高岭石吸附水溶液中铅离子的动力学研究

研究了高岭石吸附水相中铅离子的动力学行为.结果表明:高岭石对水溶液中铅离子的吸附是一个复杂的非均相固液反应,从动力学角度来看,大致可以分为2个阶段:初期阶段反应速度快,动力学过程复杂,有待于深入研究;后期阶段反应速度较慢,并符合一级反应动力学方程.吸附速率常数k与温度T之间的关系符合阿累尼乌斯公式,吸附的活化能为Ea=26.44 J/mol,吸附的频率因子A=603s-1.ln(k/T)与1/T之间的关系符合Eyring公式,其活化焓△H=23.94J/mol,活化熵△S=-200J/K·mol.同时,k与铅离子初始浓度呈负相关性,与高岭石用量、介质pH值呈正相关性.     

Second german heavy-metal survey by means of mosses,and comparison of the first and second approach in germany and other european countries

This paper shows the geographic distribution in Germany of iron (Fe), nickel (Ni) and lead (Pb) analyzed in mosses in 1995/96 and compares it with the results of the 1990/91 pilot study within a European moss-monitoring programme. Other elements (As, Cd, Cr, Cu, Ti, V, Zn) are compared on basis of the overall element medians for Germany of the 1990/91 and 1995/96 survey. Samples of Pleurozium schreberi, Scleropodium purum, Hypnum cupressiforme and Hylocomium splendens were taken at a total of 1026 sites. In the 1995/96 monitoring campaign, 95% of the original sites of the 1990/91 study were resampled. The results from 1995/96 display local elevated values and many cases of areas affected by known sources of heavy-metal emissions. The industrialized and urban regions of Germany are shown up clearly by the 1995/96 moss-monitoring results: the Ruhr area, parts of Saarland and Baden-Württemberg, as well as areas in eastern Germany. Relatively low values for many elements were found in large areas of Lower Saxony and Bavaria. A comparison of the results of the 1990/91 and 1995/96 moss-monitoring programmes shows a fall in the concentration of the presented elements (except cadmium, copper and zinc) over the relevant period. Especially in the former GDR, chromium (Cr), iron (Fe), titanium (Ti) and vanadium (V) decreased significantly. This is, firstly, a reflection of the closure of and/or technological improvements to large power plants; secondly it is due to the fact that lignite has given way to other fuels. Vanadium (V) and nickel (Ni), typical constituents of crude oil, also show a decrease in the western part and thus document changes in the type of fuel consumed. The significant fall in lead concentration in 1995/96 as compared to 1990/91 in what used to be East and West Germany probably results from the increasing use of lead-free petrol. A comparison of the median values for 1990/91 and 1995/96 in mosses to the rate of emission of heavy metals in Germany for 1990 and 1995 shows similar trends in the case of elements such as arsenic (As), chromium (Cr), nickel (Ni), and lead (Pb). The comparison of the medians of the elements analyzed for 19 European countries indicates for most of the elements a general tendency to lower values in 1995, except for Lithuania, Netherlands, Portugal, Italy and United Kingdom.     

成型膨润土和钛柱撑膨润土对水中Pb2+和氯乙酸吸附及再生

针对水中微量铅离子和氯乙酸的脱除，考察了成型膨润土及成型钛柱撑膨润土的吸附性能，得出对铅离子的吸附，成型膨润土、成型钛柱撑膨润土与粉末状活性炭性能相当，而对氯乙酸的吸附前两者要比粉末状活性炭低好多。确定了成型膨润土吸附氯乙酸后可用沸水煮沸30 min的方法再生，成型钛柱撑膨润土吸附氯乙酸后，可用500℃焙烧3 h的方法再生，再生的膨润土循环使用3次后性能降低明显。此外，还测得了成型的膨润土及成型的钛柱撑膨润土吸附铅离子和氯乙酸的等温线，计算出其对铅的最大吸附量分别为24.33 mg/g和15.47 mg/g。     

湖南省几种主要菜园土铅的化学行为及其作物效应的初步研究

温度、ｐＨ、有机质及不同价态阳离子对铅吸持－解吸量有明显的影响．土壤中的铅在低浓度范围内（红茶园土为１００μｇ／ｇ，石灰性菜园土为５００μｇ／ｇ）对小白菜生长有刺激作用，超过一定浓度（红菜园土为≥５００μｇ／ｇ，石灰性莱园土为≥１００μｇ／ｇ）则有抑制作用．小白莱的含铅量随土壤铅浓度的增加而增加，两者呈极显著正相关．三种改良剂对铅污染土壤有明显的改良效果，其中以猪粪、石灰两种改良剂的效果为好，钙镁磷肥次之．     

Preparation and characterisation of green clay-polymer nanocomposite for heavy metals removal

ABSTRACT

Natural polymer Moringa oleifera seed as coagulant and bentonite clay as adsorbent were used for preparing novel composite coagulant. Results obtained from FTIR, SEM, TEM and P-XRD show that the bentonite clay and M. oleifera seed biopolymers physico-chemically interact with each other during the preparation of clay-polymer composite. The FTIR results show that the major functional groups present in bentonite clay and M. oleifera seed are integrated at nano levels in the novel composite to remove heavy metals from aqueous systems. The coagulo-adsorption using clay-polymer composite may be used for the adsorption of heavy metals ions from the aqueous systems. It becomes possible due to the structural characteristics of the clay crystallites together with the functional attraction of the biopolymer and it results in the formation of clay-polymer metal complexes. The clay-polymer nano-composite of M. oleifera seed and bentonite clay showed considerable cadmium, chromium and lead removal property.     

Indoor and outdoor household dust contamination in Cincinnati, Ohio, USA

Despite some progress in reducing the average lead level in the USA, the streets of Cincinnati, Ohio, are still contaminated by heavy metals. High levels of heavy metals will have significant unequivocal ecological impacts and pose a potential health hazard. This study evaluates the level of heavy- metal contamination in household dust and examines its relationships with the external environment. Samples of outdoor and indoor dust were collected from middle-income residential homes in the Greater Cincinnati Metropolitan District and the metal content was analysed by inductively coupled plasma atomic emission spectrophotometry. Results showed that the mean levels of lead in outdoor and indoor dusts are 650 g g-1 and 377 g g-1 and the copper levels are 253 g g-1 and 510 g g-1, respectively. The median levels are 156 g g-1 and 139 g g-1 for outdoor and indoor lead dusts and 35 g g-1 and 124 g g-1 for outdoor and indoor copper dusts. The degree of contamination may be ascribable to the age of the dwelling unit and the neighbourhood, the time when the unit was last painted, the presence of pets and the type of space heating. In addition, car exhausts seems to be a possible source of contamination.     

Brominated flame retardants and polychlorinated biphenyls in fish from the river Scheldt, Belgium

Levels of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDs), and polychlorinated biphenyls (PCBs) were measured in several fish species originating from the river Scheldt (Belgium). Five sampling locations were chosen in a highly industrialized area along the river, while two ponds in the vicinity of the river served as reference sites. The present study is a follow-up of a survey performed in 2000 which reported extremely high levels of PBDEs and HBCDs in eel (Anguilla anguilla) collected from the same region (Oudenaarde, Flanders). The sum of tri- to hepta-BDE congeners (2270+/-2260 ng/g lipid weight (lw), range 660-11500 ng/g lw) and total HBCDs (4500+/-3000 ng/g lw, range 390-12100 ng/g lw) were one order of magnitude higher than levels usually reported from freshwater systems, indicating the presence of point sources. In most samples, levels of total HBCDs were higher than those of PBDEs, probably due to the high density of factories using HBCD as an additive brominated flame retardant (BFR). The high values of HBCDs were confirmed by both gas- and liquid-chromatography-mass spectrometry. Although BFR levels were between the highest ever reported in freshwater ecosystems, PCBs could be detected at even higher concentrations (16000+/-14300 ng/g lw, range 3900-66600 ng/g lw), being among the highest levels recorded in Belgium. The inter-sampling site variation of PBDEs, HBCDs and PCBs was comparable. All locations presented similar PBDE congener profiles, with BDE 47 being the dominant congener, followed by BDE 100, BDE 99 and BDE 49, probably originating from the former use of the penta-BDE technical mixture. In order to estimate the impact of these point sources on human exposure, we further focussed on eels which showed a considerable decrease in the PBDE and HBCD levels between 2000 and 2006. Due to the wide span in concentrations between the different sampling locations, a variable contribution to the total human exposure through local eel consumption was estimated. The calculated daily intake ranged from 3 ng to 330 ng PBDEs/day for normal eel consumers, but was as high as 9800 ng PBDEs/day for anglers, which may be considered at risk.     

锌对长柔毛委陵菜中铅的分布和化学形态的影响

通过营养液培养并采用差速离心技术和化学试剂逐步提取法,分析了Zn对Pb在长柔毛委陵菜(Potentilla griffithii var. velutina)的器官及其亚细胞分布和化学形态的影响.结果表明,除对照外,79%～88%的Pb富集在长柔毛委陵菜的根部,并且植物体内47%～77%和13%～45%的Pb分别分布在细胞壁和可溶组分中.虽然加Zn没有改变Pb在植物亚细胞分布中"细胞壁>可溶组分>细胞核和叶绿体>线粒体"的格局,但Pb和Zn的添加都增加了Pb在细胞壁的分配比例,减少其在可溶组分的富集,即Pb和Zn的添加增强了细胞壁对Pb的固持作用.长柔毛委陵菜体内的Pb以不同化学形态存在:在对照中82%～89%的Pb以乙醇提取态和水提取态存在;而在其它处理中以盐酸提取态为最高形态,占总量的28%～60%.同时,Pb和Zn的添加导致植物中Pb的乙醇提取态和水提取态等活性较强形态的分配比例减少,促进Pb向活性较弱的结合形态转移.因此,根部滞留、细胞壁固持、可溶组分的液泡区隔化和活性较强的结合形态的减少是长柔毛委陵菜耐Pb的主要机制.     

Comparative equilibrium studies of sorption of Pb(Ⅱ) ions by sodium and calcium alginate

The absorption of Pb(Ⅱ) ions from aqueous solution by different alginate compounds was studied in a batch sorption system.Water soluble sodium alginate and insoluble calcium alginate beads were investigated.The lead-binding capacity of both alginate compounds was highest within the pH range 6-8.The binding capacities and rates of Pb(lI) ions by alginate compounds were evaluated.The Langmuir,Freundlich,and Bruneaur,Emmet and Teller (BET) sorption models were applied to describe the isotherms and isotherm ...