Spontaneous Phase Transfer of Nanoparticulate Metals from Organic to Aqueous Media

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金属参与的水相烯丙基化反应

近30年来,水介质中碳-碳键的形成一直是研究的热点,其优越性也逐渐被人们所认知。在已发现的水相金属有机反应中,水相烯丙基化反应是研究得较多和较深入的反应之一。水相烯丙基化反应由于其发展速度较快,新的金属及金属体系参与的烯丙基化反应以及水相烯丙基化反应的机理研究不断被报道。本文综述了水相中金属参与烯丙基化反应的最新研究进展,并对新的反应机理作了简要的阐述。     

Visible-light-switchable Chalcone-Flavylium Photochromic Systems in Aqueous Media

The chalcone-flavylium photochromic system switches in aqueous media. However, the chalcone→flavylium conversion requires detrimental ultra-violet (UV) light for the switching which deters their applications in the biological domain. To address this issue, we have synthesized strategically modified chalcone scaffolds that can be reversibly switched to the flavylium forms with visible light ranging from 456 nm (blue) to 640 nm (red).     

Extraction of Organic Compounds from Aqueous Media by Amberlite XAD Resins

Abstract

Three Amberlite polymeric resins, XAD-2, XAD-4 and XAD-7, were evaluated for extraction efficiency from aqueous media of several organic compounds representing pesticides, polyaromatic hydrocarbons, phenols and phthalate esters. The three resins exhibited different extraction characteristics. The extraction efficiency of the resins was found to be dependent on pH conditions and, on the average, was best at pH7. At this pH the XAD-2 and XAD-4 resins yielded quantitative recoveries in the 90–100% range for most compounds at the 20–200ppb level. Recoveries by XAD-7 resins were lower for several compounds. The recovery of aldrin and o, p DDT under all conditions was relatively low (>68%) and showed a higher degree of variability than that obtained for the other compounds. Alkaline pH conditions were generally unfavourable for the extraction of phenolic compounds but acidification to pH2 was not found to be a necessary step for the quantitative extraction of the phenolic compounds. Acidification to pH2 further led to a decrease in the recovery of most compounds for XAD-4 resins. A combined resin column yielded extraction efficiencies comparable to the XAD-2 column at pH 7, but since the three resins possess different extraction characteristics, a mixture comprising all three is recommended for the preconcentration of organic compounds from environmental water samples containing a wide range of compounds.     

An Overview of Modified Chitosan Adsorbents for the Removal of Precious Metals Species from Aqueous Media

This mini-review provides coverage of chitosan-based adsorbents and their modified forms as sustainable solid-phase extraction (SPE) materials for precious metal ions, such as gold species, and their complexes in aqueous media. Modified forms of chitosan-based adsorbents range from surface-functionalized systems to biomaterial composites that contain inorganic or other nanomaterial components. An overview of the SPE conditions such as pH, temperature, contact time, and adsorbent dosage was carried out to outline how these factors affect the efficiency of the sorption process, with an emphasis on gold species. This review provides insight into the structure-property relationships for chitinaceous adsorbents and their metal-ion removal mechanism in aqueous media. Cross-linked chitosan sorbents showed a maximum for Au(III) uptake capacity (600 mg/g), while S-containing cross-linked chitosan display favourable selectivity and uptake capacity with Au(III) species. Compared to industrial adsorbents such as activated carbon, modified chitosan sorbents display favourable uptake of Au(III) species, especially in aqueous media at low pH. In turn, this contribution is intended to catalyze further research directed at the rational design of tailored SPE materials that employ biopolymer scaffolds to yield improved uptake properties of precious metal species in aqueous systems. The controlled removal of gold and precious metal species from aqueous media is highly relevant to sustainable industrial processes and environmental remediation.     

Electroflotation Recovery of Poorly Soluble Lanthanum Compounds from Highly Concentrated Salt Systems

Electroflotation of poorly soluble lanthanum compounds from model solutions simulating with high accuracy highly concentrated industrial salt systems was studied. The influence of various kinds of microadditives (flocculants and surfactants; cationic, anionic, and nonionic) on the efficiency of the recovery of lanthanum compounds from highly concentrated salt solutions was examined. For each supporting electrolyte (chloride, carbonate, sulfate, oxalate, nitrate), additives intensifying the process and enhancing its efficiency were found. The mean size and ζ-potentials of the dispersed phase particles were measured to account for the degrees of recovery reached in lanthanum electroflotation. A design of an installation for lanthanum recovery, allowing solution processing on the commercial scale, was suggested.     

Biosorption of Metals from Dilute Aqueous Solutions

Dilute aqueous solutions, generated or used by industry, can contain a variety of different metal ions. Various processes are suitable for reclamation of toxic metals and among them, attention is paid here to biosorption. The ability of microorganisms to remove metal ions from solution is a well known phenomenon. Industrial applications of biosorption often make use of dead biomass, which does not require nutrients and can be exposed to environments of high toxicity. Experimental laboratory batch experiments are described for actinomycetes, fungi and for activated sludge, as the metal biosorbents, providing insight into cadmium biosorption. Non-living biomass showed greater binding capacities for cadmium (a priority pollutant) than living biomass. Engineering considerations are central in decisions concerning the commercial future of biosorption and a practical solution is needed for certain problems, such as the efficient separation of metal-loaded biomass.     

Extraction of Lanthanide Nitrates in Multicomponent Aqueous-Organic Two-Phase Systems with D2EHPA

Lanthanum nitrate distribution in three-component aqueous-organic systems with D2EHPA from acetate or acetic acid–acetate solutions has been studied, it has been shown that variation in sodium acetate concentration or composition of CH₃COONa–CH₃COOH mixture can affect metal distribution ratios. It has been found that extraction in three-component mixture of 1: 1: 1 composition (aqueous solution Ln(NO₃)₃ + CH₃COONa + CH₃COOH–D2EHPA in hexane–isopropyl alcohol) can provide lanthanide separation, which is dependent on the ratio of sodium acetate and acetic acid in aqueous phase and on D2EHPA concentration in organic phase. Lanthanide–lanthanum separation factors have been calculated for the extraction of lanthanide nitrates from acetic acid–acetate solutions.     

New Reagents for Determination of the Quantum Efficiency of Singlet Oxygen Generation in Aqueous Media

Water-soluble anthracene derivatives containing carboxy, dihydroxyphosphinyl, or pyridinium fragments bound via methylene groups to 9- and 10-carbon atoms were prepared, and their spectra, solubility, and reactivity toward singlet oxygen were studied. Using sodium ,'-(anthracene-9,10-diyl)bis(methyl- malonate) as acceptor, it is possible to determine the quantum efficiency of singlet oxygen generation in aqueous solutions and in microheterogeneous media in the presence of biomacromolecules.     

Electroflotation Extraction of Valuable Components from Wash Waters of Electroplating Works,with Water Recycling

An electroflotation technology for extracting ions of heavy nonferrous metals from the wash and waste waters of electrolytic baths is proposed. The main regularities and basic parameters of the electroflotation extraction of ions of copper, zinc, nickel, chromium, and iron in the form of hydroxides, phosphates and sulfides of the metals are determined. Optimum technological parameters for the extraction of copper ions in the presence of complexing agents are established. Advantages of an electroflotation with electrocorrection of pH are shown.     

Rice Bran as an Excellent Sorbent for Heavy Metals from Aqueous Media, 1. Optimization of Conditions

In this two‐part report, the efficiency of rice bran in removal of heavy metals such as cadmium, lead, zinc, nickel, copper and iron(III) from aqueous solution is investigated. The different experimental conditions such as pH, temperature, volume of solution, bran amount, particle size, exchange time, stirring speed, etc. are studied, and the optimum conditions are selected in part 1 of this series of reports. The efficiency of bran in removal of heavy metals is presented with and without treatments. For treatment, heat or acid, alkali and salt solutions were used. The results obtained show that after treating with saturated sodium chloride solution, its efficiency for Ni²⁺ and Zn²⁺ improves. At pH 5, all studied cations have recoveries more than 93% (lead and cadmium 100%). The exchange speed is very high and has preference over the classical ion exchangers.     

Polymeric Sensors Based on Extraction Systems for Determination of Rare-Earth Metals

New polymeric sensors based on bidentate neutral organophosphorus compounds of varied structure with addition of chlorinated cobalt dicarbollide, which are highly sensitive to Fe³⁺, Y³⁺, La³⁺, Pr³⁺, Nd³⁺, and Eu³⁺ cations in a wide range of concentrations at pH 2, were suggested. The selectivity, detection limits, and pH-dependence of the potential of the sensors developed were studied. The influence of chlorinated cobalt dicarbollide on the electrochemical characteristics of the sensors was demonstrated.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005, pp. 575–580.Original Russian Text Copyright © 2005 by Kirsanov, Legin, Babain, Vlasov.     

Rice Bran as an Excellent Sorbent for Heavy Metals from Aqueous Media, 2. Determination of Related Parameters

In part 2 of this report related parameters of the rice bran (as a sorbent of heavy metals) such as exchange capacity, distribution coefficients and isotherms, etc. were studied. The obtained results show that selectivity of the bran towards heavy metals such as Cu(II), Cd(II), Fe(III), Ni(II), Zn(II) and Pb(II) is very high. Also, distribution coefficients between aqueous solution and bran are more than 10⁴ so that all cations are completely adsorbed by the bran in relatively low concentrations. The principal advantages of this sorbent are as follows: high efficiency, very high exchanging speed, cheapness (in comparison with conventional resins), performance in batch and continuous conditions and producing no environmental pollution. The only disadvantage of the bran is low exchanging capacity for some elements (but for lead it is comparable to classical resins); however, it is able to eliminate heavy metals in mg/L level and above. On the other hand, due to low cost of bran and high cost of recovery of ion exchangers there is no necessity to recover the bran. Reproducibility of the proposed method in removal of heavy metals is excellent and the relative standard deviations for eight repeated removals for all cations with the exception of iron are less than 1%.     

液／液界面电化学分析在双水相萃取中的应用

用循环伏安法（ＣＶ）研究了聚乙二醇（ＰＥＧ）－６０００／磷酸钾（Ｋ２ＰＯ４）双水相体系中各种组分对麦迪霉素推动质子在水／硝基苯（Ｗ／ＮＢ）界面上转移行为的影响，用液／液界面电化学分析技术检测了麦迪霉素在双水相体系中的分配情况，发现了麦迪霉在双水相体系中的选择性分配，其分配系数大于４４，测定的线性范围为５０～８００μｇ／ｍＬ，回收率大于９３％，     

Extraction Separation of BSA in Aqueous Two-Phase Systems of Anionic and Cationic Surfactant Mixtures

Aqueous two-phase systems (ATPS) are formed in mixtures of sodium dodecylsulfate (SDS), cetyltrimethyl ammonium bromide (CTAB), and sodium bromide (NaBr). Two different kinds of ATPS appear when CTAB and SDS surfactants are in excess, respectively. Such ATPS may provide a new, useful partitioning system for separation of bovine serum albumin (BSA). The partitioning of BSA was studied in these systems. The results show that the partitioning is affected by the electrical property, the hydrophobicity and the structure of liquid crystal (LC), which exists in the top phase of the ATPS. BSA is extracted into the top phase with higher distribution coefficient when LC and BSA are oppositely charged. The hydrophobicity of LC, which can be improved by increasing the length of alkyl group, enhances the distribution coefficient. The hydrophobicity of lamellar LC and hexagonal LC is stronger than that of cubic LC, which causes extractive capability of the former is higher than the latter.     

Mutual Influence of Rare-Earth Metals(III) in Their Joint Extraction from Aqueous Solutions with a Toluene Solution of Trialkylbenzylammonium Naphthenate

Extraction of nitrates of lanthanides(III) [La(III)-Lu(III) and also yttrium(III)] from their aqueous multicomponent systems with a toluene solution of trialkylbenzylammonium naphthenate was studied at 298 K and pH 3. Physicochemical and mathematical models describing the distribution and mutual influence of lanthanides(III) [Ln(III)] in their joint extraction from multicomponent aqueous solutions as influenced by the total Ln(III) concentration in the aqueous phase and composition of their mixture was developed.     

藻类去除水体中重金属的机理及应用

重金属污染水体的修复,以及含重金属工业废水的处理关乎地球上生物的健康发展。利用低耗能、高修复效率、环境友好、适用范围广泛的藻类去除水体中的重金属,已越来越受到研究者的关注。本文综述了国内外藻类去除水体中重金属的研究进展。分析了藻类去除重金属的生化结构;重点阐述了藻类吸附及富集重金属的机理;讨论了活藻体和死亡藻体用于水体中重金属去除的应用及影响因素,并比较了两者的适用范围及筛选标准;最后指出此领域尚存在的问题,展望了藻类去除重金属的未来发展方向。