Fe_3O_4@碳/氧化石墨烯复合材料制备及染料吸附性能

采用水热法合成了四氧化三铁@碳/氧化石墨烯(Fe_3O_4@C/GO)复合材料,并利用XRD、TEM、VSM等对其结构与性质进行了表征,进一步研究了其对水中染料的吸附性能.研究结果表明,Fe_3O_4比较均匀地分散在GO上;在实验范围内,随着GO用量、罗丹明B初始浓度或吸附温度的提高,Fe_3O_4@C/GO复合材料对罗丹明B染料的饱和吸附量均相应地增加;而且高GO用量条件下所制备的复合材料的吸附速率更快;随着pH值在2~11范围内增加,复合材料的饱和吸附量先增大后降低,pH值为7时达到最大值.对于GO和Fe_3O_4质量比为0.8的条件下所制备的Fe_3O_4@C/GO复合材料,当罗丹明B初始浓度为1000mg/L,其饱和吸附量可达到303.4mg/g.     

磁性壳聚糖的制备及吸附靛蓝胭脂红的性能评价

采用水热法制得磁性Fe_3O_4,利用巯基乙酸(TGA)修饰Fe_3O_4(Fe_3O_4-SH),戊二醛(GLA)为交联剂使壳聚糖(CS)与Fe_3O_4-SH进行化学交联,制备磁性壳聚糖(Fe_3O_4-SH/CS)。以靛蓝胭脂红为吸附对象,研究接触时间、pH值、温度及染料初始浓度对Fe_3O_4-SH/CS吸附靛蓝胭脂红的影响。结果表明,pH值为3,Fe_3O_4-SH/CS对靛蓝胭脂红溶液的最大吸附量可达到531 mg/g。等温吸附数据与Freundlich等温吸附模型拟合良好,吸附动力学数据符合拟二级动力学模型。Fe_3O_4-SH/CS对靛蓝胭脂红水溶液具有很高的去除率。     

Au/Fe3O4/GO复合SERS基底的制备及对水溶液中低浓度芘的富集-检测

以氧化石墨烯(GO)为载体,利用静电吸附将氨基修饰的Fe_3O_4磁性纳米颗粒负载到GO表面得到GO-Fe_3O_4复合材料,再通过静电作用将Au纳米颗粒与GO-Fe_3O_4复合材料组装,制备了Au/Fe_3O_4/GO复合材料,并考察其表面增强拉曼(SERS)活性.首先以罗丹明B(Rh B)为探针分子,考察Au纳米颗粒的粒径对SERS性能的影响,发现平均粒径为40 nm的Au纳米颗粒具有最好的SERS效果.SERS检测性能随着Au负载量的提高而逐渐变优,Au/GO中Au负载量为20%时最优.以多环芳烃分子芘为探针分子,探究Au/Fe_3O_4/GO复合材料中各组分对SERS性能的影响发现,Au纳米颗粒对拉曼信号的增强起主要作用,GO可以通过化学增强效应及对芘的吸附富集作用有效提高SERS检出限,Fe_3O_4的存在可以使基底快速分离,简化实验步骤,便于基底重复利用.该方法对水溶液中芘的检出限达到10-8mol·L-1,相对于普通拉曼的检出限有了明显的降低,有望被用于环境中痕量多环芳烃的富集-检测.     

聚合多巴胺包覆的磁性微球吸附Cr(Ⅵ)

用聚合多巴胺(PDA)包覆溶剂热法制备Fe_3O_4磁性微球,得到Fe_3O_4@PDA复合材料,并采用红外光谱、扫描电镜、透射电镜对复合材料进行表征。同时,对Fe_3O_4@PDA吸附溶液中六价铬(Cr(Ⅵ))的性能进行研究,考察了溶液pH对其吸附性能的影响。结果表明:Fe_3O_4@PDA在溶液pH为3.0时对Cr(Ⅵ)有较好的吸附性能,其吸附动力学数据符合伪二级动力学方程,等温吸附符合Langmuir吸附模型,最大吸附容量达到108.8 mg/g,热力学实验计算出的吉布斯自由能为负值,表明Cr(Ⅵ)在Fe_3O_4@PDA的吸附为自发过程。     

部分还原氧化石墨烯-Fe3O4对水中Cd (Ⅱ)的吸附性能及机理

当前,治理可溶性重金属污染是环境保护的迫切任务.以氧化石墨烯(GO)和铁盐为前驱体,一步合成了部分还原氧化石墨烯-Fe_3O_4复合材料(rGO-Fe_3O_4),探索其作为Cd(II)高效吸附剂的潜力.同时,采用多种手段表征吸附剂结构和特性,重点研究了吸附剂对Cd(Ⅱ)的吸附特性和动力学.结果表明,在吸附剂中,纳米Fe_3O_4颗粒均匀地锚在石墨烯片层之间,避免了片层团聚,赋予其优良的吸附性能.在中性溶液中,使用rGO-Fe_3O_4(500 mg·L~(-1))吸附200.09 mg·L~(-1)Cd(II),5 min即可达到吸附平衡,吸附率和吸附量分别为90.88%和363.99 mg·g~(-1).另外,磁分离回收吸附剂仅需10 s,且循环吸附性良好.进一步研究显示,复合材料对Cd(II)的吸附为吸热、自发的化学吸附,过程受化学吸附和液膜扩散控制.     

溶剂热法制备磁性生物质炭吸附对硝基苯酚

将法桐树叶煅烧得到生物质炭(BAC),以溶剂热法将Fe_3O_4原位生成负载于BAC表面制备磁性生物质炭复合材料(BAC/Fe_3O_4)。用SEM、XRD、TEM、IR、VSM等对复合材料进行表征。实验结果表明:BAC/Fe_3O_4对对硝基苯酚的吸附在溶液pH为10.0的条件下有较高的吸附量,吸附行为符合朗格缪尔吸附等温线,最大吸附量为246.3 mg/g,吸附过程符合伪二级反应动力学方程,吸附速率较快。该材料可以有效地去除对硝基苯酚,在去除有机污染物方面有较大潜力。     

壳聚糖/氧化石墨烯复合材料吸附U（Ⅵ）的特性与机理

采用溶液共混法制备了壳聚糖/氧化石墨烯(CS/GO)复合材料,探讨了GO含量、pH值、CS/GO投加量、时间以及U(Ⅵ)初始浓度等对CS/GO吸附U(Ⅵ)效果的影响.试验结果表明,GO质量分数为40%,pH值为5时吸附效果最好,吸附在5 h达到平衡.准二级动力学模型和Langmuir等温吸附方程可较好地拟合其吸附过程,30℃时饱和吸附量为227.3 mg·g-1.CS/GO对U(Ⅵ)的吸附是自发的吸热反应.SEM、FTIR和XRD分析结果表明,CS/GO表面凹凸不平,羟基和氨基是U(Ⅵ)的主要结合位点.解吸试验结果表明CS/GO具有良好的重复使用性能.     

基于聚合多巴胺的磁性碳材料的制备及其对甲基绿的吸附

以聚合多巴胺为碳源制备碳材料包覆的磁性纳米颗粒.通过多巴胺的自聚合反应将其包覆在Fe_3O_4纳米颗粒上,在氩气保护下高温灼烧得Fe_3O_4@C复合材料.包覆碳材料后,Fe_3O_4颗粒的稳定性和分散性提高.使用扫描电镜、透射电镜、红外光谱和振动磁强计对材料进行了表征.结果表明成功地制备了核壳结构的Fe_3O_4@C复合材料.用甲基绿来考察Fe_3O_4@C的吸附性能.研究表明,溶液pH对甲基绿的吸附有显著的影响,随溶液pH的升高,甲基绿的吸附容量显著增大.用朗格缪尔吸附等温模型拟合出在纯水、湖水和自来水中Fe_3O_4@C对甲基绿的最大吸附容量分别为490.1、442.5和389.1 mg·g~(-1).热力学研究计算出吸附的吉布斯自由能为负值,说明吸附是自发过程.动力学研究表明甲基绿在Fe_3O_4@C上的吸附过程符合拟二级反应动力学方程,吸附速率较快.     

改性海藻酸钠微球对Pb2+吸附性能的研究

文章以海藻酸钠(SA)为原料,与羧基化微晶纤维素(CCN)、四氧化三铁(Fe_3O_4)进行溶液共混,采用化学沉淀法制备出Fe_3O_4@CCN/SA复合微球。以硝酸铅溶液为研究对象,探讨了初始浓度、pH、吸附时间对吸附性能的影响。结果表明:Pb~(2+)浓度为1 000mg/L,pH=5,吸附时间为6 h时,饱和吸附量最大为184.2 mg/g。吸附符合Langmuir等温线模拟和拟二级反应动力学模型。该磁性微球使用盐酸解析脱附,重复使用第6次饱和吸附量仍高达165.5 mg/g,说明Fe_3O_4@CCN/SA磁性微球具有良好的再生使用性能。     

Fe3O4@SiO2-Chitosan的制备及其对水中Cu2+的吸附效能研究

以SiO_2包覆Fe_3O_4,戊二醛为交联剂,交联壳聚糖(Chitosan, CTS),制得Fe_3O_4@SiO_2-Chitosan复合磁性纳米粒子.以Fe_3O_4和Fe_3O_4@SiO_2为对照,采用X射线衍射、透射电镜和傅立叶红外光谱对其进行表征分析,并测定了投加量、pH值、吸附时间和温度等因素对Cu~(2+)吸附效果的影响,从动力学、热力学以及再生回用性能评价等方面对其吸附性能进行了探究.结果表明Fe_3O_4@SiO_2-Chitosan对Cu~(2+)的吸附过程符合准二级吸附动力学模型和Langmuir模型,为自发、放热、优惠型的单分子层化学吸附.在pH为6.0, 298 K下达到最大吸附量154.8 mg·g~(-1),吸附解吸4次后吸附容量变化不大,说明Fe_3O_4@SiO_2-Chitosan具有较高的吸附容量,可作为处理含铜废水和回收铜的高效吸附剂.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Effects of two sludge application on fractionation and phytotoxicity of zinc and copper in the soil

The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% (by weight) of digested sewage sludge (SS) and composted sludge (SC). The additions of both sludges caused a significant raise in all fractions, resulting in that exchangeable (EXCH) and organic bound (OM) became predominance of Zn and organic bound Cu occupied the largest portion. There was more available amount of Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate (CAR) and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to ΔEXCH and ΔCAR forms but also in ΔOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by ΔEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.     

Intraspecific differences in effects of co-contamination of cadmium and

A hydroponic experiment was carried out to study intraspecific differences in the effects of different concentrations of cadmium (Cd)(0-10 mg/L) and arsenate (As(V)) (0-8 mg/L) on the growth parameters and accumulation of Cd and As in six wheat varieties Jing-9428, Duokang-1, Jingdong-11, Jing-411, Jingdong-8 and Zhongmai-8. The endpoints of wheat seedlings, including seed germination,biomass, root length and shoot height, decreased with increasing the Cd and As concentrations. Significant differences in seed germination, biomass, root length, shoot height and the accumulation of Cd and As were observed between the treatments and among the varieties (p ＜ 0.05). The lethal dosage 50% were about 20, 80, 60, 60, 80 and 20 mg As/L for Jing-9428, Duokang-1, Jingdong-11,Jing-411, Jingdong-8 and Zhongmai-8, respectively, and the corresponding values for Cd were about 30, 80, 20, 40, 60 and 10 mg Cd/L, respectively. Among the six varieties, Duokang-1 was found to be the most resistant to Cd and As toxicity, and Zhongmai-8 was the most sensitive to Cd and As co-contamination. The resistance of the six varieties was found dependant on the seedling uptake of Cd and As. Duokang-1 was the most suitable for cultivation in Cd and As co-contaminated soils.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.