对浊度的去除具有显著促进作用。PEX对单一重金属体系和混合重金属体系中的二价重金属离子均具有良好的捕集效果。PEX捕集重金属离子对体系pH值的要求相对较低，在酸性条件下重金属离子也能被有效的除去。对于PEX，总体捕集能力顺序为PEX–1＞PEX–6＞PEX–60；对于重金属离子，总体捕集顺序为Cu(II)＞Pb(II)＞Cd(II)＞Ni(II)＞Zn(II)。PEX对高价重金属离子Cr(VI)在强酸性条件下去除效果较好，而对Cr(III)在酸性条件下捕集效果不理想。体系中共存的无机阳离子、无机阴离子、浊度对PEX捕集重金属离子的影响总体上均较小，促进或抑制作用不明显；而共存的有机配位剂对其捕集能力具有一定的影响，或促进或抑制，可通过增加PEX投加量来减小或消除抑制影响。当浊度存在时，PEX可同时除去体系中重金属离子和浊度，可充分发挥螯合沉淀和絮凝沉淀双重作用。螯合絮体的分形维数结果表明，重金属螯合絮体分形维数越大，相对应的重金属离子去除效果越好。红外分析谱图表明，PEX分子链上成功的接上了二硫代羧基；而PEX分子链上的二硫代羧基、胺基可与重金属离子发生螯合、配位等作用。PEX的存放稳定性、螯合絮体的稳定性均较好，PEX对实际废水的处理效果较理想，且可回收絮体中的重金属，这些均有利于PEX的实际应用。总之，本文合成的新型高分子絮凝剂PEX在捕集重金属离子时表现出优良性能，在适宜条件下能有效的捕集多种重金属离子，且絮凝沉降性能好，可作为重金属废水的处理剂，具有广阔的应用前景。更多还原

【Abstract】 A large amount of wastewater containing heavy metal ions is discharged into theenvironment, which has polluted the water environment badly. The new methods, for thetreatment of heavy metal ions from industrial effluents, have been the hot spot of researchcurrently. Therefore, it is of great significance to develop a novel reagent which canefficiently remove heavy metal ions from the wastewater. In this paper, a strong ligand ofheavy metal ions, dithiocarboxylic acid groups, is introduced to a macromolecular flocculant(polyethyleneimine). The novel flocculant synthesized in this way is calledpolyethyleneimine-sodium xanthogenate (PEX), and it has the function for trapping heavymetal ions and removing turbidity from wastewater. Because PEX has the two functions, it ispossible to reduce some treatment units in the treatment of wastewater containing heavy metalions, and the wastewater treatment system would be greatly simplified.The flocculant PEX is synthesized by using polyethyleneimine (PEI), carbon disulfide(CS2), and sodium hydroxide (NaOH). The orthogonal experiments are employed for theoptimum synthetic condition of PEX, and three kinds of products (PEX–1、PEX–6、PEX–60)are obtained in the experiments. The structures of PEX are characterized by elementalanalysis, ultraviolet analysis and infrared analysis. The PEX performances for removal ofturbidity and heavy metal ions are mainly investigated by flocculation experiments. Thesolution property and storage stability of PEX are also studied. Furthermore, the treatmentefficiency for actual wastewater containing heavy metal ions, the recovery for heavy metal,the stability and fractal of flocs are discussed. The main results are given as follows.The main influencing factors for optimum synthetic condition of PEX are the moleculeweight of PEI, dose of CS2, reaction temperature and reaction time. The optimum syntheticcondition of PEX products is different for the different molecule weight of PEI. For productPEX–1: PEI, CS2and NaOH are put into the reactor in accordance with molar ratio1:2:2. Themixture of reactants is stirred magnetically at35℃for30min, and then the temperature israised to40℃for150min under constant stirring. For product PEX–6: PEI, CS2and NaOHare put into the reactor with molar ratio1:3:3. The mixture of reactants is stirred magneticallyat20℃for30min, and then the temperature is raised to40℃for60min under constantstirring. For product PEX–60: PEI, CS2and NaOH are put into the reactor with molar ratio1:1:2. The mixture of reactants is stirred magnetically at25℃for30min, and then thetemperature was raised to60℃for60min under constant stirring.PEX is an amphoteric macromolecular flocculant, and it exists isoelectric point. The zetapotential for PEX solution is equal to zero, and the solubility is minimum at its isoelectric point. The isoelectric point (pHiep) for PEX–1、PEX–6、PEX–60is4.6、5.0、8.4in the systemof distilled water, respectively, and3.8、5.0、8.7in the system of tap water, respectively. Theperformances for removal of turbidity by using PEX are better than by using PEI, and theremoval rate of turbidity is maximum at isoelectric point of PEX. The coexistence of heavymetal ions may notably promote the removal of turbidity.PEX can effectively remove the divalent heavy metal ions in the single system ormixture system of heavy metal. The treatment efficiency for the heavy metal ions is high atthe acidity condition by using PEX, and the demand of pH value is more flexible. For productPEX, the trapping order for heavy metal ions is that PEX–1> PEX–6> PEX–60. For heavymetal ions, the trapping order is that Cu(II)> Pb(II)> Cd(II)> Ni(II)> Zn(II). Moreover,Cr(VI) ions can be efficiently removed in a strongly acidic solution, but the removalefficiency for Cr(III) ions is not ideal at the acidic condition.The presence of inorganic cations, inorganic anions and turbidity coexisting with heavymetal ions affects slightly the removal of heavy metal ions. However, the coexisting organiccomplexing agent will inhibit or promote the removal of heavy metal ions, and these effectsare not absolutely same. The inhibition influence may be minished or eliminated throughadding the dosage of PEX. When the substances causing turbidity exist in the system, heavymetal ions and turbidity will be both removed simultaneously. The removal rate of heavymetal ions increases with the increase in the fractal dimensions of chelating flocs. That is, thefractal dimensions of chelating flocs are higher, and the removal efficiency for heavy metalions is better.FTIR spectra reveals that the dithiocarboxylic acid groups have been successfully graftedto polyethyleneimine molecule, and dithiocarboxylic acid groups and amino groups on themacromolecular chains of PEX play a major role in the removal of heavy metal ions. PEXmay be well applied to the practical wastewater treatment for some advantages. For example,the storage stability of PEX and the stability of chelating flocs are good; the treatmentefficiency is high for the actual wastewater by using PEX; and heavy metal ions may beremoved from the chelating flocs.In conclusion, the novel macromolecular flocculant PEX can effectively remove heavymetal ions from wastewater under a certain condition. Therefore, PEX may be as a newtreatment agent for the wastewater containing heavy metal ions, and it has a favorableapplication prospect.更多还原