【作者】 刘亮；

【导师】 曾光明； 汤琳；

【作者基本信息】 湖南大学 ， 环境工程， 2017， 博士

【摘要】 在水体重金属污染日益严重的形势下,寻求一种发展成本低、设备运行简单、重金属去除效率高的水处理技术成为一项迫在眉睫的任务。由于微生物处理法较传统的物理化学法具有投资小、运行费用低等显著优点,被广泛用于重金属去除的研究中。但同时也存在着微生物细胞较小、易流失,很难与水溶液分离以及易造成二次污染等缺点,再加上废水中的重金属离子在一定程度上对微生物有毒害作用,导致微生物失去活性,去除效率降低。所以,如何提高微生物处理法对重金属的处理效率,成为该处理技术应用的关键。菌种固定化技术由于保持了微生物较强的活性、较强的稳定性及具有易于分离回收利用等优点,成为一种理想的选择。此外,在微生物处理技术对重金属的解毒中,微生物的新陈代谢起关键作用。因此,本文以环境领域常见的对重金属有良好去除效果的白腐真菌、枯草芽孢杆菌及铜绿假单胞菌等微生物为研究对象,探讨生物吸附剂在重金属去除中的性能,并从微生物的新陈代谢出发,深入探讨微生物的新陈代谢及其对抗污染物胁迫的调控机制。最后,通过研究重金属-有机物复合污染废水中各成分的相互影响,以及表面活性剂在重金属解毒机制中的作用,来寻求一种提高微生物处理重金属废水效率的方法。本文主要的研究工作及成果主要包括以下5个方面:第一部分是以壳聚糖包埋活性炭与黄孢原毛平革菌制备的固定化生物吸附剂对Pb(Ⅱ)的吸附及其机理研究。首先采用壳聚糖包埋活性炭与黄孢原毛平革菌制成固定化小球,再将其应用于铅污染废水的处理中,并考察了不同pH、吸附时间、重金属离子初始浓度3个条件对吸附效率的影响,最后探讨了吸附机理及该生物吸附剂的重复利用性。结果表明:(1)该生物吸附剂处理的最佳pH值为5,吸附平衡时间为4 h,最大吸附量为167.36 mg/g;(2)吸附等温线符合Langmuir模型,说明该生物吸附剂表面均一,对Pb(Ⅱ)的吸附是单层吸附;(3)该生物吸附剂对Pb(Ⅱ)的吸附符合准一级反应动力学模型,内传质阻力是吸附速率的限制因素:(4)该吸附剂的吸附效率受其他共存离子的影响;(5)该吸附剂重复利用率高,在5次循环使用后,吸附效率仅降低了 6.13%。第二部分是以海藻酸钠包埋黄孢原毛平革菌和Fe3O4纳米粒子制备成的磁性生物吸附剂对Cu(Ⅱ)和Pb(Ⅱ)的竞争性吸附研究。主要研究了磁性生物吸附剂的活性及pH值、吸附时间对Pb(Ⅱ)、Cu(Ⅱ)单、双组分重金属离子吸附效果的影响。结果发现:(1)该磁性生物吸附剂不仅具有较强的磁化强度,而且与游离的黄孢原毛平革菌相比,新陈代谢不仅没有受到抑制,反而有所促进;(2)该磁性生物吸附剂对Pb(Ⅱ)、Cu(Ⅱ)单、双组分四种组分溶液处理的最佳pH值均为5,吸附平衡时间为4h:(3)实验数据能与Langmuir等温吸附线模型很好地拟合,这说明磁性生物吸附剂对Pb(Ⅱ)、Cu(Ⅱ)单、双组分重金属离子的吸附为单层吸附;(4)动力学研究显示,化学吸附是吸附速率的限制因素,该磁性生物吸附剂对单、双组分Pb(Ⅱ)、Cu(Ⅱ)的吸附符合准二级反应动力学模型。第三部分是以重金属铅和镉胁迫下的黄孢原毛平革菌为主要研究对象,探讨重金属对菌体细胞内外新陈代谢的影响,从而揭示黄孢原毛平革菌细胞对重金属的解毒机制。结果发现,重金属离子对黄孢原毛平革菌的胞内和胞外代谢都有一定的影响:(1)黄孢原毛平革菌的胞内活性氧自由基随着镉胁迫浓度和时间的增加而减小;丙二醛(MDA)的量在8 h时达到最大值(9 μmol/g),在24 h时达到最小值(0.6 μmol/g);胞内蛋白质的量也是先增加后减小的趋势;在短时间胁迫下(2h),超氧化物歧化酶(SOD)活性与镉离子浓度成正比,但当胁迫时间增大到8h时,较高浓度的胁迫反而降低了 SOD活性;低浓度或者短时间的镉胁迫刺激了过氧化氢酶(CAT)的产生并呈现较高的酶活性,但增加浓度或接触时间,CAT活性降低,这说明Cd(Ⅱ)对于黄孢原毛平革菌的作用不是简单的抑制作用,而是既激发也抑制;随着Cd(Ⅱ)胁迫时间及浓度的增加,氧化型谷胱甘肽(GSSG)浓度增加的趋势比还原型谷胱甘肽(GSH)增加的趋势更加明显:(2)培养液和胞外聚合物(EPS)中,糖类浓度先减小,后趋于平衡;蛋白质浓度呈现出先增大后减小的趋势;在0-0.8 mMCd(Ⅱ)浓度范围内,Cd(Ⅱ)浓度越高其促进草酸分泌作用越显著,但当Cd(Ⅱ)浓度超过1.0 mM时,会严重抑制草酸的分泌,且Cd(Ⅱ)浓度越高其抑制草酸分泌作用越明显。第四部分是以多环芳烃降解菌枯草芽孢杆菌为研究对象,在研究不同浓度的Cd(Ⅱ)、不同的pH对降解菌降解能力影响的基础上,通过实验研究Cd(Ⅱ)对降解菌细胞膜蛋白和多糖含量的影响、Cd(Ⅱ)对细胞膜内外芘含量的影响,初步探讨Cd(Ⅱ)对芘在枯草芽孢杆菌上降解的影响。结果发现:(1)枯草芽孢杆菌对芘降解的最佳pH值为8:(2)Cd(Ⅱ)对枯草芽孢杆菌降解芘产生了一定的抑制作用,随着Cd(Ⅱ)浓度增大,枯草芽孢杆菌降解芘的能力逐渐变弱;(3)Cd(Ⅱ)的存在会使枯草芽孢杆菌细胞膜上的蛋白质和多糖含量降低;(4)胞内芘的浓度随着培养基中Cd(Ⅱ)浓度的增大呈现先增大,后减少的趋势,而细胞膜上芘的浓度随着培养基中Cd(Ⅱ)浓度的增大呈现先减小,后增大的趋势,所以,Cd(Ⅱ)对芘在枯草芽孢杆菌上的跨膜过程具有抑制作用,当Cd(Ⅱ)浓度为20mg/L时,其对芘在枯草芽孢杆菌上的跨膜过程具有最强的抑制作用。第五部分采用铜绿假单胞杆菌作为Cr(Ⅵ)的高效还原菌,通过分析不同表面活性剂对Cr(Ⅵ)的还原情况,研究了阴离子生物表面活性剂二鼠李糖脂(diRL)、阳离子化学表面活性剂十六烷基三甲基溴化铵(CTAB)和非离子化学表面活性剂曲拉通X-100(Triton X-100)对铜绿假单胞杆菌修复Cr(Ⅵ)的影响,探索了铜绿假单胞杆菌、表面活性剂以及Cr(Ⅵ)的相互作用,以便为表面活性剂应用于含铬废水的处理提供理论依据。结果发现:(1)diRL能被铜绿假单胞菌吸收并作为碳源,从而进行生长代谢活动,有利于还原Cr(Ⅵ),而CTAB由于能电离出阳离子干扰基团影响铜绿假单胞菌表面的活性,抑制了对Cr(Ⅵ)的还原,Triton X-100对Cr(Ⅵ)的还原没太大影响;(2)铜绿假单胞菌对Cr(Ⅵ)的还原更适宜在碱性条件下进行,且溶液pH值越大,对Cr(Ⅵ)的还原率越大;(3)diRL能够促进降解菌的分散性,CTAB的效果则相反,Triton X-100对菌体的zeta电位没有影响;(4)随着接触时间的增加,Cr(Ⅵ)还原效率逐渐降低,但微生物接种含量的增加,促进了其对Cr(Ⅵ)的还原效率,当菌种接种量从0.5%增加到8%时,Cr(Ⅵ)的去除率从17%上升到62.5%;(5)阳离子Cu(Ⅱ)促进了铜绿假单胞菌对Cr(Ⅵ)的还原,而Zn(Ⅱ)抑制菌体对Cr(Ⅵ)的还原,阴离子NO3-和SO42-几乎不影响Cr(Ⅵ)的还原。本文在一定程度上揭示了微生物与重金属离子相互作用的机制,并分析了其在处理重金属废水时效率低下的原因,也摸索出了最佳的处理工艺参数,并通过微生物固定技术,提高了重复利用性,最后通过添加表面活性剂来提高废水的处理效果,这对于提高微生物处理技术在重金属污染水体中的高效利用有一定的指导意义。更多还原

【Abstract】 In the case of heavy metal pollution becoming serious increasingly,it’s an urgent task to develop water treatment technology with low cost,simple equipment operation,high efficiency to remove heavy metals.Due to microbial treatment technology has significant advantages of smaller investment,lower operating cost than the traditional physical and chemical technology,it is widely used to study the removal of heavy metals.But there are some problems,such as,smaller microbial cells,easy activity loss,and the difficulty to separate from aqueous solution that could easily lead to secondary pollution.Also,Heavy metals in wastewater to some extent are toxic to microorganisms,which inhibits the metabolic activity of microorganism,thereby affects removal efficiency of heavy metals.So,how to improve the microbial treatment efficiency of heavy metals becomes a key of microbial treatment technology applications.Microorganism immobilization technology has maintained a strong activity of microorganisms,strong stability and feasibility to separate bacteria,which is an ideal choice.In addition,the microbial metabolism plays a key role in the detoxification process of heavy metal for microbial treatment technology.Therefore,white rot fungi,Bacillus subtilis and Pseudomonas aeruginosa that have favorable removal efficiency of heavy metals were used as objects to study the performance of biological adsorbent for heavy metals,and to discuss the mechanism between microbial metabolism and pollutant stress.Finally,a method to improve the removal efficiency of heavy metal for microbial treatment technology was proposed by studying the interaction of metal and organic compound in wastewater,and the role of surfactants in heavy metal detoxification mechanism.In this paper,the main research work and achievements mainly include the following five aspects:The first section focused on the absorption peformance and mechanism of Pb(Ⅱ)by immobilized biological adsorbent prepared by embedding chitosan,activated carbon and Phanerochaete chrysosporium(P.chrysosporium).Firstly,we successfully prepared the biological adsorbent that can be applied in removal of Pb(Ⅱ),and then studied the effect of pH,time and metal ions initial concentration on removal efficiency.Finally,recycle of biological adsorbent and a possible adsorption mechanism were investigated.The results can be concluded as follows:(1)the optimal pH for biological adsorbent in the treatment was about 5.0,adsorption equilibrium time was 7 h with maximum adsorption quantity of 167.36 mg/g;(2)the adsorption isotherm fits well with the Langmuir model,indicating that the biological adsorbent surface is homogeneous,adsorption sites are equal,and the adsorption of Pb(Ⅱ)is a monolayer adsorption;(3)the adsorption kinetics of Pb(Ⅱ)on biological adsorbent was primarily elaborated by the pseudo-first-order model,which means the internal mass transfer is limiting factor;(4)the removal efficiency of Pb(Ⅱ)is affected by other coexisting ions.(5)This biological adsorbent has a good capacity of repeatability,even after recycling 5 times,adsorption efficiency was only reduced by 6.13%.The second section describes the competitive adsorption of Cu(Ⅱ)and Pb(Ⅱ)with magnetic biological adsorbent prepared by sodium alginate embedding P.chrysosporium and Fe3O4 nanoparticle.Main research includes the activity of magnetic biological adsorbent,the effects of pH value and adsorption time on the adsorption of single and double components of Pb2+,Cu2+.The results showed that:(1)the magnetic biological adsorbent not only has a strong magnetization,but also has enhanced metabolic activity;(2)the optimal pH for magnetic biological adsorbent in the treatment was about 5.0,and adsorption equilibrium time was 7 h;(3)the adsorption isotherm fits well with the Langmuir model,meaning that the adsorptions of single and double components of Pb2+,Cu2+ are monolayer adsorption;(4)The adsorption kinetics of single and double components of Pb2+,Cu2+ on magnetic biological adsorbent fit well the pseudo-second-order model,and chemical adsorption is adsorption rate limiting factor.In the third section,we mainly discussed the influence of heavy metals on P.chrysosporium metabolism to reveal the detoxification mechanism of heavy metal.The results found that heavy metal ions have a certain influence on intracellular and extracellular metabolites of P.chrysosporium:(1)The amount of intracellular reactive oxygen free radicals decreased with the increase of Cd(Ⅱ)concentration and contact time.The quantity of malondialdehyde(MDA)reached maximum(9μmol/g)in 8 hand minimum value(0.6 μmol/g)in 24 h.The amount of intracellular protein increased and then decreased.Under the stress of short time(2 h),the SOD activity was proportional to Cd(Ⅱ)concentration,but when contact time increased to 8 h,the SOD activity decreased.Low concentration of Cd(Ⅱ)and contact time stimulate the production of the CAT and the higher enzyme activity,but increasing Cd(Ⅱ)concentration or time,the situation was exactly opposite,which implied the effects of Cd(II)on P.chrysosporium are both stimulative and suppressive with contact time and Cd(II)concentration increase,the increase trend of glutathione disulfide(GSSG)concentration was more obvious than that of glutathione(GSH);(2)In the culture medium and extracellular polymers(EPS),sugar concentration decreased and then tended to reach balance.Protein concentration showed a trend of increase and then decrease.Cd(Ⅱ)stimulated the production of oxalic acid with 0-0.8 mM,but when the concentrations of Cd(Ⅱ)exceed 1.0 mM,the secretion of oxalic acid decreased.The fourth section describes the effects of Cd(Ⅱ)concentration,pH on the degradation of pyrene with bacillus subtilis by studying the influence of Cd(Ⅱ)on bacillus subtilis cell membrane protein and polysaccharide content and the amount of pyrene inside and outside of cell membrane,to discuss the role of Cd(Ⅱ)on degration of pyrene with bacillus subtilis.It was found that:(1)the optimal pH for bacillus subtilis in the treatment of pyrene was about 8.0.(2)Cd(Ⅱ)inhibited the degradation of pyrene for bacillus subtilis,and the concentration of Cd(Ⅱ)was inversely proportional to the biodegradation efficiency.(3)Cd(Ⅱ)could inhibit the production of protein and polysaccharide in bacillus subtilis membrane;(4)the concentration of intracellular pyrene increased with the increase of concentration of Cd(Ⅱ),and then reduced,but extracellular situation is the opposite.So,Cd(Ⅱ)hinders the transmembrane process of pyrene,the strongest inhibition occured when the concentration of Cd(Ⅱ)to 20 mg/L.The fifth section studies the effects of surfactant(diRL,CTAB,Triton X-100)on reduction of Cr(Ⅵ)with Pseudomonas aeruginosa.The results were as follows:(1)diRL can be absorbed by Pseudomonas aeruginosa as carbon source,and thus promote the growth and metabolic activity of Pseudomonas aeruginosa,which is beneficial to the reduction of Cr(Ⅵ).But the cation ionized by CTAB reduced the the activity of Pseudomonas aeruginosa,resulting in inhibition of Cr(Ⅵ)reduction.Triton X-100 has no effect on the reduction of Cr(Ⅵ).(2)The reduction of Cr(Ⅵ)is more suitable in alkaline conditions,and the higher the solution pH value,the greater the reduction rate of Cr(Ⅵ).(3)Among three surfactants,only diRL could promote the dispersion of Pseudomonas aeruginosa.(4)Cr(Ⅵ)reduction efficiency is inversely proportional to the contact time,and proportional to the microbial quantity.Cr(Ⅵ)removal effeciency increased from 17%to 62.5%when the microbial quantity increased from 0.5%to 0.5%.(5)Cationic Cu2+ promoted the reduction of Cr(Ⅵ),Zn2+ inhibited reduction of Cr(Ⅵ),and anionic NO3-and SO42-almost did not affect the reduction of Cr(Ⅵ).To some extent,this article reveals the mechanism of interaction between microbial and heavy metal ions,and analyzes the reasons of low efficiency in the microbial treatment of heavy metal wastewater,also figures out the optimal operating parameters,improves the repeatability of microbial by immobilization of microbial and the treatment efficiency by addition of surfactant,which has certain guiding significance for improving efficient use of microbial treatment technology in heavy metal contaminated water.更多还原