nZVI/PANI/ATP纳米纤维复合材料制备及对Cr(VI)的去除性能

采用原位聚合法合成了硝酸掺杂的纳米零价铁/聚苯胺/凹凸棒黏土(nZVI/PANI/ATP)纳米纤维复合材料,用于去除废水中的Cr(VI)。考察了投料质量、吸附时间和p H值对其吸附性能的影响,对吸附过程进行了动力学和热力学分析。结果表明,PANI/ATP表面负载纳米零价铁(nZVI),解决了nZVI颗粒的团聚及在处理Cr(Ⅵ)时容易被腐蚀和钝化的问题。复合材料制备过程中Fe、An和ATP的质量比为0.74∶1∶4时,所制备的材料吸附容量达到87.95 mg/g,nZVI/PANI/ATP复合材料对Cr(Ⅵ)的吸附符合准二级动力学模型,吸附为化学吸附。     

零价铁、铜改性生物炭及其对Cr(Ⅵ)吸附性能的影响

针对纳米零价铁（nanoscale zero valent iron，nZVI）易团聚的特性，本文用鸡骨生物炭（BC）作载体，制备出生物炭-零价铁（Fe-BC）去除Cr(Ⅵ)，并与铜改性的生物炭-零价铁（Fe-Cu-BC）和BC对Cr(Ⅵ)的吸附性能进行了对比。通过扫描电镜（SEM）和能谱仪（EDS）、X射线衍射（XRD）、N₂吸脱附等温线和傅里叶红外光谱（FTIR）对材料表面形貌及结构性质进行分析，同时考察了溶液pH、接触时间等条件对吸附剂吸附容量的影响，通过吸附动力学和吸附等温线分析了吸附特性。结果表明，在pH=2的条件下去除Cr(Ⅵ)效果较好；吸附平衡遵从Langmuir吸附等温式；吸附动力学符合准二级动力学方程。Fe-BC材料吸附水体污染物后可用磁分离技术加以回收。Fe-Cu-BC缩短了对Cr(Ⅵ)的吸附平衡时间。制备出的吸附剂对Cr(Ⅵ)的理论最大吸附量顺序为 Fe-BC>Fe-Cu-BC>BC；同时， Fe-BC吸附量为153.60mg/g，对比于先前报道的nZVI对Cr(Ⅵ)的吸附容量85mg/g左右，有了很大的提升，说明BC作载体成功解决了nZVI易团聚的缺点，拓展了实际应用。     

纳米零价铁对水溶液中钒离子的吸附性能

采用液相还原法制备纳米零价铁(nZVI),采用PXRD, SEM, TEM, BET(N2吸脱附)和XPS等表征材料性能,考察了纳米零价铁用量、初始钒(V)浓度和初始pH对纳米零价铁吸附钒(V)性能的影响,测定了纳米零价铁对钒(V)的吸附等温线和吸附动力学曲线. 结果表明,制备的纳米零价铁具有典型的核?壳结构,粒径为10~30 nm,BET比表面积为53 m2/g. 纳米零价铁对钒(V)的吸附容量随纳米零价铁用量和初始pH增大而减小. 25℃时的平衡吸附容量为227.8 mg/g. Langmuir等温线方程可很好拟合纳米零价铁对钒(V)的吸附,纳米零价铁对钒(V)的吸附动力学曲线符合准二级动力学模型.     

纳米零价铁强化高岭石去除水中Cr(Ⅵ)及机制研究

纳米零价铁(nZVI)作为一种治理重金属、核素污染物的环保材料而被广泛关注,而黏土矿物作为常见的重金属吸附材料虽成本低廉、来源广泛,但去除性能又普遍有限。通过液相还原法制备nZVI/高岭石复合材料来强化高岭石去除水中Cr(Ⅵ)的性能,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)技术对其结构进行表征,考察了Cr(Ⅵ)初始浓度、nZVI/高岭石投加量、温度等条件对Cr(Ⅵ)去除率的影响,并探讨了其对水中Cr(Ⅵ)的去除能力及机制。结果表明,nZVI/高岭石中的nZVI结晶度低,粒径在50～100 nm, nZVI/高岭石在60 min时对Cr(Ⅵ)的去除率达91.7%,分别比nZVI和高岭石提高了2.7倍和18.5倍。nZVI/高岭石对Cr(Ⅵ)的去除动力学符合准二级动力学模型,表观反应活化能为27.97 kJ/mol,去除是吸附、还原和共沉淀共同作用的结果。通过nZVI强化可提升高岭土在水处理和环境修复中的应用前景。     

悬浮静置聚合制备PANI/ATP复合材料对Cr(Ⅵ)的吸附研究

采用悬浮静置聚合的方法合成了硝酸掺杂的聚苯胺/凹凸棒黏土(PANI/ATP)纳米复合材料,用于含Cr(VI)废水的吸附。考察了吸附时间、物料配比、投料质量、温度和溶液pH值对吸附性能的影响,进行了动力学和热力学分析。结果表明,吸附过程是化学过程,化学配位作用起主要吸附作用,质量配比An∶ATP=1∶0.75,投料质量为0.5 g,吸附50 mg/L的Cr(VI)溶液,1 h时吸附率为99.60%,残留Cr(VI)的浓度为0.2 mg/L,达到国家排放标准。     

高分散性纳米铁的制备及其表征

以可生物降解的聚苯乙烯磺酸钠(PSS)为分散剂,制备了能稳定分散于水中的零价纳米铁(nZⅥ).未改性的零价纳米铁呈规则的球形或椭球形,平均粒径为60～80 nm,经PPS分散后的纳米铁nZVI/PSS则呈现微小的粒状分散在PSS中.pH=8时,与nZVI相比,nZVI/PSS的ζ电位由+9.4 mV降至-36.7 mV,同时等电点也由8.7变为小于5.XPS分析结果显示,nZVI和nZVI/PSS表面元素构成相同,但nZVI/PSS表面有零价铁存在,而nZVI表面则主要由铁的氧化物组成.实验结果表明,两种纳米铁对Cr(VI)的去除率非常接近,在纳米铁投加量为1.0g·L-1,Cr(VI)初始浓度为100 mg·L-1的条件下,Cr(VI)的去除率在10 min内均能达到95％,在30 min内能达99％,表明nZVI/PSS具有较高活性.     

纳米零价铁去除水中六价铬的研究

以聚乙二醇(PEG)为分散剂,在乙醇-水混合溶剂中合成改性纳米级零价铁颗粒(nZⅥ)。利用透射电子显微镜(TEM),X射线衍射仪(XRD)对其结构、组成和物理性质进行表征,讨论了n ZVI去除Cr(Ⅵ)的影响因素,并对反应产物进行XPS检测。结果表明,乙醇比例为50%时制备出的纳米零价铁直径在30⁶0 nm,对Cr(Ⅵ)的去除率最高,为95.30%。nZⅥ投加量越大,Cr(Ⅵ)初始浓度越小,p H越小,温度越高,均有利于水中Cr(Ⅵ)的去除。纳米零价铁将Cr(Ⅵ)吸附后将其还原为Cr(Ⅲ),反应过程主要以还原作用为主。并且对Cr(Ⅵ)的去除能用准一级反应动力学方程描述。     

生物炭负载纳米零价铁活化过硫酸盐降解地下水盐酸金霉素的性能研究

制备不同质量比的水稻秸秆生物炭负载纳米零价铁(RS-nZVI)复合材料,利用XRD及SEM对其进行表征,并对复合材料吸附降解盐酸金霉素(CTC)过程进行吸附动力学、等温吸附及降解动力学分析。采用Central-Composite方法(CCD)并结合响应面分析方法(RSM)对降解过程中CTC初始质量浓度、RS-nZVI投加量、pH以及过硫酸钠(PS)投加量的影响进行讨论,对反应条件进行优化。结果表明,nZVI与RS质量比为1∶1时RS-nZVI吸附降解效果最佳;响应面优化参数为CTC初始质量浓度为220.965 mg/L、RS-nZVI质量浓度为0.62 g/L、pH为5、PS浓度为0.655 mmol/L,该条件下CTC降解率为99.672%。     

纳米零价铁强化高岭石去除水中Cr(VI)及机制研究

纳米零价铁(nZVI)作为一种治理重金属、核素污染物的环保材料而被广泛关注,而黏土矿物作为常见的重金属吸附材料虽成本低廉、来源广泛,但去除性能又普遍有限。通过液相还原法制备nZVI/高岭石复合材料来强化高岭石去除水中Cr(VI)的性能,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)技术对其结构进行表征,考察了Cr(VI)初始浓度、nZVI/高岭石投加量、温度等条件对Cr(VI)去除率的影响,并探讨了其对水中Cr(VI)的去除能力及机制。结果表明,nZVI/高岭石中的nZVI结晶度低,粒径在50~100 nm,nZVI/高岭石在60 min时对Cr(VI)的去除率达91.7%,分别比nZVI和高岭石提高了2.7倍和18.5倍。nZVI/高岭石对Cr(VI)的去除动力学符合准二级动力学模型,表观反应活化能为27.97 kJ/mol,去除是吸附、还原和共沉淀共同作用的结果。通过nZVI强化可提升高岭土在水处理和环境修复中的应用前景。     

硅酸钙负载零价纳米铁吸附去除水中六价铬

利用液相还原法制备硅酸钙负载零价纳米铁(CS-nZⅥ)进行去除水中Cr(Ⅵ)的实验研究.结果表明,CS-nZⅥ对Cr(Ⅵ)的去除效果明显优于还原铁粉和硅酸钙,略差于零价纳米铁;低pH值、越低初始Cr(Ⅵ)浓度及较大投加量均有利于Cr(Ⅵ)去除,最大去除率可达98.9％;反应后CS-nZⅥ颗粒扫描电镜及X射线能谱分析结果表明Cr占3.06wt％;等温吸附实验结果表明较好拟合Langmuir和Freundlich等温吸附模型,CS-nZⅥ对Cr(Ⅵ)的最大吸附容量达253.8 mg/g.     

Polymorphism of LiGa5O8 and of LiGa5O8-MgGa2O4Solid Solutions

High-temperature X-ray diffraction and differential thermal analyses showed that LiGa₅O₈ exists in two polymorphs related by the first-order transition at 1138°±3°C of the low-temperature simple-cubic form, space group (probably) O⁷, to the high-temperature spinel (fcc) form, space group O _h ⁷. The transition is rapid, and the high-temperature form in pure LiGa₅O₈ could not be quenched to room temperature under the conditions used. However, the high-temperature polymorph can be quenched under equilibrium conditions when 40 mol% or more MgGa₂O₄ is present. The subsolidus equilibrium relations in the system MgGa₂O₄-LiGa₅O₈ are discussed.     

Magnetoresistance of CuxCo1-xFe2O4 Ferrites

Magnetoresistance measurements (Δ/R) were carried out on Cu _x Co_{1- x} Fe₂O₄ samples with x =1, 0.75, 0.50, 0.25 and cobalt ferrite in the range of magnetic intensity (H) from 1.0 to 4.5 kG. Linear plots were obtained between log (Δ/R) and log H for all compositions except that of cobalt ferrite. The values of n at x =0.5 do not agree with the results of some authors. The discrepancy may be attributed to the value of magnetic field intensity at which such measurements were carried out. The similarity of features of n and μ_D with composition leads us to believe that the magnetoresistance may arise from the scattering of conduction electrons by localized electrons involving the s-d exchange interaction.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Expansive properties of the mixture C4ASH12 − 2CS III. Effects of temperature and restraint

The effects of temperature and restraint upon the hydration and the expansion of $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}\text{? 2}\text{C}\text{S}$ mixture compacts in different contact solutions have been investigated. Temperatures above 20°C do apparently hinder the formation of an impervious felt-like layer of ettringite around the $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}$ particles, thus greatly reducing the retarding effect of the lime. An uniaxial restraint of 1 Kg/cm² is enough to reduce sensibly the expansions which remain however high (about 100%). The results can be satisfactorily interpreted by the reaction and expansion mechanism hypothesized in our previous papers.     

Raman Study of Glasses of Ba2TiSi2O8 and Ba2TiGe2O8

Raman spectra are reported for fresnoite (Ba₂Ti(Si,Ge)₂O₈ glasses, and comparison is made between the Raman spectra of the corresponding crystalline powders and glasses of Ba₂TiSi₂O₈ and Ba₂TiGe₂O₈. The Ba₂TiGe₂O₈ glass spectra show correspondence with the Ba₂TiGe₂O₈ crystalline Raman spectra; the v _s(Ge–O–Ge) mode occurs at 518 cm⁻¹ in the glass and at 521 cm⁻¹ in the crystalline material. Five-fold coordinated titanium is the majority species present in the Ba₂TiGe₂O₈ glass as revealed by a strong band at 824 cm⁻¹ in the I glass spectrum. The Ba₂TiSi₂O₈ glass spectra are similar to the Ba₂TiSi₂O₈ crystalline spectrum; the strongest band is found at 836 cm⁻¹ in the I glass spectrum. Through comparison with the previous Raman data of other titania silicate glasses, we conclude that the Ba₂TiSi₂O₈ glass has a structure similar to the crystalline phase.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Effects of metal-support interactions on the hydrogenation of CO over PdSiO2 and PdLa2O3

A study of CO hydrogenation over $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$ has been carried out for the purpose of identifying the effects of Pd dispersion, Pd morphology, and support composition on the catalytic activity of supported Pd. The specific activity of each catalyst for methanol and methane synthesis was determined from microreactor studies carried out at a fixed set of reaction conditions. Palladium dispersion was measured by H₂O₂ titration, and the morphology of the Pd crystallites, as expressed by the distribution of Pd(100) and Pd(111) planes, was determined from in situ infrared spectra of adsorbed CO. The crystallite morphology of the $\text{Pd}\text{SiO}{}_2$ catalysts is the same, independent of Pd weight loading: 90% of the surface is comprised of Pd(100) planes and 10% of the surface is comprised of Pd(111) planes. By contrast, the crystallite morphology of the $\text{Pd}\text{La}{}_2\text{O}{}_3$ catalysts changes with Pd loading. Primarily Pd(100) planes are exposed at low-weight loadings while Pd(111) planes are exposed at high-weight loadings. The Pd dispersion has little effect on the methanol turnover frequency over both $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$, for dispersions between 10 and 20%. On the other hand, the methane turnover frequency is independent of Pd dispersion over $\text{Pd}\text{SiO}{}_2$, but increases with decreasing dispersion over $\text{Pd}\text{La}{}_2\text{O}{}_3$. It is further observed that the Pd morphology influences the specific activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ for methanol synthesis: Pd(100) is nearly threefold more active than Pd(111). For a fixed morphology, the specific methanol synthesis activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ is a factor of 7.5 greater than that of $\text{Pd}\text{SiO}{}_2$.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

In situ laser raman spectroscopy of the sulfiding of Moγ-Al2O3 catalysts

Raman spectra of sulfided $\text{Mo}\text{γ-}\text{Al}{}_2\text{O}{}_3$ catalysts were obtained using in situ techniques for two sulfiding methods. For samples sulfided by 10% $\text{H}{}_2\text{S}\text{H}{}_2$ at 400 °C, MoS₂ structures were observed. A stepwise sulfiding using 10% $\text{H}{}_2\text{S}\text{H}{}_2$, with spectra recorded at 150, 250, and 350 °C, resulted in observation of molybdenum oxysulfide, reduced molybdate, and surface “MoS₂” phases. Reexposure of these samples to air led to radical modification of the oxysulfide structures as well as transformation of some sulfide phases. A model incorporating terminal and bridging MoS bonding and anion vacancies is proposed. This model is based on the conversion of isolated and aggregated molybdate and MoO₃ species to oxysulfide and reduced molybdenum phases. Conversion of reduced molybdenum phases to sulfides is observed to be slow.