【作者】 汤烜祎；

【导师】 鲁军；

【作者基本信息】 华东理工大学 ， 环境工程， 2010， 博士

【摘要】 疏水性有机污染物(HOCs)如多环芳烃(PAHs)和环境激素-双酚A (BPA)在人类的生产和生活中广泛存在。由于HOCs具有较高的脂溶性,一旦进入水体,容易在悬浮物和底泥中累积,并在生物体内富集,从而对生态环境造成严重的危害。因此,有必要开发出一种高效而经济的吸附材料用于受HOCs污染水体的修复和净化。泥炭是一种具有潜在吸附能力并且来源广泛,价格低廉的天然生物质材料。将泥炭作为吸附剂用于废水处理,可以实现环保有效性和经济性的统一。本研究采用季铵盐阳离子表面活性剂对天然草本泥炭进行接枝改性,制备出一种有效,低成本且环境友好的新型生物质吸附剂,用于去除水体中的HOCs。同时,选取典型的非离子型疏水性有机污染物-PAHs和离子型疏水性有机污染物-BPA作为目标污染物,研究了改性泥炭对这两类HOCs的吸附特性,并探讨了吸附机理。采用季铵盐阳离子表面活性剂对泥炭进行接枝改性,优化了改性条件。考察改性时间,改性剂浓度以及不同的表面活性剂对改性效果的影响。结果表明,表面活性剂对泥炭的接枝量随改性时间以及改性剂浓度的增加而提高。在相同的改性条件下,泥炭中表面活性剂接枝量顺序为：十六烷基三甲基溴化铵(HTAB)＞溴代十六烷基吡啶(HPB)＞四丁基溴化铵(TBAB)。在此基础上,分别选用天然草本泥炭和经磺化处理的草本泥炭作为改性基质制备了季铵盐阳离子表面活性剂改性泥炭,并对改性前后的泥炭进行了傅立叶红外光谱表征和元素分析。分析结果表明季铵盐阳离子表面活性剂可以通过离子交换反应有效接枝到泥炭上,并增加了泥炭中有机碳的含量。采用扫描电镜观察了泥炭的表面构型,发现改性后草本泥炭的纤维结构得以完整保留,从而使改性泥炭具有一定的机械强度。通过分析泥炭在水中的zeta电位发现天然草本泥炭和磺化泥炭具有较强的电负性,改性过程有效减小了草本泥炭和磺化泥炭表面的负电位。此外,通过测定泥炭在正己烷中的相对接触角,发现改性后泥炭表面的疏水性显著增强。研究了改性前后草本泥炭对PAHs的吸附特性,并对吸附机理进行了探讨。考察了接触时间、初始浓度、PAHs脂溶性等因素对改性泥炭吸附PAHs的影响。结果表明,改性泥炭对PAHs的吸附符合准二级动力学模型,改性后草本泥炭对PAHs的吸附速率提高。改性泥炭对PAHs的等温吸附曲线符合线性分配方程。改性后,萘、菲、芘在草本泥炭上的分配系数分别由675,12870,88590 mL·g-1增加到979,26074,178388 mL·g-1。此外,还发现PAHs在改性泥炭上的分配作用随着PAHs脂溶性的提高而加强。研究了BPA在改性草本泥炭和改性磺化泥炭上的吸附特性和吸附机理。考察了接触时间、初始浓度、pH、水中无机盐浓度等因素对吸附的影响。结果表明,BPA在改性草本泥炭上的吸附符合准二级动力学模型,其在改性磺化泥炭上的吸附符合颗粒内扩散模型。BPA在两种改性泥炭上的等温吸附曲线均符合BET模型和Freundlich模型。改性后草本泥炭和磺化泥炭对BPA的吸附量分别提高了322%和33%以上。吸附热力学研究显示,改性草本泥炭和改性磺化泥炭对BPA的吸附为放热过程,吸附热分别为8.926 kJ·mol-1和19.393 kJ·mol-1。研究证实,改性泥炭对离子型疏水性有机污染物的吸附主要通过分配和表面吸附的共同作用进行。分配作用随着泥炭中有机质含量的增加而加强；表面吸附作用随着泥炭表面电负性的减弱以及疏水性的提高而加强。采用海藻酸钠对改性草本泥炭进行包埋固定以提高其在水中的可分离性和化学稳定性,并研究了固定化改性泥炭颗粒对BPA的静态和动态吸附特性以及再生的可行性。结果表明,固定化改性泥炭颗粒吸附BPA的等温曲线符合BET模型和Freundlich模型,吸附的最佳pH范围为4.0-9.0,其对BPA的吸附符合准二级动力学模型,且吸附初始阶段受颗粒内扩散作用的控制。流速和初始浓度对固定化改性泥炭颗粒动态吸附双酚A的效果具有显著影响。此外,固定化改性泥炭颗粒具有一定的再生能力。更多还原

【Abstract】 Hydrophobic organic contaminants (HOCs) such as polycyclic aromatic hydrocarbons (PAHs) and environmental hormone-bisphenol A (BPA) are widely produced and used. Due to strong organophilicity, HOCs can accumulate in sediments, suspension solids and organisms when discharged into water body, which cause harm to both animals and human beings. It is essential to develop an effective and affordable sorbent which can be used in restoration and treatment of HOCs polluted water.Peat is a biomaterial of natural origin with potential sorption capability and low cost. The application of peat in removal of contaminants from water can archieve both satisfactory treatment performance and cost effectiveness. In this study, a noval biosorbent for sorption of HOCs was prepared through modification of peat by quaternary ammonium cationic surfactant. The nonionic HOCs-PAHs and ionic HOC-BPA were selected as the target contaminants. And the sorption behavior of PAHs and BPA on modified peat as well as the sorption mechanism was investigated.The modification process of peat was optimized through investigation of the effects of modification time, modifier concentration and different modifiers on the content of surfactant grafted into peat. Results show that the content of grafted surfactant increased with increase of modification time and modifier concentration. HTAB is more effective in modification of peat when compared with HPB and TBAB.The modified peat was prepared from raw fibric peat and sulfonated fibric peat. The results of FTIR and element analysis show that the surfactant was grafted into peat effectively through ion-exchange and the organic carbon content of peat increased after modification. SEM results indicate that the fibric structure of peat remained after modification, which suggests that modified peat had same mechanical strength as the raw peat. The zeta potential measurement shows that raw peat and sulfonated peat are negative-charged. The surface negative charge was reduced after modification. In addition, it was also found that the hydrophobicity of modified peat was significantly enhanced.The effect of contact time, initial concentration, PAHs properties on PAHs sorption capacity of modified peat were investigated to show the sorption characteristics and sorption mechanism of PAHs on modified peat. It is suggested that the uptake rate of PAHs by peat increased after modification; the sorption experimental data followed pseudo-second-order kinetic model and the sorption isotherms fitted well to linear partitioning equation. After modification, the sorption rate constant of naphthalene, phenanthrene and pyrene by peat increased from 675,12870,88590 mL-g"1 to 979,26074,178388 mL·g-1. The partitioning coefficients were positively correlated with octane-water partitioning coefficients of PAHs.The sorption characterisitics and sorption mechanism of BPA were explored by investigating the effects of contact time, initial concentration, pH etc. on BPA sorption capacity of modified peat. Results show that the sorption experimental data followed the pseudo-second-order kinetic model. The sorption isotherms and followed both BET model and Freundlich model. The BPA sorption capacity of modified fibric peat and modified sulphonated peat increased by more than 322%and 33%, respectively. It was also found that sorption of BPA by modified fibric peat and modified sulfonated peat were exothermic processes which haveΔH of 8.926 kJ-mol"1 and 19.393 kJ·mol-1, respectively. The results also verified that the sorption of BPA on modified peat were predominated by both partitioning and surface adsorption. The sorption capacity of peat increased with the enhancement of hydrophobicity and the reduction of surface negative charge.To achieve easy separation of peat sorbent from water as well as improve the chemical stability of the sorbent, the modified peat was embedded by sodium alginate for preparation of granular modified peat. The batch sorption characteristics of granular modified peat as well as the feasibility of using granular peat sorbent as filter packer were investigated. Results show that BPA sorption experimental data of granular modified peat followed both pseudo-second-order kinetic model and intraparticle diffusion model. The sorption isotherm followed both BET model and Freundlich model. The optimum pH range for BPA sorption by granular modified peat is 4.0-9.0 and the dynamic sorption performance was found to be affected by intial BPA concentration. In addition, the granular modified peat can be regenerated by bleaching with warm water.更多还原