高性能正渗透—膜蒸馏耦合技术处理高盐废水的研究

发布时间：2018-02-21 15:44

本文关键词： 正渗透碳纳米管膜蒸馏 FO-MD耦合工艺高盐废水　出处：《湘潭大学》2017年硕士论文　论文类型：学位论文

【摘要】：正渗透(FO)及膜蒸馏(MD)由于特有的优势,在高盐废水处理方面应用得越来越多,但正渗透面临着缺乏高性能正渗透膜以及选取合适汲取液的问题,而膜蒸馏膜容易被表面活性有机物润湿,造成膜污染。本文探究了如何制备高水通量、截盐效果好、机械性能优异的正渗透膜,并将正渗透膜应用在正渗透-膜蒸馏(FO-MD)耦合工艺中,探究了两种工艺的影响参数以及FO-MD耦合工艺处理污染废水的效果,最后对耦合工艺的传质传热过程进行了探究。主要成果如下:(1)以聚丙烯腈、掺入碳纳米管和石墨烯的聚丙烯腈作为原料液,制得正渗透膜基底,在界面聚合一层聚酰胺功能层,制成正渗透膜。考察了制膜方式、纺丝电压、接收距离和原料液组成对膜结构的影响,重点探究了静电纺丝法中PAN浓度和MWCNT浓度对膜形貌、亲水性和机械性能的影响。随着电压增大,纤维直径先增大后减小,随着接收距离增大,纤维直径变小。PAN浓度增大使纤维直径和机械强度变大,孔隙率增大后减小。多壁碳纳米管降低了平均直径,增强了膜的亲水性,提高了膜的机械强度,但使膜韧性变差。(2)分别以相转化法和静电纺丝制备PAN正渗透基底,但相转化法水通量较低。用静电纺丝法制备了聚丙烯腈/石墨烯和聚丙烯腈/碳纳米管正渗透膜,结果表明石墨烯和碳纳米管都提高了膜水通量,且碳纳米管影响更大。着重研究了PAN和MWCNT对正渗透膜性能的影响,一定范围内PAN浓度增大、f-MWCNT增加有利于提高膜水通量和截盐率。聚丙烯腈浓度为12%,f-MWCNTs浓度为1.44%的正渗透膜,表现出高水通量和高截盐率,以1.0 mol/L NaCl为汲取液,纯水作为原料液,水通量可达到70.1 L/(m2·h),反向盐通量仅50.4(g/m2·h)。(3)探究了汲取液浓度、温度、流速等参数在正渗透过程对水通量和反向盐通量的影响,以及在膜蒸馏过程中待处理液热端进料温度、膜两侧流速对水通量、水质的影响。结果表明正渗透过程水通量随着汲取液浓度、温度、流速的增大都有一定程度的增大,升温对水通量的影响最大,对溶质反向渗透量的影响不大。温差增大、膜厚度减小、流速的增大都会促进膜蒸馏水通量的增大。(4)对比经MD过程与RO过程,MD过程、与FO-MD集成过程处理的废水,结果显示FO-MD集成系统处理的膜污染较低,且长时间运行结果稳定,具有良好的耐污性。对不同汲取液选择的能耗计算,表明使用NaCl溶液为正渗透单元汲取液时,相比于NH4HCO3为汲取液能耗更低。而且NaCl溶液浓缩回收具有良好效果,可以实现零排放。
[Abstract]:Due to its unique advantages, normal osmosis (FOO) and membrane distillation (MDD) are more and more widely used in the treatment of high salt wastewater. However, due to the lack of high performance forward osmotic membrane and the selection of suitable solution, positive osmosis is faced with many problems. However, membrane distillation membrane is easy to be wetted by surface active organic compounds, resulting in membrane fouling. In this paper, the preparation of high water flux, good salt cutting effect, excellent mechanical properties of normal osmotic membrane has been investigated. The normal osmotic membrane was applied to the FO-MD coupling process. The influence parameters of the two processes and the effect of the FO-MD coupling process on the treatment of polluted wastewater were explored. Finally, the mass transfer and heat transfer process of the coupling process is studied. The main results are as follows: (1) Polyacrylonitrile (pan) with carbon nanotube (CNT) and graphene as the raw material liquid is used to prepare the normal permeable membrane substrate, and a layer of polyamide functional layer is polymerized at the interface. The effects of film preparation mode, spinning voltage, receiving distance and composition of raw material liquid on the membrane structure were investigated. The effects of PAN concentration and MWCNT concentration on the morphology of the membrane were investigated. The effect of hydrophilicity and mechanical properties. With the increase of voltage, the diameter of the fiber increases first and then decreases, and with the increase of the receiving distance, the diameter of the fiber becomes smaller and the concentration of pan increases, the diameter and mechanical strength of the fiber become larger. With the increase of porosity, the average diameter was decreased, the hydrophilicity and mechanical strength of the membrane were enhanced, but the toughness of the membrane became worse, which resulted in the preparation of PAN positive permeable substrates by phase inversion and electrospinning, respectively. But the water flux of phase inversion method was low. Polyacrylonitrile / graphene and polyacrylonitrile / carbon nanotubes were prepared by electrospinning. The results showed that both graphene and carbon nanotube increased the water flux of the membrane. The effects of PAN and MWCNT on the properties of the membrane were studied. The increase of PAN concentration in a certain range is beneficial to the increase of water flux and salt interception rate of the membrane, and the concentration of polyacrylonitrile is 12% f-MWCNTs with the concentration of 1.44%. Using 1.0 mol/L NaCl as absorbent, pure water as feedstock solution, water flux can reach 70.1 L / m ~ 2 路hm ~ 2 路h ~ (-1), reverse salt flux is only 50.4 g / m ~ (2 路h ~ (2) 路h ~ (-1)). The influence of flow rate and other parameters on water flux and reverse salt flux during the normal osmotic process, as well as the feed temperature at the hot end of the liquid to be treated during membrane distillation, and the water flux on both sides of the membrane were studied. The results show that the water flux increases to a certain extent with the concentration, temperature and flow rate of the solution in the normal osmotic process, the effect of heating on the water flux is the greatest, and the effect on the reverse osmotic capacity of solute is not significant, but the temperature difference increases. Compared with MD process, RO process, MD process and FO-MD integrated process, membrane fouling was lower in FO-MD integrated system. The results of long time operation are stable and have good resistance to pollution. For the calculation of energy consumption of different extraction fluids, it is shown that when NaCl solution is used as normal osmotic unit extract solution, Compared with NH4HCO3 solution, the energy consumption is lower, and NaCl solution concentration and recovery have good effect, and can achieve zero emission.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ028.8;X703

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