原子吸收光谱法比较研究3种不同改性吸附剂对Cr(Ⅵ)离子的吸附

从吸附时间、pH值、吸附剂加入量、铬离子初始浓度4个方面,通过原子吸收光谱法比较了改性甘蔗渣、改性花生壳和改性梨渣的吸附特性.在铬离子浓度100mg·L-1、吸附剂投量15g·L-1、最佳pH值、吸附时间120min的实验条件下,三者吸附率不同,改性甘蔗渣的吸附率达86.7％以上,改性花生壳吸附率达64.8％,改性梨渣的吸附率达60.8％.3种改性吸附剂对Cr(Ⅵ)离子的吸附均符合Langmuir等温模型,其最大吸附能力分别为23.92、22.09、20.47mg·g-1.准一级反应动力学方程可描述3种改性吸附剂对Cr(Ⅵ)离子的吸附过程.     

原子吸收光谱法研究纳米纤维膜对Cr(Ⅵ)的吸附性能

利用静电纺丝技术制备了醋酸纤维素和聚乙烯吡咯烷酮纳米纤维膜.此纤维膜材料经水和NaOH处理后,除去了聚乙烯吡咯烷酮,脱乙酰化后进一步在表面接枝氨基(-NH2).用红外光谱图和扫描电镜图表征了合成的功能化纳米纤维膜,然后将胺基化纳米纤维膜用于Cr(Ⅵ)离子的吸附研究,重点用火焰原子吸收光谱法分析了溶液酸度和吸附时间对吸附容量的影响;同时通过Langmuir、弗兰德列希等吸附模型和一级、二级动力学方程对吸附行为进行线性拟合,发现改性后的纳米纤维膜材料对Cr(Ⅵ)离子的最大吸附量为55.55mg/g;符合二级动力学模型,化学吸附是主要的吸附方式.     

负载型纳米钛酸锶钡对水中Cd2+吸附行为研究

采用络合溶胶-凝胶法制备了钛酸锶钡溶胶,将其浸渍在硅胶G上,经高温煅烧后,制得固载于硅胶G上的纳米钛酸锶钡,以X射线衍射(XRD)、扫描电镜(SEM)和傅里叶变换红外光谱(FTIR)进行了表征.以火焰原子吸收为检测手段,系统地研究了负载型纳米钛酸锶钡对水中CA2+的吸附行为.结果表明,纳米钛酸锶钡能够牢固地负载于硅胶G表面.当介质的pH值为4～7时,该吸附剂对水中的CA2+具有很强的吸附能力,其吸附行为符合Freundlich吸附等温模型和HO准二级动力学方程式,并分别计算了吸附过程的焓变(△H),自由能变(△G)和熵变(AS)等热力学参数,表明该吸附过程是自发的吸热物理过程.被吸附的CA2+可用1 mol·L-1的硝酸完全洗脱回收.将其应用于水中痕量CA2+的吸附,建立了负载型纳米钛酸锶钡吸附富集,火焰原子吸收法测定水中痕量Cd2+的新方法.用于自来水和地表水中镉的测定,结果满意.     

原子吸收光谱法研究巯基改性膨润土对Pb2+的吸附解吸

通过红外光谱(FTIR)法和扫描电镜(SEM)对钙基和巯基改性膨润土的官能团和表面结构进行了比较分析,以火焰原子吸收光谱法(FAAS)为检测手段,研究了巯基改性膨润土对Pb2+吸附的影响因素并优化了吸附条件,讨论了模拟酸雨解吸Pb2+的条件。比较了钙基和巯基改性膨润土作为吸附剂对水溶液中Pb2+的吸附、固定能力。研究表明：25 ℃下,吸附时间为60 min、离子强度为0.1 mol·L-1的KNO₃、pH 6.0时,5.0 g·L-1巯基改性膨润土对100 mg·L-1的Pb2+的吸附率达到98%以上,平衡吸附量达到67.27 mg·g-1,吸附能力明显优于钙基膨润土(9.667 mg·g-1),吸附过程符合Langmuir和Freundlich等温线方程。用pH 3.50的极限酸度模拟酸雨进行解吸,解吸率为0。表明该巯基改性膨润土对Pb2+具有很强的吸附、固定能力,适于重金属铅污染土壤中铅的吸附固定修复之用。     

有机金属化学气相沉积法制备的Ni/Al2O3纳米复合材料的氢吸附

研究了通过有机金属化学气相沉积技术及单源分子前躯体方法制备的Ni/Al₂O₃纳米复合材料的氢吸附(存储). 在冷壁的有机金属化学气相沉积反应器中,通过降解Ni(acac)₂粉末基底上的[H₂Al(OtBu)]₂制备的Ni/Al₂O₃纳米复合材料. 通过X射线粉末衍射、扫描电镜、透射电镜以及能量色散型X射线荧光光谱等技术表征该复合材料. 采用自制Sievert's设备研究该复合材料的氢吸附(存储),可以储存约2.9%(重量比)的氢.     

原子吸收光谱法研究自然沙粒对pb2+的吸附性能

通过扫描电镜(SEM)、静态氮吸附(NSA)和红外光谱(FTIR)法对塔卡拉玛干沙漠自然沙粒(简称沙粒)的粒状及其表面结构、比表面积和功能基团进行了分析,以FAAS作为检测手段,动态法研究了沙粒对pb2+的吸附性及其影响因素并优化了吸附条件;将沙粒作为填料制备了5.0 cm×5 mm i.d.预富集分离微柱,将其与FA...     

Determining germanium and tin by atomic absorption in an acetylene-N2O flame

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 2, pp. 183–187, February, 1988.     

Electronic and magnetic properties of Ti(2)O(3), Cr(2)O(3), and Fe(2)O(3) calculated by the screened exchange hybrid density functional

The electronic and magnetic properties of the transition metal sesqui-oxides Cr(2)O(3), Ti(2)O(3), and Fe(2)O(3) have been calculated using the screened exchange (sX) hybrid density functional. This functional is found to give a band structure, bandgap, and magnetic moment in better agreement with experiment than the local density approximation (LDA) or the LDA+U methods. Ti(2)O(3) is found to be a spin-paired insulator with a bandgap of 0.22?eV in the Ti d orbitals. Cr(2)O(3) in its anti-ferromagnetic phase is an intermediate charge transfer Mott-Hubbard insulator with an indirect bandgap of 3.31?eV. Fe(2)O(3), with anti-ferromagnetic order, is found to be a wide bandgap charge transfer semiconductor with a 2.41?eV gap. Interestingly sX outperforms the HSE functional for the bandgaps of these oxides.     

Chemical etching of p-type Si(lOO) by K2Cr2O7

Chemical etching of the (100) face of p-type Si by aqueous K₂Cr₂O₇ was investigated with a contactless transient photoconductivity method, i.e. the time-resolved microwave conductivity (TRMC) method, after ns laser pulse excitation and with XPS, UPS, and LEED. TRMC transients after etching show a much slower decay that is explained by a decrease of surface recombination velocity. XPS indicates the formation of a mixed oxide of Si^III and Cr^v. During heating to 600°C this layer first transforms to a Si^IV-Cr^III oxide. After heating to 1200°C the oxide and Cr at the surface have disappeared, as indicated by UPS (He I and He II) and LEED (sharp 2×1 LEED pattern). However, XPS still shows the presence of Cr^o which evidently is diffused into the bulk. This can also be deduced from the transient photoconductivity measurements as TRMC transients at this stage show a fast decay rate that must be due to an increased bulk decay rate of excess charge carriers.     

紫外可见光谱法测定Cr3+电化学氧化过程中的Cr2O2-7

应用紫外可见光谱法对以二氧化铅为阳极,硫酸介质中Cr~(3 )电化学氧化过程中反应生成的Cr_2O_7~(2-)进行了分析测定,并测定了该反应过程的现场光谱。实验结果表明,以350nm作为Cr_2O_7~(2-)的定量吸收波长,可以测定Cr~(3 )电化学氧化过程中的Cr_2O_7~(2-)浓度,其摩尔吸光系数为1.98×10~3L·mol~(-1)·cm~(-1),体系中Pb~(2 )的存在对测定没有干扰。该反应过程的现场光谱测定表明,在以硫酸为介质、二氧化铅为阳极的Cr~(3 )电化学氧化反应生成Cr_2O_7~(2-)过程中,没有检测到中间体。     

The adsorption geometry of the (2 × 1)-2O oxygen phase formed on the Co(10 0) surface

The bond geometry of the (2 × 1)-2O-p2mg overlayer on Co(10 0) was determined by analyzing low-energy electron diffraction (LEED) intensity data. Oxygen occupies the three-fold coordinated hcp site along the densely packed rows on the unreconstructed surface. The O atoms are attached to two atoms in the first Co layer and to one Co atom in the second layer. The strong interaction between O and Co is indicated by the bond lengths of 1.83 ± 0.10 Å and 1.99 ± 0.10 Å to the top-layer Co and the Co atoms in the second layer, respectively. The most striking result of our work is that oxygen adsorption causes a marked expansion (by 25%) of the first Co layer spacing (0.90 Å) with respect to the bulk value of 0.72 Å. This strong expansion might offer diffusion channels for O atoms to penetrate further into the subsurface region.     

Investigation into the adsorption of atomic nitrogen on an Al2O3 (0001) surface

Computer simulation of sapphire nitridation used to obtain nitride-based heterostructures (GaN) on an Al₂O₃ substrate has been performed. The adhesion of atomic nitrogen to the sapphire (0001) surface is investigated ab initio. The possibility of replacing surface-layer oxygen atoms with nitrogen atoms has been examined. The calculated results indicate that adsorbed nitrogen atoms occupy the most stable positions above surface oxygen atoms at different nitrogen concentrations. The changes in the total system energy after replacement of surface oxygen atoms with nitrogen atoms have been calculated. It turns out that oxygen replacement is energetically unfavorable for a single nitrogen adatom. However, this process becomes energetically favorable if the concentration of nitrogen atoms increases. This outcome, obtained for the first time, enables better understanding of the atomic-scale mechanism of sapphire nitridation.     

The adsorption of CO on Pd(100) studied by IR reflection absorption spectroscopy

High resolution vibrational spectra of the C-O stretching region have been measured for the system CO/Pd(100) at temperatures between 80 and 340 K. LEED and flash desorption studies enabled the absolute coverage for each spectrum to be determined. The C-0 stretching frequency was found to shift linearly with coverage for the three adsorption temperatures 80, 200 and 300 K. At saturation coverage (θ ~ 0.8) the total shift is of the order of 100 cm⁻¹. Experiments with ¹²CO /¹³CO mixtures showed that the contribution of vibrational coupling is ~ 35 cm⁻¹ the rest being due to a static, partly chemical, lateral interaction. The apparent commensurate-incommensurate transition at θ = 0.5 has no significant influence on shift, width or intensity of the absorption band.     

α-Al2O3(0001)表面原子缺陷对ZnO吸附影响

采用基于密度泛函理论的分子动力学方法，对α-A12O3(0001)表面A1，O原子空位缺陷及其对ZnO吸附进行了理论计算．电子局域函数显示了表面空位处的电子密度变化，表面Al原子空缺处有非常明显的缺电子区域，悬挂键临近O的电子密度增大，有利于对Zn的吸附；O原子空缺处的Al原子处存在孤立电子，其ELF值为0．05-0．3，将有利于同电负性较大的O或O^2-结合．通过吸附动力学模拟与体系能量的计算发现，表面缺陷显著增强了表面的化学吸附，空缺原子处都被吸附原子填补，吸附结合能远大于单晶表面的情况．在Al空缺的表面，由于ZnO的O与表面O形成双键，破坏了α-Al2O3(0001)表面O六角对称结构，减小了O的表面扩散，从而不利于规则的ZnO薄膜生长．相反，O的空缺表面，弥补了α-Al2O3(0001)表面O空位缺陷，不影响基片表面O六角对称结构．