中国镉矿的区域分布及土壤镉污染风险分析

系统地分析和评价了中国镉矿的区域分布及长期采选冶活动所带来的土壤镉污染风险。研究结果表明,截至2005年底,中国累计探明镉资源储量约为719.47kt,保有镉资源储量约为587.37kt,且多与铅矿、锌矿等以共、伴生形式存在。中国镉矿主要分布在中部、西南部及华东地区,这些地区的镉资源探明储量占中国累计探明总储量的88.0%,保有储量占中国总保有储量的87.1%。据统计,中国镉采出量约为136.10kt,主要集中在西南地区,其镉采出量占中国总采出量的59.4%。镉污染事件主要发生在镉矿相对丰富及采选冶活动较密集的云南、广东、湖南、贵州等地区,大部分矿冶区及周边土壤呈现重度镉污染,农作物中含镉量超出《食品中污染物限量》(GB 2762—2005)中限值。

贵州牛角塘镉锌矿床中发现原生硫镉矿

在贵州牛角塘镉锌矿床中既有次生硫镉矿的存在,也发现了原生硫镉矿。硫镉矿的产状如下:①呈包裹体形式产于硫化物中;②以不规则晶粒赋存于硫化物粒间:③形成硫镉矿 方铅矿细脉或硫镉矿微脉穿插硫化物;④分布在黄铁矿中方铅矿或闪锌矿周围;⑤被菱锌矿胶结并交代,形成硫镉矿残骸状角砾;⑥组成菱锌矿 硫镉矿疏松集合体或菱锌矿 硫镉矿细脉;⑦呈皮壳状或薄膜状分布在氧化矿石表面或裂隙面上。前五种形式产出的硫镉矿为原生硫镉矿,主要分布在原生矿石或弱氧化的矿石中。后两种产状的硫镉矿为次生硫镉矿,分布于氧化矿石晶洞中或矿石表面和裂隙面上。并从Cd、Zn地球化学特性、热力学和结晶化学性质探讨了原生硫镉矿形成机制。

中国首次发现菱镉矿

国外菱镉矿早在1951年前就已被发现,近期在贵州牛角塘镉锌矿床中发现的菱镉矿为中国首次报道。菱镉矿的晶粒微小,一般只有几个微米,大者几十微米,常与菱锌矿、硫镉矿共生或伴生在一起,呈疏松集合体、皮壳或薄膜状产出。这一发现填补了中国矿物学上一个空白,菱镉矿在环境保护上具有重要意义。

广东阳春黑石岗硫铁矿床溶洞矿中镉的地球化学及硫镉矿的成因意义

一、矿区地质简况阳春黑石岗硫铁矿区位于广东湛江地区,硫铁矿床中溶洞矿矿体赋存于黑石岗背斜两侧。背斜轴部为燕山期花岗闪长岩,翼部为下石炭统石磴子段大理岩、结晶灰岩。矿体产于接触带。主矿体(Ⅱ号)呈似层状产于背斜的北西侧。矿床中银、铅、锌的硫化物溶洞矿矿体多受原生硫铁矿体或后期构造的控制。

贵州都匀牛角塘镉锌矿床中硫镉矿的存在形式及成因讨论

贵州牛角塘隔锌矿床是目前世界上最富镉的矿床：其含量是世界上其它铅锌矿床Cd含量的几到几百倍。在一个矿床中发现如此高含量和多种存在形式的硫镉矿在国内外尚未见报导。硫镉矿的存在状态如下：①呈包裹体产于硫化物中；②以不规则晶粒赋存于硫化物粒间：③硫镉矿一方铅矿或硫镉矿微脉基本都局限在闪锌矿内：④围绕黄铁矿中方铅矿包裹体四周分布：

广西某含镉铅锌尾矿综合回收利用研究

这是一篇矿物加工工程领域的论文。本研究选取了广西某含镉铅锌尾矿作为研究对象,在原生电位的条件下进行了含镉铅矿物及锌矿物的回收利用实验。研究结果表明,采用S19捕收剂可以对铅矿物进行较好的回收,CZ008新型选锌捕收剂可对活化后的含锌矿物进行高效回收,浮选尾矿经过摇床重选脱硫后可作为水泥用硅酸盐辅料。实验生产的废水无需处理即可循环利用,且不会对回收指标造成影响。

贵州都匀牛角塘富镉锌矿同位素地球化学研究

通过对牛角塘富镉锌矿的硫和铅同位素研究发现,该矿床同位素组成与其他含镉铅锌矿床明显不同,其硫同位素组成以富重硫为特征,δ34S值变化范围不大,集中在+22‰～+30‰;硫化物单矿物、矿石和乌训组地层岩石具有极其相近的铅同位素组成和高μ值(9.66～9.884)。表明该矿床的硫主要来源于寒武系地层硫酸盐或油田卤水,成矿物质铅主要来自铀钍相对富集的上部地壳岩石即清虚洞组白云岩(含矿地层)下伏地层乌训组页岩夹薄层灰岩,因此,牛角塘富镉锌矿成矿物质主要来源于上地壳即乌训组地层岩石,成矿时代为加里东运动的中晚期。

云南龙陵勐糯铅锌矿床中镉元素赋存状况

矿床中镉元素异常明显,以硫镉矿、不规则粒状、脉状充填嵌布于闪锌矿中。提出矿石生成顺序,为进一步找矿提供新依据。

近中性溶液条件下富镉铅锌矿矿石的风化淋滤实验研究

在近中性溶液条件下对富镉锌矿石进行了风化淋滤实验研究,发现淋滤液中产生大量以石膏为主要成分的沉淀物。淋滤液呈碱性,淋滤出来的Zn、Cd以水溶态和沉淀态形式存在,而以后者为主。淋滤50天后,黄铁矿闪锌矿石中Zn、Cd的淋滤率为0.03%和0.01%,而半氧化闪锌矿石Zn、Cd的淋滤率则高得多,分别0.10%和0.60%。

富镉铅锌矿矿石的风化淋滤实验研究——以贵州都匀牛角塘铅锌矿为例

0 前言 一般而言,矿石的开采和选冶导致大量硫化物矿石及尾矿暴露于地表,改变了矿石原有的物理和化学状态,黄铁矿等硫化物矿物经风化淋滤作用将产生大量的酸性矿山废水,致使周围水体pH值降低,重金属和硫酸盐浓度严重超标,破坏矿区生态环境[1]. ……

硫酸盐还原活性污泥矿化固定酸性矿山废水中的镉

为了实现硫酸盐生物还原法处理酸性矿山废水(AMD)中镉(Cd)的稳定去除,受自然界硫酸盐还原菌诱导的生物矿化现象启发,以驯化的硫酸盐还原活性污泥为种泥,在上流式厌氧反应器内,通过维持进水浓度比COD/SO_(4)^(2-)=2∶1、水力停留时间(HRT)=72h实现了AMD中Cd的稳定矿化,其固化率为100%,且连续36d未见Cd^(2+)的溶出;污泥特性分析表明,硫酸盐还原产生的S2−将废水中的Cd^(2+)转移至污泥中,污泥中的Cd则逐步从不稳定态(可交换态、碳酸盐结合态、铁锰氧化态、硫化物结合态)向稳定态(残渣态)转化,并在污泥表面形成大量离群的微米级镉硫矿;微生物群落结构分析表明,反应器中Desulfovibrio、Desulfuromonas、Acinetobacter、Delftia等丰度明显增加,推测协同代谢实现了Cd的稳定矿化。由此表明,硫酸盐还原活性污泥可通过矿化实现AMD中Cd的稳定去除,为AMD的高效处理及资源回收提供了新思路。

中国镉资源现状分析及可持续发展建议

镉是一种重要的有色金属,广泛的应用于工业领域。进入21世纪以来,随着轻、重工业的快速发展,全球镉消费量大增。我国是世界镉资源大国,储量和产量均居世界首位。本文在分析我国镉资源分布、特征、储量、产量及消费的基础上,提出了我国镉资源开发利用过程中存在的环境污染严重、回收利用率低和产量过大等问题。对此,提出增强环保意识,提高应对能力;重视回收再生,充分循环利用;严格控制产量,提高采选冶技术的可持续发展建议。

Adsorption of lead and cadmium ions from aqueous solutions using manganoxide minerals

Removal of lead and cadmium ions from aqueous solutions by adsorption process was investigated. Low cost and locally available natural mineral of manganoxide mineral was used as an adsorbent. The kinetics of adsorption process data was examined using the pseudo-first-order, pseudo-second-order kinetics and the intra-particle diffusion models. The rate constants of adsorption for all these kinetics models were calculated and compared. The adsorption kinetics was best described by the pseudo second-order model. The Langmuir and Freundlich adsorption isotherm models were applied to the experimental equilibrium data at different temperatures. The experimental data well fitted to Langmuir isotherm model. The maximum adsorption capacities of manganoxide mineral for lead and cadmium ions were calculated from the Langmuir isotherm and were 98 and 6.8 mg/g, respectively. Thermodynamic parameters such as the change of Gibbs free energy, enthalpy and entropy of adsorption were also calculated and it was found that the lead and cadmium uptake reactions by manganoxide mineral were endothermic and spontaneous in nature. Therefore, manganoxide mineral can be used as adsorbents for lead and cadmium ions removal processes as an alternative natural mineral among the others.

Adsorption behavior of Pb^(2+) and Cd^(2+) ions on bauxite flotation tailings

The adsorption behavior of Pb2+ and Cd2+ ions on bauxite flotation tailings was investigated to demonstrate the adsorptivity of the bauxite flotation tailings.The adsorption percentage of Pb2+ and Cd2+ ions as a function of adsorbent dosage,solution pH value and shaking time were determined by batch experiments.The maximum adsorption percentage of 99.93% for Pb2+ ions and 99.75% for Cd2+ ions were obtained by using bauxite flotation tailings as adsorbent.The methods,such as zeta potentials,specific surface area measurements and the analysis of adsorption kinetics,were introduced to analyze the adsorption mechanisms of the Pb2+ ions on bauxite flotation tailings.The isoelectric point of bauxite flotation tailings shifts from 3.6 to 5.6 in the presence of Pb2+ ions.The specific surface area of bauxite flotation tailings changes from 12.57 to 20.63 m2/g after the adsorption of Pb2+ ions.These results indicate that a specific adsorption of the cation species happens on the surface of bauxite flotation tailings.Adsorption data of Pb2+ ions on the surface of bauxite flotation tailings can be well described by Langmuir model,and the pseudo-second-order kinetic model provides the best correlation for the adsorption data of Pb2+ and Cd2+ ions on bauxite flotation tailings.

Interaction of salinity and cadmium stresses on mineral nutrients, sodium, and cadmium accumulation in four barley genotypes

Interaction of salinity （NaCI） and cadmium （Cd） on growth, mineral nutrients, Na and Cd accumulation in four barley genotypes differing in salt tolerance was studied in a hydroponic experiment. Cd, NaCI and their combined stresses reduced Ca and Mg concentrations in roots and shoots, K concentration in shoots, increased K and Cu concentrations in roots relative to control, but had non-significant effect on micronutrients Cu, Fe and Mn concentrations in shoot. The three stresses reduced accumulation of most tested nutrients in both roots and shoots, except NaCI and NaCl＋Cd stresses for root K and shoot Cu accumulation in salt tolerant genotypes. The salt tolerant genotypes did not have higher nutrient concentration and accumulation than the sensitive ones when exposed to Cd and NaCI stresses. In conclusion, the affecting mechanism of Cd stress on nutrients was to some extent different from salinity stress, and the NaCl＋Cd stress was not equal to additional Cd and NaCI stresses, probably due to the different valence and competitive site of Na^＋ and Cd^2＋. NaCI addition in the Cd-containing medium caused remarkable reductions in both Cd concentration and accumulation, with the extent of reduction being also dependent on genotypes. The salt-tolerant genotypes had lower Na concentration than sensitive ones.

Influence of Aluminum and Cadmium Stresses on Mineral Nutrition and Root Exudates in Two Barley Cultivars

A hydroponic experiment was carried out to study the effect of aluminum （Al） and cadmium （Cd） on Al and mineral nutrient contents in plants and Al-induced organic acid exudation in two barley varieties with different Al tolerance. Al- sensitive cv. Shang 70-119 had significantly higher Al content and accumulation in plants than Al-tolerant cv. Gebeina, especially in roots, when subjected to low pH （4.0） and Al treatments （100 μmol L^-1 Al and 100 μmol L^-1 Al ＋1.0 μmol L^-1 Cd）. Cd addition increased Al content in plants exposed to Al stress. Both low pH and Al treatments caused marked reduction in Ca and Mg contents in all plant parts, P and K contents in the shoots and leaves, Fe, Zn and Mo contents in the leaves, Zn and B contents in the shoots, and Mn contents both in the roots and leaves. Moreover, changes in nutrient concentrations were greater in the plants exposed to both Al and Cd than in those exposed only to Al treatment. A dramatic enhancement of malate, citrate, and succinate was found in the plants exposed to 100 μmol L^-1 Al relative to the control, and the Al-tolerant cultivar had a considerable higher exudation of these organic acids than the Al-sensitive one, indicating that Al-induced enhancement of these organic acids is very likely to be associated with Al tolerance.

Study on Mechanisms of Cd^(2+) Sorption on Goethite byMicrocalorimetry

A study on energy changes and mechanisms of Cd sorbed on goethite was performed using the technique ofmicrocalorimetry. The data of the amount of Cd sorption (Aq) and concentration of Cd in equilibrium solution(Ce), and the data of Aq and the heat effect (AH) caused by Cd^2+ sorption on goethite all fitted Langmuirisotherm. The amount of heat released from Cd sorption on goethite increased with the amount of Ce or Aq.The reaction process of Cd sorption on goethite may be divided into five stages and three plateaus, dependingon the variation of enthalpy change (.Hm) of Cd sorption with Aq, which implied three mechanisms ofinteraCtion between Cd and goethite. The experimental results showed that the microcalorimetry may beuseful for determination of microcalorie variation in soil.

Effects of Cd on reductive transformation of lepidocrocite by Shewanella oneidensis MR-1

We investigated the reduction of lepidocrocite(γ-FeOOH) by Shewanella oneidensis MR-1 in the presence and absence of Cd. The results showed that Cd^(2+) retarded microbial reduction of γ-Fe OOH and avoided formation of magnetite. The inhibitory effect on γ-Fe OOH transformation may not result from Cd^(2+) toxicity to the bacterium; it rather was probably due to competitive adsorption between Cd^(2+) and Fe^(2+) on γ-Fe OOH as its surface reduction catalyzed by adsorbed Fe^(2+) was eliminated by adsorption of Cd^(2+).