稀土铬酵母的制备及其铬含量研究

研究了稀土元素La、Nd、Sm、Er的添加浓度分别为50μg·g-1、75μg·g-1、100μg·g-1和125μg·g-1时对富铬酵母中铬含量的影响 研究结果表明,稀土元素能够提高富铬酵母中的总铬和有机铬含量,当添加100μg·g-1Nd时,富铬酵母中的总铬含量和有机铬含量最高,分别为784.24μg·g-1和755.85μg·g-1,是未加稀土的富铬酵母的3倍以上     

稀土元素对铬酵母中铬含量影响的研究

研究了稀土化合物在铬酵母制备过程中对总铬和有机铬含量的影响作用。镧、铈、镨、钕等轻稀土化合物均能明显提高铬酵母中总铬和有机铬的含量 ,其中镧化合物对铬酵母中总铬和有机铬含量的提高作用最显著 ,总铬含量可达到 70 8.33μg·g- 1 ,有机铬含量可达到 6 39.0μg·g- 1 ,是未加稀土铬酵母样品的近 3倍 ;添加钕化合物的铬酵母中有机铬占总铬的比例最高 ,可达到 97.5 %。通过紫外光谱分析 ,发现有机铬在 2 6 0nm处有特征吸收峰 ,通过红外光谱分析 ,发现有机铬在 478cm- 1 处有特征吸收峰 ,而加稀土化合物的铬酵母样品在此两处的吸收峰值均高于未加稀土的铬酵母样品     

铬与健康

对铬与人体健康的关系进行了综述，主要内容包括：三价铬的作用、六价铬的作用和环境中的铬。     

Chromium removal technologies

Chromium can exist in different oxidation states (e.g. 0, III, VI). Chromium can be both beneficial and toxic to animals and humans depending on its oxidation state and concentration. At low concentration, Cr(III) is essential for animal and human health. Chromium(VI) compounds are highly soluble, mobile and bioavailable compared to trivalent chromium. Chromium(VI) is dangerous for humans due to its toxicity and carcinogenic properties. The presence of hexavalent chromium in waste water is a potential hazard to aquatic animals and humans. Various methods are adopted for the removal of hexavalent chromium from industrial effluents. Among these different techniques, biosorption is the most promising one. In this process, the various components present in biomaterial reduce the toxic hexavalent chromium to non-toxic trivalent chromium. Algae, fungi and bacteria have biosorption properties, and cell walls are responsible for biosorption of dead biomaterial. But this process removes chromium from waste water very slowly. So for chemical modification of biosorbents, optimization of biosorption parameters is required to increase the effectiveness of this process.     

New Chromium Enolates

Three new (η²‐acrylate)(η⁶‐arene)dicarbonylchromium complexes are reported. They were obtained either by CO/acrylate exchange in [Cr(η⁶‐benzene)(CO)₃] ( 1 ) via the photolytically generated η²‐cyclooctene intermediate or by arene exchange in [Cr(η²‐methyl acrylate)(η⁶‐benzene)(CO)₂] ( 3 ) (Scheme 1). On crystallization, [Cr(η²‐methyl acrylate)(η⁶‐o‐xylene)(CO)₂] ( 5 ) underwent partial resolution. The degree of this resolution was analyzed via X‐ray crystal‐structure determination (Fig. 1) and was correlated to the CD spectra in solution (Fig. 6), thus allowing the assignment of the absolute configuration. The reaction of [Cr(η²‐acrylate)(η⁶‐benzene)(CO)₂] complexes with cyclopentad‐1,3‐diene or 1H‐indene afforded new (η⁶‐cyclopenta‐2,4‐dien‐1‐yl)‐ or (η⁶‐1H‐inden‐1‐yl)(η³‐oxaallyl)chromium complexes (Scheme 2). A mechanism is proposed that involves arene‐ligand substitution by the diene ligand, initiated by haptotropic rearrangement of the acrylate from a η²‐ to a η⁴‐coordination mode, followed by hydride migration from the diene to the acrylate (Scheme 3). An X‐ray crystal‐structure determination of [Cr(CO)₂(η⁵‐1H‐inden‐1‐yl){η³‐CH(CH₂CF₃)C(O)OEt}] ( 8 ) reveals a metal enolate that is best described as η³‐oxaallyl species (Fig. 2). A shorter, more‐efficient route to the [Cr(η⁵‐1H‐inden‐1‐yl)(η³‐oxaallyl)] complexes was devised via the reaction of [Cr(CO)₂(η²‐cyclooctene)(η⁶‐1H‐indene)] with methyl acrylate (Scheme 4).     

Chromium(III) and Chromium(IV) Tetraphenylporphine Complexes

Stable chromium complex (AcO)CrTPP was synthesized through the reaction of meso-tetraphenylporphine with chromium(III) acetate in boiling phenol. Coordination properties of chromium porphyrin in reaction with imidazole and pyridine in o-xylene were studied by electronic absorption spectroscopy and computer modeling. A single-electron oxidation of chromium(III) complex was found to be affected by peroxide compounds. The stability of an extra complex depends on the basic properties of the extra ligand and oxidation number of the central metal atom. The complex stability correlates with the calculated energy of formation of the metal–extra ligand bond. The geometrical structure and energy parameters of hexacoordinated chromium porphyrins were calculated using the quantum-chemical method. The effect of the cis and trans position of ligands in the composition of a macrocyclic compound was established to be significant only in the extra complexes (AcO)CrTPP.     

Bacterial Reduction of Chromium

A mixed culture was enriched from surface soil obtained from an eastern United States site highly contaminated with chromate. Growth of the culture was inhibited by a chromium concentration of 12 mg/L. Another mixed culture was enriched from subsurface soil obtained from the Hanford reservation, at the fringe of a chromate plume. The enrichment medium was minimal salts solution augmented with acetate as the carbon source, nitrate as the terminal electron acceptor, and various levels of chromate. This mixed culture exhibited chromate tolerance, but not chromate reduction capability, when growing anaerobically on this medium. However, this culture did exhibit chromate reduction capability when growing anaerobically on TSB. Growth of this culture was not inhibited by a chromium concentration of 12 mg/L. Mixed cultures exhibited decreasing diversity with increasing levels of chromate in the enrichment medium. An in situ bioremediation strategy is suggested for chromate contaminated soil and groundwater.

     

铬与人体健康研究

对铬与人体健康关系作了综述，包括：铬作为人体必需微量元素的生理功能，葡萄糖耐量因子定义和结构推测，以及与人体健康有关的生理临床作用研究进展状况，以引起更多的科技工作者对这一领域的关注和重视。     

Chromium carbides and cyclopropenylidenes

Carbon tetrabromide can be reduced with CrBr₂ in THF to form a dinuclear carbido complex, [CrBr₂(thf)₂)][CrBr₂(thf)₃](μ-C), along with formation of [CrBr₃(thf)₃]. An X-ray diffraction (XRD) study of the pyridine adduct displayed a dinuclear structure bridged by a carbido ligand between 5- and 6-coordinate chromium centers. The carbido complex reacted with two equivalents of aldehydes to form α,β-unsaturated ketones. Treatment of the carbido complex with alkenes resulted in a formal double-cyclopropanation of alkenes by the carbido moiety to afford spiropentanes. Isotope labeling studies using a ¹³C-enriched carbido complex, [CrBr₂(thf)₂)][CrBr₂(thf)₃](μ-¹³C), identified that the quaternary carbon in the spiropentane framework was delivered by carbide transfer from the carbido complex. Terminal and internal alkynes also reacted with the carbido complex to form cyclopropenylidene complexes. A solid-state structure of the diethylcyclopropenylidene complex, prepared from 3-hexyne, showed a mononuclear cyclopropenylidene chromium(iii) structure.

Carbon tetrabromide can be reduced with CrBr₂ in THF to form a dinuclear carbido complex, [CrBr₂(thf)₂)][CrBr₂(thf)₃](μ-C), along with formation of [CrBr₃(thf)₃].     

铬与人体健康

介绍了铬的生理功能,指出三价铬是人体必需的微量元素,六价铬则是严重危害人体健康的有害元素,必须适量补铬和严防六价铬的中毒,才能维持人体健康。     

铬和环境保护

重金属污染是当今世界必须解决的环境污染问题之一。重金属进入环境后不易除去,它们在环境中迁移、转化和长期累积,对生物和人体产生毒害作用。本文侧重谈一谈重金属铬的污染和环境保护问题。     

超痕量六价铬分析仪检测制革场地中六价铬

为解决制革等污染场地中Cr(III)-有机络合物会干扰六价铬测定的问题,通过优化仪器色谱条件、在现有行标基础上改进前处理方式,使用超痕量六价铬分析仪检测六价铬,并通过在土壤中投加低、中、高浓度的三价铬、六价铬以及Cr(III)-有机络合物考察三价铬、色度和Cr(III)-有机络合物对六价铬测定的影响。结果表明仪器的最佳色谱条件为：流动相浓度为0.1 mol/L、流动相pH为9、浓硫酸用量为5 mL、流动相流速为1.2 mL/min,衍生试剂流速为0.7 mL/min。样品预处理方式由抽滤提取改进为离心提取,上机前样品pH无需调节,可提高检测效率;该方法与现行行标相比操作简便、耗时短且不受三价铬、样品色度及Cr(III)-有机络合物的干扰。方法精密度和正确度均显著提高,相对标准偏差为1.7%~5.2%,回收率均在94.6%~103%之间。通过与液相色谱-电感耦合等离子体质谱仪对实际样品测定结果的统计学检验发现,结果无显著性差异。该方法适用于制革、电镀等富含Cr(III)-有机络合物场地中六价铬的测定。     

Chromium(III)-Selective Electrodes Based on Titanium Dichalcogenides Intercalated with Chromium

Solid-contact chromium-selective film electrodes were prepared on the basis of titanium diselenide and titanium ditelluride intercalated with chromium. It was found that the titanium diselenide–based electrode with the lowest concentration of the intercalant (Cr_0.1TiSe₂) exhibits the best properties and provides the determination of 5 × 10^–5–1 × 10⁰M chromium(III) in the pH range 2.75–4.7. The slope of the electrode function for all chromium-selective electrodes depends on the pH of the solution and is close to the theoretical slope for the singly charged Cr(OH)⁺ ₂ ion. It was demonstrated that chromium-selective electrodes can be used as indicator electrodes in determining chromium(III) by direct titration with the potentiometric detection of the titration end-point using EDTA and KMnO₄as titrants.     

Interaction of Chromium with Thiol-Containing Proteins Evidence for The Formation of Trivalent Chromium

Abstract

In this paper a method for the separation of protein-bound chromium and trivalent and hexovalent chromium is described, as well as the reduction of hexovalent chromium to the trivalent form by sulfhydryl containing proteins such as albumin and hemoglobin.     

Spectrophotometric Determination of Trace Chromium(VI) in Mass Chromium(III)

There is little conclusive evidence of the toxic effects of Cr(III) so far, but Cr(VI) has carcinogenic activity, so the analysis of the chromine ions is very important in environmental research and the quality control of industry products. Usually Cr(III) and Cr(VI) interfere with each other in the species analysis, the measurement of Cr(VI) of numerous previous papers is related to the Cr(VI) samples, which contain a little Cr(III). When the amount of trivalent chromine exceeds ten …