电化学法去除电镀废水中高浓度硝酸盐的研究

发布时间：2018-08-23 15:17

【摘要】：电镀过程中会产生大量的有毒有害废水,包括高浓度的硝酸盐废水。硝酸盐由于其全球性与致癌性受到广泛关注,但绝大多数学者对硝酸盐的研究领域集中在地下水中低浓度的硝酸盐污染,对废水中高浓度的硝酸盐污染研究极少。很多方法虽然对低浓度硝酸盐的去除效果较好,但并不适用高浓度硝酸盐废水。电化学技术作为环境友好技术,能高效去除污染物且无二次污染,既可以单独处理也可以结合其他工艺,是处理废水的有效方法。零价铁还原法具有毒性低、材料廉价易得、反应速度快、易操作等优点,能有效去除废水中的多种污染物而备受关注。本文以高浓度硝酸盐模拟废水为研究对象,首先以铜为阴极,钛为阳极组成的电化学系统对其进行去除,其次结合活泼金属还原法,加入铁粉做成电化学强化还原系统,可以高效去除硝酸盐且产生较少的副产物,更多地转化为氮气等含氮气体从而使水中的总氮降低。主要的研究内容如下:探索单独使用电化学技术对高浓度硝酸盐模拟废水(NO3--N 1000mg/L)的去除效果,考察了pH、电流密度、电压强度、反应时间、搅拌强度、处理水量和氯离子浓度等因素对硝酸盐的去除影响。实验表明,电流密度、电压强度、反应时间和处理水量对硝酸盐的还原效果影响较大,一定的搅拌强度可以促进传质过程,氯离子浓度是控制副产物氨氮生成的重要因素,pH在反应系统中作用不大。结合铁还原法和电化学法去除模拟废水中高浓度硝酸盐,采用响应面(RSM)的Box-Behnken功能进行优化实验设计,并对结果进行数学建模。通过考察零价铁质量、电压强度、pH和氯离子浓度四因素分别在低、中、高三个水平上对硝酸盐的去除效果进行了中心复合设计,通过建立数学模型了解影响因素与去除效率之间的关系。结果表明设置电压强度13V,pH为1,极板距离1.2cm,0.5g还原铁粉,氯离子浓度3000mg/L,搅拌强度450rad/min,电解60min后,硝酸盐的去除率达到84.04%,总氮去除率81.37%。可见本反应系统可有效去除电镀废水中高浓度硝酸盐。这些研究结果表明,电化学法可以有效还原高浓度硝酸盐,结合零价铁还原法对硝酸盐的还原和总氮的去除效果更好。这些研究为电镀废水中高浓度硝酸盐废水的处理提供了初步的思路,有一定的推动作用。
[Abstract]:A large amount of toxic and harmful wastewater, including high concentration of nitrate wastewater, can be produced in electroplating process. Nitrate has attracted wide attention due to its global and carcinogenic properties. However, most scholars focus on the low concentration of nitrate pollution in groundwater, and rarely on the high concentration of nitrate pollution in wastewater. Although the removal effect of low concentration nitrate is better, many methods are not suitable for high concentration nitrate wastewater. As an environment-friendly technology, electrochemical technology can effectively remove pollutants without secondary pollution, and can be treated separately or in combination with other processes. It is an effective method for wastewater treatment. Zero-valent iron reduction method has the advantages of low toxicity, cheap materials, fast reaction speed, easy operation and so on. It can effectively remove many kinds of pollutants in wastewater and has attracted much attention. In this paper, the simulated wastewater of high concentration nitrate was used as the research object. Firstly, the electrochemical system composed of copper cathode and titanium anode was used to remove the wastewater. Secondly, combined with the active metal reduction method, iron powder was added to make the electrochemical enhanced reduction system. It can remove nitrate efficiently and produce less by-products, which can be converted to nitrogen and other nitrogen-containing gases, so that the total nitrogen in water can be reduced. The main contents are as follows: the removal efficiency of high concentration nitrate simulated wastewater (NO3--N 1000mg/L) by electrochemical technique was studied. The pH, current density, voltage intensity, reaction time and stirring intensity were investigated. The effect of water treatment and chloride concentration on nitrate removal was studied. The results show that current density, voltage intensity, reaction time and the amount of water treated have great influence on the reduction effect of nitrate, and a certain stirring intensity can promote the mass transfer process. The concentration of chloride ion is an important factor to control the formation of ammonia nitrogen, and pH has little effect in the reaction system. Combined with iron reduction method and electrochemical method, the high concentration nitrate in simulated wastewater was removed. The Box-Behnken function of response surface (RSM) was used to optimize the experimental design, and the result was modeled by mathematics. Through the investigation of zero valent iron mass, voltage intensity, pH and chloride concentration, the central composite design of nitrate removal efficiency was carried out at three levels, namely, low, middle and high levels, respectively. A mathematical model was established to understand the relationship between factors and removal efficiency. The results show that the removal rate of nitrate is 84.04 and the removal rate of total nitrogen is 81.37 after electrolysis of 60min with voltage intensity of 13V ~ (-1) pH = 1, electrode distance 1.2 cm ~ (-1) ~ (0.5) g reduction of iron powder, chloride ion concentration of 3000mg / L, stirring intensity of 450 mg / min. It can be seen that this reaction system can effectively remove high concentration nitrate from electroplating wastewater. These results show that the electrochemical method can effectively reduce the high concentration of nitrate, and the reduction of nitrate and removal of total nitrogen by zero-valent iron reduction method are better. These studies provide a preliminary idea for the treatment of high concentration nitrate wastewater from electroplating wastewater.
【学位授予单位】：广东工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X781.1

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