EFFECT OF THE EXISTING STATES OF CHROMIUM ION ON THE COLOR CHARACTERISTICS OF DOPED β-C_2S

According to the theory of crystal field, the existing state of chromium ions in β-C_2S was studied with optical spectra and EPR. The energy levels of chromium ions were calculated. Chromium ions exist in form of Cr^(4+) and Cr^(5+) coordinated with distorted octahedra. The reason of fading of β-C_2S hydrate is that the strength of light absorption declines be- cause of the valence change of chromium ions and chroninm dissolves out and loses in water.

Spectrophotometric Method for Determination of Chromium Ion in Aqueous Solution Using Ninhydrin

A simple, precise, inexpensive and reproducible spectrophotometric method was investigated for the determination of chromium ion (III) in aqueous media, this method based on the formation of a complex between chromium ion (III) and ninhydrin, a deep greenish-violet colored product in the presence of potassium hydroxide was obtained. The absorption of this product was measured at λmax = 375 nm. The reaction proceeds quantitatively at room temperature. The linear calibration curve was constructed over range of (4.8 × 10-4 - 1.6 × 10-2) mol/L of chromium ions with molar absorptivity of 2.90 × 102 and correlation coefficient R2 = 0.9989. The calculated Sandell’s sensitivity value is 0.179 μg/cm2, the limits of detection (LOD) and the limit of quantification (LOQ) are found to be 3.74 × 10-5 and 1.24 × 10-4 mol/L, respectively. The method was successfully applied for determination of the chromium ion in aqueous solution. The stoichiometry of the reactions was determined molar combining ratio of 1:2 between chromium and ninhydrin.

Interpenetrating polymers supported on microporous polypropylene membranes for the transport of chromium ions

Modifying polypropylene membranes with interpenetrating polymer networks(IPNs) through the incorporation of poly(glycidyl methacrylate-N-methyl-D-glucamine)(P(GMA-NMG)) was performed by in situ synthesis via radical polymerization. The surface of the polypropylene membrane was activated by hydrophilic grafted polyelectrolyte, and then, pressure injection was used for the impregnation of the reactive solution in the membrane.Two types of pore-filled membranes were synthesized, chelating interpenetrating homopolymer networks of P(GMA-NMG), and chelating-ion exchange interpenetrating polymer networks(e.g., P(GMA-NMG)/P(AA),P(GMA-NMG)/P(AMPSA), and P(GMA-NMG)/P(Cl VBTA)). After their synthesis, the modified polypropylene membranes were characterized using techniques such as the electrokinetic potential, SEM, FT-IR, and Donnan dialysis to corroborate the chromium ion transport. The P(GMA-NMG) and complex network membranes exhibited a hydrophilic character with a water-uptake capacity between 20% and 35% and a percentage of modification between 4.0% and 7.0% in comparison with the behavior of the unmodified polypropylene membrane.Hexavalent chromium ions were efficiently transported from the food chamber at p H 9.0 when the 65.2%MTA1 P(Cl VBTA) homopolymer IPN membrane and 48.5% MTAG P(GMA-NMG)/P(Cl VBTA) IPN membrane were used. Similarly, hexavalent chromium ions were removed from the food chamber at pH 3.0 when MTAG(63.30%) and MTA1(35.68%) were used in 1 mol·L^(-1)Na Cl solution as the extraction reagent.

Highly Selective Fluorescence Turn-on Chemosensor Based on Naphthalimide Derivatives for Detection of Trivalent Chromium Ions

一新荧光灯探查， NPQ-C，被综合。NPQ-C 基于 naphthalimide 衍生物并且为 Cr3+ 离子展出了高选择和敏感。作为一放大 Cr3+ 荧光灯探查，它的荧光光谱显示出 5.5 褶层在在有 Cr3+ 的绑定上的 500 nm 的信号的紧张的改进。基于荧光滴定系列和 Job's-plot 分析，有 Cr3+ 的 NPQ-C 的有约束力的模式被建议。荧光紧张与在从 0 ～ 10 的一个范围的 Cr3+ 阳离子的集中是线性的吗？？

Effect of partial pressure of reactive gas on chromium nitride and chromium oxide deposited by arc ion plating

The effects of reactive gas partial pressure on droplet formation, deposition rate and change of preferred orientation of CrN and Cr2O3 coatings were studied. For CrN coatings, as nitrogen partial pressure increases, the number and size of droplets increases, the deposition rate initially increases obviously and then slowly, and the preferred orientation of CrN changes from high-index plane to low-index one. For Cr2O3 coatings, with the increase of oxygen partial pressure, the number and size of droplets decreases, the deposition rate decreases and the (300) becomes the preferred orientation. These differences are ascribed to the formation of CrN (with a lower melting point) and Cr2O3 (with a higher melting point) on the surface of Cr target during the deposition of CrN and Cr2O3. Complete coatings CrN or Cr2O3 film can be formed when reactive gas partial pressure gets up to 0.1 Pa. The optimized N2 partial pressure for CrN deposition is about 0.1?0.2 Pa in order to suppress the formation of droplets and the suitable O2 partial pressure for Cr2O3 deposition is approximately 0.1 Pa for the attempt to prevent the peel of the coating.

The Electrode for Potentiometric Determinаtion of Chromium (III, VI) in Wаter Solutions

The possibility of determining of chromium (III, VI) ions was investigated in this paper. It is shown that the electrode on а basis of heаzlewoodite has high selectivity to chromium (III) ions. Also the stability constants of complexes, forming in system “Cr3+-Mohr’s salt-Ca(OH)2-PVA ÷ PAA” were determined by potentiometric titration with ion-selective electrode.

Removal of Chromium(III) from the Waste Solution of an Indian Tannery by Amberlite IR 120 Resin

The extraction of chromium(III) from a model waste solution and also from a waste solution of an Indian tannery with Amberlite IR 120 resin is described, and the performance of this resin is compared with other similar resins. The parameters that were optimized include effect of mixing time, pH, loading and elution behaviours of chromium(III) for this resin. Sorption of chromium(III) on Amberlite IR 120 followed Freundlich isotherm and Langmuir isotherm model, and the maximum sorption capacity was determined to be 142.86 mg Cr(III)/g of the resin. Higher Freundlich constant (Kf) values (6.30 and 13.46 for aqueous feed of 500 and 1000 ppm Cr(III)) indicated strong chemical interaction through ion exchange mechanism of the metal ion with the resin. The kinetic data showed good fit to the Lagergren first order model for extraction of chromium(III). Desorption of chromium(III) from the loaded resin increased with the increase in concentration of eluent (5-20% H2SO4). With 20% (v/v) sulphuric acid solution 94% chromium(III) was eluted in three stages. Elution of the Cr(III) in the column experiments was however, found to be lower (82%) than that of the shake flask data. In case of Indian tannery’s waste solution, it was observed that almost total chromium was extracted in four stages with Amberlite IR 120.

Deposition of chromium aluminum nitride coatings by arc ion plating

Cr-Al-N ternary coatings were deposited by arc ion plating method using isolated Cr target and Al target. The influence of AlN content on the phase change was studied by synthesizing Cr1-xAlxN coatings with different x values. The effects of substrate negative bias on the surface morphology,deposition rate and phase structure were investigated. As the aluminum content increases,the structure of(Cr1-xAlx)N changes from B1(NaCl) phase to B4(wurtzite) phase. The critical content of AlN solubilized in B1(NaCl) lattice is close to 0.7. With the increasing pulse negative bias,the deposition rate decreases constantly,the droplet contamination is more serious,the ion-etching effect on coating surface is more obvious,and the change of preferred orientation and the shift of XRD peak take place.

Potential of <i>Artocarpus heterophyllus</i>Seed Powder in the Adsorption of Chromium(VI) from Aqueous Solution

The potential of Artocarpus heterophyllus (Jackfruit) seed powder in adsorption of chromium(VI) from aqueous solution was studied using batch technique. The performance of the adsorption process was evaluated against contact time, pH, adsorbent dose, temperature and initial chromium(VI) ion concentration. The influence of the presence of interfering anionic species including chlorides, nitrates and sulphates on the adsorption process was also evaluated. The adsorption of chromium(VI) by Jackfruit seed powder reached equilibrium after 60 minutes. Higher chromium(VI) adsorption was observed at lower pH values with maximum removal (96.05%) occurring at pH 2. A great deal of adsorption (92.53%) was observed at the adsorbent dosage level of 1.0 g/100 ml solution. There was an improvement in the adsorption process when the temperature was increased from 25&#176C (95.35%) to 60&#176C (99.56%) followed by a decrease to 98.76% at 70&#176C. Adsorption decreased with increasing initial chromium(VI) ion concentration. The adsorption followed both Freundlich and Langmuir adsorption models with correlation coefficients of 0.998 and 0.994 respectively, and Qm of 0.57 mg/g. The presence of nitrate and chloride ions significantly lowered the adsorption, with all the p values 0.05. From the obtained Qm, Jackfruit Seed Powder is a good adsorbent for the aqueous solutions of Cr(VI). The adsorption process is slowed by the presence of the interfering anionic species.

Using Ferrous Ion for the Reductive Degradation of Hexavalent Chromium

This paper discusses the toxicity and mobility of chromium species. And it presents the extent and kinetics of reductive remediation of hexavalent chromium, Cr+ using ferrous ion, Fe2+. Molar ratios of 1:3 and 1:6 of Cr (VI) to Fe (II) were used. Integral method of data analysis showed reaction followed second-order kinetics with R square values near unity. Reaction was initially fast but with a rapid precipitation attributed to Cr (III)-Fe (III) in previous studies. This colloidal precipitate ultimately stops the reaction, which explains while conversion efficiency increases with increased molar ratio of Cr (VI) to Fe (II). The impact of pH was investigated by adjusting the Cr (VI)-Fe (II) medium to pH 2.78, 5.24, 7.00, 9.00 and 11.96 using predetermined drops of acid or base. Reaction was more rapid under alkaline conditions with higher extent of degradation consistent with previous research. In soil system, mass transfer limitation was hardly noticed as high extent of reduction was recorded relative to aqueous phase. The high solubility of Cr (VI) aided the release into the aqueous media for reduction by ferrous sulfate.

Trace-Level Analysis of Hexavalent Chromium in Lake Sediment Samples Using Ion Chromatography Tandem Mass Spectrometry

The analysis of hexavalent chromium, Cr(VI), in soil and sediment samples has been predominantly carried out in materials containing elevated levels. Reliable analysis of trace-level of Cr(VI) in sediment samples remains challenging. Cr(VI) analyses with multipoint calibration and speciated isotope dilution (SID) adapted from U.S. EPA method 6800 were used to measure lower-level Cr(VI) on an ion chromatograph coupled with a tandem mass spectrometer (IC-MS/MS). Lake sediment samples were collected from various locations in Northern Ontario and Cr(VI) was extracted using both alkaline digestion and ethylene diaminetetraacetic acid (EDTA) extraction. Certified reference materials were extracted and analyzed by IC-MS/MS and UV-VIS detection. The SID-MS approach allowed for the quantification of Cr(VI) in samples with concentration levels below 0.5 μg.g-1 wet weight.

Thickness Dependence of Structural and Optical Properties of Chromium Thin Films as an Infrared Reflector for Solar-thermal Conversion Applications

The thermal emittance of Cr film, as an IR reflector, was investigated for the use in SSAC. The Cr thin films with different thicknesses were deposited on silicon wafers, optical quartz and stainless steel substrates by cathodic arc ion plating technology as a metallic IR reflector layer in SSAC. The thickness of Cr thin films was optimized to achieve the minimum thermal emittance. The effects of structural, microstructural, optical, surface and cross-sectional morphological properties of Cr thin films were investigated on the emittance. An optimal thickness about 450 nm of the Cr thin film for the lowest total thermal emittance of 0.05 was obtained. The experimental results suggested that the Cr metallic thin film with optimal thickness could be used as an effective infrared reflector for the development of SSAC structure.

基于4-巯基苯甲酸和聚乙烯亚胺功能化纳米银的Cr^(3+)检测研究

水体中重金属离子含量过高会导致生态环境及人体健康的严重损害,检测水体中重金属离子含量十分重要。针对目前重金属离子检测灵敏度的问题,合成了4-巯基苯甲酸和聚乙烯亚胺修饰的纳米银材料,并构建了水溶液中铬离子检测体系。考察了不同修饰剂的浓度、体系pH对检测体系的影响。研究结果表明,当4-巯基苯甲酸浓度为1×10^(-6)mol/L、聚乙烯亚胺质量浓度为2×10^(-8)g/mL、pH=9.73时,该检测体系对Cr^(3+)具有良好的检测效果,在最优条件下检测限可达8×10^(-7)mol/L。另外,该检测体系能够有效抵抗Al^(3+)、Ni^(2+)、K^(+)、Sr^(2+)、Co^(2+)、Cu^(2+)、Fe^(3+)、Zn^(2+)的干扰。在Cr^(3+)浓度为8×10^(-7)~1×10^(-5)mol/L时,符合曲线方程y=0.05906+0.50402/[1+10^(2.59349×10^(-6)-x)×569909.68](R^(2)=0.997)。该研究在检测污水中Cr^(3+)浓度方面具有较大的应用价值。

钛白副产硫酸亚铁中镁离子的含量分析

本文研究以酸性铬蓝K为指示剂,以草酸铵为沉淀剂排除Fe^(2+)干扰,用紫外分光光度法测定钛白副产物FeSO_(4)中的Mg^(2+)的含量。实验结果表明,Mg-铬蓝K的最大吸收峰波长为540nm,最佳pH值为9.5,最佳沉淀剂草酸铵的用量为10mL。经加标回收的方法验证了方法的可行性,测出钛白副产物FeSO_(4)中Mg^(2+)含量为1.07%。

壳聚糖/明胶复合微球的制备及吸附性能研究

以壳聚糖和明胶为原料,span 80为乳化剂,戊二醛为交联剂,采用乳化交联法制备了壳聚糖/明胶复合微球并用于Cr(Ⅵ)的吸附。考察了复合微球的各制备因素对微球形貌的影响,通过单因素分析研究了壳聚糖与明胶的比例、乳化剂用量、乳化时间对复合微球吸附性能的影响。结果表明,壳聚糖与明胶的比例为1∶2、span 80用量为6mL、乳化时间为50min时,制备的复合微球对Cr(Ⅵ)的吸附性能良好,吸附量较大,Cr(Ⅵ)的去除率可达95.3%。

乙二胺改性聚苯乙烯树脂对水体中铅(Ⅱ)、铬(Ⅵ)的吸附研究

采用乙二胺对氯甲基化聚苯乙烯树脂进行改性,利用改性后的树脂去除溶液中的铅(Ⅱ)和铬(Ⅵ)。通过改变pH、时间、浓度和吸附剂投加量,确定最佳吸附实验条件,得到改性后的树脂对铅(Ⅱ)和铬(Ⅵ)的最大吸附容量分别为119.60mg/g和128.28mg/g。动力学研究表明,该模型符合Langmuir模型。

Novel Cr^(3+)-activated far-red emitting phosphors withβ-Ca_(3)(PO_(4))_(2)-type structure for indoor plant cultivation

Cr^(3+)-activated far-red and near-infrared phosphors have drawn considerable attention owing to their adjustable emission wavelengths and wide applications.Herein,we reported a series of Cr^(3+)-doped phosphors withβ-Ca_(3)(PO_(4))_(2)-type structure,of which Ca_(9)Ga(PO_(4))_(7):Cr^(3+) possessed the highest far-red emission intensity.At an excitation of 440 nm,the Ca_(9)Ga(PO_(4))_(7):Cr^(3+) phosphors exhibited a broad emission band ranging from 650 to 850 nm and peaking at 735 nm,and the broadband superimposed two sharp lines centering at 690 and 698 nm.The optimal sample Ca_(9)Ga_(0.97)(PO_(4))_(7):0.03 Cr^(3+) had an internal quantum efficiency of 55.7%.The luminescence intensity of the Ca_(9)Ga_(0.97)(PO_(4))_(7):0.03 Cr^(3+) phosphor obtained at 423 K could maintain 68.5%of that at room temperature,demonstrating its outstanding luminescence thermal stability.A phosphor-conversion light-emitting diode was fabricated,indicating that the Ca_(9)Ga(PO_(4))_(7):Cr^(3+) phosphor has potential applications in indoor plant cultivation.

铬离子污染快速可视化检测方法研究

开发了一种基于壳聚糖的酰基化改性、利用含巯基碳量子点(S,N-CQDs)与点击反应制备的荧光修饰的改性壳聚糖(NMCS-SNCQDs)的简易方法,并对NMCS-SNCQDs进行了表征。结果表明:该方法具有成本低、便捷快速、可视化等特点;NMCS-SNCQDs保留了S,N-CQDs的良好荧光性能,可对Cr^(6+)有选择性地进行荧光淬灭响应,其临界响应浓度为52μmol/L;NMCS-SNCQDs具有很好的成凝胶性,可用于开发荧光试纸/凝胶,实现快速、实时检测水体中的Cr^(6+)污染。

钙钛矿修饰玻碳电极测定铬离子

制备了有机-无机-钙钛矿材料(C_(2)H_(7)NPbBr_(3)NCs),并用于修饰玻碳电极。使用该电极研究了Cr^(3+)的电化学行为,同时优化了Cr^(3+)浓度、溶液pH值、缓冲溶液pH值及缓冲溶液用量等实验条件。在Na_(2)HPO_(4)-C(OH)(COOH)(CH_(2)COOH)_(2)(枸橼酸)缓冲溶液(pH=5.60)中,采用循环伏安法发现,在1.0~8.0μmol·L^(-1)浓度范围内,Cr^(3+)的浓度与电流呈线性关系。所制备的修饰电极可直接用于废水中Cr^(3+)的测定,且具有较强抗干扰能力。

关于次氯酸根离子对水中六价铬测定的干扰的探讨

探讨了用国家标准方法《GB/T 7467—1987》测定水中六价铬时,次氯酸根离子在不同浓度下对测定结果的影响,同时考察了不同的抗干扰方法测定时,次氯酸根离子在不同浓度下对测定结果的影响。