Separating Criterion of Pb,Cd, Bi and Zn from Metallic Particles of Crushed Electronic Wastes by Vacuum Evaporation

The crushing process is usually adopted during the treatment of electronic wastes. Mixed metallic particles can be obtained after several kinds of separation methods. Most of the metals exist as elementary substances and their vapor pressure is quite different. For the metals with high vapor pressure, vacuum metallurgy separation is used to separate these metals. However, the vacuum evaporation rule of metallic particles is different from the traditional theory. Satisfactory parameters for separating these metallic particles could not be obtained merely according to the boiling point difference between metals. In this paper, the evaporation kinetics and mechanism of single metallic particles (Pb, Zn, Cd, and Bi) are investigated first. Then the criterion of separating these metals from each other is obtained. Under the instruction of separation criterion, different kinds of mixed metallic particles are successfully separated with the separation efficiency of the target metal more than 90 wt%. This study provides theoretical foundations for separating the heavy metals with high vapor pressure from e-wastes.     

Solvent Extraction Behavior and Mutual Separation of Some Bivalent Metal Ions Using Thiocarbohydrazide as the Complexing Agent

Abstract

Thiocarbohydrazide (NH₂. NH. CS. NH. NH₂) was used as a complexing agent for the solvent extraction separation of some bivalent metals. Separation of Cd from Co, Cu, and Pd, and of Pb from Ni and Pd was carried out using the effect of pH on their extractability. The separation of Cu from Zn and Hg, and of Pb from Zn and Cd was also carried out using various masking agents.     

水泥窑铅镉等重金属的污染及防治

利用原子吸收分光光度法、振荡溶出等方法,研究了水泥窑铅镉等重金属污染的防治.氟会促进Pb,Cd,Zn和Cu的逸放.无论何种水泥窑,Hg逸放率高达89%～96%.Pb,Cd,Zn和Cu在不同类型水泥窑中其逸放率有明显差别,立窑的逸放率较高,Pb和Cd为84%～90%,Zn和Cu为36%～47%;湿法回转窑次之;新型干法窑的逸放率最低.使用高效的除尘设备,不仅可减少粉尘的污染,还可减少Pb等重金属的逸放.把Pb等重金属含量较高的窑灰用作水泥混合材既可使Pb等重金属被固封于水泥混凝土中不会产生二次污染,又能减少因窑灰循环入窑而导致Pb等重金属的再次逸放.     

The availability and binding of heavy metals in compost derived from household waste

Organic waste can be recycled as compost which has traditionally been used as a soil improver. As more waste is recycled as compost, it is becoming increasingly important to find alternative uses for compost. Leachability data are used to determine the environmental availability of Cd, Cu, Pb, and Zn contained in natural compost. Batch sorption data are used to determine uptake of additional Cd, Cu, Pb, and Zn by compost and assess its potential use in remediation work, as an alternative to natural materials such as peat. The relative binding of these additional metals to compost is found to be in the order Pb > Cd ≈ Cu > Zn. The sorption of metals on compost takes place, at least in part, by exchange of calcium bound to the compost and there is evidence that the sorption occurs in both humic and non‐humic sites in the compost. The use of compost to bind metals in remediation work is discussed. © 1999 Society of Chemical Industry     

还原挥发氧化锌烟尘中有价金属分离工艺研究

针对含多种有价金属的还原挥发氧化锌烟尘,提出一条全湿法分离烟尘中有价金属的工艺路线。首先采用加双氧水氧化稀硫酸浸出,经过滤和洗涤,分别获得含硫酸锌、硫酸铟浸出液和含铅、铋浸出渣,实现锌、铟与铅、铋分离;对含硫酸锌和硫酸铟浸出液采用P204萃取,实现锌与铟的分离;对含铅、铋浸出渣采用碳酸氢铵转化生成碳酸铅,加硝酸溶解,实现铅与铋的分离。该工艺不仅可有效分离烟尘中的有价金属,而且获得的硫酸锌、硫酸铟、硝酸铅、富铋渣可用于生产其他化工产品,为氧化锌烟尘高效综合利用提供了一条新的途径。     

合肥市南淝河表层沉积物重金属污染评价

对合肥市南淝河表层沉积物中重金属污染状况进行采样调查,选取了8个采样点,测定了沉积物中Cr、Cd、Pb、Ni、Zn、Cu 6种重金属的含量,并采用地质累积指数法和Hakanson潜在生态风险指数法对其污染程度进行分析评价。地质累积指数评价结果表明:南淝河6种重金属的生态风险等级由强至弱依次为Cd、Zn、Cu、Ni、Pb、Cr;生态风险指数评价结果显示:在南淝河沉积物重金属中,Cd存在一定的潜在生态风险,Cr、Pb、Ni、Zn、Cu均处于轻微等级,重金属生态风险等级由强至弱依次为Cd、Cu、Ni、Pb、Zn、Cr,多数采样点的沉积物重金属综合潜在生态风险等级处于轻微级,个别采样点达到了中等甚至强生态风险等级。     

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。     

Heavy metal uptake by wheat from a sewage sludge-amended calcareous soil

The objective of this 4-year study was to determine single and repetitive effects of sewage sludge applications on the accumulation of lead (Pb), cadmium (Cd), zinc (Zn) and copper (Cu) in soil and wheat (Triticum aestivum). A single sludge application at a rate of 100 Mg ha⁻¹ (for all the metals) and at a rate of 50 Mg ha⁻¹ (for Cu) significantly increased DTPA-extractable metal concentrations 4 years later. DTPA-extractable concentrations of Pb, Zn and Cu were closely correlated with the total concentrations in soil. Their relationships between metal uptake in stalks and DTPA-extractable metal concentrations in soil were approximately linear for Pb, Cd and Cu, but better described by a quadratic equation for Cd and Zn. TF for Pb, Zn and Cu, BF for all metals and BCF for Pb, Cd and Zn were lower in wheat grown on sludge-treated than control plots.     

添加剂对污泥焚烧过程中重金属迁移特性的影响

利用管式炉研究了Cl、S、P对重金属迁移特性的影响,研究结果表明：C促进了重金属Cd、Pb、Zn、Cu的挥发,而对重金属Ni、Cr的挥发特性影响不大;S对重金属的挥发特性影响不大,在一定程度上抑制霞金属Zn、Cd、Ni的挥发,而对重金属Pb则促进其挥发;P对不同重金属的挥发特性影响不同,随着P含量的增加,重金属Cr和Ni的挥发的挥发率逐渐增大,而重金属Cd、Pb和Zn的挥发率逐渐降低。     

活性炭对重金属离子的吸附研究

研究了活性炭分别对铅、镉、铜及锌离子的吸附作用,研究了pH值、温度及活性炭的投加量等因素对吸附效果的影响。结果表明,当pH〉5时对四种离子的去除率均达到98％以上,能达到很好的吸附。低温有利于吸附的进行。随着活性炭的增加．重金属离子的去除率增加．而且铜离子的活性炭最佳用量是0．3000g．铅、镉和锌的活性炭最佳用量均为1．000g。随着吸附时间的增加,去除率上升。铜、铅、镉和锌离子的吸附平衡时间分别为3．5h、1h、1．5h和1．5h。铜离子的吸附符合Langmuir等温模式,而锌、铅和镉离子的吸附符合Freundlich等温模式。     

瓯江口表层沉积物重金属时空分布特征研究

调查采集了瓯江口春季10个站位的表层沉积物样品,对其Cu、Pb、Zn、Cd四种重金属含量进行了化学分析和评价,研究认为：瓯江北口总体沉积物质量优良,总体达到国家1类标准,符合其海洋功能区划的要求;铜为该区主要重金属污染影响因子;从空间角度看,主要重金属含量有由近岸向外海减小的趋势;从时间角度看,主要重金属含量除铅含量略有增加外,其他重金属含量均由一定幅度的下降,显示该区底质环境有改善的迹象。     

Removal of Heavy Metals from Missouri Lead Mill Tailings by Froth Flotation

Abstract

The U.S. Bureau of Mines investigated froth flotation techniques to remove heavy metals (Pb, Cu, and Zn) from southeast Missouri lead mill tailings. It has been estimated that southeast Missouri contains between 200 and 300 million st of Pb tailings stored above ground. The tailings were classified as two distinct types: (1) pre-1968 tailings from the Old Lead Belt (some more than 100 years old) and (2) post-1968 tailings from the New Lead Belt. The objectives of the investigation were to reduce the Pb remaining in the tailings to <500 ppm (<0.05 pct Pb) and to attempt to recover a marketable concentrate to offset a portion of the remediation costs. The remaining dolomite-limestone would then be used as mining backfill or agricultural limestone. Bench-scale froth flotation removed, in percent, 95 Pb, 84 Cu, and 54 Zn, leaving 94 pct of the original weight containing, in parts per million, 400 Pb, 40 Cu, and 300 Zn from the Old Lead Belt tailings. Separate flotation tests also removed, in percent, 85 Pb, 84 Cu, and 80 Zn, leaving 75 pct of the original weight containing, in parts per million, 400 Pb, 200 Cu, and 500 Zn from the New Lead Belt tailings. Concentrates recovered from the Old Lead Belt were retreated to produce a final Pb concentrate containing 72 pct Pb with a cleaner flotation recovery of 79 pct. Froth flotation proved to be a viable method to remove the heavy metals.     

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。     

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.     

Packed-bed columns with dye-affinity microbeads for removal of heavy metal ions from aquatic systems

A dye ligand Cibacron Blue F3GA, was covalently coupled with polyhydroxyethylmethacrylate (PHEMA) microbeads in the 150–200 μm particle size range. The sorbent carrying 22.3 μmol Cibacron Blue F3GA per gram of polymer was then used to remove Pb(II), Cd(II), Cu(II) and Zn(II) from aqueous solutions in a packed-bed column system. Heavy metal ion adsorption capacity of the column was investigated as a function of heavy metal ion-bearing solution flow rate and the inlet heavy metal ion concentration. The maximum metal ion uptake values found were: 80.60, 96.98, 78.36, 103.98 μmol/g polymer for Pb(II), Cd(II), Cu(II) and Zn(II), respectively. The heavy metal adsorption capacity of the microbeads decreased with an increase in the circulation rate of aqueous solution. The order of affinity based on molar uptake was Zn(II)>Cd(II)>Pb(II)>Cu(II). Removal percentages of heavy metals related to flow time were determined for different flow rates and initial metal ion concentrations. It was observed that PHEMA microbeads carrying Cibacron Blue F3GA can be regenerated by washing with a solution of nitric acid (0.05 M). The desorption ratio was as high as 98.5%.     

流动顺序注射分离富集-火焰原子吸收光谱法检测污水和废水中Pb Cd Cu Zn

采用D412螯合树脂作为流动顺序注射分离富集微柱填充材料,同火焰原子吸收光谱仪联用,结合所优化的样品酸度,进样速度,淋洗条件和洗脱条件,快速测定污水和废水样品中Pb,Cd,Cu和Zn的含量,样品上柱10 mL富集时,相对标准偏差(RSD)<5.00%,以空白溶液11次测定的标准偏差的3倍求得检出限Pb:1.3μg/L,Cd:0.56μg/L,Cu:0.91μg/L,Zn:0.48μg/L,加标回收率89%-98%。     

垃圾水分对垃圾焚烧过程重金属迁移转化影响的实验研究(英文)

The effect of moisture in municipal solid waste (MSW) on partitioning of lead (Pb), zinc (Zn), copper (Cu) and cadmium (Cd) was studied in a laboratory tubular furnace by using simulated MSW. The moisture in MSW influences heavy metals in following ways, to increase the moisture in flue gas and decrease the combustion temperature, to prolong the combustion time, and to prolong the releasing time of volatiles with the furnace temperature decreased by increasing the moisture. The volatilization of Pb, Zn and Cd was enhanced by increasing the moisture in MSW because of the prolonged combustion time. For Pb and Zn, the combustion time was important at higher temperature, while for Cd, it was important at low temperature. The moisture content showed slight effect on Cu partitioning. When extra chlorine was added to MSW, such as 1%PVC + 0.5%NaCl, the volatilization of Pb, Zn and Cu was enhanced by increasing the moisture because water evaporation reduced the temperature and increased devolatilization time. At higher temperature, NaCl tends to decompose and generates more free chlorine, producing more metal chlorides. Since Cd is a strong volatile heavy metal in MSW, the effect of moisture content on its volatilization is less than that of Pb, Zn or Cu during the MSW incineration.     

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。     

On the fate of heavy metals in municipal solid waste combustion Part I: devolatilisation of heavy metals on the grate

The aim of this study has been to investigate the chemistry and volatility of the heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn on the grate of a MSW fired furnace, using equilibrium calculations. Focus has been on the influence of varying MSW composition and operational parameters such as air/fuel ratio and temperature. Equilibrium distributions at 950–1600 K, under reducing and oxidising conditions on the grate, showed that Cd, Hg and Pb are fully volatilised. However, Cr is found to be stable in solid phase, in the entire temperature range. The volatile behaviour of Cd, Cr, Hg and Pb show no significant influence, while As, Cu, Ni and Zn are strongly influenced by one or more of the parameters; temperature, fuel/air and chlorine/metal ratios.     

Heavy metal pollution in the territory of Chelyabinsk upon coal combustion

The pollution of the territory of Chelyabinsk by heavy metals (Cu, Co, Ni, Zn, Pb, Cd, Cr, Mo, and Hg) upon coal combustion is evaluated. The concentrations of Zn, Pb, Cd, and Hg in the soils of this territory and the concentrations of Cd and Hg in water were found higher than health standard values (approximate permissible concentrations and maximum permissible concentrations) by factors of 1.5–20, 6, and 2, respectively.