基于中性盐提取的土壤重金属固液分配与自由态金属离子浓度测定

采用0.01mol·L-1CaCl2、0.002mol·L-1Ca(NO3)2和纯水(UPW)3种常用提取剂对我国南方两种典型农田重金属污染土壤进行提取试验.同时,应用土壤重金属固液分配多表面模型来预测提取液中重金属含量,结合道南膜技术(DMT)测定Ca(NO3)2提取液中自由态金属离子浓度,并与ECOSAT模型计算值进行比较.结果表明,提取剂中Ca2+浓度增加能显著提高土壤重金属溶出率,而提取液pH、溶解态有机碳(DOC)浓度却随溶液Ca2+浓度增加而降低.多表面模型(Multi-Surface Model)对大部分提取液金属浓度有较好的预测效果,部分土样提取液Cu、Pb、Zn浓度的预测效果较差.DMT测定的Ca(NO3)2提取液自由态重金属浓度与模型计算值较为一致,能够较准确地测定土壤溶液自由态重金属离子浓度.     

纳米TiO2吸附HgCl2水溶液中Hg(Ⅱ)

通过室内模拟实验研究了3种不同粒径TiO_2添加量、溶液pH、吸附时间及初始Hg~(2+)浓度等因素对模拟废水中Hg(Ⅱ)吸附效果的影响.由单因素研究可知最优条件为:5 nm TiO_2和100 nm TiO_2添加量分别为7.5 g·L~(-1)和2.0 g·L~(-1),其它条件相同,溶液pH为8.0,初始Hg~(2+)浓度均为15 mg·L~(-1),吸附5 min,汞的去除率分别为99.5%和99.3%;25 nm TiO_2添加量为10 g·L~(-1),溶液pH为8.0,初始Hg~(2+)浓度为15 mg·L~(-1),吸附60 min时,汞的去除率为62.8%.3种粒径TiO_2吸附Hg(Ⅱ)强弱顺序为:100 nm TiO_25 nm TiO_225 nm TiO_2.分两次量吸附结果表明,5nm TiO_2分量吸附效果明显优于单独吸附效果;100 nm TiO_2的分量吸附与单独吸附差异不大.正交试验结果表明,影响Hg(Ⅱ)去除率的因素排序为:溶液pH初始Hg~(2+)浓度吸附时间TiO_2添加量.最优实验方案为:溶液pH=8.0,100 nm TiO_2添加量为2.0 g·L~(-1),初始Hg~(2+)浓度为25 mg·L~(-1),吸附10 min.在此实验条件下,Hg(Ⅱ)去除率为99.9%,吸附后溶液中Hg(Ⅱ)平衡浓度为0.033 mg·L~(-1)0.05mg·L~(-1),低于目前企业规定的水污染物中汞的排放限值,Hg(Ⅱ)的最大吸附量为26.95 mg·g~(-1).吸附等温线符合Langmuir等温方程,说明100 nm TiO_2对Hg(Ⅱ)的吸附是典型的单分子层吸附.     

活性焦负载MnO2对气态Hg0的吸附脱除研究

研究了活性焦(AC)及负载MnO2的活性焦(MnO2/AC)对气态Hg0的吸附脱除,发现负载MnO2到AC明显提高了其对Hg0的吸附脱除能力.考察了MnO2负载量、温度、Hg0浓度和烟气成分等对MnO2/AC吸附脱除Hg0的影响.结果表明,MnO2/AC对Hg0的吸附脱除能力随MnO2负载量的增加而增强;在120～200℃的温度范围内,随着温度升高,MnO2/AC对Hg0的吸附脱除能力增强;O2和HCl对MnO2/AC吸附脱除Hg0具有促进作用,而SO2和H2O具有抑制作用.SEM-EDX和逐级化学提取结果证实,MnO2将Hg0催化氧化为HgO并吸附在AC上,这是MnO2/AC具有较高的吸附脱除Hg0能力的原因.     

CuBr2分解缓释-膜催化对零价汞的氧化性能研究

以置于多孔陶瓷膜中的CuBr2受热分解所释放的Br2为氧化剂,利用膜催化装置对Hg0氧化效率进行研究,并设计反应-就地检测一体化装置,避免下游气体管壁效应对实验结果带来的影响.结果表明,MnO x/α-Al2O3催化膜对CuBr2分解所产生Br2的释放有较好的"缓释"作用.Hg0和Br2在催化膜表面的吸附和反应可用Langmuir-Hinshelwood机制描述.Hg0氧化效率随Br2浓度增大而升高,但在达到一定浓度后,Hg0和Br2的吸附速率及两者在催化膜表面的反应速率成为限速因素.473~573 K时Hg0氧化效率变化较稳定.烟气中SO2对Hg0氧化有一定抑制作用,NO无明显影响.     

NOx在长江三角洲地区冬小麦农田与大气间的交换

利用4动态箱体系测定了NOx(NO NO2)在长江三角洲平原地区典型冬小麦农田与大气间的交换通量.NO和NO2的平均交换通量分别为169.7ng·m-2·s-1和-18.5ng·m-2·s-1,表明该地区麦田是大气中NO的一个重要源,是NO2的汇.在冬小麦主要生长期(拔节-抽穗期),NO的交换通量与地表土壤温度呈指数关系.NO2的交换通量与其在环境中的浓度存在明显的负线性关系,其在农田与大气间交换的补偿点(交换通量为0时环境大气中NO2浓度)为11.9μg·m-3.正常耕作的小麦农田以NO-N方式排放的N占施肥总N的2.3%,表明NO挥发为农田氮肥损失的重要形式.追加尿素木质素混合肥料虽然提高了小麦产量,但也显著刺激了农田对NO的排放.     

阴离子型聚丙烯酰胺在离子交换膜上的吸附规律

研究了阴离子交换膜对阴离子型聚丙烯酰胺的吸附规律和影响因素.采用静态吸附的方法,测定了不同温度、不同浓度的阴离子型部分水解聚丙烯酰胺(HPAM)溶液在阴离子交换膜上的吸附量、吸附平衡时间,考察了初始HPAM溶液浓度、pH值以及溶液中其他离子浓度对其在离子交换膜上吸附的影响,目的是阐明阴离子交换膜对HPAM分子的吸附动力学过程、探讨各影响因素对吸附过程的影响.结果表明,阴离子型部分水解聚丙烯酰胺在阴离子交换膜上有明显的吸附作用,但在阳离子交换膜上吸附量几乎为0;阴离子交换膜对聚合物的吸附平衡时间随聚合物溶液初始浓度的增大而延长,且不同浓度、不同温度下的吸附过程动力学特征都能很好地遵循准二级动力学模型;303、308和313 K温度下,阴离子交换膜对聚合物的等温吸附可用Freundlich等温吸附模型很好地拟合,相关系数R2均达到0.99以上,温度越高,吸附量越大;聚合物溶液pH值和离子浓度对吸附效果有显著影响:pH=6时,吸附量达到最大值;吸附量随着离子浓度的增加而增大.     

预处理对小球藻吸附Cd(Ⅱ)、Pb(Ⅱ)和Cu(Ⅱ)的影响

为了研究不同预处理方式对小球藻藻体吸附Cd2+、Pb2+和Cu2+的影响,文章将经过高温灭菌、Ca(NO3)2溶液浸泡和HNO3溶液浸泡预处理的小球藻藻体冷冻干燥,然后在单、两和三组份重金属离子溶液中进行吸附实验。结果表明,在单一系统中,经过Ca(NO3)2溶液浸泡过的藻体吸附效果较好;在混合系统中,冷冻干燥的藻体吸附效果较好。小球藻藻体对重金属吸附动力学曲线表明,在单一或混合系统中,高温灭菌的藻体对Cd2+、Pb2+的吸附于360 min内基本达到平衡,Ca(NO3)2或HNO3溶液浸泡过的藻体对Cd2+、Cu2+的吸附于360 min内基本达到平衡。运用红外光谱仪和扫描电镜对吸附重金属离子前的藻体进行表征。结果表明,不同预处理藻体细胞的功能性基团和形态结构存在着差异,进而影响其对Cd2+、Pb2+、Cu2+的吸附能力。     

FP(FilterPacks)法同时测定大气中的SO2和颗粒物

用二层采样头同时采集大气中的二氧化硫和颗粒物的方法。分别用国产玻璃纤维滤膜和中速定量滤纸,1％K₂CO₃－10％Gly溶液制作浸渍膜,两种浸渍膜现场采集二氧化硫的效率分别为99．4％和95．7％。通过降低碳酸钾溶液浓度(由25％降为1％)及使用强酸性阳离子交换树脂,大大降低了样品中碳酸根离子的浓度,减小了基体效应,提高了测定硫酸根离子的准确度和灵敏度。经测定,1％K₂CO₃－10％Gly溶液浸渍膜(90mm)对二氧化硫的采集容量为160 μg／cm2。试验结果表明,浸渍膜法和盐酸副玫瑰苯胺法测定大气中二氧化硫的结果相近,相对偏差为4．3％,两种方法测定二氧化硫浓度有着良好的线性关系(r＝0．993)      

SO2诱导的萱草保卫细胞凋亡及其信号调节

SO2是一种常见的大气污染物,急性和慢性暴露都会对植物造成伤害.因此,本文以景观绿化植物萱草叶片下表皮为材料,研究了SO2对气孔保卫细胞的致死效应及其可能的信号调节途径.结果表明,利用SO2体内衍生物-亚硫酸钠和亚硫酸氢钠混合液处理萱草表皮3 h后,随着处理浓度(1.0~5.0 mmol·L-1)的增加,萱草保卫细胞生理活性下降,甚至死亡;浓度超过2.0 mmol·L-1时,细胞死亡率显著增高(p0.05),死细胞出现核固缩、核拉长、核碎片等典型凋亡特征,保卫细胞内的活性氧种(ROS)、一氧化氮(NO)和Ca2+水平显著升高.采用不同浓度的抗氧化剂过氧化氢酶(CAT)、抗坏血酸(AsA),Ca2+螯合剂乙二醇双四乙酸(EGTA)和Ca2+通道抑制剂氯化镧(LaCl3)及NO清除剂羧基-2苯-4,4,5,5-四甲基咪唑-1-氧-3氧化物(C-PTIO)和合成抑制剂叠氮钠(NaN3)处理后,均可使SO2衍生物诱发的细胞死亡率降低,以200 U·mL-1CAT、0.05 mmol·L-1的AsA、EGTA、LaCl3及0.20 mmol·L-1的C-PTIO、NaN3的效果最佳,同时胞内ROS、NO和Ca2+水平下降.以上结果表明,一定浓度的SO2可诱导萱草保卫细胞死亡,可能通过诱导ROS和NO爆发,激活细胞质膜钙通道,进而引起胞内Ca2+增加,通过ROS-NO-Ca2+信号途径介导细胞死亡.SO2诱导的萱草细胞死亡可能存在细胞凋亡过程.     

钙预处理对磁性锆铁改性膨润土吸附水中磷酸盐的影响

本研究制备了2种不同Ca2+含量的磁性锆铁改性膨润土(ZrFeBTs),即磁性锆铁改性原始膨润土(ZrFeRBT)和磁性锆铁改性钙预处理膨润土(ZrFeCaBT),并通过吸附实验考察了ZrFeRBT和ZrFeCaBT对水中磷酸盐的吸附特征,以确定Ca2+预处理对ZrFeBTs吸附水中磷酸盐的影响。结果发现,本研究所制备的ZrFeBTs包含Fe3O4和Zr,并且ZrFeCaBT中可交换Ca2+的含量明显高于ZrFeRBT。ZrFeBTs对水中磷酸盐吸附平衡实验数据可以很好地采用Langmuir等温吸附模型加以描述,动力学实验数据可以很好地采用准二级动力学模型和颗粒内扩散模型进行描述。根据Langmuir模型确定的ZrFeRBT和ZrFeCaBT对水中磷酸盐的最大单位吸附量(以磷计)分别为8.70mg·g-1和11.5mg·g-1。ZrFeBTs吸附水中磷酸盐的过程属于化学吸附。随着pH值的增加,ZrFeBTs对水中磷酸盐的吸附效果逐渐降低。当溶液共存Cl-、HCO3-、SO42-、NO3-、Na+、K+、Mg2+和Ca2+等阴阳离子时,ZrFeBTs对水中磷酸盐的吸附具有很好的选择性,并且溶液共存的Ca2+会极大地促进了ZrFeBTs对水中磷酸盐的吸附。采用Ca2+对膨润土进行预处理,极大地提高了ZrFeBTs对水中磷酸盐的吸附能力。     

CO2 adsorption using TiO2 composite polymeric membranes: A kinetic study

CO₂ is the main greenhouse gas which causes global climatic changes on larger scale. Many techniques have been utilised to capture CO₂. Membrane gas separation is a fast growing CO₂ capture technique, particularly gas separation by composite membranes. The separation of CO₂ by a membrane is not just a process to physically sieve out of CO₂ through the controlled membrane pore size. It mainly depends upon diffusion and solubility of gases, particularly for composite dense membranes. The blended components in composite membranes have a high capability to adsorb CO₂. The adsorption kinetics of the gases may directly affect diffusion and solubility. In this study, we have investigated the adsorption behaviour of CO₂ in pure and composite membranes to explore the complete understanding of diffusion and solubility of CO₂ through membranes. Pure cellulose acetate (CA) and cellulose acetate-titania nanoparticle (CA-TiO₂) composite membranes were fabricated and characterised using SEM and FTIR analysis. The results indicated that the blended CA-TiO₂ membrane adsorbed more quantity of CO₂ gas as compared to pure CA membrane. The high CO₂ adsorption capacity may enhance the diffusion and solubility of CO₂ in the CA-TiO₂ composite membrane, which results in a better CO₂ separation. The experimental data was modelled by Pseudo first-order, pseudo second order and intra particle diffusion models. According to correlation factor R², the Pseudo second order model was fitted well with experimental data. The intra particle diffusion model revealed that adsorption in dense membranes was not solely consisting of intra particle diffusion.     

La-EDTA coated Fe3O4 nanomaterial: Preparation and application in removal of phosphate from water

La-EDTA-Fe3O4 was prepared by a chemical co-precipitation method. The magnetic composite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the adsorption properties of La-EDTA-Fe3O4 toward phosphate in water were investigated. The uptake rate of phosphate in water by La-EDTA-Fe3O4 was 3-1000 times than that of EDTA-Fe3O4 , and reached 97.8% at 7 hr. The adsorption process agreed well with the Freundlich model and kinetics studies showed that the adsorption of phosphate proceeds according to pseudo second-order adsorption kinetics. The maximum removal rate was achieved at pH 6.0-7.0. The La-EDTA-Fe3O4 had good adsorption properties and could be separated well from aqueous solution by a permanent magnet. Therefore, this nanomaterial has potential application for the removal of phosphate from large water bodies.     

磁性核壳CoFe2O4@SiO2@PIL-AO复合材料的制备及其吸附U (VI)性能研究

通过化学合成法制备了磁性核壳CoFe₂O₄@SiO₂@PIL-AO复合材料,采用傅立叶变换红外光谱（FTIR）、扫描电镜（SEM）和X射线光电子能谱（XPS）对其进行了表征,研究了溶液pH、吸附时间、U （VI）初始浓度和温度等参数对U （VI）吸附性能的影响.实验结果表明：在c₀=0.2 mg·L^-1、pH=6.00±0.05、T=298.15 K、m=0.02 g和t=8 h的条件下,CoFe₂O₄@SiO₂@PIL-AO对U （VI）的吸附作用最强,吸附率达到了97.54%;CoFe₂O₄@SiO₂@PIL-AO吸附U （VI）是一个自发进行的吸热反应,U （VI）吸附动力学符合准二级动力学模型,吸附等温线符合Freundlich模型;CoFe₂O₄@SiO₂@PIL-AO复合材料具有良好的可循环使用性,循环使用5次后它对U （VI）的吸附容量没有明显下降,可重复使用.     

四氧化三铁/聚乙烯亚胺纳米颗粒的制备及除磷性能的研究

采用化学共沉淀法,以聚乙烯亚胺(PEI)为改性剂,制备了聚乙烯亚胺改性的纳米四氧化三铁复合材料(Fe3O4/PEI).Zeta电位、透射电镜和FTIR表征结果显示,PEI修饰提高了纳米Fe3O4在水中的分散性和稳定性,同时也增强了其表面正电荷,从而提高了Fe3O4对水中磷酸根的去除能力.在磷酸根初始浓度为50 mg·L~(-1),Fe3O4/PEI投加量为200 mg,p H=3,温度为25℃的条件下,Fe3O4/PEI对100 m L磷酸根的吸附去除率达到91%.吸附过程在3 h内达到平衡.吸附等温数据表明,该吸附过程符合Langmuir吸附等温方程,可决系数R2达到0.99,最大吸附量为29.88 mg·L~(-1).Fe3O4/PEI复合材料重复利用性好,在第5次吸附-解析后还能保持对磷酸根75%以上的吸附去除率.磷的解析效率随着p H增加而增加,在p H=13时,解析效率达到65%.     

Effect of TiO2 calcination temperature on the photocatalytic oxidation of gaseous NH3

Carbon-modified titanium dioxide(TiO2) was prepared by a sol-gel method using tetrabutyl titanate as precursor, with calcination at various temperatures, and tested for the photocatalytic oxidation(PCO) of gaseous NH3 under visible and UV light. The test results showed that no samples had visible light activity, while the TiO2 calcined at 400℃ had the best UV light activity among the series of catalysts, and was even much better than the commercial catalyst P25. The catalysts were then characterized by X-ray diffractometry, Brunauer-Emmett-Teller adsorption analysis, Raman spectroscopy, thermogravimetry/differential scanning calorimetry coupled with mass spectrometry, ultraviolet-visible diffuse reflectance spectra, photoluminescence spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy. It was shown that the carbon species residuals on the catalyst surfaces induced the visible light adsorption of the samples calcined in the low temperature range( 300℃). However, the surface acid sites played a determining role in the PCO of NH3 under visible and UV light over the series of catalysts. Although the samples calcined at low temperatures had very high SSA, good crystallinity, strong visible light absorption and also low PL emission intensity, they showed very low PCO activity due to their very low number of acid sites for NH3 adsorption and activation. The TiO2 sample calcined at 400℃ contained the highest number of acid sites among the series of catalysts, therefore showing the highest performance for the PCO of NH3 under UV light.     

TiO2/膨润土复合材料对Hg2+的吸附性能研究

利用纳米TiO_2对膨润土进行复合改性,制备TiO_2/膨润土复合材料.采用电镜扫描、X-射线衍射表征改性前后膨润土的结构和形貌.通过室内模拟实验,以膨润土为对照,研究不同添加量、pH、吸附时间及初始Hg~(2+)浓度等条件下,TiO_2/膨润土复合材料对Hg~(2+)的吸附特性与性能,同时通过正交试验,探究TiO_2/膨润土复合材料吸附Hg~(2+)的最优条件.结果表明,改性后的膨润土颗粒明显变小,且颗粒疏松多空孔,层间距增大.相比于膨润土,TiO_2/膨润土复合材料吸附性能得到极大提高.TiO_2/膨润土复合材料对Hg~(2+)的吸附率均随着添加量、pH、吸附时间的增大而增大,添加量为1.5 g·L~(-1)、pH为7.0、吸附时间为120 min时,吸附率达98.0%以上.但TiO_2/膨润土复合材料对Hg~(2+)的吸附率随着初始Hg~(2+)浓度的增大而减小.通过4种动力学模型拟合发现,吸附过程符合假二级动力学方程,吸附以化学吸附为主.吸附等温线更符合Langmuir等温方程,属于典型的单分子层吸附,最大吸附量为20.66 mg·g-1.吸附Hg~(2+)的最优实验条件:添加量为2.0 g·L~(-1),pH为8.0,初始Hg~(2+)浓度为45 mg·L~(-1),吸附时间为16 h,此时吸附率99.9%,平衡浓度为0.034 mg·L~(-1).     

淀粉稳定Fe3O4纳米粒子对水中As(V)的吸附特性研究

以可溶性淀粉作为稳定剂制备纳米Fe_3O_4粒子,探讨了反应时间、p H值、初始砷浓度和腐殖酸对Fe_3O_4纳米粒子吸附水体中As(V)的吸附效果影响.实验结果表明,淀粉稳定的Fe_3O_4纳米粒子对水体中As(V)的吸附动力学过程符合准二级动力学,吸附等温线符合Langmuir吸附模型;吸附容量随着溶液p H的增加逐渐降低,在p H为8.0的弱碱性水体中对As(V)的最大吸附容量可达202.56 mg·g~(-1);此外,腐殖酸(HA)能降低纳米粒子对As(V)的吸附能力.     

过氧化钙重塑底泥对水中磷酸盐的吸附作用

本研究模拟原位覆盖CaO₂流失后状态,以修复后表层2cm底泥为研究对象,通过扫描电子显微镜（SEM）和X射线能谱仪（EDX）对底泥修复前后表面进行观察和元素分析,发现CaO₂重塑明显改变了底泥结构,去除底泥表面附着的大部分有机物和铁锰氧化物,提高底泥颗粒孔隙率,增加底泥表面Ca²⁺含量;CaO₂重塑使底泥内源磷更加稳定,TP含量减少约20%,潜在活性磷含量减少约30%,Ca-P和Res-P含量明显增加,同时厌氧环境下重塑底泥磷释放量明显小于原始底泥,表明CaO₂重塑极大降低了底泥内源磷释放风险;Langmuir模型与Freundlich和Dubinin-Radushkevich模型相比,更适用于描述CaO₂重塑底泥对水中磷酸盐的等温吸附行为,CaO₂重塑明显提高底泥对水中磷酸盐的吸附能力,其最大磷吸附量由1.44 mg·g^-1增加到20.91 mg·g^-1,其对水中磷酸盐的吸附机制由化学吸附转变为物理化学吸附共同作用,此外准二级动力学模型可以较好地描述CaO₂重塑底泥对水中磷酸盐的吸附动力学过程,且CaO₂重塑显著提高底泥对水中的磷酸盐的吸附速率.     

Adsorption of carbon dioxide on amine-modified TiO2 nanotubes

TiO2 nanotubes (TiNT) were prepared by a hydrothermal treatment and modified by three kinds of amines,namely ethylenediamine,polyetherimide and tetraethylenepentamine (TEPA),to study their CO2 adsorption properties from gas streams.The resultant samples were characterized by X-ray diffraction,transmission electron microscopy,and infrared spectroscopy,as well as low temperature N 2 adsorption.CO2 capture was investigated in a dynamic packed column at 30℃.TEPA-modified TiO2 nanotubes showed the highest adsorption capacity of 167.64 mg/g because it had the highest amino-group content among the three amines.CO2 fixation on TiNT impregnated by TEPA was investigated at 30,50,and 70℃,and the adsorption capacity increased slightly with temperature.Following the adsorption step,the sorbents were regenerated by temperature programmed desorption,and the TiNT-TEPA sample,as CO2 sorbent,was found to be readily regenerated and energy-efficient.The cycle test also revealed that the TiNT-TEPA adsorbent is fairly stable,with only a 5% drop in the adsorption capacity after 10 adsorption/desorption cycles.In addition,the CO2 adsorption behavior was investigated with the deactivation model,and which showed an excellent prediction for the TiNT-TEPA breakthrough curves.     

Steady-state kinetics and osillation phenomena for complete oxidation of benzene over Pt/Al2O3 catalyst

The steady-state kinetics for complete oxidation of benzene over Pt/Al₂O₃ has been investigated by the external recycling reactor. The kinetics equation was described by the L-H model of adsorption of benzene and oxygen with the inhibition of carbon dioxide. The parameters of the kinetics model were estimated by the method of orthogonal design. The heats of adsorption of benzene, oxygen and carbon dioxide were determined by the method of gas-adsorption chromatography. The details of oscillations of complete oxidation of benzene were investigated.