【作者】 于婉婷；

【导师】 柴立元； 王海鹰；

【作者基本信息】 中南大学 ， 冶金环境工程， 2013， 博士

【摘要】 摘要：随着我国工业的快速发展,大量重金属废水排入江河水体中,污染环境。铬(Ⅵ)废水由于其毒性强、浓度高、形态复杂多变,仍然是水污染治理的重点与难题。吸附法是处理重金属污染物有效且环保的方法,开发新型高效铬(Ⅵ)吸附剂成为国内外的研究热点。本文提出聚间苯二胺吸附剂除铬(Ⅵ)新思路,创新了聚间苯二胺的化学氧化合成方法,揭示了聚间苯二胺的电位调控合成机理,开展了聚间苯二胺去除铬(Ⅵ)的性能和机理研究。主要研究内容及创造性成果如下：创新了聚间苯二胺化学氧化合成方法,实现了聚间苯二胺产率和性能的显著提高。确定了聚间苯二胺的最佳合成条件C032-浓度2molL-1,合成时间5h、温度25℃、初始pH值8。合成的聚间苯二胺无定形程度高、热稳定好、与传统合成法相比产率提高了15%。研究了聚间苯二胺在水处理过程中对水体总有机碳的影响,在不同酸碱程度的水体中总有机碳含量低于6.64mg g-1,低于污水综合排放标准20mg g-1。进一步证实了聚间苯二胺作为吸附剂不会对水体产生二次污染。揭示了间苯二胺电位调控聚合机理。碱(OH-、CO32-)可以显著降低间苯二胺聚合体系的开路电位,基于能斯特方程,溶液中氧化剂的电位和氧化能力下降,获得的聚间苯二胺产物氧化态降低。碱同时控制了聚合体系的矿浓度,促使反应向正向进行,提高聚合物产率。研究发现反应溶液的初始pH值在碳酸盐体系的缓冲pH范围之内,C032-可有效控制反应溶液pH值的剧烈波动,稳定氧化剂的氧化能力。研究了聚间苯二胺对铬(Ⅵ)的吸附行为。优化了除铬(Ⅵ)工艺条件：pH为2、反应时间5h。聚间苯二胺对铬(Ⅵ)的最大吸附量随温度上升而提高,30℃时为598.5mg g-1,45℃时为666.8mg g-1。探明了共存阴离子对铬(Ⅵ)脱除率的影响,SO42可占据接近35%的吸附位点,Cl-和N03-存在时,铬(Ⅵ)的脱除率仍在90%以上。聚间苯二胺吸附铬(Ⅵ)的过程符合准二级动力学模型,说明吸附反应是化学吸附。吸附过程焓变为正值表明吸附为吸热过程。吉布斯自由能为负值说明吸附反应在实验研究的温度范围内是自发的。筛选0.1mol L-1NaOH为解吸试剂,5次循环累计吸附量为1545mg L-1。阐明了聚间苯二胺去除铬(Ⅵ)的机制。X射线光电子能谱分析表明聚间苯二胺分子链上的醌型亚胺和苯型仲胺分别是参与静电吸附和还原铬(Ⅵ)的主要官能团；阐明了铬(Ⅲ)以CrCl3形式吸附于聚间苯二胺表面。构建了聚间苯二胺与铬(Ⅵ)之间的氧化还原反应方程式。揭示了聚间苯二胺与除铬(Ⅵ)效果之间的构效关系。通过ChemBioOffice的Minimize Energy模块计算得到低氧化态聚间苯二胺具有较低的能量状态,更容易被质子化,吸附铬(Ⅵ)的能力更强。根据吸附反应前后苯型仲胺和铬离子的摩尔变化量计算吸附在聚间苯二胺表面铬(Ⅵ)和铬(Ⅲ)的量,明确了低氧化态聚间苯二胺能够更有效的还原铬(Ⅵ)。更多还原

【Abstract】 Abstract:Along with the rapid growth of intrustry, more heavy metal wastewater is diacharged to rivers, then the environment is polluted. The governance of chromium(Ⅵ) wastewater is one of the important and difficult problem, because of its toxicity, high concentration and complex state. Adsorption method is an effective way to remove pollutant, then the exploitation of new-type adsorbents became the research hotspot. The removal of chromium(Ⅵ) with poly(m-phenylenediamine) adsorbent was proposed as a new thought in this paper. The potential regulation polymerization mechanism of poly(m-phenylenediamine) was illuminate, and the chromium(Ⅵ) removal ability and mechanism by poly(m-pheylenediamine) was investigated. The main research contents and creative achievements are as follows:The innovative chemical oxidation synthesis flow of poly(m-phenylenediamne) was designed. The yield and performance of poly(m-phenylenediamine) was increased. The optimal polymerization conditions were decided:CO32-concentration2mol L1, polymerization time5h, polymerization temperature25℃, polymerization initial pH8. The poly(m-phenylenediamine) achieved in the optimal condition had higher amorphism degree and thermostability, the yield enhanced15%compared with traditional method. The effect on the total organic carbon (TOC) during water treatment with poly(m-phenylenediamne) was investigated. The TOC datum in different pH value were all lower than6.64mg g-1, which are less than20mg g-1in integrated wastewater discharge standard. The data illustrate that there is no secondary pollution when poly(m-phenylenediamine) was used as adsorbent.The potential regulation polymerization of poly(m-phenylenediamine) was revealed. Alkali (OH-、CO32-) could observably decrease the polymerization potential of m-phenylenediamine. Base on the nernst equation, the potential of oxidant in solution decreased, oxidation capacity decreased, the oxidation of poly(m-phenylenediamine) decreased. Alkali could control the H+concentration in solution, the reaction was prompted to proceed, the yield of polymer was increased. The polymerization initial pH is in the pH butter range of carbonate system. The study found that adding CO32-could control the sharp fluctuation of polymerization pH and stabilize the oxidizing ability of oxidant.The chromium(Ⅵ) adsorption behavior with poly(m-pheny-lenediamine) was investigated. The reasonable chromium(Ⅵ) adsorption condition were pH2and reaction time5h. The chromium(Ⅵ) maximum adsorbance was510.9mg g-1in15℃,598.5mg g-1in30℃,666.8mg g-1in45℃. The effect of coexisting ions on adsorptivity was proved. SO42-could grab35%adsorption site, however, when Cl-and NO3-exsited, the chromium(Ⅵ) adsorptivity still remained above90%. The chromium(Ⅵ) adsorption process can be better described by pseudo-second-model, which illustrates that the adsorption is chemisorption. The value of enthalpy is positive, which indicates the adsorption is endothermic process. The values of free energy are negative, which indicates the adsorption reactions are spontaneous at experiment temperature.0.1mol L-1NaOH was selected as the desorption reagent. The five times accumulated adsorbance was1545mg L-1.The removal mechanism of chromium(Ⅵ) with poly(m-phenylenediamine) was illuminated. X-ray photoelectron spectroscopy analysis indicates that quinoid imine and benzenoid amine are the main functional groups for electrostatic adsorption and chromium(Ⅵ) reduction, respectively; chromium(Ⅲ) was adsorbed to poly(m-phenylenediamine) surface as CrCl3. The redox reaction equation between chromium(Ⅵ) and poly(m-phenylenediamine) was builded. The structure-function relationship between poly(m-phenylenediamine) and chromium(Ⅵ) adsorption was builded. Poly(m-phenylenediamine) with lower oxidation state has lower energy state which was calculated by Minimize Energy in ChemBioOffice. It could be protonized easier, and has strongher chromium(Ⅵ) adsorption ability. The quality of chromium(Ⅵ) and chromium(Ⅲ) in the surface of poly(m-phenylenediamine) was calculated according to the molar cariation of benzenoid amine and chromium ions before and after adsorption. Poly(m-phenylenediamine) with lower oxidation state has stronger chromium(Ⅵ) reduction ability was confirmed.更多还原