【作者】 陈润华；

【导师】 柴立元；

【作者基本信息】 中南大学 ， 冶金环境工程， 2013， 博士

【摘要】 摘要：工业生产过程产生的大量含重金属废水严重污染环境,是国内外研究的热点。含重金属配合物及含氧酸根废水由于具有形态复杂多变、稳定等特征,且大多以配合物或阴离子存在,仍然是水污染治理的重点与难题。本论文分别选取工业废水中典型的重金属配合物Cu-EDTA与重金属含氧酸根Cr2O72-两种污染物为研究对象,开展了活性炭、碳纳米管载铁新材料的制备及其处理污染物的研究,旨在探索复杂重金属废水处理的新途径。主要研究内容及创新性成果如下：基于脉冲电镀的特点,研发了翻转电镀法制备铁碳材料Fe/AC的新装置,实现了活性炭表面零价铁的均匀负载。确定了Fe/AC的最佳合成条件为电镀时间30min,电流强度2.5A,电解液离子浓度150mg/L。最佳合成条件下制备的Fe/AC表面富含羟基、羧基、碳氧双键和零价铁碳基团,铁碳材料表面的基团使得铁碳材料Fe/AC有利于Cu-EDTA污染物的去除。提出并研发了制备磁性纳米铁碳材料Fe3O4/CNTs的原位还原再氧化新方法。所制备的铁碳材料具有152emu/g的高磁性,克服了普通吸附材料处理废水后难以回收的局限性；形成的羟基、羧基、基团能够有效的与废水中重金属配合物结合,使其在处理重金属含氧酸根废水方面潜力巨大。基于含Cu-EDTA配合物水化学形态的基础研究,探明了Cu-EDTA铁碳材料Fe/AC处理的影响因素与Cu-EDTA破坏机理。确定了合理的Cu-EDTA处理条件为pH=4和反应温度为298K,废水中铜离子含量由处理前的60mg/L降低至1.718mg/L。明确了羟基自由基与Cu-EDTA配合物降解的关系,提出了羟基自由基产生的必要条件为水溶液中pH<7且含有溶解氧,和羟基自由基的含量表达式为lg [O H]=36.69-lg[Fe3+]+lgP0-3pH,为铁碳材料处理重金属配合物废水提供了重要理论依据。研究揭示了常温下浓度为0.5mol/L的重铬酸钾水溶液离子分布规律：当pH<5.8时,铬的含氧酸根离子形态为Cr2O72-, KCr2O7和HCrO4存在；当pH>8.3时,铬的含氧酸根的离子存在形态为Cr042-和KCrO4-;在5.8<pH<8.3之间时以上离子共存的离子形态关系。在pH为6、温度313K、反应时间30min的优化条件下,Fe3O4/CNTs对Cr(VI)的吸附量达54.79mg/g,表明Fe3O4/CNTs的吸附性能优于目前同类吸附剂。研究阐明了Fe3O4/CNTs处理重铬酸根废水的机制,发现Fe3O4/CNTs吸附重铬酸根过程符合Langmuir模型、D-R模型和伪二级动力学模型,表明Fe3O4/CNTs对重铬酸根的吸附过程为单分子层吸附、离子交换型吸附过程,而且化学吸附过程是重铬酸根吸附的速率控制步骤。Fe3O4/CNTs的磁性全部为Fe3O4产生,且重铬酸根吸附后铬的最终状态为Cr(OH)3和Cr2O3,揭示了重铬酸根离子首先通过离子交换吸附于Fe3O4/CNTs表面,再还原为低价态的过程。计算了该类材料基团与重金属的稳定构型和轨道能量。利用Materials Studio5.5的DMol3模块对铁碳材料基团的基本结构进行了量子力学计算。从前线轨道理论和密度泛函理论的视角对铁碳材料处理重金属前后的稳定化能进行了模拟和分析比较,明确了铁碳材料表面各官能团的吸附功能,并获得了铁碳材料Fe3O4/CNTs处理重铬酸根前后能量与能隙的变化,揭示了羧基与重铬酸根杂化形成的配合物稳定化能最高、羟基次之,碳氧双键最弱的吸附机制,为铁碳材料应用于重金属复杂废水的深度处理奠定了基础。更多还原

【Abstract】 Abstract:Large amount of heavy metals and oxacid root pollutants were discharged into the environment, which may results in serious environmental pollution and human health risk. Heavy metals and oxacid root contaminated wastewater with the characteristics of bioaccumulation, high residue and semi-volatile were focused by wastewater researcher. In this study, the typical heavy metal complexes Cu-EDTA and dichromate oxacid root were chosen as the object. Two novel methods were developed for synthesis of iron carbon materials Fe3O4/CNTs and Fe/AC, and the new materials were explorerd for removal of Cu-EDTA and dichromate from aqueous solution effectively. The main research contents and creative achievements are as follows:Based on the characteristics of the pulse plating, a novel flip plating iron-carbon material production device was designed, which was used to load zero-valent iron on the carbon surface. Optimum conditions to prepare the iron-carbon materials were investigated, plating time is30min, current intensity is2.5A, ion concentration of electrolyte is150mg/L. Under the above conditions, the Fe/AC materials prepared was rich in hydroxyl group, carboxyl group, carbon-oxygen double bond, and zero-valent iron-carbon complex structure on its surface, which enable the iron-carbon material Fe/AC conducive to the removal of the Cu-EDTA pollutants.A novel method for synthesis of high ferromagnetism nanoparticles (Fe3O4/CNTs) were proposed to efficiently remove Cr(VI) from aqueous solution. The Fe3O4/CNTs were prepared via an in-situ reduction with post-oxidation (RPO) method by using cheap and environmental friendly precursor under the mild condition. Magnetic hysteresis loops revealed that Fe3O4/CNTs had superior saturation magnetization (152emu/g) enabling the high-efficient recovery of Fe3O4/CNTs from aqueous solution by magnetic separation at low magnetic field gradients. The hydroxyl and carboxyl groups generated during preparation process can conjunct effectively with heavy metals in wastewater. Fe3O4/CNTs is an effective and environmental friendly adsorbent to remove heavy metals from wastewater attribute to the efficient removal ability and separation property.Batch experiments were performed to explore the optimium conditions of Cu-EDTA wastewater treatment by Fe/AC material. The removal efficiency is optimal at pH value of4.0, temperature of298K. Under the above conditions, the residual concentration of Cu(Ⅱ) decreased from60mg/L to1.718mg/L. Based on the Cu-EDTA treatment results, the reasonable organic compounds degradation mechanism were proposed firstly. The mechanism identified the relationship between organic heavy metal complexes destruction and hydroxyl radicals. Futhermore, the necessary hydroxyl radical generating conditions were authenticated by electrochemical theory, which is pH<7, dissolved oxygen, and electron transfer on Fe/AC surface. The hydroxyl radical generating chemical equation was derived. The concentration of hydroxyl radical can be calculated by equation of lg[·OH]=36.69-lg[Fe3+]+lgPo-3pH and the Gibbs free energy of the equation is-64.73KJ/mol, which reasonably revealed the degradation mechanism of heavy metal-organic complexes.Cr(VI) ionic forms in wastewater were analyzed. The effect of Fe3O4/CNTs on dichromate containing wastewater was investgated via batch experiments. Visual MINTEQ3.0modeling program was adopt to determine aqueous speciation of chromium ions at different pH values. Illustrated that the different forms of chromium ions such as Cr2O72-, KCr2O7-and HCrO4-coexist with predominant KCr2O7-in the pH range of1.0-6.0, these forms transformed to CrO42-and KCrO4-with pH increasing.The optimal conditions of Cr(VI) treatment experiments is as follows:pH value is6, temperature is313K and contact time is30min, Under the above conditions, the maximum Fe3O4/CNTs adsorption capacity reached to57.49mg/g, which is higher than the common adsorbents Kinetics, thermodynamics and the Cr(VI) removal mechanism indicated that Cr(VI) adsorption process in accordance with Langmuir model, D-R model and pseudo-second-order kinetic model. Thereinto, the adsorption energy is11.61KJ/mol, Langmuir constants are0.103-0.386. which revealed Cr(VI) adsorption process on Fe3O4/CNTs is monolayer adsorption, ion-exchange adsorption, and chemical adsorption process is rate determining step. Futhermore, Raman analytical results clarified the magnetic of Fe3O4/CNTs were all generated by Fe3O4, and the final state of Cr(VI) adsorpt on the Fe3O4/CNTs are Cr(OH)3and Cr2O3crystal structure. The change of surface properties of Fe3O4/CNTs provided the reliable evidence for the adsorption mechanism.According to the on surface groups and metal valence analysis, stable configurations and orbital energies of Fe/AC and Fe3O4/CNTs were calculated. The steady relationship between pollutants and various group on Fe/AC and Fe3O4/CNTs surface was deduced. Dmol3module of Materials Studio5.5program was used to construct the stable structures of complexes formed between a variety of functional groups present and the different heavy metal ions. Moreover, In order to guide the modification of AC and CNTs the energies of the frontier molecular orbital for the complexes were calculated. This research reveals the highest stabilization energy is carboxyl and dichromate complexes, and followed by hydroxyl and dichromate groups, carbon-oxygen double and dichromate bond is the weakest. Fe/AC and Fe3O4/CNTs developed in this study have great potential for the advanced treatment of wastewater containing heavy metal complexs and heavy metal oxacid roots. Figures86, Tables22, References209.更多还原