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1.
Almost all metallurgical processes are associated with the generation of wastes and residues that may be hazardous or non-hazardous in nature depending upon the criteria specified by institutions such as the US Environment Protection Agency, etc. Wastes containing heavy and toxic metals such as arsenic, cadmium, chromium, nickel, lead, copper, mercury, zinc, etc., that are present beyond permissible limits deemed to be treated or disposed of, and non-hazardous wastes can be utilized for metal recovery or safe disposal. Zinc is in growing demand all over the world. In India, a major amount of zinc is imported and therefore processing of zinc secondaries will assist in satisfying the gap between demand and supply to some extent. This report mainly focuses on the current practices and recent trends on the secondary processing of zinc. Attempts made by various laboratories to develop ecofriendly processes for the recovery of zinc from secondary raw materials are also described and discussed.  相似文献   

2.
Yttrium is important rare earths (REs) used in numerous fields, mainly in the phosphor powders for low-energy lighting. The uses of these elements, especially for high-tech products are increased in recent years and combined with the scarcity of the resources and the environmental impact of the technologies to extract them from ores make the recycling waste, that contain Y and other RE, a priority.The present review summarized the main hydrometallurgical technologies to extract Y from ores, contaminated solutions, WEEE and generic wastes. Before to discuss the works about the treatment of wastes, the processes to retrieval Y from ores are discussed, since the processes are similar and derived from those already developed for the extraction from primary sources.Particular attention was given to the recovery of Y from WEEE because the recycle of them is important not only for economical point of view, considering its value, but also for environmental impact that this could be generated if not properly disposal.  相似文献   

3.
Clean processing of copper converter slag to reclaim cobalt and copper could be a challenge. An innovative and environmentally sound approach for recovering valuable metals from such a slag has been developed in the present study. Curing the slag with strong sulphuric acid, without re-smelting or roasting as practiced currently in the industry, render it accessible to leaching, and more than 95% of cobalt and up to 90% of copper was extracted together with iron by water leaching, leaving silica behind in a residue. The copper in the leach liquor was recovered by cementation with iron and the dissolved iron crystallized as ferrous sulphate monohydrate. The cobalt in the mother-liquor rich in iron was recovered by either cementation or sulphide precipitation. Operation variables in the new process were also investigated and optimized.  相似文献   

4.
The present work focuses on investigation of the effective recovery of heavy metals from molten fly ash by applying chloride-induced volatilization. In particular, the effect of unburned carbon on the chloride-induced volatilization of lead, zinc, and copper from model and real molten fly ashes was investigated in the temperature range 873–1173 K under a N2 atmosphere. As a result, almost 100% of lead and a significant proportion of zinc were volatilized from the real molten fly ash samples at 1173 K. In contrast, for the model fly ash, volatilization ratios of lead and zinc at 1173 K were only 85% and 25%, respectively. Further, the results of X-ray diffraction analysis suggested that PbO in molten fly ash was converted either to Pb2OCl2 or Pb by respective chlorination and reduction reactions. Meanwhile ZnO and CuO in the molten fly ash were reduced to Zn and Cu by reaction with unburned carbon. Subsequently, Pb, Zn, and Pb2OCl2 were volatilized, but Cu remained in the solid residue. Finally, the volatilization ratio of zinc increased with the addition of carbon, and more than 98% of zinc was volatilized at 1173 K from a fly ash with a carbon content of 20%.  相似文献   

5.
The aim of this paper is the recovery of manganese and zinc from a mixture of zinc-carbon and alkaline spent batteries, containing 40.9% of Mn and 30.1% of Zn, after preliminary physical treatment followed by removal of mercury. Separation of the metals has been carried out on the basis of their different boiling points, being 357°C and 906°C the boiling point of mercury and zinc and 1564°C the melting point of Mn(2)O(3). Characterization by chemical analysis, TGA/DTA and X-ray powder diffraction of the mixture has been carried out after comminution sieving and shaking table treatment to remove the anodic collectors and most of chlorides contained in the mixture. The mixture has been roasted at various temperatures and resident times in a flow of air to set the best conditions to remove mercury that were 400°C and 10min. After that, the flow of air has been turned into a nitrogen one (inert atmosphere) and the temperatures raised, thus permitting the zinc oxide to be reduced to metallic zinc by the carbon present in the original mixture and recovered after volatilization as a high grade concentrate, while manganese was left in the residue. The recovery and the grade of the two metals, at 1000°C and 30min residence time, were 84% and 100% for zinc and 85% and 63% for manganese, respectively. The recovery of zinc increased to 99% with a grade of 97% at 1200°C and 30min residence time, while the recovery and grade of manganese were 86% and 87%, respectively, at that temperature. Moreover, the chlorinated compounds that could form by the combustion of the plastics contained in the spent batteries, are destroyed at the temperature required by the process.  相似文献   

6.
Electrical electronics constitute a significant quantity of municipal solid wastes which are discarded after use in open dumpsites especially in the developing countries. The aim of this study was to characterise the material and chemical components, evaluate current management practices and investigate recovery of lead from battery electrodes (BEs) of waste rechargeable electric lamps (RLs). Twenty-six waste RLs of different models were sampled in Nigeria and characterised. Their BEs were analysed for Pb, Cr, Mn, Cu, Zn, Ni and Fe after acid digestion. Questionnaires were distributed to unselected respondents to assess usage and disposal of the lamps. Reaction of citric acid solutions with Pb in the presence of H2O2 was used for the recovery of Pb. 69 % of the respondents disposed their waste RLs in open dumpsites. The mean ± SD concentrations of Pb, Cr, Mn, Cu, Zn, Ni and Fe in the BEs were 600 ± 0.2 g/kg, 65.4 ± 40 mg/kg, 5.05 ± 4.0 mg/kg, 6.81 ± 5.0 mg/kg, 5.98 ± 3.0 mg/kg, 50.0 ± 30 mg/kg and 40.2 ± 35 mg/kg, respectively. The results show that the batteries are lead-acid batteries which require management. At the optimal conditions of S/L = 0.14, temperature = 20 °C and leaching time = 5 h, about 95 % Pb was recovered in form of lead citrate from the battery. High recovery of Pb is possible with simple and environment-friendly reactions.  相似文献   

7.
Lead can be recovered from funnel glass of waste cathode ray tubes via reduction melting. While low-temperature melting is necessary for reduced energy consumption, previously proposed methods required high melting temperatures (1400 °C) for the reduction melting. In this study, the reduction melting of the funnel glass was performed at 900–1000 °C using a lab-scale reactor with varying concentrations of Na2CO3 at different melting temperatures and melting times. The optimum Na2CO3 dosage and melting temperature for efficient lead recovery was 0.5 g per 1 g of the funnel glass and 1000 °C respectively. By the reduction melting with the mentioned conditions, 92% of the lead in the funnel glass was recovered in 60 min. However, further lead recovery was difficult because the rate of the lead recovery decreased as with the recovery of increasing quantity of the lead from the glass. Thus, the lead remaining in the glass after the reduction melting was extracted with 1 M HCl, and the lead recovery improved to 98%.  相似文献   

8.
This two-part paper assesses four strategies for energy recovery from municipal solid waste (MSW) by dedicated waste-to-energy (WTE) plants generating electricity through a steam cycle. The feedstock is the residue after materials recovery (MR), assumed to be 35% by weight of the collected MSW. In strategy 1, the MR residue is fed directly to a grate combustor. In strategy 2, the MR residue is first subjected to light mechanical treatment. In strategies 3 and 4, the MR residue is converted into RDF, which is combusted in a fluidized bed combustor. To examine the relevance of scale, we considered a small waste management system (WMS) serving 200,000 people and a large WMS serving 1,200,000 people. A variation of strategy 1 shows the potential of cogeneration with district heating. The assessment is carried out by a Life Cycle Analysis where the electricity generated by the WTE plant displaces electricity generated by fossil fuel-fired steam plants. Part A focuses on mass and energy balances, while Part B focuses on emissions and costs. Results show that treating the MR residue ahead of the WTE plant reduces energy recovery. The largest energy savings are achieved by combusting the MR residue "as is" in large scale plants; with cogeneration, primary energy savings can reach 2.5% of total societal energy use.  相似文献   

9.
This two-part paper assesses four strategies for energy recovery from Municipal Solid Waste (MSW) by dedicated Waste-To-Energy (WTE) plants. In strategy 1, the residue of Material Recovery (MR) is fed directly to a grate combustor, while in strategy 2 the grate combustor comes downstream of light mechanical treatment. In strategies 3 and 4, the MR residue is converted into Refuse Derived Fuel (RDF), in a fluidized cumbuster bed. The results of Part A, devoted to mass and energy balances, clearly show that pre-treating the MR residue in order to increase the heating value of the feedstock fed to the WTE plant has marginal effects on the energy efficiency of the WTE plant. When considering the efficiency of the whole strategy of waste management, the energy balances show that the more thorough the pre-treatment, the smaller the amount of energy recovered per unit of MR residue. Starting from the heat/mass balances illustrated in Part A, Part B examines the environmental impacts and economics of the various strategies by means of a Life Cycle Assessment (LCA). Results show that treating the MR residues ahead of the WTE plant does not provide environmental or economic benefits. RDF production worsens almost all impact indicators because it reduces net electricity production and thus the displacement of power plant emissions; it also increases costs, because the benefits of improving the quality of the material fed to the WTE plant do not compensate the cost of such improvement.  相似文献   

10.
Remediation processes for recovery and reuse of chromated-copper-arsenate- (CCA) treated wood are not gaining wide acceptance because they are more expensive than landfill disposal. One reason is the high cost of the nutrient medium used to culture the metal-tolerant bacterium, Bacillus licheniformis, which removes 70-100% of the copper, chromium, and arsenic from CCA-treated southern yellow pine (CCA-SYP) in a two-step process involving oxalic acid extraction and bacterial culture. To reduce this cost, the nutrient concentration in the culture medium and the ratio of wood to nutrient medium were optimized. Maximum metal removal occurred when B. licheniformis was cultured in 1.0% nutrient medium and at a wood to nutrient medium ratio of 1:10. Also, malted barley, an abundant by-product of brewing, was evaluated as an alternative nutrient medium. Tests were done to determine absorption of metals by barley, and the results indicate that the barley acted as a biosorbent, removing heavy metals from the liquid culture after their release from CCA to SYP. For comparison, tests were also performed with no nutrient medium. Following bacterial remediation, 17% copper and 15% arsenic were removed from an aqueous slurry of CCA-SYP (no medium). When oxalic acid extraction preceded the aqueous bacterial culture, 21% copper, 54% chromium, and 63% arsenic were removed. The two-step process (oxalic acid extraction and bacterial culture with nutrient medium) appears to be an effective, yet costly, way to remove metals.  相似文献   

11.
The immobilization of MSWI-scrubber residues with soluble PO4(3-) was studied and compared to the immobilization using cement. The DIN 38414-S4 leaching protocol and pH dependent leaching were used to evaluate the leaching of Pb and Zn. Four different scrubber residues from MSW combustion (Pb concentration: 2.8-4.8 mg/g; Zn concentration: 3.0-12.3 mg/g) were mixed with water and cement or Na2HPO4 as source of soluble PO4(3-) at dosages of at least 0, 0.1, 0.2, 0.3 and 0.4 g per g residue. With cement as well as with PO4(3-) a reduction in Pb and Zn leaching was observed. With 0.4 g cement per g residue, the Pb leaching was reduced by a factor ranging from 70 to 100, but still exceeded the Pb landfill limit of 2 mg/l. With PO4(3-) the Pb leaching was reduced with a factor of 100-300 to below 2 mg/l. The Zn landfill limit (10 mg/l) was only exceeded by one untreated residue. Adding 0.2 g cement or 0.1 g PO4(3-) per g of that residue was enough to reduce leaching below 10 mg/l. However, when 0.6 g Na2HPO4 per g residue was added to a lime based scrubber residue, an increase in Zn leaching up to 12.5 mg/l was observed due to an increase in pH of up to 13.0. When using NaH2PO4 and H3PO4 no such increase in Zn leaching was observed. pH dependent leaching performed on one of the four residues showed that in the pH range of 2.5-6, Pb leaching was 100-50 times lower with Na2HPO4 treatment than with cement. In the pH range from 7-11, almost equal results were obtained for cement treated and Na2HPO4 treated residue. Above a pH of 12, Pb leaching was three times lower for the PO(4)(3-)-treated residue than for the cement treated residue. With soluble PO4(3-), Pb leaching below 2 mg/l could be attained at a dosage of 0.27 g PO4(3-)/g residue. With cement, Pb leaching was never below 2 mg/l.  相似文献   

12.
Used batteries contain numerous metals in high concentrations and if not disposed of with proper care, they can negatively affect our environment. These metals represent 83% of all spent batteries and therefore it is important to recover metals such as Zn and Mn, and reuse them for the production of new batteries. The recovery of Zn and Mn from used batteries, in particular from Zn–C and alkaline ones has been researched using hydrometallurgical methods. After comminution and classification of elemental components, the electrode paste resulting from these processes was treated by chemical leaching. Prior to the leaching process the electrode paste has been subjected to two washing steps, in order to remove the potassium, which is an inconvenient element in this type of processes. To simultaneously extract Zn and Mn from this paste, the leaching method in alkaline medium (NaOH solution) and acid medium (sulphuric acid solution) was used. Also, to determine the efficiency of extraction of Zn and Mn from used batteries, the following variables were studied: reagents concentration, S/L ratio, temperature, time. The best results for extraction yield of Zn and Mn were obtained under acid leaching conditions (2 M H2SO4, 1 h, 80 °C).  相似文献   

13.
##正##(接上期)4.5签定销售合同售方和购方之间应签定标的为制备批次电子废件的标准合同。合同中应指明双方义务,含贵金属废件与废料的准备与发货方法,验收、取样分析方法,结算方法和双方责任。4.6运输批次电子废件的运输必须遵守以下条件。4.6.1含金及铂族金属大于5%的废件与废料,其运输应按照俄罗斯联邦通信部关于贵重品运输的细则并经专用通道实施。  相似文献   

14.
俄罗斯国家电讯委员会根据政府会议纪要(ИК-П8-5)制定并批准实行的《从报废的计算技术器材中综合回收贵金属的方法》,旨在为不同所有制企业实施从报废的国产或进口计算机中综合回收贵金属提供规范的方法,对我国报废计算机回收利用方法的制定和实行具有重要的借鉴意义。  相似文献   

15.
钴镍金属二次资源回收利用现状及发展对策研究   总被引:1,自引:0,他引:1  
介绍了世界钴镍金属资源分布及其二次资源综合利用概况.以国内外废旧电池和催化剂中的钴镍资源为例,对其回收体系和利用技术现状进行了概述,并提出了存在的问题和解决问题的建议.  相似文献   

16.
Fly ash generated from MSW ash-melting and gasification-melting plants, known as Melting Furnace Fly Ash (MFA), contains considerable amounts of heavy metals such as Pb and Zn. These metals can be recovered using a smelting furnace after "pre-treatment" for removal of unnecessary elements such as Cl, Sn and Si. Chemical methods have been studied for pretreatment in the past. However, they have been discussed only with regard to treatment cost and the concentration of Pb and Zn recovered, but neither applicability to various types of MFA nor the environmental impact have been considered. In this study, acid, alkaline and ammonia/chloride leaching methods were compared from the standpoints of: (1) applicability to MFA, (2) concentration of Pb and Zn recovered, (3) treatment cost, and (4) environmental impact. Twenty-three samples of MFAs were collected and classified into 4 types based on element contents. A Pb and Zn recovery experiment was conducted for the representative MFA of those types. The results showed: (1) MFA from gasification-melting plants cannot be treated by chemical methods; (2) the other MFA can be treated to an acceptable quality by existing smelting furnaces; (3) only MFA from electric resistance ash-melting plants can be treated easily by the water washing method; and (4) alkaline and ammonia/chloride leaching methods were more effective than acid leaching.  相似文献   

17.
In this study, three possible improvements to a remediation process for chromated-copper-arsenate- (CCA) treated wood were evaluated. The process involves two steps: oxalic acid extraction of wood fiber followed by bacterial culture with Bacillus licheniformis CC01. The three potential improvements to the oxalic acid extraction step were (1) reusing oxalic acid for multiple extractions, (2) varying the ratio of oxalic acid to wood, and (3) using a noncommercial source of oxalic acid such as Aspergillus niger, which produces oxalic acid as a metabolic byproduct. Reusing oxalic acid for multiple extractions removed significant amounts of copper, chromium, and arsenic. Increasing the ratio of wood to acid caused a steady decline in metal removal. Aspergillus niger removed moderate amounts of copper, chromium, and arsenic from CCA-treated wood. Although A. niger was effective, culture medium costs are likely to offset any benefits. Repeated extraction with commercial oxalic acid appears to be the most cost-effective method tested for the two-step process.  相似文献   

18.
This article presents a review of in situ technologies for the remediation of soils contaminated with lead, zinc, and/or cadmium. The objective of this review is to assess the developmental status of the available in situ technologies and provide a general summary of typical applications and limitations of these technologies. The literature review identified seven in situ remediation technologies—solidification/stabilization, vitrification, electrokinetic remediation, soil flushing, phytoextraction, phytostabilization, and chemical stabilization. These technologies were considered for their ability to meet a specific set of remediation objectives under a range of conditions. Each of these technologies has both strengths and weaknesses for addressing particular remedial situations discussed in the article for each of the technologies. A general summary of which technologies are most applicable to common remedial scenarios is also provided. © 2004 Wiley Periodicals, Inc.  相似文献   

19.
Mixed metal-containing waste, polychlorinated biphenyls (PCB) containing capacitors, printed circuit boards, steel mill dust and metal sludge were among the most common wastes exported from Taiwan. Before the implementation of the self-monitoring model programme of the Basel Convention (secretariat of the Basel Convention 2001) in the Asia region, Taiwan conducted a comprehensive 4-year follow-up project involving government authorities and the waste disposal facilities of the importing countries. A total of five countries and nine plants were visited in 2001-2002. The following outcomes can be drawn from these investigations. The Chinese government adopts the strategies of 'on-site processing' and 'relative centralization' on the waste management by tightening permitting and increasing site inspection. A three-level reviewing system is adopted for the import application. The United States have not signed the Basel Convention yet; the procedures of hazardous waste import rely on bilateral agreements. Importers are not required to provide official notification from the waste exporting countries. The operation, administration, monitoring and licensing of waste treatment plants are governed by the state environmental bureau. Finland, France and Belgium are members of the European Union. The procedures and policies of waste import are similar. All of the documents associated with transboundary movement require the approval of each government involved. Practically, the notification forms and tracking forms effectively manage the waste movement.  相似文献   

20.
Recycling of carpet waste is not extensively carried out because of its complex combination of materials. A representative type of carpet consists of three layers: nylon fibers, adhesives, and backing materials made of poly(vinyl chloride), PVC. Thermal treatment of carpet waste, thus, leads to the emission of hazardous chlorinated compounds. In the present work, we have employed the one-directional thermal treatment of the backing materials under the presence of zinc oxide, which promotes the thermal degradation of PVC. Nylon fibers could be effectively recovered by the consequent milling treatment from the brittle backing materials. The influence of process parameters, such as pyrolysis temperature and reaction time, on the separation efficiency is discussed.  相似文献   

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