Bacterial Leaching of Metals from Tannery Sludge by Indigenous Sulphur-Oxidizing Bacteria—Effect of Sludge Solids Concentration

An investigation on the effect of sludge solids concentration on bioleaching of Cr(III) and other metals from tannery sludge by indigenous sulphur-oxidizing bacteria was carried out. The sludge solids concentrations ranged from 13 to 60 g/L. The concentration of elemental sulphur was fixed at 30 g/L. The results showed that the lowest pH reached after 25 days of bioleaching at all studied sludge solids concentration was about 1.3. The optimum sludge solids concentration for maximum metal leaching from tannery sludge was 40 g/L and about 87% of Cr(III), 73% of Al, 72% of Fe, 62% of Mg, and 73% of Zn could be leached in this case. During bioleaching, the concentrations of total and volatile suspended solids of the tannery sludge significantly decreased. The sulphur-oxidizing bacteria could tolerate a Cr(III) concentration as high as 5,930 mg/L at pH 1.3. The leaching efficiencies of Cr(III), Al, and Fe for both chemical leaching and bioleaching of tannery sludge were similar at pH 1.3. The leaching efficiency of Ca, Mg, and Zn in both leaching processes were identical for pH values in the range of 1.3 to 3.0.     

磷酸盐沉淀法除铬热力学研究

除铬是含铬电镀污泥湿法冶金过程重要步骤.针对磷酸盐沉淀法从溶液中净化除铬过程进行热力学分析,绘制了25 ℃时Me-P-H₂O(Me: Cr(III), Zn(II), Cu(II), Fe(II), Fe(III), Ni(II))系组浓度对数-pH图,利用热力学平衡图对磷酸盐沉淀法从含铁等金属元素中净化除铁和磷酸铬碱分解过程进行热力学分析.结果表明,pH值为1.0 ~ 5.0磷酸盐形成由易至难依次为Cr(III)>Fe(III) >Fe(II)>Ni(II)>Cu(II)>Zn(II); 磷酸盐沉淀法难以有效地将Cr(III)与Fe(III)分离,而可分离Cr(III)和Fe(II),且较优pH约为2;整个pH值范围Me-P-H₂O系可以分为难溶磷酸盐稳定区、Me(OH)_n稳定区; 高pH区磷酸盐中的Me转变为稳定的Me(OH)_n,实现磷酸盐碱分解.验证实验表明,加入1.1倍理论量的磷酸钠,控制沉淀pH值为2.0,铬、铁、锌、铜、镍沉淀率分别为94.12 %、5.51 %、0.33 %、0.22 %、0.34 %; 氢氧化钠分解磷酸铬时,磷、铬浸出率分别为90.63 %、5.10 %,实现磷铬有效分离.实验与理论基本相符.      

Leaching Behavior of Metals Released from Cement-Stabilized/Solidified Refinery Oily Sludge by Means of Sequential Toxicity Characteristic Leaching Procedure

In this study, stabilization/solidification (S/S) of refinery oily sludge was applied using two types of cement (I and II), in cement-to-waste ratio from 0.1 to 0.7. The leaching behavior of heavy metals was investigated, by means of a five-point sequential toxicity characteristic leaching procedure (TCLP) test. Sequential TCLP was used to provide an improved assessment of long-term contaminant potential leachability, because the acidic leachant is renewed, whereas in the single TCLP, contaminant leachability is limited by the pH neutralization of the alkaline binder. Cement-based S/S of real refinery oily sludge resulted in very low leachability of heavy metals. Pb and Cd were not detected in any TCLP leachate. The maximum leachability of Fe, Zn, and Ni occurred in the pH range between 5.5 and 6.5. The leachability of Cu and Cr increased with increasing pH. Maximum cumulative percentage of Fe, Ni, and Zn leaching after five consecutive TCLP extractions (for worst case conditions, i.e., 10% II42.5) were 0.01, 22, and 1.2%, respectively, on the basis of metal content of each solidified sample. Further, the leaching behavior of Zn and Ni was modeled using the chemical equilibrium program Visual MINTEQ. Using several combinations of suspected solid phases of Zn and Ni hydroxides, carbonates and sulfides, and surface complexation onto ferrihydrite the diffuse double layer model did not accurately describe the leaching behavior of Zn and Ni.     

影响赤泥中浸出锌铜钒铬的主要因素探讨

重金属元素的浸出研究对提高赤泥中元素的综合回收和环境保护具有重要意义,因此需要对赤泥中Zn、Cu、V、Cr元素的主要浸出因素进行探讨。实验以盐酸浓度、浸出温度、浸出时间为考察因素,各元素浸出量为考察指标,采用L₁₆(4³)的正交试验,借助电感耦合等离子体原子发射光谱法(ICP-AES),对影响赤泥中浸出Zn、Cu、V、Cr的主要因素进行探讨。结果显示,各待测元素校准曲线的线性相关系数均大于0.999 7。盐酸浓度与浸出温度对元素的浸出影响较为显著,而浸出时间影响较弱,4种元素浸出的最佳条件为盐酸浓度9 mol/L、浸出温度100 ℃、浸出时间60 min。上述浸出条件下,赤泥样品中Zn、Cu、V、Cr的浸出率分别为86.67%、85.88%、88.55%和87.57%。研究表明,合理控制盐酸浓度、浸出温度和浸出时间,可以有效地提高赤泥中Zn、Cu、V、Cr浸出量,为赤泥中重金属元素的回收提供参考。     

湿法炼锌渣中银的回收

在湿法炼锌工艺中锌精矿中的银主要富集在酸性浸出渣中,此矿样的浸出渣中Ag的品位约为234 g/t,还含有Zn、Pb等可重复利用金属,研究Ag、Zn、Pb等的回收再利用具有十分重要的意义。本文以酸性浸出渣为原料进行了物理分选、还原焙烧、直接熔炼法以及氧化焙烧-氰化提银的试验,重点研究了物理分选过程Ag、Zn、Pb的富集走向及氧化焙烧-氰化提银工艺中氯化钠用量、焙烧时间及温度对Ag浸出率的影响。研究得出:高温高酸浸出后浮选可使Zn和Ag得到富集;浸出渣酸浸后熔炼使粗铅中的Ag和Pb富集,Ag品位可提高6倍;并通过试验得到了较优的氧化焙烧和氰化浸出提银工艺参数。      

Microbial Dissolution of Zn-Pb Sulfide Minerals Using Mesophilic Iron and Sulfur-Oxidizing Acidophiles

The purpose of this study is to test the feasibility of using mixed culture of iron and sulfur-oxidizing bacteria for the dissolution of metals from high-grade zinc and lead sulfide ore. Considering that the roll crusher could reduce the ore size to less than 2 mm, this size fraction was selected in order to study the possibility of removing mill circuit. Effects of parameters such as pulp density, initial pH, Fe²⁺, oxidation–reduction potential (ORP), and pH fluctuations were investigated, as well. The maximum Zn dissolution was achieved under the conditions of initial pH 2, initial 75 g/L FeSO₄ · 7H₂O, and pulp density of 50 g/L. The results indicated that under the optimum conditions, about 68.8% of zinc was leached during 24 days of bacterial leaching treatment. The lead recoveries were low (about 1%), because of precipitation of Pb as lead arsenate chloride. Furthermore, the surface studies by using SEM images showed that during chemical leaching the ore dissolution starts from surface discontinuities, but in bacterial leaching all surface becomes involved. In addition, in another process the ore was leached separately with sulfuric acid and sodium hydroxide, and then final results were compared to the bacterial leaching tests in order to find the optimum hydrometallurgical method to extract zinc and lead from these ores.     

Selective adsorption of chromium(VI) from zinc(II) and other metal ions using persimmon waste gel

An adsorption gel was prepared from persimmon waste, a cellulosic material, rich in polyphenolic compounds, which exhibits a high affinity for chromium(VI). It was prepared by cross-linking persimmon waste with concentrated sulphuric acid. Adsorption tests for different metal ions such as Cr(VI), Cr(III), Fe(III), Zn(II), Cd(II) and Pb(II) from aqueous solution at pH values ranging from (pH 1 to 5) found Cr(VI) to be selectively adsorbed on the cross-linked gel over the other metal ions studied. The adsorption isotherm of Cr(VI) followed the Langmuir type of adsorption and exhibited a maximum loading capacity of 7.18 mol kg^− 1 at pH 1. Selective removal of Cr(VI) from Zn(II) was successfully demonstrated by using a column packed with the persimmon waste gel.     

Understanding Environmental Leachability of Electric Arc Furnace Dust

Dust from production of steel in an electric arc furnace (EAF) contains a mixture of elements that pose a challenge for both recovery and disposal. This paper relates the leachability of six Canadian EAF dusts in four leaching tests [distilled water, Ontario Regulation 347 Leachate Extraction Procedure, Amount Available for Leaching (AALT), and pH 5 Stat] to their mineralogy. Chromium and nickel contaminants in EAF dust are largely unleachable (<5% available in AALT and pH 5 Stat), as they are found with the predominant spinel ferrite phase in EAF dust. However, even a small proportion of oxidized chromium can result in significant leachate concentrations of highly toxic chromate. The leachability of zinc (7–50% available), lead (2–17% available), and cadmium (9–55% available) can be significant, as large fractions of these contaminants are found as chlorides and oxides. The leaching of these metals is largely controlled by pH. The acid neutralization capacity of the EAF dusts appeared to be controlled by dissolution of lime and zincite, and results from regulatory leaching tests can be misleading because the variable acid neutralization capacity of EAF dusts can lead to very different final leachate pHs (5–12.4). A more informative approach would be to evaluate the total amounts of contaminants available in the long term, and the acid neutralization capacity.     

炼铜烟灰碱浸脱砷的热力学及动力学

基于热力学计算,绘制了常温(298K)条件下Me-S-H2O系(Me:Cu,Pb,Zn,As)Eh-pH图,并对pH=13～15时As2S3、CuS、Cu2S、PbS、ZnS热力学稳定区进行分析。结果表明,在碱浸体系中,砷与铜、铅、锌等有价金属的分离在热力学上是可行的。基于NaOH与(NaOH+Na2S)两种体系中砷的浸出行为研究,为提高铜烟灰碱浸脱砷效率,选择(NaOH+Na2S)浸出体系是适宜的。在该体系中,在303～363K范围内,铜烟灰中砷的浸出过程受内扩散控制,浸出动力学方程遵循未反应收缩核模型。     

从锡熔炼烟尘生产七水硫酸锌及粗锡和粗铅的工艺

文章叙述了从锡熔炼烟尘生产七水硫酸锌及粗锡和粗铅的工艺。用稀硫酸浸出分离锌,锌溶液制备七水硫酸锌;富锡渣熔炼锡铅合金;高温真空蒸馏分离锡和铅。该工艺流程生产粗锡和粗铅工艺处理锡熔炼烟尘效果好,能综合回收锡、铅、锌、铜等金属,锌的回收率≥94%,锡和铅的回收率≥96%。     

Metal-induced modulation of nitric oxide production in vitro by murine macrophages: lead, nickel, and cobalt utilize different mechanisms

Macrophages (M phi) can be induced to produce nitric oxide (NO), which has been suggested to be important for macrophages to exercise various functions. We have previously reported that an environmental toxicant, lead (Pb), can significantly inhibit NO production by murine splenic M phis. Herein, eight additional metal ions, gold (Au), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), and zinc (Zn), were assessed. In addition to Pb, Hg and Cd significantly suppressed NO production by cytokine (interferon-gamma and tumor necrosis factor-alpha)-stimulated murine M phis. Au and Cu also were inhibitory, but less than Pb, Hg, and Cd. In contrast, Cr and Zn were not modulatory, and Ni and Co significantly enhanced NO production by cytokine-stimulated M phis. The enhancement by Ni and Co was inhibited by the arginine analog N-monomethylarginine. The metals showed different activating/inhibiting profiles when added to a cell-free (activated M phi lysate) NO-producing-system in which inducible NO synthase (iNOS) is already expressed. Cr, Cu, Pb, and Zn moderately suppressed iNOS, which suggests that they may directly modify enzyme or cofactor activity. Cd, Hg, Mg, Ni, or Co did not produce any significant effect on NO production by the cell-free system. Inhibition of NO production by Pb-exposed M phis was not due to decreased expression of iNOS nor limited to its modest direct inhibition of iNOS; thus, other mechanism(s) must be accountable for the efficient Pb-induced inhibition of NO production by M phi. Ni or Co did induce a substantial increase of iNOS protein. Overall, these observations provide additional insight into the means by which metals via inhibition or enhancement of NO production may be pathogenic, by suppression of defense mechanisms or induction of hypersensitivity, respectively.     

Metals Removal from Municipal Waste Incinerator Fly Ashes and Reuse of Treated Leachates

Incinerator fly ash from municipal solid waste is considered as a hazardous waste and can release toxic metals such as Pb and Cd into the environment. This research verifies the performance of a sequential, closed circuit treatment process involving chemical leaching (alkaline washings followed by an acid washings) and precipitation (neutralization at pH = 5 and 7). This method also includes the recirculation of treated leachates during the acid washing steps. In total, ten recirculation loops were executed in laboratory pilot scale. The three alkaline leaching steps effectively solubilized the leachable Pb. Two acid leaching steps were required to solubilize Cd, Al, and Zn. Toxic metals, Cd and Pb, were removed from the fly ash at 72 and 30%, respectively. The toxicity characteristic leaching procedure (TCLP), the synthetic precipitation leaching procedure (SPLP), and a simple test using neutral water were conducted on the treated ash in order to validate the process. The results obtained were below the norm for the TCLP and near 0.01?mg/L of Cd and Pb in solution for the other two tests. The removal efficiency during the precipitation step were 21% Cd, 99% Pb, 100% Al, and 63% Zn. The metallic residue produced at pH = 7 contained 23% Zn which is potentially recyclable in the metallurgical industry. The recirculation of treated leachates reduced water consumption for the decontamination process by 60%.     

Fibroblast growth factor-2 and fibroblast growth factor receptor-1 mRNA expression and peptide localization in placentae from normal and diabetic pregnancies

Soils developed on serpentine rocks cover a large area in Albania which contains large reserves of iron, nickel, chromium and copper and is characterised by a high density of mines and metal smelters. This work was conducted to study the flora associated with serpentine and former industrial and mining sites in Albania. Eight sites were investigated in the south-eastern, central and northern parts of the country. Soils were sampled in the Ap horizon and plants were collected and identified. Plant material was allowed to dry before being ground. Soil and plant samples were analysed for total Ca, Cd, Co, Cr, Cu, Mg, Ni, Pb and Zn. Results showed that each site exhibited a high concentration of one or more metals. The maximum concentrations of metals in soils dry matter (DM) were 14 mg Cd kg-1, 476 mg Co kg-1, 3865 mg Cr kg-1, 1107 mg Cu kg-1, 3579 mg Ni kg-1, 172 mg Pb kg-1 and 2495 mg Zn kg-1. The Mg/Ca ratio in serpentine soils varied from 1 to 7.8. A collection of 58 plant species, members of 44 genera and 17 families, were collected. Alyssum markgrafii in the north and Alyssum murale in the south-eastern serpentines had a concentration of 1.26 and 0.85% Ni in DM, respectively. In the species Herniaria hirsuta, a serpentine plant, concentrations of 808 mg Ni kg-1 and 275 mg Cr kg-1 in DM were recorded. Other taxa (Filago, Inula, Picris, Galamintha, Marrubium, Teucrium, Lotus, Ononis and Xeranthemum) from serpentines had a high, but not exceptional Ni content. Some species collected on serpentines and industrial sites presented rather high concentrations of lead or copper in their above-ground parts, probably related to contamination by soil dust.     

某铅锌尾矿库周边土壤重金属污染特征及其来源分析

以某铅锌尾矿库周边土壤为研究对象,测定土壤中Cd、Hg、As、Pb、Cr、Cu、Zn、Ni重金属含量,采用地质统计分析掌握重金属含量空间分布,再利用单因子污染指数、内梅罗综合污染指数和地质累积指数评价重金属污染状况,并结合相关性分析和主成分分析探重金属来源。结果表明,土壤中Cd、Hg、As、Pb、Cr、Cu、Zn、Ni平均含量分别为10.4、1.54、132、653、62.8、73.8、1 392、31.6 mg/kg,越靠近尾矿库,Cd、As、Pb、Cu、Zn、Hg含量越高。内梅罗综合污染指数表明,研究区综合污染指数为11.2,为重污染,单因子污染指数和地质累积指数表明,研究区土壤Cd污染最严重,其次是As、Zn、Pb、Cu、Hg污染,Cr和Ni无污染。相关性分析和主成分分析表明,Cd、Hg、As、Pb、Zn之间存在显著正相关关系,主要受铅锌尾矿库长期堆存、转运及加工等人为活动影响,Cr、Ni主要来自土壤母质,Cu主要受矿业活动和农业活动共同影响。     

Determination of urinary zinc, chromium, and copper in steel production workers

The aim of our investigation was to determine the concentrations of Cu, Zn, and Cr in urine samples under routine clinical laboratory conditions. To assess the reliability of these methods, critical factors such as detection limit(s), calibration range(s), cost, accuracy, and precision were studied. Our method was employed for the quantitative determination of zinc, chromium, and copper in urine samples from steel production and quality control (QC) workers and healthy unexposed controls. After pretreatment with acids, the samples were digested via a microwave oven. Zinc was determined by flame absorption spectrophotometry (FAAS), whereas chromium and copper were determined by a graphite-furnace atomic absorption spectrophotometry (GFAAS). Our results indicate that urinary zinc, chromium, and copper levels of the exposed workers are significantly higher than those of the controls. The possibility that these metals are involved in the etiology of diseases is discussed and recommendations are made to improve workplace ventilation and industrial hygiene practices.     

复杂含锌矿物高效复合配位提取研究

针对复杂含锌矿物多金属伴生、物相组成复杂、碱性脉石含量高的特点,提出了第一配体为NH3、第二配体为氨三乙酸（NTA）,复杂含锌矿物复合配位提取新技术。在分析复杂含锌矿物物性特点的基础上,对单配体模型和复合配体模型中锌组分配位溶解过程进行了计算,确定了可配位溶解硅酸锌的配体,及复合配位体系的稳定常数,并利用NTA在等电点条件下溶解度最低原理,提出采用蒸氨―加酸工序从浸出溶液中回收NTA。研究证明,第一配体NH3仅能配位提取碳酸盐类含锌矿物,一定程度上限制了氨性配位浸出的广泛应用;NH4Cl-NH3-NTA（0.5 mol/L）复合体系的配位稳定常数为14.08,比NH4Cl-NH3体系配位能力提高4.62;NTA中氨基的N原子和羧基中的O原子与锌离子形成稳定的金属螯合物,促进传统的Zn(NH3)42+配合物向更为稳定的ZnNTA(NH3)2多配位配合物转变,锌浸出率提高113.4%;当浸出溶液pH调至1.30时,浸出溶液中NTA浓度降低至1.15 g/L,NTA回收率为96.0%。复杂含锌矿物高效复合配位提取新技术对于突破温和化学环境下多矿相有价金属的高效提取与利用具有重要指导意义。     

Thermal Treatment for Incinerator Ash: Evaporation and Leaching Rates of Metals

The disposal of different residues containing high concentrations of heavy metals causes environmental problems. To understand the effects of various properties of the residues on the evaporation and leaching rates of heavy metals (Cd, Pb, Zn, Cr, and Cu) by thermal treatment, three types of residues (including bottom ash, spray dryer ash, and baghouse ash) generated from various incineration conditions including spray dryer additives (SiO2, CaCl2, and NaHCO3), and feedstock additives [polyvinyl chloride (PVC), and NaCl] were investigated in the present study. The results indicated that the evaporation rate of Cd and Pb in the spray dryer ash and in the baghouse ash was higher than that in the bottom ash. The leaching rate of heavy metals in the spray dryer ash was less than 20% before the thermal treatment when Ca(OH)2 was used in the spray dryer. The addition of PVC could increase the evaporation rate of Zn in the spray dryer ash, whereas the addition of NaCl could decrease the leaching rate of Zn and Cu in the baghouse ash after the thermal treatment.     

硫酸铵对离子型稀土矿区土壤重金属的释放和形态转化影响

针对离子型稀土矿区浸矿过程导致的土壤氨氮、重金属复合污染问题,研究硫酸铵残留对土壤重金属迁移转化和形态的影响机制。通过土柱淋滤和室内土壤培养考察不同浓度浸矿剂输入土壤后,氨氮、重金属Zn、Cu和Cr的形态和迁移性变化。实验结果表明,与无浸矿剂淋滤对照组相比较,浸矿剂在重金属污染土壤中主要以氨氮形式存在,硝态氮占比低。在培养期间,浸矿剂硫酸铵淋滤降低了土壤pH值和土壤阳离子交换量（CEC）,重金属活性增加,当浸矿剂淋滤浓度为5%时,弱酸态Cr、Cu、Zn比例分别提高8.29%、5.21%、4.53%。研究结果表明：硫酸铵加剧了土壤酸化,提高重金属迁移性,促进重金属形态从生物不可利用态向可利用态转化。     

某矿区农田土壤重金属分布特征与生态风险评价

为探明贵州六盘水某矿区周边农田土壤重金属的分布特征及污染程度,以矿区周边农田为研究对象,采集表层土壤测定Cr、Ni、Cu、Pb、Zn和As含量,分析重金属空间分布特征,评价土壤重金属污染程度及潜在生态风险,并探究其来源。结果显示,6种重金属元素含量均高于贵州省土壤重金属背景值,超标倍数依次为Cu(5.82)>Ni(2.52)>Zn(2.46)>Pb(1.81)Cr(1.51)>As(1.18),重金属分布显示矿区煤矸石山和洗选厂周边的农田土壤重金属富集较为严重。单项污染指数均值显示Cu处于重度污染水平,Ni、Zn为轻度污染水平,Pb、Cr、As为轻微污染水平;综合污染处于重度污染级别。地质累积指数法评价结果显示:Cu、Ni、Zn、Pb处于轻度污染,Cr、As表现为尚未污染水平。研究区重金属的综合潜在生态风险指数为68.02,已经达到轻度危害程度,其中Cu、Ni对综合潜在生态风险(RI)的贡献最大。多元统计分析结果显示,Zn与Pb、Zn与As以及Cu与Pb的相关性较强,表明Zn、Pb、AS、Cu的来源较相似,为第一类来源,主要源于采矿活动产生的三废;Ni、Cr分别为第二、三类来源,第二类重金属来源与汽车尾气的排放、机械损耗有关;第三类重金属主要受土壤母质影响。4种评价结果基本一致,矿区周边农田土壤重金属处于重度污染,轻度危害程度,Cu、Ni是研究区土壤影响最显著的生态风险因子,重金属主要源于采矿活动产生的三废。     

湖南有色黄沙坪矿业公司铅-硫混浮工艺研究

文章针对黄沙坪矿业公司铅锌选厂铅矿物在高pH的情况下才有良好的可浮性,锌矿物在pH达到9～10才具有良好的可浮性,以及黄铁矿在pH值为弱酸性时才有良好可浮性的特点,采用了A01＋A02混合抑制剂来抑制锌矿物并改善介质pH值的方法,获得了较理想的指标,其中铅精矿：β=68．7％,ε=90．97％;锌精矿：β=45．47％,ε=92．77％;硫精矿：β=45％,ε=56％。