【作者】 张小璇；

【导师】 韦朝海；

【作者基本信息】 华南理工大学 ， 能源环境材料及技术， 2009， 博士

【摘要】 考虑到有机氯污染物存在于自然水体并可能存在于自来水和达标排放的污(废)水中,对人体和生态环境造成严重危害,受到有机氯化物易在生物体脂肪内富集的启示,选取微生物降解废物和污染物产生的聚羟基丁酸酯(PHB)为原料,引进改良的复乳液溶剂挥发法制备仿生吸附剂,希望从受污染水体中富集分离出低浓度的脂溶性有毒有机氯化物,以数量级倍数提高浓度实现其污染控制动力学的可行性。对生活污水、焦化废水和精细化工废水的调查发现,其达标排放出水中仍含有三氯甲烷、氯苯、氯硝基苯、氯苯胺、氯苯酚等多种有毒有机氯化物,是重要的微污染源。首次以PHB为原料成功制成了多孔性仿生吸附剂(命名为PHBBMA),经多种表征证实该制备过程是纯粹的物理过程,无化学变化,不产生副产物,保持了PHB本身的亲脂性。PHBBMA是一种无毒、安全、高效、环境友好的仿生吸附剂。正交试验结果表明,PHB浓度(wPHB)、聚乙烯醇(PVA)浓度(wPVA)及它们间的交互作用是影响PHBBMA比表面积(SBET)的主要因素。PHBBMA制备的最优条件:wPHB和wPVA均为5%,去离子水与PHB的体积比(Vwater/VPHB)为40%,PHB与PVA的体积比(VPHB/VPVA)为30%,初乳化转速和时间分别为10 000 r min-1和2 min,复乳化转速和时间为800 r min-1和4 min。该条件下制备的PHBBMA的SBET为58.78 m2 g-1。PHBBMA对氯苯和邻氯硝基苯的吸附符合Sips等温线模型,吸附容量和富集倍数与温度成负相关,与辛醇水分配系数Kow成正相关,对Kow高的有机氯化物有更好的富集效果。在20 ~ 40℃条件下吸附36 h,PHBBMA0(SBET为8.45 m2 g-1)对氯苯和邻氯硝基苯的富集倍数可达1000倍,最大吸附容量分别可达125.99和39.56 mg g-1。PHBBMA比表面积对其吸附富集能力有很大的影响。在30℃条件下用1 g L-1的吸附剂处理36 h,PHBBMA0对氯苯(初始浓度c0为5.62 mg L-1)和邻氯硝基苯(c0为9.76 mg L-1)的去除率仅为45.2%和35%;而优化所得的PHBBMA27(SBET为58.78 m2 g-1)对两者的去除率均可达到100%,甚至还有剩余的吸附能力。该吸附过程符合拟二级动力学模型,包含3个阶段,最初液膜扩散是速率控制步骤,速率常数可由初始浓度决定;第二和第三阶段分别是中孔和微孔扩散过程,颗粒内扩散为速率控制步骤。PHBBMA吸附氯苯和邻氯硝基苯的ΔG0和ΔH 0是负值,说明该吸附过程是自发放热过程,低温有利于吸附;ΔS0为负值,说明氯苯和邻氯硝基苯从水溶液吸附到PHBBMA表面的过程是有序度增加的过程。更多还原

【Abstract】 Considering organochlorine compounds (OClCs) in natural water, tap water and effluent of wastewater treatment plants, they will have serious hazard for people and environment. Poly-3-hydroxybutyrate (PHB), produced by microorganism degrading wastes and contaminants under unbalanced growth conditions, was used as a new material to prepare a biomimetic adsorbent by a modified double emulsion solvent evaporation technique, though OClCs are liable to bioaccumulation in organisms containing abundant lipid. The biomimetic adsorbent was hoped to accumulate the toxic liposoluble OClCs with low concentration from aqueous.The municipal wastewater, coking wastewater and chemical wastewater were studied, and the results showed that there were many OClCs, such as chloroform, chlorobenzene, nitrochlorobenzene, chloroaniline and chlorophenol in the effluents.PHBBMA, prepared with PHB, was porous spherical particles. The PHBBMA preparation is a physical process without chemical reation. PHBBMA was innocuous, biodegradable and environmental friendly owing to no by-products.The PHB concentration (wPHB), PVA concentration (wPVA) and their interaction played the most important roles for specific surface area (SBET) of PHBBMA. The optimization conditions were: wPHB of 5%, wPVA of 5%, volume ratio of deionized water to PHB of 40%, and volume ratio of PHB to PVA of 30%, the primary emulsion stirring rate of 10000 r min-1 for 2 min, double emulsion stirring rate of 800 r min-1 for 4 min. The SBET of optimization PHBBMA was 58.78 m2 g-1.The adsorption isotherm of chlorobenzene (CB) and o-nitrochlorobenzene (o-NCB) on PHBBMA was fitted well by Sips model. The adsorption capacity and enrichment factor (EF) had a negative effect on the temperature, and a positive correlation with Kow, so PHBBMA had a higher EF for OClCs with higher Kow. The maximum EF of PHBBMA0 with SBET of 8.45 m2 g-1 could reach 1000 for CB and o-NCB at 20 ~ 40℃for 36 h, while the maximum adsorption capacity was 125.99 and 39.56 mg g-1.The SBET played an important role on the enrichment capacity of PHBBMA. The removals were 45.2% and 35% for CB and o-NCB using PHBBMA0 at 30℃for 36 h, while the removals both reached 100% using PHBBMA27 with SBET of 58.78 m2 g-1, when their initial concentrations were 5.62 and 9.76 mg L-1, and the adsorbent dose was 1 g L-1. The pseudo-second order kinetic model fitted the adsorption kinetics well. The adsorption process included three fractions. The first fraction was controlled by liquid film diffusion, and the rate parameter could be calculated by initial concentration. The second and third fractions were mesopore and micropore diffusion respectively, and the intraparticle diffusion was the control step. The values ofΔG0 andΔH 0 for adsorption of CB and o-NCB on PHBBMA were negative, which showed that the adsorption was a spontaneous exothermic process. It was favorable for adsorption at at low temperature. The value ofΔS0 was negative, which showed that CB and o-NCB molecules had strong restriction when they were adsorbed from aquous to the surface of PHBBMA.更多还原