H+反应对土壤重金属分级提取形态分析的影响

探讨了普遍存在于重金属分级提取形态分析体系中的H 反应的影响因素,分析了H 反应与提取剂的选择性、金属离子的重分配现象的关系,以及H 反应对分级提取法数据结果的影响,并对分级提取方法作了进一步的改进。研究表明提取剂pH、提取体系、土壤理化性质及土壤 溶液比是影响H 反应的主要因素;H 反应可降低提取剂选择性,减弱金属离子的重分配能力,影响分析结果的有效性,且对于不同的重金属离子、不同的提取体系,H 反应所造成的影响不同。     

KIO_3-KSCN-H~+反应体系的非线性动力学研究

研究了 KIO3-KSCN-H+反应体系在连续搅拌流动反应器 ( CSTR)中的非线性动力学行为 .在 CSTR中 ,该反应体系的 Pt电极电位显示出持续振荡现象 ,振荡的浓度范围非常宽 .通过酸度及各种金属离子对体系振荡行为影响的研究发现 ,对振荡体系具有催化作用的可能物种是 H+ 离子而不是金属离子     

KIO3-KSCN-H+反应体系的非线性动力学研究

研究了KIO₃-KSCN-H+反应体系在连续搅拌流动反应器(CSTR)中的非线性动力学行为.在CSTR中,该反应体系的Pt电极电位显示出持续振荡现象,振荡的浓度范围非常宽.通过酸度及各种金属离子对体系振荡行为影响的研究发现,对振荡体系具有催化作用的可能物种是H+离子而不是金属离子.     

土壤中重金属铊的分级提取形态分析法研究

以自然高铊污染土壤为样品, 对BCR标准分级提取形态分析法中争议较大的HAc和NH2OH·HCl提取剂pH、提取剂浓度和提取体系温度对土壤中相应形态Tl提取量的影响进行了研究。实验发现标准条件的HAc提取体系可有效提取土壤中可交换态的Tl, 而标准的NH2OH·HCl提取体系不能有效提取土壤中易还原态的Tl。根据实验结果, 对标准BCR法进行如下改进: NH2OH·HCl提取剂pH由2.0酸化至1.5, 提取剂浓度由0.1mol/L增至0.5 mol/L, 提取体系温度由室温(28℃)增至60℃; 其他提取条件不变。     

CMPO-离子液体体系对Ce3+的萃取

本文研究了CMPO[辛基(苯基)-N,N-二异丁基氨甲酰基甲基氧化膦]溶于疏水性离子液体BmimNTf2(1-丁基-3-甲基咪唑双三氟甲磺亚酰胺盐)和BmimPF6(1-丁基-3-甲基咪唑六氟磷酸盐)对硝酸水溶液体系中Ce3+的萃取行为,详细考察了稀释剂、酸度、金属离子浓度、盐析剂、萃取剂浓度、温度等对萃取性能的影响。研究结果表明:离子液体BmimNTf2体系中Ce3+的萃取率远高于BmimPF6体系;硝酸浓度、金属离子浓度的增大会导致萃取率下降;温度升高萃取率降低;萃取剂CMPO浓度升高萃取率增大;而盐析剂(C=0.001~1 mol.L-1时)对Ce3+的萃取几乎没有影响。萃取机理的推测表明萃取反应形成三配位的配合物,其结构为Ce3+.3CMPO,萃取平衡常数为lgK=6.49,反应焓变为-47.29 kJ.mol-1。     

铜和铝离子/UV催化臭氧降解偶氮二异丁腈废水研究

利用多相催化臭氧(O3)工艺处理偶氮二异丁腈(AIBN)废水,探讨不同催化O3体系(Cu2+、Al3+、Cu2++Al3+/UV催化O3)对AIBN废水中氰类污染物的降解特性,并对不同催化O3体系的动力学特性进行研究。结果表明,金属离子对催化O3工艺的处理效率具有明显影响,不同催化O3工艺对CN-去除作用都呈现起始去除速率较高而后减弱的特点,其中Cu2+和Al3+共同催化O3工艺的整体去除率较高,优于单独Cu2+和Al3+的催化性能。这可能是由于p H变化、金属离子与CN-配合作用、金属离子和O3作用的综合影响结果。动力学研究结果表明,不同催化O3体系降解AIBN废水中的CN-污染物的氧化反应符合准一级动力学反应,表观反应速率常数k在0.0245~0.00301 min-1之间。     

HEHEHP-HCl-NaAC体系萃取铥的机制研究

针对工业上广泛应用的氨水皂化HEHEHP[2-乙基己基磷酸单乙基己基脂]萃取剂分离稀土元素产生含有很高浓度NH+4的废水,对环境污染严重的问题,通过在稀土氯化物溶液中加入配合剂醋酸钠(CH3COONa),采用非皂化的HEHEHP萃取剂萃取重稀土元素Tm。研究了该体系中水相酸度、有机相浓度、乙酸钠浓度等因素对Tm3+分配比的影响。结果表明:HEHEHP-HCl-Na AC体系对Tm3+萃取过程遵循阳离子交换机制;萃取液中形成的乙酸-乙酸盐缓冲溶液能够维持萃取水相酸度恒定,萃取过程中有机相不再需要皂化,有效避免HEHEHP皂化产生含NH+4废水污染环境的问题。     

N,N′-二(十二烷基)乙二胺二乙酸萃取汞的研究

研究了N ,N′ 二 (十二烷基 )乙二胺二乙酸 (简写为H2 R2 Y)的氯仿溶液对汞 (Ⅱ )的萃取行为。考察了酸度、萃取剂浓度、相比及温度等因素对萃取率的影响 ;用电导法及摩尔比法测得萃合物的摩尔比为 1∶1 ;测定了新试剂H2 R2 Y对Hg2 与Fe3 、Co2 、Ni2 、Zn2 、Cr3 、Mn2 等金属离子的分离效果 ;并根据分配比与温度的关系求出了萃取反应的ΔH0 、ΔS0 、ΔG0 和lgKex值 ,该萃取反应为放热反应。     

H2O2氧化降解海藻酸钠

研究了清洁高效的氧化剂H2O2对海藻酸钠的降解,探讨了溶液pH值、反应温度、H2O2用量及金属离子浓度对降解速度的影响. 结果表明,随着溶液pH值的降低、反应温度的升高及H2O2用量的增加,降解速度加快. 当反应pH=5.3、反应温度50 ℃、H2O2用量0.5%时,反应2 h即可降低海藻酸钠的分子量. 4 mg/L的Cu2+或Fe2+可明显加快降解速度,反应30 min的粘度变化相当于不加Cu2+或Fe2+时300 min的变化. GPC结果表明,海藻酸钠被氧化降解后,分子量下降,分布变宽;FTIR显示降解前后海藻酸钠的糖环结构没有改变,主要是糖苷键的断裂.     

β-蒎烯和马来酸酐的反应及产物表征

研究了β-蒎烯和马来酸酐的烯反应、溶剂中自由基共聚反应和本体热共聚反应,得到了β-蒎烯和马来酸酐烯反应产物和共聚产物,并用IR、1H NMR、13C NMR、GPC、DSC进行表征,研究了引发剂浓度、溶剂体系、单体配比、温度等因素对产物的影响.对聚合物进行皂化改性,测量了皂化物浓度对水表面张力的影响.     

A rapid fractionation method for heavy metals in soil by continuous-flow sequential extraction assisted by focused microwaves

A microwave-assisted continuous-flow sequential extraction system was developed for rapid fractionation analysis of heavy metals in soil. Insertion of pressure-adjusted air between the extractants provided stable flows of the extractants without mutual mixing and back-pressure influence of a column packed with soil, thereby facilitating reliable continuous-flow extractions. In addition, use of pure water as a pumping solvent removed metal contamination because of direct contact between corrosive extractants and the pump containing metallic materials. Focused microwave irradiation to the soil accelerated the selective extractions of the acid-soluble and reducible fractions of heavy metals in soil in the first and second steps of the sequential extraction conditions, as defined by the Commission of the European Bureau of Reference (BCR). The microwave-assisted continuous-flow extraction provided high correlations in amounts of six heavy metals except Zn in the first step and Cu in the second step extracted from a reference sludge soil, BCR CRM 483, with a conventional batchwise extraction proposed by BCR; continuous-flow extraction assisted by conductive heating provided lower correlations for all the six metals. The proposed method drastically reduced the time required for the sequence extraction to ca. 65 min without losing accuracy and precision of the fractionation analysis of heavy metals in soil, whereas the BCR batchwise method requires ca. 33 h. An erratum to this article can be found at     

Synergistic solvent extraction of Eu, Sr and Cs into chlorobenzene solutions of the three conformers of tetrathiocalixarene and dicarbollide

Solvent extraction of several long-lived fission products from diluted nitric acid in pronounced synergistic systems involving dicarbollide and conformers of a specific thiacalix[n]arene were investigated using mainly chlorobenzene as the diluent. The following factors were experimentally investigated: molar ratio of the two extractants, total extractants concentration, aqueous acidity, nature of the mineral acid used, relative phase volumes, repeated extractions and metal concentration. Data are given on the rather slow kinetics of extraction and stripping, limited chemical stability of the extractants, selectivity and interference of foreign metals. The three different conformers of the basic compound with identical chemical composition exhibit very differing extraction properties. The plots of distribution ratios of all metals tested versus the varying concentration of one extractant keeping the concentration of the other extractant constant invariably exhibit maxima, interpreted as the result of an existence of several extracted species in the extract. Suggestions are given concerning possible practical applications of two of the conformers studied.     

海湾河口表层沉积物中重金属形态连续萃取方法的优化研究

采用单一萃取程序对建立的重金属形态连续萃取方法的萃取条件进行优化.分别以Ca和Mg、Fe、有机质(OM)和酸可挥发性硫(AVS)作为萃取剂释放酸溶态、还原态、有机质结合态和硫化物结合态等重金属目标形态的表征参量,考察萃取剂对相应目标形态的萃取能力和选择性.分别根据表征参量和重金属在萃取溶液中的含量变化确定最优萃取时间和萃取样液比.结果表明,优化萃取条件后,萃取剂对目标形态重金属均有很强的释放能力.酸溶态萃取剂对其它非残留态影响很小;还原态萃取剂除对酸溶态有少量提取外,对其它形态影响较小;有机质结合态萃取剂对硫化物结合态有少量萃取,对其它形态影响较小.硫化物结合态在酸溶态、还原态和有机质结合态之后萃取,避免了对这三种形态的影响.优化后的连续萃取方法对重金属形态有较好的选择性,可对海湾和河口表层沉积物中重金属的目标形态进行较为合理地分离和评价.     

Extraction of scandium ions by new aminophosphinyl extractants

Extraction of Sc(III) ions by new aminophosphinyl compounds containing one or two methylenediorganylphosphinyl groups at the nitrogen atom was studied with a target of the development of effective and selective extractants of trace elements. The selection of extractants was due to their high hydrolytic stability in the acid media, commonly used at the extraction of metal ions in the industrial hydrometallurgical processes. The study of extraction of hydrogen chloride and nitric acids with the selected aminophosphinyl compounds allowed a discovery of substances with the low basicity, which were characterized by the low coefficient of the acids extraction. Highly effective extractants of Sc(III) were found possessing high coefficients of extraction and high degree of selectivity in the separation of Sc(III) ion from the ions of satellite metals.     

Die entwicklung edelmetallselektiver extraktionsmittel und ihre anwendbarkeit in der analytischen chemie

Summary The classical fire assay technique is still the most important procedure for the isolation and determination of precious metals. However, the lead collection system is basically suitable for extracting gold and silver, less for platinum, palladium and the rare precious metals. Extensive corrections are required to achieve accurate results. Many attempts are published to improve the situation by applying alternate collectors, additional chemical separations and instrumental determinative methods, such as atomic absorption and plasma emission spectrometry.Promising methods could be employed if certain separating media (solvent extractants, ion-exchange resins) are provided which extract precious metals selectively and reversibly. In such a case the final calibration step can be carried out with standard solutions of definite composition.The designing of ler made extractants has to consider the complex nature of the solution chemistry of precious metals. Hence, the relationship between metal properties and solvent extraction and ion exchange is briefly surveyed. The outlook with respect to the authors' research activities is focussed on the synthesis, characterization and application of new organic liquid and solid extractants (modified polystyrene and silica gel). These materials are based on chelating formazans and ion-exchanging tetrazolium salts. The selectivity, efficiency and mechanism of metal extraction and re-extraction are reviewed with respect to the effects of substituents attached to the metal binding groups, the influence of organic solvents and the nature of various supports (silica gel, polystyrene). Certain analytical applications are presented, e.g. the determination of silver, gold, platinum and palladium by means of formazan extraction, sorption on to tetrazolium-resins and DCP-emission spectrometry. The methods offer the advantages of selectivity and simplicity.

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Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet     

A Short Review of the Separation of Iridium and Rhodium from Hydrochloric Acid Solutions by Solvent Extraction

Iridium and rhodium are among the platinum group metals. The properties, production processes, and aqueous chemistry of both metals are reviewed. The separation of Ir(IV) and Rh(III) from hydrochloric acid solution is dependent on the characteristics of the solvent extraction systems. In most of the extraction conditions, Ir(IV) is selectively extracted over Rh(III) by either amines or neutral extractants. Rh(I) can be selectively extracted over Ir(III) by neutral extractants after Rh(III) is reduced in the presence of a reducing agent. The separation of these two metals using cationic extractants has also been reported. Although selective extraction of one metal over the other is possible, more efficient solvent extraction systems need to be developed.     

Comparison of three sequential extraction procedures (original and modified 3 steps BCR procedure) applied to sediments of different origin

The 3 steps sequential extraction procedure proposed by the Standards Measurements and Testing program (SM&T--formerly BCR) of the European Union has been applied for the speciation of metals in sediments. Results obtained by the application of the BCR standardized procedure were compared to those of two four step sequential extraction procedures, which are different from the BCR procedure only for the introduction of an additional step with NaOCl, as 2nd and 3rd step respectively. Five different metals have been taken into consideration: Cd, Cu, Ni, Pb and Zn. The analytical performances of the laboratory have been evaluated using three certified reference materials: the BCR 601 lake sediment for the BCR sequential extraction procedure, PACS-1 and MESS-1 for total metal concentration. Results showed that the efficiency of NaOCl treatment is higher or at least equal to that of H2O2 treatment and that its selectivity is quite satisfying. Moreover the NaOCl treatment doesn't significantly influence the extraction of the easily reducible fraction.     

Single and Sequential Extraction in Sediments and Soils

Abstract

The determination of extractable trace metal contents in soils and sediments is currently performed in many laboratories to assess the bioavailable metal fraction (and related potential phyto-toxic effects) and the importance and possibility of mobilization of trace metals from polluted soil, sludge and sediment upon landfill application. Single and sequential extraction schemes are used for the assessment of the different “forms” of trace metals (e.g. “mobile/bioavailable”, “carbonate-bound” etc.). The lack of uniformity in the different extraction procedures used throughout the world does not allow the results to be compared or the procedures to be validated which has led to many criticisms in the past few years. Moreover, the lack of suitable reference materials for this type of operationally defined determinations did not enable the quality of the measurements to be controlled. Owing to the need for establishing common schemes for single and sequential extractions as well as for the improvement of the quality of extractable trace metal determinations in soil and sediments, the Community Bureau of Reference (BCR) has organised a project which results along with the state of the art of extractable trace metal determinations, use and applicability of extraction schemes and analytical limitations were decided to be thoroughly discussed in a workshop. This paper presents its main conclusions.     

Selective extraction of palladium(II) with theophylline derivatives.

Theophylline derivatives with some kinds of alkyl chains were synthesized and used in extraction experiments involving metal ions. Theophylline derivatives have exhibited a high selectivity for palladium over other precious metals and base metals. The extraction of palladium from acidic chloride media has been investigated using theophylline derivatives (= RN) as extractants. Palladium(II) was found to be extracted with 7-octyltheophylline according to the following reaction: PdCl2 + 2RN <==> PdCl2(RN)2. The extraction equilibrium constant was determined to be K = 2.67 x 10(8) ( moldm(-3))(-2). In addition, the stripping of palladium was performed to an extent of 100% by a single batchwise treatment with a 1.0 mol dm(-3) ammonia solution. The stoichiometric relation in the extraction of palladium was supported by an analysis using mass spectrometry.