重金属离子在水泥砂浆中的浸出性研究

采用在生料中掺重金属化学试剂在实验室条件下烧制出的熟料,研究了重金属元素在水泥应用过程中的流向,模拟德国的水槽试验法测试了水泥砂浆中重金属离子Ph、Cd、As和Cr在不同pH值浸出液条件下的长期浸出行为,探讨了酸性条件对重金属浸出的影响。结果表明：Pb、Cd及Cr^3＋均可以稳定固化在砂浆内部,长期浸出固化率可达99．9％以上;酸性条件可以抑制Cr^3＋的浸出,促进Cr^6＋的浸出,对Pb、Cd、As的浸出影响较小。     

扬州古运河三湾段沉积物中重金属潜在生态风险评价及形态变化特征

扬州古运河是京杭大运河最古老的一段,为了解沉积物中重金属污染状况,采用Hakanson潜在生态风险评价扬州古运河三湾段沉积物中重金属Cr、Ni、Cu、Zn、Cd和Pb的风险水平,并对形态分布特征进行了研究。结果表明:扬州古运河六种重金属的含量均高于背景值,其中Cd含量为其背景值的13.15倍。沉积物中重金属的累积潜在生态风险指数RI高达456.55,沉积物的总体潜在生态风险等级为强。沉积物中Pb的主要赋存形态主要以铁锰氧化态存在,而Zn和Cd主要以酸可溶态形式存在,说明这三种重金属的潜在生态风险水平较高。     

用DIOSO从水溶液中萃取镉的研究

为探究亚砜类化合物对水中重金属镉的萃取效率和萃取机理，报道了利用二异辛基亚砜(DIOSO)萃取水溶液中镉的情况，实验制备了DIOSO，以其为萃取剂探索其对水溶液中镉的萃取情况，得出最佳萃取条件，在此条件下最高萃取率为99.7%。为达到萃取剂的回收循环利用，实验研究了不同反萃剂对Cd(Ⅱ)的反萃情况，得出利用0.2 mol/L NaOH为反萃剂时能把有机相中的Cd(Ⅱ)全部洗脱出来，反萃率达99.86%。在此基础上，结合光谱和热力学分析，DIOSO对Cd(Ⅱ)的萃取过程可能是离子间发生了缔合作用。DIOSO对水中Cd(Ⅱ)的成功萃取，可以为工业废水污染中Cd(Ⅱ)的处理提供重要理论研究基础。     

崇明岛典型河道底泥重金属污染及农用潜在风险评价

采集了崇明岛型环岛运河综合整治工程示范段（南横引河老激港段）的底泥样品,对其中的Cd、As、Cr、Cu、Zn、Pb、Ni等重金属元素的浓度进行了分析测定。结果表明,所采集的表层底泥中Cd、As的含量均低于最低检测限。Cr、Cu、Pb、Ni的最高浓度都出现在南横引河与老激港交汇处,但相对于全球背景值而言,其最高浓度都不超过背景值的两倍。运用Pearson相关系数法发现,Cr、Cu、Zn、Ni、Pb具有很强的相关性,即这几种重金属可能来自同一污染源。Hakanson潜在生态危害指数法评价结果发现,研究区域河道底泥重金属生态风险较小,其重金属含量均远低于污泥农用标准（GB18918—2003）以及国际上相关标准,所以示范河段疏浚底泥农用应该是安全的,但需要进行跟踪监测与评价。     

炼油废催化剂中分离有害重金属工艺条件研究

以炼油废催化剂为原料,用硫酸、盐酸、硝酸3种不同的酸处理含高镍等重金属元素的炼油废催化剂。采用火焰原子吸收光谱法测定其中镍、汞、铅、铬、镉5种重金属的含量,探讨炼油废催化剂中分离有害重金属的最佳工艺条件。结果表明：在煅烧温度为400 ℃,煅烧时间为3 h,质量分数为10%的硫酸,液固体积比为5∶1,浸出时间为5 h的条件下,镍、汞、铅、铬、镉的浸出效果最好。     

Removal of lead (II) and cadmium (II) from aqueous solutions using spent Agaricus bisporus

The sorption of Pb and Cd from aqueous solutions by spent Agaricus bisporus was investigated. The effects of contact time, pH, ionic medium, initial metal concentration, other metal ions presence and ligands were studied in batch experiments at 25°C. Maximum sorption for both metals was found to occur at an initial pH of around 5.5. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacities of 0.2345 and 0.1273 mmol g^?1 for Pb and Cd respectively. Kinetic data followed the pseudo‐second‐order kinetic model. The presence of NaCl and NaClO₄ caused a reduction in Cd sorption, while Pb sorption was not remarkably affected. The presence of other metals did not affect Pb removal, while the Cd removal was much reduced. HCl or EDTA solutions were able to desorb Cd from the spent Agaricus bisporus (SAB) completely, while an approximately 60% and 15% desorption yield was obtained for Pb when HCl 0.01 mol L^?1 or EDTA 0.001 mol L^?1 were used, respectively. The results of FTIR, SEM and EDX analysis indicated that other mechanisms, such as surface complexation and electrostatic interactions, must be involved in the metal sorption in addition to ion exchange. © 2012 Canadian Society for Chemical Engineering     

Extraction of Soft Metals from Acidic Media with Nitrogen-Donor Ligand TPEN and its Analogs

Abstract

Soft metals were extracted from acidic solution (pH 1 to 4) using two hydrophobic analogs of N,N,N′,N′-tetrakis[2-pyridyl-methyl]-1,2-ethylenediamine (TPEN). N,N,N′,N′-tetrakis[4-(2-butyloxy)-2-pyridyl-methyl]-1,2-ethylenediamine (TBPEN) and N,N,N′,N′-tetrakis(2-quinolinylmethyl)-1,2-ethylenediamine (TQEN) have shown enhanced extraction performance in more acidic media than TPEN. TBPEN showed enhanced extraction of Cd(II) from highly acidic solutions (pH < 2). This is because the distribution of this ligand to the aqueous phase is suppressed by the formation of a metal complex encapsulating Cd(II) with TBPEN. The percent extraction of Cd(II) for TBPEN was 100% at pH 1, whereas TPEN extracts less than 10% of the Cd(II) under these conditions. TBPEN also exhibited selective extraction of a variety of soft metals, such as Au(III), Pt(II), Pd(II), and Cd(II), from the acidic solution at pH 1. These results suggest that a hydrophobic TPEN analog combining alkyl chains to four pyridyl groups is applicable to the practical extraction process of soft metals.     

电感耦合等离子体发射光谱仪检测玩具中有害元素

对不同材料类型玩具中8种重金属元素(As、Pb、Cr、Ba、Se、Sb、Hg、Cd)进行测定并分析,选用不同浓度的盐酸溶解样品,样液定容后用电感耦合等离子体发射光谱仪(ICP-AES)进行测定.其涂层、塑胶、色粉、PVC皮革样品中各重金属含量符合GB 6675-2003标准,为合格品;软胶中Pb重金属元素含量超出标准范...     

微波消解ICP-AES法评估蔬菜重金属污染情况

采用微波消解法对惠州市五个县区采集的71个蔬菜样品进行前处理,用ICP-AES测定蔬菜中As、Cd、Cr、Cu、Ni、Pb、Zn等7种元素含量,并对五个县区蔬菜重金属污染情况进行统计分析。结果表明:五县区蔬菜主要受Cd和Zn的污染,As、Cr、Cu、Ni、Pb等含量均未超过国家限量标准,叶菜类蔬菜重金属含量相对较高,瓜果类及卷心类蔬菜重金属含量比较低。     

广州河涌底泥重金属污染及潜在生态风险评价

通过对广州市区六条河涌底泥样品重金属总量的实验分析,探讨河涌重金属污染的分布特征,并进行潜在生态风险评价。结果表明:除Cu之外,Ni、Cr、Cd、Pb、Zn、Fe的平均含量远高于广东省土壤重金属环境背景值;从富集系数看,Zn的富集程度最高,其次是Cd、Pb、Cr、Cu。;由潜在生态危害系数i r E的平均值可知各重金属元素对生态风险的影响程度大小依次为Cd>Pb>Zn>Cr>Cu。     

Solid Phase Extraction and Preconcentration of Trace Heavy Metal Ions in Natural Water with 2,2′‐Dithiobisaniline Modified Amberlite XAD‐2

Abstract

A solid phase extraction and preconcentration methodology utilizing a new chelating resin is described for the separation of Cd, Ni, Co, Cu, and Zn. The chelating resin matrix was prepared by covalently linking 2,2′‐dithiobisaniline synthesized from 2‐aminothiophenol with the benzene ring of polystyrene‐divinylbenzene resin Amberlite XAD‐2 through a –N?N– group. Its adsorption and preconcentration behavior for Cd, Ni, Co, Cu, and Zn in aqueous solution was studied using batch and column procedures in detail. The newly designed resin quantitatively adsorbs Cd, Ni, Co, Cu, and Zn above pH 5.0. Subsequent elution with 2 M HCl readily strips the sorbed metal ions from the resin. The sorption capacity is 360, 230, 170, 200, and 150 mol g^?1 for Cd, Ni, Co, Cu, and Zn, respectively. Their preconcentration factors are 80–200. The time for 80% sorption was less than 10 min for all five metal ions. The effects of electrolytes on the preconcentration were also investigated with the recoveries >95%. The procedure was validated by analysis of a standard reference river sediment material (GBW 08301 China). The developed method was successively utilized for the determination of Cd, Ni, Co, Cu, and Zn in tap water and river water by flame atomic absorption spectrometry (FAAS) after column SPE and preconcentration. The 3σ detection limits for these metal ions were found to be 0.10, 0.34, 0.42, 0.16, and 0.52 g L^?1, respectively. The relative standard deviation was <10% for the determination of 10 g each of Cd, Ni, Co, Cu, and Zn in a 100 mL water sample.     

Solvent Extraction Separation of Chromium(VI), Iron(III), Cobalt(II), and Nickel(II) with Di-n-pentyl Sulfoxide

Abstract

Di-n-pentyl sulfoxide (DPSO) was employed for the solvent extraction separation of some transition metals from hydrochloric acid medium. It was found that chromium(VI) gets extracted at low acid concentrations (3 to 4.5 M), and iron(III) and cobalt(II) only above 5 M HCl. Nickel was not extracted at any of the test conditions. These transition metals were separated from one another by suitable choice of the extraction conditions.     

The Solvent Extraction Performance of N,N’-Dimethyl-N,N’-Dibutylmalonamide Towards Platinum and Palladium in Chloride Media

The solvent extraction performance of N,N’-dimethyl-N,N’-dibutylmalonamide (DMDBMA) in 1,2-dichloroethane (1,2-DCE) towards platinum(IV) and palladium(II) in hydrochloric acid media was systematically evaluated. Pt(IV) extraction (%E) increases with the HCl concentration in the aqueous phases, being always higher than 72%, whereas Pd(II) extraction decreases from 65% at 1 M HCl to 22% at 8 M HCl. Several stripping agents for the two metals were tested: Pt(IV) is successfully recovered by a 1 M sodium thiosulfate solution, whereas the best result for Pd(II) was achieved with 0.1 M thiourea in 1 M HCl. The loading capacity of DMDBMA for Pt(IV) is high, and data obtained from successive extraction-stripping cycles suggest a good DMDBMA stability pattern. Attempts to replace 1,2-DCE by more environmentally-friendly diluents showed, in general, worse %E for Pt(IV). The dependence of Pt(IV) distribution coefficients on DMDBMA and chloride ion concentrations, as well as on acidity, are the basis of a proposal for the composition of Pt(IV) extracted species.     

Zirconium and Hafnium Separation,Part 1. Liquid/Liquid Extraction in Hydrochloric Acid Aqueous Solution with Aliquat 336

Abstract

The extraction of zirconium and hafnium from aqueous HCl solutions by means of Aliquat 336 in organic diluents was systematically studied. The following three aspects were discussed: the extraction dependence on HCl, the Aliquat 336 concentrations, and the nature of diluents. Both of the metals were stripped with deionized water and the influence of phase ratio on the efficiency of the stripping has been investigated. The stoichiometry of the extracted Zr and Hf species from single metal ion were studied and a possible extraction mechanism for the Zr‐Hf mixture is discussed in the light of the results obtained.     

Décontamination à l'échelle pilote de sédiments pollués en métaux toxiques par lixiviation chimique et biologique

Pilot studies were carried out to evaluate different options for metal‐polluted (Cd, Cr, Cu, Ni, Pb and Zn) sediment decontamination. Chemical and biological leaching tests were done in a 350‐L capacity stirredtank reactor. The use of short acidic sediment washing steps (pH 2.0–3.0) was not an efficient approach for metal removal. The addition of an oxidant agent during the first washing step resulted in a large increase of removal yields for Pb (53–76%), Cd (54–92%) and Zn (69–93%). However, other metals were not well leached from sediments: Cr (6–30%), Cu (0–34%) and Ni (1–16%). The bioleaching treatment, with or without chemical washing steps, allows very good removal yields for Cd (82–100%), Cu (44–70%) and Zn (80–87%). On the other hand, this method was not efficient to remove other metals like Cr (6–16%), Ni (12–21%) and Pb (14–33%). The metals solubilized by chemical and/or biological leaching techniques can be efficiently removed from solution by precipitation using lime.     

铜污泥中重金属形态分布及浸出毒性分析

结合目前有色冶金工业上普遍采用的石灰铁盐法工艺特点,首次采用改进的BCR连续提取法与毒性浸出实验相结合的方法对铜污泥（中和渣与铁砷渣污泥）的重金属形态分布与浸出毒性进行了系统的研究。结果表明：采用改进的BCR方法对铜冶炼污泥重金属元素形态进行提取,形态提取具有较高的回收率;As、Zn、Pb与Cd为中和渣与铁砷渣污泥中主要的重金属元素（质量含量As＞Zn＞Pb＞Cd）,其中中和渣含As高达58 566 mg/kg（折合5.85%）,铁砷渣含As为12 582 mg/kg（折合1.26%）;两种重金属形态分布差异主要体现在As的形态分布上,铁砷渣污泥中重金属稳定性较好,特别是砷的稳定性较中和渣高;中和渣污泥中,As主要以弱酸态形式存在（占68.01%）,Zn、Pb与Cd主要以残渣态存在;铁砷渣污泥中,As、Zn、Pb与Cd主要以残渣态存在,其中残渣态As占59.21%;浸出毒性结果显示两种污泥中砷的浸出毒性都远远超过国标GB 5085.3-2007规定值,因此铜冶炼厂污泥属于含高砷危险废弃物,而以弱酸态As为主的中和渣污泥浸出毒性较高,而主要以残渣态As存在的铁砷渣污泥浸出毒性较低。     

铜镉渣综合利用研究

利用铜、镉和锌氧化还原电位相差较大的原理,对铜镉渣有价金属进行了分离。结果表明,控制浸出温度为50 ℃、硫酸质量分数为17%、液固体积质量比为4 mL/g、浸出时间为2.5 h时,金属铜可以得到优先分离。采用二段逆向锌还原镉,一段采用连续加锌置换,锌粉加入量为理论量的90%,加锌时间控制在20 min左右,二段置换中锌加入量为理论量的1.2~1.3倍,溶液中99.6%的镉被除去。除镉后溶液除钴后,硫酸锌溶液能够满足电锌要求。     

异戊醇从氯化物-磷酸体系中萃取盐酸的动力学

采用上升液滴法研究异戊醇萃取盐酸的动力学,考察二相接触面积、水相中初始盐酸、磷酸浓度对盐酸萃取速率的影响,以比较磷酸和盐酸的萃取行为。实验结果表明,盐酸的初始正向萃取速率与二相界面积无关,随水相初始盐酸、磷酸浓度的增大而增大,异戊醇萃取盐酸可能属相内反应控制模式。水相中盐酸的存在促进磷酸的萃取,用较高浓度的工业盐酸分解开阳磷矿有利于湿法磷酸的分离和净化。经非线性最小二乘法回归实验数据,得出25℃时异戊醇萃取盐酸的动力学方程,其决定性指标为0.993 9,速率常数的相对标准偏差为7.69%。     

Assessment of Cadmium in Aquatic Sediment Using Dialysis Samplers with Ion-Exchangs-Resin Collection

ABSTRACT

Simultaneously extracted metals (SEM) and acid volatile sulflde (AVS) show the potential for toxicity on the basis of their ratio. Accordingly, we spiked cadmium in a range for which Cd/AVS ratios were from 0.2 to 10 in the sediment with its weight about 8 kg in each batch. Dialysis samplers with a cation ion-exchange resin (Dowex 50W-X4) collection were used in a laboratory for the determination of free cadmium concentrations in pore water of the collected sediment. When equilibrium was reached among cadmium in pore water, sediment, and ion-exchange resin, cadmium exchanged onto resin phase was regenerated with 1 N hydrochloric acid (OPTIMA grade) and determined using an atomic absorption spectrophotometer (Zeeman 5000) with a graphite furnace accessory. Cadmium determined using the dialysis sampler is considered as free cadmium which is related to the metal bioavailability toward aquatic biota. The developed methodology provides a new technique for assessment of free metal in aquatic sediment systems.     

Verminderung des Cadmium-Gehaltes von Rohphosphaten und Mineraldüngern

Reducing the cadmium content of crude phosphates and mineral fertilizers . Crude sedimentary phosphates generally contain cadmium together with traces of other heavy metals. These Cd traces generally end up in fertilizers produced from the crude phosphates. Processes have therefore been developed to separate the Cd from the crude phosphate or from the crude phosphoric acids arising therefrom as intermediates. In this way, the Cd content of the crude phosphate can be reduced to less the 10% of its original value, and to 50% thereof by extractive treatment with acidic calcium nitrate solution. Older calcination processes for crude phosphate have been improved to give residual Cd contents of 10 to 50% at temperatures of 800 to 1000°C. Cadmium can be removed almost quantitatively from crude phosphate by means of dialkyl dithiophosphoric acid esters by extraction, binding to adsorbents, or ion flotation. Cadmium can be extracted from crude acids in high yield by long-chained amines. After partial neutralization of the crude acids, precipitation as cadmium sulphide is also possible.