【作者】 陈雪芬；

【导师】 吴祖成；

【作者基本信息】 浙江大学 ， 环境工程， 2005， 硕士

【摘要】 电镀是当今全球三大污染工业之一。电镀废水是全球主要的重金属污染源,如不加以处理直接排放,不仅造成受纳水体的污染,影响水资源环境,而且造成水资源和有价金属的巨大浪费。现有的处理方法如化学法、生物法、离子交换法、电渗析等方法均能有效的处理重金属废水,但同时也存在着不足之处。针对这一问题,本文的电去离子法结合了离子交换法和电渗析的优点,既能深度处理重金属电镀废水,又能避免电渗析法的极化问题,是一种具有发展前景的水处理方法。 传统电去离子过程处理含重金属废水中存在的问题,即在混合离子交换床的树脂颗粒表面或离子交换膜表面生成氢氧化物沉淀,严重地影响着电去离子过程的稳定运行。本文通过改变膜堆的排列和离子交换树脂的填充方式,设计和制作了由四离子交换膜隔成的五隔室反应装置。阳离子和阴离子分别在阳离子树脂室和阴离子树脂室经交换和电场作用下迁移至浓缩室被除去;模拟废水先后经过阳离子和阴离子树脂填充室得到连续的净化水以及浓缩的盐溶液。 采用该装置研究了吸附于阳离子交换树脂上的Ni²⁺在电场中的迁移行为,实验发现浓缩室溶液中Ni（OH）₂的离子积Q_C远远小于其溶度积常数K_sp,根据溶度积规则,浓缩室不会形成Ni（OH）₂沉淀,因此解决了通常的电去离子装置在运行过程中的沉淀问题。在此基础上,还考察了电压对Ni²⁺离子电迁移速率的影响,结果表明Ni²⁺的迁移速度随着电压的增加而增大。当外加电压=20V时,Ni²⁺在较低的能耗下获得较高的迁移速率,反应3小时后,树脂的再生效率达到50%。 通过对比单纯的离子交换床和电去离子过程处理模拟电镀废水,显示了电去离子过程在净化废水所具有的明显优势,即电去离子过程能够同时实现废水的净化和离子交换树脂的连续在线再生。 最后采用了连续净化废水的运行方式,对含Ni²⁺浓度为100mg L^-1的硫酸镍模拟废水进行处理。通过去除效率和电流效率两个参数考察了整个装置的运行状况,计算得到该方法的去除效率>98%,电流效率约为34%。 电去离子方法技术先进,运行稳定,能够实现低浓度含重金属电镀废水的处理和对重金属浓缩液的回收,因而可实现污染物的零排放。该工艺的推广应用,将使电镀废水的治理实现闭路循环,不仅促进电镀行业的可持续发展,而且也有利于环境保护,具有显著的经济效益、社会效益和环境效益。更多还原

【Abstract】 Nowadays electroplating is one of the most polluting industries all over the world. As being the main heavy metal pollutant source, electroplating wastewater would, if it discharged without treatment, not only pollute the waters and destroy the water environment but also lead to the great waste of water resources and expensive metals. Though many technologies such as chemical precipitation, biological method, ion exchange and electrodialysis （ED） can be used to remove the metal ions from the wastewater, they also have their own disadvantages. For these reasons, electro-deionziation （EDI） in this paper combining the advantages of the ion exchange and ED is a polishing process for electroplating wastewater without the polarization problem in the ED. Therefore, it will be a promising technology in the field of water purification.The problem using conventional EDI for the metal removal from electroplating wastewater is that hydroxide deposit in the interface of ion exchange resins or in the surface of ion exchange membrane would affect the stability of the process. By rearranging the membranes and assembling the cation exchange resins and anion exchange resins separately, it was found that the ionic product of the nickel ion and the hydroxyl ion is far lower than the solubility product constant. According to the solubility product principle, there is no nickel hydroxide precipitation in the concentrate compartment. Furthermore, by investigating the effect of voltages on the migration rate of the nickel ions under the electric field, we found that nickel ions transfer at higher rate by lower electric energy consumption when the applied voltages are 20V. After 3 hours, the regeneration efficiency is 50%.Finally, the comparison is made between the process of ion exchange and EDI for the purification of the simulated electroplating with the nickel ion concentration of 100 mg L^-1 which exhibits the merits of the latter. Moreover, the performance is evaluated in terms of percent extraction and current efficiency, respectively. We calculated the percent extraction is larger than 98% and the average current efficiency is 34%.This paper shows that EDI is advance and steady process, which can be used for the purification of the electroplating wastewater and recycle the concentrate containing heavy metal ions. The further application of this method can realize the closed-loop of electroplating wastewater so that it is favorable for the economic development and environmental protection.更多还原