烟束曲霉菌丝球对Cr(Ⅵ)的去除—还原与吸附作用

采用投加烟束曲霉(Aspergillus fumisynnematus)菌丝球的方法去除含铬废水中的Cr(Ⅵ),通过研究模拟含铬废水中Cr(Ⅵ)与总Cr浓度及pH值的变化规律来确定烟束曲霉菌丝球对Cr(Ⅵ)的去除作用.结果表明,烟束曲霉菌丝球对Cr(Ⅵ)的去除作用包括还原与吸附,以还原作用为主,兼有一定程度的吸附.适宜条件(30℃,150 r·min-1,pH=1.30,投加量10.0 g)下菌丝球能在48 h内将100 mL浓度为10～200 mg·L-1Cr(Ⅵ)溶液中的Cr(Ⅵ)全部去除,其中对总Cr的吸附率为30%～50%,对Cr(Ⅵ)的还原率则达到了99%以上,吸附平衡后解吸出来的Cr的形态95%以上为Cr(Ⅲ).考察了溶液初始pH值、Cr(Ⅵ)初始浓度、菌丝球投加量及温度对菌丝球去除Cr(Ⅵ)作用的影响.结果表明,菌丝球只有在低pH值时才能达到对Cr(Ⅵ)较好的去除效果.溶液初始pH值及Cr(Ⅵ)初始浓度的降低、菌丝球投加量及温度的升高均能提高菌丝球对Cr(Ⅵ)的去除率,溶液初始pH值的降低及菌丝球投加量的增加均可提高菌丝球对总Cr的吸附率,温度则主要通过改变菌丝球的结构形态来影响菌丝球对总Cr的吸附作用.菌丝球对Cr(Ⅵ)及Cr(Ⅲ)均存在吸附作用,吸附在菌丝球上的Cr(Ⅵ)在酸性环境下易被还原成Cr(Ⅲ).     

硫酸盐还原颗粒污泥对溶液中Cr(Ⅵ)去除特性及总Cr平衡吸附研究

利用小型EGSB反应器培养的硫酸盐还原颗粒污泥进行Cr(Ⅵ)去除实验,考察硫酸盐还原颗粒污泥对Cr(Ⅵ)的去除特性及对总Cr的平衡吸附并进行吸附等温式拟合.结果表明,颗粒污泥对Cr(Ⅵ)的去除是物理、化学及生物过程共同作用的结果,主要包括了还原及吸附作用.颗粒污泥对Cr(Ⅵ)的去除作用与环境因素、颗粒污泥的化学组成和结构的完整程度等密切相关.对Cr(Ⅵ)的去除速率随颗粒污泥投加量及Cr(Ⅵ)初始浓度的增加而提高;提高振荡速度和温度均可提高Cr(Ⅵ)的去除效率及对总Cr的吸附速率,但当振荡速度达到150r·min-1时或温度达到40℃时颗粒污泥会出现结构的离散并降低总Cr的平衡吸附量;pH值越低颗粒污泥对Cr(Ⅵ)的去除效率就越高,但颗粒污泥表面的硫化物在pH值为酸性时会转化成H2S气体逸出,并因此影响对总Cr的吸附效率.颗粒污泥对总Cr的最大吸附量为6.84mg·g-1,其对总Cr的吸附过程符合Langmuir吸附等温式.     

茶树菇废菌体对水中Cr(Ⅵ)吸附的响应面优化及机理研究

采用响应面优化(Box-Behnkendesign,BBD)法对茶树菇废菌体吸附水中Cr(Ⅵ)的过程进行了优化,并设定pH值、Cr(Ⅵ)初始浓度、反应时间、摇床转速和吸附剂用量为5个影响因子,Cr(Ⅵ)吸附率为响应值,对吸附过程的热力学特征及吸附机理进行了研究.结果表明,对废菌体吸附Cr(Ⅵ)有显著影响的因素是pH值、Cr(Ⅵ)初始浓度和吸附剂用量;废菌体对Cr(Ⅵ)吸附的最佳条件为pH=1.19,Cr(Ⅵ)初始浓度为148.58mg·mL-1,反应时间为89.02min,摇床转速为180.12r.min-1,吸附剂用量为10.90g.L-1,在此条件下,实测Cr(Ⅵ)的吸附率达96%以上.用Langmuir、Freundlich及Dubinin-Raduskevich吸附等温模型对吸附过程进行拟合发现,Langmuir模型可以很好地反映茶树菇废菌体对Cr(Ⅵ)的吸附特性,在298K时最大吸附量为46.95mg·g-1.对表观热力学参数ΔG、ΔS及ΔH的计算表明,废菌体对Cr(Ⅵ)吸附为吸热的自发过程,并且吸附过程增加了体系的混乱度.最后结合FTIR图对吸附机理进行了探讨,结果表明,废菌体对Cr(Ⅵ)具有良好的吸附效果,可用于处理含铬废水,达到以废治废的目的.     

零价纳米铁吸附去除水中六价铬的研究

利用液相还原法制备的零价纳米铁(nZVI)进行了去除水中Cr(Ⅵ)的实验研究.结果表明,nZVI对Cr的去除效果明显优于还原铁粉和粉末活性碳;pH值越小、初始Cr浓度越低、nZVI放置时间越短及投加量越大均有利于水中Cr(Ⅵ)的去除,最佳去除率近100%;反应动力学拟合结果表明,nZVI去除六价铬符合准二级动力学模型;反应后nZVI颗粒的扫描电镜及电子能谱结果显示Cr占12.02%(wt),结合对反应溶液中Cr(Ⅵ)和Cr(Ⅲ)分析,说明吸附、还原与共沉淀可能是nZVI去除水中六价铬的主要机理.     

豆角秸秆生物炭对水中Cr（Ⅵ）吸附性能研究

为了解生物炭对水中Cr（Ⅵ）的吸附效果,本文选用蔬菜废物豆角秸秆为原材料,采用限氧升温法在400℃和700℃温度下制备了两种生物炭。并研究了投加量、初始浓度、pH值、吸附时间、温度等因素对生物炭吸附Cr（Ⅵ）的影响。研究结果表明,2种豆角秸秆生物炭对水中Cr（Ⅵ）均有较好的吸附率,吸附最佳条件略有不同;D400对水中Cr（Ⅵ）的最佳吸附条件为投加量8g/L,初始浓度小于40mg·L^-1,pH值2—3;D700对水中Cr（Ⅵ）的最佳吸附条件为投加量8g/L,初始浓度小于60mg·L^-1,pH值2—4;基本达到吸附平衡的时间均为60min;温度对生物炭吸附Cr（Ⅵ）的影响很小。     

YSQ-2活菌体及死菌体对溶液中Cr(Ⅵ)的去除过程及机理解析

分别考察了YSQ-2菌丝球活体、菌丝球死菌体及死菌体粉末3种菌体对溶液中Cr(Ⅵ)的去除过程。实验结果表明3种YSQ-2菌体均能在48 h内完全去除溶液中的Cr(Ⅵ),对Cr(Ⅵ)的去除效率排序为:死菌体粉末菌丝球死菌体菌丝球活体;3种YSQ-2菌体均能有效吸附溶液中的Cr,对Cr的吸附效果排序为:菌丝球活体菌丝球死菌体死菌体粉末,48 h后的平衡吸附率分别为32.2%、23.0%和11.4%。对解吸实验表明3种菌体所吸附的Cr的形态均为Cr(Ⅲ)。菌体对Cr的吸附效率与溶液中的Cr(Ⅵ)浓度有密切关联,在其他条件不变的情况下,溶液中Cr(Ⅵ)浓度越高,菌体对Cr的吸附效果会相对越好。     

啤酒酵母吸附去除水中Cr(Ⅵ)的研究

研究了吸附剂用量、重金属初始浓度、pH对非活性啤酒酵母菌体吸附Cr(Ⅵ)的影响.结果表明,吸附剂的用量越高,对Cr(Ⅵ)的去除率也越高,但单位菌体吸附量却越低;相反,Cr(Ⅵ)初始浓度越高,对Cr(Ⅵ)的去除率就越低,但单位菌体吸附量却越高;溶液的pH也是影响吸附去除效果的重要因素之一,当pH为1时,吸附去除效果最好,非活性啤酒酵母菌体对Cr(Ⅵ)的吸附过程可用Langmuir和Freundlich等温吸附模型来拟合,但Langmuir等温吸附模型的拟合效果更好,由Langmuir等温吸附方程得到最大吸附量为9.17mg/g干菌体.     

细菌X07吸附Cr(Ⅵ)的研究

从不同来源的样品中分离出一株吸附Cr(Ⅵ)较强的菌株X07,经鉴定为蜡状芽孢杆菌(Bacillus.cereus)。通过吸附实验探讨了X07死菌体对Cr(Ⅵ)的吸附特性,结果表明,X07死菌体吸附Cr(Ⅵ)的最适pH值为6.0;其吸附Cr(Ⅵ)是一个快速、非温度依赖过程,吸附50min达到饱和,在最初的5min内,吸附量达到最大吸附量的76.8%;菌体浓度的增加有利于对Cr(Ⅵ)的吸附:其吸附等温线符合Langmuir和Freundlich吸附模型,在试验的条件下,对Cr(Ⅵ)的饱和吸附容量为146.9mg/g干菌体。     

Cr(Ⅵ)在Fe(Ⅲ)-柠檬酸盐体系中紫外光还原研究

研究了在紫外光照射下,Fe(Ⅲ)-柠檬酸盐溶液对Cr(Ⅵ)的光还原反应.同时,考察了溶液pH值、Fe(Ⅲ)浓度、柠檬酸盐浓度、Cr(Ⅵ)初始浓度对光还原效率的影响,并分析了光还原反应的动力学.研究结果表明,Fe(Ⅲ)-柠檬酸盐体系能光还原Cr(Ⅵ),在pH为2.0～6.0的范围内,Cr(Ⅵ)的还原率随着溶液初始pH值的降低而增大.当pH值为2.0、Fe(Ⅲ)浓度为10μmol·L-1、柠檬酸盐浓度为250μmol·L-1及Cr(Ⅵ)初始浓度为19.2μmol·L-1时,光照反应8min后Cr(Ⅵ)的最大还原率达到100%,但当pH值增加到6.0时,Cr(Ⅵ)的最大还原率下降到19%;当Cr(Ⅵ)的初始浓度在9.6～96.0μmol·L-1的范围内时,Cr(Ⅵ)光还原反应的初始速率随着Fe(Ⅲ)、柠檬酸盐(cit3)、Cr(Ⅵ)初始-浓度的增加而增加.表观动力学方程为:-dCCr(Ⅵ)/dt=0.1019[Cr(Ⅵ)]0.[Fe(Ⅲ)]0.[cit3]0..536-25     

二硫代羧基化小麦秸秆对水中Cr（Ⅵ）的吸附性能及机理

选取小麦秸秆(WS)为原材料，采用化学合成法向WS上引入了二硫代羧基，制备了一种新型重金属吸附剂二硫代羧基化小麦秸秆(DTWS)，考察了DTWS投加量、振荡速率、pH值、吸附温度以及Cr(Ⅵ)初始浓度等对DTWS吸附Cr(Ⅵ)性能的影响，并通过吸附动力学、吸附等温线、吸附热力学、FTIR、SEM-EDS等方法探究了DTWS对Cr(Ⅵ)的吸附机制.结果表明，在振荡速率为200 r·min^-1、吸附温度为30℃时，DTWS对Cr(Ⅵ)初始浓度为25 mg·L^-1、pH值为6.0的含Cr(Ⅵ)水样吸附效果最好，最高去除率可达99.12%.DTWS对Cr(Ⅵ)的吸附更加符合准二级动力学方程和Langmuir模型，且DTWS对Cr(Ⅵ)的整个吸附过程是一个自发的放热过程.DTWS对Cr(Ⅵ)的吸附过程中主要发生了静电吸附、物理吸附以及包括氧化还原反应、配位反应在内的化学吸附，其中小麦秸秆中引入的二硫代羧基发挥了很大的作用.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.     

Removal of cadmium using MnO2 loaded D301 resin

MnO2 loaded weak basic anion exchange resin D301 （Anion exchange resin, macroreticular weak basic styrene） as adsorbent has been prepared and applied to the removal of cadmium. The adsorption characteristics have been investigated with respect to effect of pH, equilibrium isotherms, removal kinetic data, and interference of the coexisting ions. The results indicated that the Cd^2＋ could be efficiently removed using MnO2 loaded D301 resin in the pH range of 3-8 from aqueous solutions with the co-existence of high concentration of alkali and alkaline-earth metals ions. The saturate adsorption capacity of the Cd^2＋ was 77.88 mg/g. The adsorption process followed the pseudo first-order kinetics. The equilibrium data obtained in this study accorded excellently with the Langmuir adsorption isotherm.     

Evaluation of phytoextracting cadmium and lead by sunflower, ricinus, alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium(Cd)and lead(Pb)is hard to be remediated.Phytoremediation may be a feasible method to remove toxic metals from soil,but there are few suitable plants which can hyperaccumulate metals.In this study,Cd and Pb accumulation by four plants including sunflower(Helianthus annuus L.),mustard(Brassica juncea L.),alfalfa(Medicago sativa L.), ricinus(Ricinus communis L.)in hydroponic cultures was compared.Results showed that these plants could phytocxtract heavy metals, the ability of accumulation differed with species,concentrations and categories of heavy metals.Values of BCF(bioconcentration factor)and TF(translocation factor)indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals.Changes on the biomass of plants,pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures.Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals,such as pH and Eh regulations,and so forth.     

Effect of coagulation pretreatment on the fouling of ultrafiltration membrane

The purpose of this study is to understand the effect and mechanism of preventing membrane fouling, by coagulation pretreatment, in terms of fractional component and molecular weight of natural organic matter （NOM）. A relatively higher molecular weight （MW） of hydrophobic compounds was responsible for a rapid decline in the ultrafiltration flux. Coagulation could effectively remove the hydrophobic organics, resulting in the increase of flux. It was found that a lower MW of neutral hydrophilic compounds, which could remove inadequately by coagulation, was responsible for the slow declining flux. The fluxes in the filtration of coagulated water and supernatant water were compared and the results showed that a lower MW of neutral hydrophilic compounds remained in the supernatant water after coagulation could be rejected by a membrane, resulting in fouling. It was also found that the coagulated flocs could absorb neutral hydrophilic compounds effectively. Therefore, with the coagulated flocs formed on the membrane surface, the flux decline could be improved.     

Penetration analysis of elements and bioleaching treatment of spent refractory for recycling

Acidithiobacillus ferrooxidans ATCC23270 and Acidithiobacillus thiooxidans TM-32 were used for bioleaching of spent refractories of aluminium and copper melting furnaces for their recycling.Firstly,penetration of elements into aluminium melting furnace refractory was investigated and it was found that up to 7 cm from surface was contaminated.Comparison on leaching efficiency by the strains ATCC23270 and TM-32 found that the strain ATCC23270 could treat larger amount of the refractories than the strain TM-32 could do.In the experiment of bioleaching of spent refractory aluminium melting furnace by the strain ATCC23270,high leaching efficiency were obtained on Al,Si,and Ca,and extremely low leaching performance was,however,shown on the rest of elements i.e.,Na,Mn,and Zn.Under the strain TM-32 use,relatively high leaching performance was recognized on Al,Si,Ca,Na,Mn,and Zn.In the experiment of bioleaching for spent refractory copper melting furnace,almost the same leaching trends were shown on Cu,Zn,Al,and Si under the strains ACTT23270 and TM-32 uses.