【作者】 魏新渝；

【导师】 王志； 刘广春；

【作者基本信息】 天津大学 ， 环境化工， 2007， 硕士

【摘要】 抗生素制药废水有机物含量高,还含有残余抗生素。传统的物理化学和生物法处理这类废水,效果不好,难以达到行业排放标准;用集成膜技术深度处理这类废水有可能使其达标排放甚至回用。本文研究了膜技术处理制药废水中膜污染机理和防治,以及添加药剂对膜结构和性能的影响等关键问题。针对深度处理抗生素制药废水的超滤-纳滤集成膜过程,采用多种先进分析手段,探讨了过程中膜污染机理;考察了各种因素对膜污染的影响;研究了不同清洗方案对膜性能恢复的效果。柠檬酸和亚硫酸氢钠是膜技术中常用的药剂。本文系统考察了药剂的浓度,与膜的接触方式、接触时间和接触温度等对聚砜和聚丙烯腈膜结构和性能的影响。采用电感耦合等离子(ICP)发光法和离子色谱(IC)法分析了进水水质;使用能谱法(EDX)、扫描电镜法(SEM)以及傅里叶变换衰减全反射红外光谱法(ATR-FTIR)对各种条件下得到的污染膜表面进行了分析。由此推断出,引起膜污染的主要物质是含钙、铁的无机盐以及酚类、醚类、羧酸类等有机物质。这些物质在膜面上沉积吸附,引起膜污染。对于纳滤过程,进料液的CODCr和电导率越大,膜污染越严重;控制较低的操作压力、较大的膜面流速以及适宜的温度能有效地控制膜污染。此外,在料液中添加柠檬酸(0.03 wt%)、盐酸(pH=3)或EDTA(0.5 mM)溶液,都能降低纳滤膜渗透通量的衰减程度。其中,添加EDTA溶液时的效果最好。对污染膜采用水力清洗的方法。结果显示,在压力0.2MPa、膜面流速23.6cm·s-1、温度35.0℃下,清洗100min后,膜通量恢复系数为98.2%。在室温下,对严重污染膜采用纯水浸泡或化学清洗的方法。实验结果显示,在纯水中浸泡10~40小时,膜通量能够恢复。考察化学清洗时,比较了NaOH(pH=11)、盐酸(pH=3)、0.3wt%的柠檬酸溶液以及1.0mM的EDTA溶液的清洗效果。结果表明,清洗效果随以上溶液依次递增;用EDTA溶液清洗时所需的时间最短,约10分钟就能使膜通量完全恢复。对清洗后的膜表面进行SEM和EDX分析。SEM照片显示,膜表面光洁程度依次递增,EDTA清洗后的膜表面SEM照片与清洁膜的最接近;EDX分析表明,膜表面含有的Ca元素依次递减,EDTA清洗后的膜面基本不含Ca元素。系统考察了各种操作条件下柠檬酸和亚硫酸氢钠对聚砜和聚丙烯腈膜性能的影响。结果表明,柠檬酸溶液只与膜表面接触后,膜纯水通量变化较小;而柠檬酸溶液与膜整体(包括表面和孔内)充分接触后,膜纯水通量下降。膜整体与柠檬酸充分接触一定时间后,膜截留聚氧化乙烯时的通量衰减变小,膜对聚氧化乙烯的截留率略有提高,膜的抗污染性能提高。对于膜整体与柠檬酸溶液接触,随着柠檬酸浓度增大,膜通量下降百分比有增大的趋势,膜接触角有先增大后减小的趋势。随着接触时间延长或接触温度升高,膜通量下降百分比先增大后趋于稳定。随着膜面流速的增大或操作压力的减小,柠檬酸对膜通量的影响降低,膜通量下降百分比减小。在本文实验条件下,PAN和PS膜与柠檬酸溶液接触充分后,其通量下降百分比分别为15.44%~28.30%和11.38~28.94%。对于亚硫酸氢钠,当其与膜表面接触后,膜纯水通量增大;当其与膜整体充分接触后,膜纯水通量也增大,但增大百分比降低。膜整体与亚硫酸氢钠充分接触一定时间后,膜截留聚氧化乙烯时的通量衰减变小,膜对聚氧化乙烯的截留率基本不变,膜的抗污染性能提高。对于膜整体与亚硫酸氢钠溶液接触,随着亚硫酸氢钠浓度的增大, PAN膜的通量增大百分比先增大后趋于稳定,而PS膜通量增大百分比先降低后趋于稳定,两种膜的接触角均减小。随着接触时间的延长,膜通量增大百分比先增大后趋于稳定。随着接触温度的升高,膜通量增大百分比先降低后趋于稳定。随着膜面流速的增大,亚硫酸氢钠对膜通量的影响降低,膜通量增大百分比减小。随着操作压力的增大,亚硫酸氢钠对PAN膜通量的影响增大,膜通量增大百分比提高;而对PS膜通量的影响减小,通量增大百分比减小。在本文实验条件下,PAN和PS膜与亚硫酸氢钠溶液接触充分后,其通量增大百分比分别为-5.28%~5.22%和26.49%~45.24%。对吸附药剂后的膜表面进行了SEM和ATR-FTIR分析以及接触角的测定,由此并根据柠檬酸、亚硫酸氢钠、PAN膜和PS膜的不同化学结构推断出两种药剂与膜的不同作用机理。对于柠檬酸溶液,在膜面上吸附时,可能形成碳氢基向外的表面层,使膜的润湿性降低,膜通量下降。而对于亚硫酸氢钠,可能形成SO32-、HSO3-等极性基团吸附在外表面的结构,使膜的亲水性增强,膜通量增大。比较了药剂对PAN和PS膜影响的差异,结果表明,药剂对PAN和PS膜的影响的差异除了与膜的亲疏水性有关外,还与膜在药剂中化学性质的变化有关。本文工作对膜技术深度处理成分复杂的工业废水有一定参考价值,为广泛深入研究药剂对膜结构和性能的影响提供了思路和方法。更多还原

【Abstract】 The antibiotic wastewater contains high organic content and toxic antibiotic residues. Most existing physical and chemical treatment methods are not effective in treating the wastewater, and the effluent is difficult in compliance with industrial emission standards. Integrated membrane systems could sufficiently remove the pollutants in the wastewater and enable the wastewater to be discharged into the receiving water or even be reused for industrial purposes. In this work, the key problems that membrane fouling mechanism and control during the process of treating antibiotic wastewater by integrated membrane system and impacts of adding reagents in the process on membranes’structure and performance were studied.For ultrafiltration-nanofiltration integrated membrane system,membrane fouling mechanism was explored by several advanced analytical methods. Various influencing factors of membrane fouling and cleaning methods in the process were investigated. The impacts of reagents used in the process on the performances of poly acrylonitrile (PAN) membrane and polysulfone (PS) membrane were studied, respectively. Typical reagents citric acid and sodium bisulfite were chosen to investigate in detail. The impacts of various factors including concentration of reagents, contacting ways with membranes, contacting time, contacting temperature etc. on the membranes’structures and performances were investigated.The water quality was analyzed by Inductively Coupled Plasma Atomic Emission Spectrometer (ICP) and Ion Chromatography (IC). Fouled membrane samples under different conditions were analyzed by Energy Dispersive X-Ray (EDX), Scanning Electron Microscope (SEM), and Attenuated Total Reflection Spectra-Fourier Transform Infrared Spectrometry (ATR-FTIR). It can be deduced from the analytical results that the membrane fouling in the process is caused by adsorption and deposition of inorganic compounds of calcium and iron, and complex organic compounds which may contain phenolic, etheric and carboxylic functional groups etc. on membrane surface and inside membrane pores. In the nanofiltration process, with increasing COD and conductivity of feed water, the membrane fouling becomes more severe. Under the conditions of lower applied pressure, higher crossflow velocity and proper temperature, the membrane fouling can be efficiently suppressed. In addition, the decline of nanofiltration membrane permeate flux becomes slight after adding citric acid (0.03wt%), HCl (pH=3) or ethylene diamine tetraacetic acid diasodium salt (EDTA, 0.5mM) to feed water, and adding EDTA reaches the best result. The fouled membrane was cleaned with pure water for 100 minutes under conditions of TMP 0.2MPa, crossflow velocity 23.6cm·s-1 and temperature 35.0℃. The flux recovery is 98.2%. The severe fouled membrane was cleaned by immerging it in pure water or washing it with different chemicals under room temperature. The results indicate that immerging severe fouled membrane in pure water for 10~40 hours can recover membrane permeate flux. Chemical cleaning with NaOH (pH=11), HCl (pH=3), citric acid (0.3wt%) and EDTA (1.0mM) were carried out, respectively. The results show that the cleaning efficiency increases in the sequence of solutions mentioned above and it is the highest with EDTA which costs only 10 minutes to recover membrane permeate flux completely. The membrane surfaces were analyzed by SEM and EDX after chemical cleaning. The SEM photos show that the smooth and cleanly degree of membrane surface increases in the above sequence and the SEM photo after cleaning with EDTA is close to that of unfouled membrane. EDX analytical results indicate that the containing percent of element Ca on the membrane surfaces decreases in the above sequence and it is null after cleaning with EDTA.The impacts of citric acid and sodium bisulfite on PAN membrane and PS membrane under various operational conditions were systematically investigated. The results show that citric acid has minor influence on membranes’performance when it contacts membranes’surface only. And when citric acid contacts membranes’entirety (including surface and pores) sufficiently, the membranes’pure water permeate flux decreases. After citric acid contacting membranes’entirety for a certain time, the decline of membranes’permeate flux decreases during the process of filtering Poly(ethylene oxide) (PEO) solution, and membranes’rejection of PEO increases. The membranes’antifouling performance is improved. When citric acid contacts membranes’entirety, with increasing concentration of citric acid, the decreasing percent of membranes’permeate flux increases and the contact angle increases first and then decreases. With increasing contacting time or contacting temperature, the decreasing percent of membranes’permeate flux increases first and then becomes stable. With increasing crossflow velocity or decreasing applied pressure, the impact of citric acid on membranes’performance decreases, i.e., and the decreasing percent of membranes’permeate flux decreases. In this work, the permeate flux decreasing percents of PAN and PS membranes after contacting citric acid sufficiently are 15.44%~28.30% and 11.38~28.94%, respectively. As far as sodium bisulfite is concerned, when it contacts membranes’surface only, the membranes’pure water permeate flux increases, and when it contacts membranes’entirety sufficiently, the membranes’pure water permeate flux increases too, but the increasing percent decreases. After sodium bisulfite contacting membranes’entirety for a certain time, the decline of membranes’permeate flux decreases during the process of filtering PEO solution, and membranes’rejection of PEO has no obvious changes. The membranes’antifouling performance is improved. When sodium bisulfite contacts membranes’entirety, with increasing concentration of sodium bisulfite, the increasing percent of membrane permeate flux increases for PAN membrane, but decreases for PS membrane, and the contact angle decreases for two kinds of membranes. With increasing contacting time, the increasing percent of membranes’permeate flux increases first and then becomes stable. With increasing contacting temperature, the increasing percent of membranes’permeate flux decreases first and then becomes stable. With increasing crossflow velocity, the impact of sodium bisulfite on membranes’performance decreases, i.e., the increasing percent of membranes’permeate flux decreases. With increasing applied pressure, the impact of sodium bisulfite on PAN membrane performance increases, i.e., and the increasing percent of membrane permeate flux increases, while, the influence of sodium bisulfite on PS membrane performance decreases, i.e., the increasing percent of membrane permeate flux decreases. In this work, the permeate flux increasing percents of PAN and PS membranes after contacting sodium bisulfite sufficiently are -5.28%~5.22% and 26.49%~45.24%, respectively.The membranes’surfaces after adsorbing reagents were inspected by SEM and ATR-FTIR, and their contact angles were measured. According to the results and the chemical structures of citric acid, sodium bisulfite, PAN membrane and PS membrane, it can be concluded that the mechanisms for impacts of citric acid and sodium bisulfite on membranes’performance are different. When the citric acid adsorbs on membranes’surface, carbon hydrogen functional groups are outward to solution, which makes membranes difficultly be wetted, and thus the membranes’permeate flux declines. However, when the sodium bisulfite adsorbs on membranes’surface, the functional groups such as SO32- and HSO3- are on exterior of surface, which helps improve the wetting property of membranes, and thus the membranes’permeate flux increases. With comparisons of the impacts of citric acid and sodium bisulfite on PAN and PS membranes, it can be concluded that the differences of impacts of the reagents on the membranes are not only caused by the hydrophilic/hydrophobic property of the membranes, but also by the chemical characters of the membranes in the reagents.This work provides a good example for the membrane technique applying in advanced treatments of industrial wastewater containing complicated compounds. The understanding of impacts of reagents on membranes’structure and performance provides a good basis for further study.更多还原