吸附条件对活性碳纤维SACF氧化还原吸附Ag^＋的影响

本文研究了吸附条件对活性碳纤维ＳＡＣＦ氧化还原吸附Ａｇ＾＋的影响。结果表明：Ａｇ＾＋初始浓度的提高，反应温度的升高均可提高ＳＡＣＦ对Ａｇ＾＋的吸附量；Ａｇ＾＋的吸附量还强烈地依赖于溶液的ＰＨ值，用ＮａＡＣ、ＨＡＣ＋ＮａＡＣ或ＮＨ３．Ｈ２Ｏ调高Ａｇ＾＋溶液的ＰＨ，可有效地增加ＳＡＣＦ对Ａｇ＾＋的吸附量；用ＮＨ３．Ｈ２Ｏ调节会再现一个最佳的ＰＨ值；通过增加ＳＡＣＦ用量，Ａｇ＾＋的吸附率可达９９％以上。     

笼形聚偕氨肟树脂的研究：酸处理树脂的吸附性能

笼形聚偕氨肟树脂（ＣＡＯ）经盐酸处理垢，伯胺基转变成胺盐。酸处理笼形聚偕氨肟树脂（ＡＣＡＯ）对Ｍｇ＾２＋，Ｃａ＾２＋，Ｂａ＾２＋，Ｍｎ＾２＋，Ｃｏ＾２＋，Ｎｉ＾２＋离子不吸附；对Ｚｎ＾２＋，Ｃｄ＾２＋，Ｃｕ＾２＋，Ｐｂ＾２＋离子的吸附效率在２０％以下，但对Ｈｇ＾２＋离子的吸附效率则高达７１．２％；对一些金属络阴离子的吸附效率顺序是Ｆｅ（ＣＮ）＾２－６＞Ｃｒ２Ｏ＾２－７＞ＭｏＯ＾２－４＞ＰｔＣｌ＾２     

磷酸三丁酯萃淋树脂吸附铬(Ⅵ)的性能及机理

研究了磷酸三丁酯萃淋树脂吸附的性能及机理。在３－５ｍｏｌ／Ｌ ＨＣｌ介质中,Ｃｒ以「Ｃｒ２Ｏ＾２－７（ＴＢＰＨ＾＋）形式被吸附,吸附反应在３－５ｍｉｎ内即可达到平衡,其ΔＨ＝－４６．０８ｋＪ／ｍｏｌ饱和吸附容量为２５ｍｇ／ｇ。用减压微色谱柱技术,吸附在柱上的Ｃｒ仅用１ｍＬ水可完全洗脱。此法用于电镀废水中Ｃｒ的测定获得了满意的结果。     

合并带流动注射分光光度法研究硫羟乳酸掩蔽性能

本文运用合并带流动注射分析技术，建立了以Ｙｂ＾３＋ＸＯ显色体系为参考体系研究硫羟乳酸掩蔽性能的方法，在ｐＨ５．６硫羟乳酸能掩蔽Ｓｎ＾４＋，Ｂｉ＾３＋，Ｔｌ＾３＋，Ｈｇ＾２＋，Ｃｕ＾２＋，Ｃｒ＾３＋和Ｃｄ＾２＋测定Ｙｂ＾３＋的线性范围为１．３６×１０＾－６～２．７２×１０＾－５ｍｏｌ／Ｌ，采样频率可达１２０次／ｈ。     

模板交联壳聚糖对Cu^2＋,Ni^2＋,Co^2＋离子的吸附作用研究

用市售的壳聚糖在水介质中与Ｃｕ＾２＋生成络合物，用二醛处理进行交联，稀酸洗去Ｃｕ＾２＋离子，制得Ｃｕ＾２＋离子模板交联壳聚糖树脂。这种树脂在ＰＨ值５－６条件下对其模板离子Ｃｕ＾２＋离子有最大的吸附量，对过渡金属离子的吸附次序为Ｃｕ＾２＋〉Ｎｉ６２＋〉Ｃｏ＾２＋。在酸性再生条件下不会发生软化和溶解，重复使用性能良好。     

流动注射碳硅凝胶微柱预富集ICP—AFS法测定高纯氧化铕中的非…

利用自合成的碳硅凝胶为吸附材料，以铜试〔二乙基二硫代氨基甲酸钠（ＮａＤＤＴＣ）〕为衍生化试剂。柱前衍生的方法，在优化的实验条件下，于ｐＨ４．６的缓冲介质中在线预富集Ａｌ＾１２＋、Ｃｒ＾５＋、Ｃｕ＾２＋、Ｆｅ＾３＋、Ｐｂ＾２＋、Ｖ＾５＋、Ｚｎ＾２＋。采用停流技术洗脱，富集倍数可达８．１￣１２．６倍，检出限为ｎｇ／ｍｌ级。对高纯氧化铕（Ｅｕ２Ｏ３）中的非稀土杂质进行测定，可避免大量稀土基体对测定的干扰     

PTFE—乙醚柱反相萃取层析连续分离和测定镓（Ⅲ）铟（Ⅲ）的研究

研究了在抗坏血酸存在下的６ｍｏｌ／Ｌ ＨＢｒ介质作流动相，以ＰＴＦＥ（聚四氟乙烯）负载的乙醚作固定相，反相萃取层析使微量Ｇａ（Ⅲ），Ｉｎ（Ⅲ）与Ｆｅ＾３＋、Ｔｌ＾３＋、Ｍｏ＾６＋、Ａｕ＾３＋、Ｔｉ＾４＋、Ｂｉ＾３＋、Ａｌ＾３＋、Ｍｇ＾２＋、Ｃａ＾２＋、Ｎｉ＾２＋、Ｃｏ＾２＋、Ｃｄ＾２＋、Ｚｎ＾２＋、Ｐｂ＾２＋、Ｃｕ＾２＋等多种离子分离。留于柱上的铟、镓分别用ＨＣｌ（４ｍｏｌ／Ｌ）－Ｈ２Ｏ２（３％）     

La^3＋和Ca^2＋对金电极上谷胱甘肽单分子膜离子闸门的影响

谷胱甘肽能自组装吸附到金电极上形成单分子膜。该膜能阻止Ｆｅ（ＣＮ）６离子在金电极上还原，起离子闸门的作用。当溶液中加入Ｌａ＾３＋或Ｃａ＾２＋时，了穿透膜的能力得到改善。本课题应用循环伏安法和计时库仑法，在ＰＨ５．６的溶液中研究了Ｌａ＾３＋的调控能力，与Ｃａ＾２＋比较，发现在改变谷胱甘肽单分子膜的结构和Ｆｅ（ＣＮ）６离子的扩散系数方面，Ｌａ＾３＋具有更强的能力。     

硫脲基纤维的制备及其对Au^3＋氧化还原吸附性能的研究

本文合成了一种硫脲基螯合纤维，其含硫量为２．９ｍｍｏｌ／ｇ，它对Ａｕ＾３＋的吸附量在９６０ｍｇ／ｇ（４０℃）。Ｘ射线衍射实验表明：纤维能把Ａｕ＾３＋还原成单质金，脱附实验结果表明溶液ＰＨ为１－２时，纤维对吸附态Ａｕ＾３＋的还原率达９０％以上；在扫描电子显微镜下可观察吸附态金聚集成粒状。文中还研究了该纤维吸附Ａｕ＾３＋量随溶液ＰＨ值、温度变化、吸附动力学规律，并对硫脲官能团的半波电值进行了表征。     

不同金属离子对Co/Al2O3中Co的分布和CoMoK/Al2O3催化活性的影响

在γ－Ａｌ２Ｏ３咖入Ｚｎ＾２＋，Ｍｇ＾２＋，Ｃｕ＾２＋或Ｃｒ＾３＋后用漫反射光谱法研究了它们对随后加入的Ｃｏ分布的影响，同时还研究了这些离子对水煤气变换反应催化剂ＣｏＭｏＫ／Ａｌ２Ｏ３的催化活性的影响，发现Ｚｎ＾２＋，Ｍｇ＾２＋具有阻止Ｃｏ进入载体内层的作用，Ｃｕ＾２＋，Ｃｒ＾３＋的作用则相反，四面体配位倾向强的金属离子能阻Ｃｏ进入载体内层，从而促进水煤气变换反应的催化活性，而八面配位倾向强度金属     

Thermodynamics of Chromium(VI) Anionic Species Sorption onto Surfactant-Modified Montmorillonite Clay

Batch sorption experiments performed on Cr(VI) species sorption showed a significantly enhanced removal of inorganic hexavalent chromium anionic species from aqueous solution by montmorillonite clays modified with quaternary amine, hexadecyltrimethylammonium (HDTMA) bromide. Unmodified clay had no affinity for chromium(VI) species. The sorption of Cr(VI) species has been carried out as a function of pH, contact time, adsorbate concentration (4.14x10(-5) to 8.62x10(-3) M), and temperature (5-45 degrees C). The surfactant-modified clay surface was stable when exposed to extremes in pH. The optimum pH for maximum sorption of Cr(VI) species was found to be at pH 1 and was constant between pH 2 and pH 6. The sorption data obtained was well described by DKR and Langmuir sorption isotherms. Sorption energy (E) for (i) surfactant sorption by montmorillonite clay and (ii) sorption of chromium(VI) species by surfactant modified clay have been computed from the DKR equation. Sorption energy evaluated for the sorption of both surfactant and Cr(VI) species showed that an ion-exchange mechanism was operative. The mechanism of retention appears to be replacement of counterion of the surfactant by Cr(VI) anionic species. Adsorbent capacity for the sorption of Cr(VI) species has been evaluated from the Langmuir sorption isotherm data. Thermodynamic parameters (Delta H degrees, Delta S degrees and Delta G degrees ) for surfactant sorption on montmorillonite clay and Cr(VI) sorption by modified clay have been evaluated. The specific rate constant for sorption of Cr(VI) species on modified montmorillonite was rapid during the first 10 min and equilibrium was found to be attained within 30 min. The sorption of Cr(VI) species onto modified montmorillonite clay followed first-order rate kinetics. Copyright 2000 Academic Press.     

Preparation, characterization and metal sorption studies of a Chrome-Azurol-S-loaded anion-exchange resin

Chrome Azurol S (CS) was mobilized on an strongly basic anion-exchange resin (Dowex 2 x 4, in Cl(-) form) by batch equilibration. The modified resin was stable in acetate buffer solution and in 0.1 M HCl and H(2)SO(4), but it was readily degraded with 2-6 M HCl and HNO(3). Retention of Ba(II), Sr(II), Ca(II), Mg(II), Al(III), Cr(III), Zn(II), Fe(III), Ti(IV), Mn(II), Co(II), Ni(II), Cu(II), Cd(II) and Pb(II) was studied using the batch equilibration method. The uptake and recovery yields were determined by using inductively-coupled plasma atomic emission spectroscopy (for Mg, Al, Cr, Ti, Fe, Mn, Ni, Zn, Cu, Cd and Pb) and atomic absorption spectrophotometry (for Ba, Sr, Ca and Co). The optimum pH value was established for performing a selective separation of Al(III) from the other metal ions. The sorption capacities of the CS-loaded resing for Al(III), Cr(III), Mg(II) (at pH 6), Fe(III) (at pH 5) and Ti(IV) (at pH 4) were 14, 2.9, 0.3, 3 and 3.9 mumoles g(-1) respectively. On this basis a method for separating Al(III) from other cations was established.     

Hydrogen chromate PVC matrix membrane sensor for potentiometric determination of chromium(III) and chromium(VI) ions

A novel potentiometric Cr(6+) PVC matrix membrane sensor incorporating nickel tris(1,10-bathophenanthroline) hydrogen chromate as an electroactive material and 2-nitrophenyl phenyl ether as solvent mediator is described. In a phosphate buffer solution of pH 5, the sensor displays a rapid and linear response for Cr(6-) over the concentration range 2 x 10(-2)-8 x 10(-6) M with an anionic slope of 55.5 +/- 0.2 mV decade(-1) and a detection limit of the order of 0.4 microg ml(-1). The sensor is used for sequential determination of Cr(6+) and Cr(3+) by direct monitoring of Cr(6+) followed by oxidation of Cr(3+) and measurement of the total chromium. The average recoveries of Cr(3+) and Cr(6+) at concentration levels of 0.5-50 microg ml(-1) are 98.1 +/- 0.4% and 99.1 +/- 0.4% respectively. Redox and precipitation titrations involving Cr(6+) as a titrant are monitored with the sensor. Cr(3+) and/or Cr(6+) in wastewaters of some industries (e.g., leather tanning, electroplating, aluminum painting) and the chromium contents of some alloys and refractory bricks are assessed. The results agree fairly well with data obtained using the standard diphenylcarbazide spectrophotometric method.     

Rapid spectrophotometric determination of chromium(III)

A spectrophotometric procedure is suggested for the determination of Cr(III). The reaction between Cr(III) and 2-(5-bromo-2-pyridylazo)-5-dimethylaminophenol is accelerated by sodium dodecyl sulphate(SDS), sodium benzoate causes a further increase in the absorbance of the chelate. The optimum pH range for the reaction is 5-5.8(benzoate buffer). The chelate exhibits maximum absorbance at 590 nm, obeys Beer's law over the concentration range 0.02-0.56 microg/ml of Cr(III), has molar absorptivity of 7.8 x 10(4) 1. mol(-1) cm(-1) and a Sandell sensitivity of 0.66 ng/cm. The metal to ligand ratio is 1:2 in the absence of SDS and 1:1 in its presence. A procedure for the determination of Cr(III) and Cr(VI), when present together, is described. The method has been applied to the analysis of Cr(III) in tap water.     

Second chemiluminescence behavior of Fe2+, Fe3+ and Cr3+ in the luminal-KMnO4 system.

A novel flow injection chemiluminescence (CL) method has been developed for the determination of three metal ions, namely Fe2+, Fe3+ and Cr3+, based on the second CL (SCL) signal of the mixture of luminal with KMnO4 in a sodium hydroxide medium by the catalysis of Fe2+, Fe3+ or Cr3+. The possible CL mechanism of the systems, the influencing factors, and the optimum conditions for the reactions were investigated based upon the kinetic curve of the CL reaction, CL spectra, UV-visible spectra and some other experiments. Under the optimum conditions, the SCL intensity was directly proportional to the concentration of these metal ions in solution in the range of 0.10 - 100.00 mg l(-1) for Fe(2+), 0.50 - 7.50 and 7.50 - 200.00 mg l(-1) for Fe3+, 0.01 - 0.25 and 0.25 - 10.00 mg l(-1) for Cr3+. The detection limits (3 sigma/s) were 9.87 x 10(-6) g l(-1), 2.71 x 10(-6) g l(-1) and 5.25 x 10(-7) g l(-1) for Fe2+, Fe3+ and Cr3+, respectively.     

A potentiometric rhodamine-B based membrane sensor for the selective determination of chromium ions in wastewater.

The construction and performance characteristics of a novel chromate ion-selective membrane sensor are described and used for determining chromium(III) and chromium(VI) ions. The sensor is based on the use of a rhodamine-B chromate ion-associate complex as an electroactive material in a poly(vinyl chloride) membrane plasticized with o-nitrophenyloctyl ether as a solvent mediator. In a phosphate buffer solution of pH 6 - 7, the sensor displays a stable, reproducible and linear potential response over the concentration range of 1 x 10(-1) - 5 x 10(-6) mol l(-1) with an anionic Nernstian slope of 30.8 +/- 0.5 mV decade(-1) and a detection limit of 1 x 10(-6) mol l(-1) Cr(VI). High selectivity for Cr(VI) is offered over many common anions (e.g., I-, Br-, Cl-, IO4-, CN-, acetate, oxalate, citrate, sulfate, phosphate, thiosulfate, selenite, nitrate) and cations (e.g., Ag+, Ca2+, Sr2+, Co2+, Ni2+, Cu2+, Mn2+, Fe2+, Zn2+, Cd2+, Al3+, Cr3+). The sensor is used for determining Cr(VI) and/or Cr(III) ions in separate or mixed solutions after the oxidation of Cr(III) into Cr(VI) with H2O2. As low as 0.2 microg ml(-1) of chromium is determined with a precision of +/-1.2%. The chromium contents of some wastewater samples were accurately assessed, and the results agreed fairly well with data obtained by atomic absorption spectrometry.     

Redox and complexation chemistry of the Cr(VI)/Cr(V)-D-galacturonic acid system

The oxidation of d-galacturonic acid by Cr(VI) yields the aldaric acid and Cr(III) as final products when a 30-times or higher excess of the uronic acid over Cr(VI) is used. The redox reaction involves the formation of intermediate Cr(IV) and Cr(V) species, with Cr(VI) and the two intermediate species reacting with galacturonic acid at comparable rates. The rate of disappearance of Cr(VI), Cr(IV) and Cr(V) depends on pH and [substrate], and the slow reaction step of the Cr(VI) to Cr(III) conversion depends on the reaction conditions. The EPR spectra show that five-coordinate oxo-Cr(V) bischelates are formed at pH < or = 5 with the uronic acid bound to Cr(V) through the carboxylate and the alpha-OH group of the furanose form or the ring oxygen of the pyranose form. Six-coordinated oxo-Cr(V) monochelates are observed as minor species in addition to the major five-coordinated oxo-Cr(V) bischelates only for galacturonic acid : Cr(VI) < or =10 : 1, in 0.25-0.50 M HClO(4). At pH 7.5 the EPR spectra show the formation of a Cr(V) complex where the vic-diol groups of Galur participate in the bonding to Cr(V). At pH 3-5 the Galur-Cr(V) species grow and decay over short periods in a similar way to that observed for [Cr(O)(alpha-hydroxy acid)(2)](-). The lack of chelation at any vic-diolate group of Galur when pH < or = 5 differentiates its ability to stabilise Cr(V) from that of neutral saccharides that form very stable oxo-Cr(V)(diolato)(2) species at pH > 1.     

Novel Pathways in the Reactions of Superoxometal Complexes

The reaction of a 1:1 mixture of (H(2)O)(5)Cr((16)O(2))(2+) and (H(2)O)(5)Cr((18)O(2))(2+) at pH 1 did not yield measurable amounts of (16)O(18)O. This result rules out a Russell-type mechanism (2(H(2)O)(5)CrO(2)(2+) --> 2(H(2)O)(5)CrO(2+) + O(2)) for the bimolecular decomposition reaction. Evidence is presented in support of unimolecular (S(H)1) and bimolecular (S(H)2) homolyses as initial steps in the decomposition of (H(2)O)(5)CrO(2)(2+) in strongly acidic solutions (pH 相似文献   

Optimization of the Conditions for the Cr (III) Adsorption on Activated Carbon

In order to understand the patterns of the adsorption equilibrium of Cr (III) on activated carbon, the adsorption process was studied by two different ways: classical batch experiments on commercial Norit and Merck activated carbons and their oxidized forms in a wide range of pHs; and extended time-based tests at the same pH values on the same adsorbents. This approach allowed us to understand the role of texture, chemical carbon surface functionality and experimental conditions (initial pH of the solution, contact time and adsorbate/adsorbent ratio) on the effectiveness of Cr (III) removal. The adsorption process of Cr (III) at (24 ± 1^∘C) on Merck and Norit activated carbons and their oxidized forms were studied at pH values between 1.5 and 5 (either adjusted or buffered). Chromium concentration was fixed at 200 ppm. The carbon loading ranged from 1.2 to 20 g/l. The carbon/Cr (III) solution contact time was varied from 0.5–1 month to 5 months, to ensure that the saturation of the carbon level was reached. According to the data obtained, the presence of carboxylic groups on carbon surface seems to enhance Cr (III) uptake at initial pH of the solution in the range between 2 and 4. Depending on the nature of the adsorbent surface chemistry, the contact time to reach equilibrium may range from 3 to 5 months. There is an optimum carbon loading which limits the Cr (III) uptake/removal at given pH value. In order to understand the adsorption process, an ion exchange, surface complex and surface precipitation were considered. This paper was presented in the 5th Brazilian Meeting on Adsorption, held at Natal, Brazil, 18-21 July, 2004.     

Simultaneous determination of Cr(III)-EDTA and Cr(VI) by ion interaction chromatography using a C18 column

The simultaneous determination of Cr(III) and Cr(VI) by ion interaction chromatography has been investigated. The mobile phase consisted of a 5 mM octylammonium orthophosphate at pH 4.0 with 35% (v/v) MeOH. The Nucleosil-100, C18 (5 microm, 250 x 4.6 mm) was used as the separating column and the component was detected at 200 nm. The separation of Cr(III) and Cr(VI) was based on anionic interaction. Since the Cr(III) did not exist as an anionic form like the Cr(VI) (Cr2O7(2-)) presented at the optimum condition, Cr(II) was firstly reacted with EDTA (1:40 mole ratio) to form the anionic complex prior to injecting into the chromatographic system. The characteristics of the method for separation of Cr(III)-EDTA and Cr(VI) were satisfactory. The wide linear range (0.3-50.0 mg l(-1)) was achieved. The repeatabilities (%R.S.D.) calculated from peak areas were 0.49% and 0.14%, detection limit (signal to noise ratio of 3) of 0.02 mg l(-1) and 0.3 mg l(-1) were obtained and the average of percent recoveries were found to be 98.5% and 99.6% for Cr(III) and Cr(VI), respectively.