【作者】 陈世洋；

【导师】 施周；

【作者基本信息】 湖南大学 ， 市政工程， 2013， 博士

【摘要】 水溶性污染物铬(Ⅵ)和磷若超标，会对环境和人体健康产生严重的危害。目前对于水中铬(Ⅵ)去除的研究报道绝大多数是针对工业废水中铬(Ⅵ)的去除，而专门针对饮用水中铬(Ⅵ)去除的研究报道则相对较少。污水处理厂出水中总磷以磷酸盐、聚磷酸盐和有机磷的形式存在，而磷酸盐为主要存在形式，对二沉池出水中磷酸盐进行深度处理对于控制总磷排放含量有着极其重要的意义。本研究通过构建离子交换膜化学反应器，并用于水中铬(Ⅵ)和磷酸盐的去除。阴离子交换膜分离铬(Ⅵ)和磷酸盐试验结果表明，当原水中铬(Ⅵ)初始浓度为1.0mg/L，pH值为6.95左右，补偿溶液NaCl浓度为0.1mol/L，原水和补偿溶液进水流量为2.5mL/min，膜两侧溶液搅拌强度为500r/min，水温为25℃时，阴离子交换膜对铬(Ⅵ)的分离去除率为86.4%，相同试验条件下阴离子交换膜对磷酸盐的分离去除率为84.3%。采用Na2SO4作为补偿溶液时，阴离子交换膜对铬(Ⅵ)和磷酸盐的分离去除率降低，且其对磷酸盐分离效果的影响较大。不同补偿溶液NaCl浓度条件下阴离子交换膜对铬(Ⅵ)和磷酸盐的分离去除率相差不大，但离子通量随NaCl浓度的增加而增大。当原水pH值分别为11.0和3.0时，阴离子交换膜对铬(Ⅵ)和磷酸盐的分离去除率降低。膜两侧溶液搅拌强度和水温增大时，铬(Ⅵ)和磷酸盐的分离效果提高。增加原水进水流量，阴离子交换膜对铬(Ⅵ)和磷酸盐的分离去除率降低。二价共存离子SO42-对铬(Ⅵ)和磷酸盐离子竞争作用大于一价共存离子NO3-和Cl-，共存离子浓度越高，离子交换竞争作用越强。正交试验结果表明，各因素中原水进水流量和补偿溶液种类分别对铬(Ⅵ)和磷酸盐的分离影响最大，其对分离试验结果有显著影响。在最佳分离运行参数条件下，单位时间内化学反应池铬(Ⅵ)和磷酸盐富集含量均随原水初始浓度的增加而增加。铬(Ⅵ)最佳还原剂投加量为FeSO4·7H2O:Cr(Ⅵ)=20:1，可适当过量投加硫酸亚铁，不调节原水pH值。投药量系数增加时，磷酸盐化学沉淀去除效果增加。在3种不同运行方式条件下，离子交换膜化学反应器对铬(Ⅵ)和磷酸盐处理水中浓度均小于或接近于相应的水质标准要求。铬(Ⅵ)和磷酸盐离子交换动力学试验结果表明，阴离子交换膜对铬(Ⅵ)和磷酸盐的饱和交换容量分别为1.59mmol/g(干膜)和0.51mmol/g(干膜)。铬(Ⅵ)和磷酸盐离子交换过程均符合颗粒扩散控制(PDC)动力学模型，增加铬(Ⅵ)和磷酸盐初始浓度和温度，离子交换表观速率常数和颗粒扩散系数增大。铬(Ⅵ)和磷酸盐离子从给体池通过阴离子交换膜至化学反应池的迁移交换过程从宏观上可分为3步，膜采用NaCl溶液浸泡预处理和增加补偿Cl-离子浓度，分别促进铬(Ⅵ)和磷酸盐离子的第1步和第3步迁移交换过程，而铬(Ⅵ)和磷酸盐离子第2步迁移交换过程主要取决于交换离子和阴离子交换膜的基本特性。补偿溶液NaCl浓度增加时，阴离子交换膜内铬(Ⅵ)和磷酸盐含量明显降低。两层膜试验中，铬(Ⅵ)含量基本都分布在膜1内，膜2内铬(Ⅵ)含量较少；补偿溶液NaCl浓度较低和较高时，膜内磷酸盐含量的分布由给体池至化学反应池分别呈递增和递减趋势。原水中存在带电胶体颗粒是造成膜污染的主要原因，阴离子交换膜可采用酸碱化学清洗。离子交换膜化学反应器分离和去除技术在给水、饮用水源铬(Ⅵ)突发性应急处理以及污水中磷酸盐的处理等方面，尤其在有自然咸水可利用的地区，具有潜在的应用价值。更多还原

【Abstract】 When the concentration of water-soluble pollutants such as Cr(Ⅵ)andphosphorus exceeds the water standard, there will be a serious danger to theenvironment and human health. Currently, most of the research of Cr(Ⅵ)removal wasfocused on Cr(Ⅵ)removing in industrial effluent, while relatively fewer literatureswere specially involved in Cr(Ⅵ) uptake in drinking water. Phosphorus exists in theform of phosphate, polyphosphate and organic phosphorus in the sewage effluent,while phosphate is the main form. Advanced treatment for phosphate of the effluent ofsecondary sedimentation tank has an extremely important significance for the controlof total phosphorus discharge to receiving waters. The aim of this study is to developean ion-exchange membrane chemoreactor, which will be used for Cr(Ⅵ) andphosphate removal from aqueous solution.The results of our experiments with Cr(Ⅵ) and phosphate separation byanion-exchange membrane showed that the separation efficiency of Cr(Ⅵ) fromfeeding chamber reached86.4%under the conditons of influent Cr(Ⅵ) concentration1.0mg/L, pH6.95, NaCl concentration0.1mol/L in counterion solution, flow rate offeed and counterion solutions2.5mL/min, stirring speed500r/min, and phasetemperature25℃. In addition, the separation efficiency of phosphate byanion-exchange membrane could achieve84.3%under the identical experimentalcondition. Using Na2SO4as counterion solution, the separation efficiency of Cr(Ⅵ)and phosphate was reduced, and the latter got a comparatively greater decrease. Withthe different NaCl concentrations in counterion solution, no change was likely to befound in the separation efficiency of Cr(Ⅵ) and phosphate by anion-exchangemembrane; however the ion flux rised dramatically with the increase of NaClconcentration in counterion solution. When initial pH of feed solution was11.0and3.0, the separation efficiency of Cr(Ⅵ) and phosphate dropped. It was also found thatthe separation efficiency of Cr(Ⅵ) and phosphatewas greatly improved with theincrease of stirring speed and phase temperature in feed and counterion solutions. Theseparation efficiency of Cr(Ⅵ) and phosphate decreased significantly with increasingthe flow rate of feed solution. The competitive removal experiments indicated that thedivalent ion (SO42-) had a profound interfering effect compared to monovalent ions(NO3-and Cl-), and the higher the concentration of coexisting ions, the more stronger of the competitive effect. Orthogonal experiments showed that the flow rate of feedsolution and counterion solution species mostly affected the separation of Cr(Ⅵ) andphosphate, respectively, which had a significant impact on the results of separationexperiments of Cr(Ⅵ) and phosphate by anion-exchange membrane.In the optimum operating parameters of separation, the enrichment content ofboth Cr(Ⅵ) and phosphate in chemoreactor per unit time were increased with theincrease of influent concentration in feed solution. The optimum dosage ofFeSO4·7H2O: Cr(Ⅵ) was found to be20:1with reductant removal of Cr(Ⅵ), andappropriately excessive dosage of FeSO4could be added without adjustment of pH inraw water. Increasing dosage coefficient with the ratio of PFS to P, the removalefficiency of phosphate by chemical precipitation was enhanced. Effluentconcentrations of Cr(Ⅵ) and phosphate treated by ion-exchange membranechemoreactor were less than or close to the corresponding water quality standardsunder three different operation conditions.Ion exchange kinetics of Cr(Ⅵ)and phosphate were also specially investigated.The experimental results showed that the saturated exchange capacity of Cr(Ⅵ) andphosphate with anion-exchange membrane were1.59mmol/g(dry membrance) and0.51mmol/g(dry membrance), respectively. The ion exchange process of both Cr(Ⅵ)and phosphate could be described by the Particle Diffusion Control(PDC) kineticmodel. With the increase of initial concentration and phase temperature of Cr(Ⅵ) andphosphate, the apparent rate constant and particle diffusion coefficient of the two ionsincreased. The transport process of Cr(Ⅵ) and phosphate ions transferred fromfeeding chamber to chemoreactor through the anion-exchange membrane could bedivided into three steps on the whole. Using pretreated anion-exchange membraneimmersing in NaCl solution and increasing Cl-concentration in counterion solutioncould efficiently promote the first and third transport process of Cr(Ⅵ) and phosphateions, respectively. However, the second transport process of Cr(Ⅵ) and phosphateions was mainly depended on the basic characteristic of exchange ion andanion-exchange membrane. When NaCl concentration in counterion solution wasincreased, the content of Cr(Ⅵ)and phosphate ions in anion-exchange membranedecreased significantly. In the experiments with two overlapping membranes, Cr(Ⅵ)ions mainly distributed in membrane1, and fewer were found in membrance2. Withlower and higher NaCl concentration in counterion solution, the content of phosphateions distribution in two overlapping membranes presented increasing and descendingtrend from side of feeding chamber to side of chemoreactor respectively. The charged colloidal particles existed in raw water were the main reason for membrane fouling,and the membrane could be restored by acid-alkali chemical cleaning.In consequence, separation and removal technology using ion-exchangemembrane chemoreactor might be a promise potential process for emergencytreatment of raw water polluted by Cr(Ⅵ)and advanced treatment of phosphatecontaining wastewater, especially in the area where high salted nature water can beutilized.更多还原