【作者】 陈晨；

【导师】 王津南；

【作者基本信息】 南京大学 ， 环境工程， 2015， 硕士

【摘要】 近几十年来我国采矿、冶炼、农药等行业得到迅速发展,然而相应管理监督不严,导致目前重金属污染事故频发。现有重金属废水的处理方法有混凝法、化学沉淀法、电化学法、膜分离法以及吸附法等,其中螯合纤维由于吸附容量高、吸附选择性好、易再生等优点被广泛应用于水中重金属的去除。本文采用静电纺丝法制备聚丙烯腈（PAN）纳米纤维膜,纤维直径在100nm左右,经化学修饰法制得新型偕胺肟基螯合纤维膜吸附材料PAN-AM。论文重点研究PAN-AM对重金属离子Cu²⁺、Cd²⁺的吸附行为和机理,考察其吸附-脱附性能,阐明溶液介质条件（pH值、共存碱土金属离子和天然有机质）对新型纤维膜吸附性能的影响。最后对模拟废水进行膜过滤吸附工艺小试研究,为PAN-AM纤维膜今后在实际废水治理中的应用提供理论指导和技术支撑。论文主要研究结论如下:（1）通过静电纺丝法制备纳米级PAN纤维膜,其优化反应条件为pH=7,反应温度为60℃,反应时间2h,盐酸羟胺溶液浓度为4g/100 mL,制备偕胺肟基螯合纤维膜PAN-AM,氰基的转化率为52.4%。利用扫描电子显微镜、元素分析、傅里叶变换红外光谱等现代分析手段对新型纤维膜进行分析表征,结果表明PAN-AM表面成功修饰偕胺肟基团,氰基转化率达到52.7%,且BET比表面积高达 75.6 m2/g。（2）吸附动力学研究表明,PAN-AM纤维膜对Cu²⁺和Cd²⁺的吸附平衡时间约为80分钟,吸附25分钟即可达到平衡吸附量的50%。准一级和准二级吸附动力学模型均能较好地拟合吸附动力学曲线,表明膜扩散与颗粒内扩散过程均为控制吸附速率的主要因素。吸附热力学研究表明Langmuir吸附等温方程能更好的拟合PAN-AM纤维膜对重金属离子的吸附等温线,其对Cu²⁺和Cd²⁺最大单层饱和吸附量分别为 153.09mg/g 和 269.12mg/g。（3）吸附热力学参数表明PAN-AM纤维膜对Cu²⁺和Cd²⁺吸附过程表现为吸热反应,是熵推动的自发吸附过程。XPS图谱分析表明PAN-AM通过配位作用与Cu²⁺和Cd²⁺络合,其机理为4个N原子/O原子与一个重金属离子络合。0.1M盐酸溶液和0.1M EDTA溶液可作为脱附剂脱附纤维吸附的重金属离子,连续五次循环使用后,纤维膜对Cu²⁺和Cd²⁺的平衡吸附量依然保持初始平衡吸附量80%以上,脱附率保持在90%以上。（4）实验pH值范围内,pH值为4.0左右PAN-AM纤维膜对Cu²⁺和Cd²⁺有较高的吸附量,升高温度能增加PAN-AM纤维膜对Cu²⁺和Cd²⁺的吸附量。溶液中共存Ca²⁺对PAN-AM纤维膜吸附Cu²⁺和Cd²⁺的影响取决于Ca²⁺的浓度,低浓度Ca²⁺对吸附没有明显影响,但当Ca²⁺浓度升高至10mmol/L时,PAN-AM纤维膜吸附Cu²⁺和Cd²⁺的吸附容量会下降30%左右。溶液中共存天然有机质对PAN-AM纤维膜吸附Cu²⁺和Cd²⁺没有显著影响;（5）通过自制新型纤维膜组件,开展基于PAN-AM纤维膜的膜过滤吸附工艺小试研究,3组膜纤维吸附材料串联,进水流量4mL/min,进水Cu²⁺和Cd²⁺浓度分别为50和100mg/L,其对Cu²⁺和Cd²⁺吸附穿透点出现在180min左右。Thomas模型能够较好地描述其吸附穿透曲线。更多还原

【Abstract】 In recent years,industries such as mining,smelting,pesticide have been developing rapidly in China.However,the absence of appropriate management and supervision indirectly leaded to the heavy metal pollution accidents occurring frequently.Many methods were used to treat heavy metal wastewater including coagulation,chemical precipitation method,electrochemical method,membrane separation and adsorption.Among these technologies,chelating fibers is considered as an efficient adsorbent to remove heavy metal ions from water due to its high selective adsorption capacity and easy regeneration.In this paper,new PAN nanofiber was prepared by electrospinning and its diameter was about 100 nm.Then amidoxime chelating fiber PAN-AM was synthesized by chemical modification in hydroxylamine hydrochloride aqueous solution.The adsorption behavior and mechanism of PAN-AM on heavy metal ions(Cu2+and Cd2+)were studied.The adsorption-desorption performance was investigated,and the effect of pH value,the coexistence of alkaline earth metal ions and natural organic matter on the adsorption performance were studied.At last,the membrane filtration adsorption process is simulated.The result can provide theoretical guidance for the application of PAN-AM in wastewater treatment.The main results are as follows:(1)PAN nanofiber membranes are prepared by electrostatic spinning method.After chemical modification of amidoxime,chelating fiber PAN-AM was successfully synthesized.Optimum reaction conditions were confirmed as:pH=7.0,T=60℃,Time=2h,and concentration of hydroxylamine hydrochloride solution=4g/100mL.SEM,EA and FT-IR analysis were used to characterize PAN-AM.The BET specific surface area of PAN-AM was 75.6m2/g.(2)The adsorption kinetics curves indicated that the adsorption of heavy metal ions onto PAN-AM could reach equilibrium in 80 minutes.Within the nitial 25 min,more than 50%of the equlibrilium adsorption capacity was reached.Both the pseudo-first-order kinetic and pseudo-second-order kinetic equations could fit the kinetic adsorption curves well,suggesting both film diffusion and intra-particl diffusion process as the rate-limiting steps of adsorption in solution.Langmuir equation could fit adsorption isotherms well,which indicated that maximum monolayer adsorption capacity of Cu2+and Cd2+were 153.09mg/g and 269.12mg/g,respectively.(3)The adsorption thermodynamic parameters indicated that adsorption process was an endothermic and spontaneous process which was propelled by entropy.XPS analysis indicated that ’N’ and ’O’ chelated heavy metal ion.Both 0.1 M hydrochloric acid solution and 0.1 M EDTA solution could be used as eluant to desorb heavy metal ions from PAN-AM.After continuous adsorption and desorption for 5 cycles,the adsorption capacity and desorption rate of PAN-AM for heavy metal ions still maintained 80%and 90%,respectively.(4)At pH 4.0,the adsorption capacity of Cu2+and Cd2+ by PAN-AM fiber was the highest.As the temperature increased,the adsorption capacity of Cu2+and Cd2+increased.The effect of Ca2+on adsorption depends on the concentration of Ca2+.Low concentration of Ca2+showed slight adverse effect on Cu2+and Cd2+removal.When the concentration of Ca2+increased to 10mmol/L,the adsorption capacity of PAN-AM fiber decreased 30%.The natural organic matters had no significant effect on adsorption of metal ions by PAN-AM.(5)The membrane filtration experiment was based on PAN-AM fiber.Three pieces of PAN-AM membrane were used in series as filters.The influent rate was 4mL/min.The initial concentration of Cu2+and Cd2+were 50mg/L and 100mgL,respectively.The breakthrough point appeared at 100min.Thomas model can fit the adsorption process well.We can predict the breakthrough curves by the Thomas model.更多还原