Conversion of chromium-containing solid wastes into value-added products through a plasma-assisted aluminothermic process

Chromium-containing solid wastes have been generated by chemical and leather/tanning industries, and the management and proper disposal of the same wastes have been challenging tasks. A significant fraction of these wastes contains chromium compounds with chromium present in the hexavalent (Cr⁺⁶) form, which is hazardous to human beings, animals, and ecosystems. Since these wastes are discarded largely without proper treatments, soil and groundwater get contaminated and they can cause several health issues to human beings. Conventional methods developed to convert hazardous Cr⁶⁺ to Cr³⁺/Cr metal either generate secondary toxic wastes and unwanted by-products and/or are time-consuming processes. In this work, a plasma-assisted aluminothermic process is developed to convert the toxic waste into non-toxic products. The waste was mixed with aluminium powder and subjected to transferred arc plasma treatment in a controlled air atmosphere. Chemical analysis and Cr leachability studies of the waste material prior to plasma treatment have shown that it is highly toxic. Analysis of the products obtained from the plasma treatment showed that Cr and Fe present in the waste could be recovered as a metallic mixture as well as oxide slag, which were found to be non-toxic. Easy separation of the metallic fraction and the slag from the treated product is one of the merits of this process. Besides converting chromium-containing toxic waste to non-toxic materials, the process is rapid and recovers the metals from the waste completely.

     

Vermicomposting as an advanced biological treatment for industrial waste from the leather industry

The leather industry (tanneries) generates high amounts of toxic wastes, including solid and liquid effluents that are rich in organic matter and mineral content. Vermicomposting was studied as an alternative method of treating the wastes from tanneries. Vermicompost was produced from the following tannery residues: tanned chips of wet-blue leather, sludge from a liquid residue treatment station, and a mixture of both. Five hundred earthworms (Eisenia fetida) were added to each barrel. During the following 135 days the following parameters were evaluated: pH, total organic carbon (TOC), organic matter (OM), cation exchange capacity (CEC), C:N ratio, and chromium content as Cr (III) and Cr (VI). The results for pH, TOC and OM contents showed decreases in their values during the composting process, whereas values for CEC and total nitrogen rose, indicating that the vermicompost reached maturity. For chromium, at 135 days, all values of Cr (VI) were below the detectable level. Therefore, the Cr (VI) content had probably been biologically transformed into Cr (III), confirming the use of this technique as an advanced biological treatment. The study reinforces the idea that vermicomposting could be introduced as an effective technology for the treatment of industrial tannery waste and the production of agricultural inputs.     

Incineration of hazardous wastes from the petroleum industry in Nigeria

Persistent hazardous wastes are produced in the recovery, processing and upgrading of crude petroleum in Nigeria. However, recent developments in environmental pollution control are drawing increasing attention to the problems of hazardous wastes. The ever-increasing need to control these wastes from the petroleum industry often compels the chemical engineer to specify methods of treatment and disposal. Present methods for disposal are becoming increasingly undesirable for a number of reasons, and incineration is being considered as an alternative. This paper reviews the extent of hazardous waste generation from the Nigerian petroleum industry and its environmental implications. It also examines the current disposal methods and the incineration technology option. The major chemical engineering concepts of the incineration process and the principles guiding their operations are discussed. The potential for the use of incineration is examined, as well as information that would aid the choice of incineration system for new applications.     

PVC废物及其处理技术

PVC广泛应用于工业和日常生活中 ,PVC废物的产生量将会在将来一段时间内持续增长 ,对PVC废物处理处置问题研究成为固体废物处理处置的一个方向。目前 ,PVC废物还缺乏系统、完善的管理手段和处理技术。本文在分析PVC废物特点其环境潜在危害特性的基础上 ,比较分析各种PVC废物处理技术的优势和存在的问题 ,及国内外在PVC废物处理处置方面的具体实践 ,以期探讨PVC废物的处理对策并提出今后PVC废物处理的发展趋势和研究方向     

Environmental impact and diversity of protease-producing bacteria in areas of leather tannery effluents of Sialkot,Pakistan

Environmental Science and Pollution Research - Massive discharge of wastes produced by the processing of leather so far confers the most important environmental challenge facing the tanneries...     

The Development of Open Pit Incinerators for Solid Waste Disposal

A discussion is presented of a newly developed incinerator for the disposal of solid wastes. It is distinguished from conventional types by its open top, and features a system of closely spaced nozzles admitting a screen of high-velocity air over the burning zone. Results, with a variety of solid industrial wastes, show high burning rates, leading to complete combustion and high flame temperature.     

Treatment Technologies for Hazardous Wastes: Part 1 Treatment Alternatives for Dioxin Wastes

The 1984 Amendments to the Resource Conservation and Recovery Act (RCRA), called the Hazardous and Solid Waste Amendments, (HSWA) direct the EPA to determine if dioxin bearing wastes should be prohibited from landfills. This determination is to made by November 1986. Barring a determination by the Agency that the land disposal of dioxin wastes does not represent a threat to the environment, ot that appropriate alternative treatment technology is not available, a land disposal prohibition would go into effect at that time.¹ The purpose of this paper is to discuss the state of the art for several treatment processes for dioxin wastes that have been proposed to be used instead of land disposal for disposing of solid and liquid wastes containing dioxins.     

安全土地填埋技术在我国的应用

沈阳市固体废物处置中心对工业危险废物采用了安全土地填埋技术 ,它的主要特点是安全、工艺简单、可操作性强。能够杜绝危险废物渗析液下渗污染地下水 ,同时又避免了危险废物污染环境卫生。本文主要以沈阳工业危险废物处置填埋场为例 ,介绍安全土地填埋的技术要求、设计要点等     

Ammonia emissions from the composting of different organic wastes. Dependency on process temperature

Ammonia emissions were quantified for the laboratory-scale composting of three typical organic wastes with medium nitrogen content: organic fraction of municipal solid wastes, raw sludge and anaerobically digested sludge; and the composting of two wastes with high nitrogen content: animal by-products from slaughterhouses and partially hydrolysed hair from the leather industry. All the wastes were mixed with the proper amount of bulking agent. Ammonia emitted in the composting of the five wastes investigated revealed a strong dependence on temperature, with a distinct pattern found in ammonia emissions for each waste in the thermophilic first stage of composting (exponential increase of ammonia emitted when increasing temperature) than that of the mesophilic final stage (linear increase of ammonia emissions when increasing temperature). As composting needs high temperatures to ensure the sanitisation of compost and ammonia emissions are one of the main environmental impacts associated to composting and responsible for obtaining compost with a low agronomical quality, it is proposed that sanitisation is conducted after the first stage in large-scale composting facilities by a proper temperature control. CAPSULE: Ammonia emission pattern and correlation with process temperature are presented for the composting process of different organic wastes.     

Waste incineration in cement plants: constraints and development opportunities (a French-German comparison)

Is it possible to reconcile economic and ecological concerns? This article examines, through a French-German comparison, the case of obtaining a calorific value for wastes used as substitute fuels in cement kilns. On the one hand, this new strategy for obtaining needed inputs offers to the cement industry an economic opportunity for lowering production costs (the main determinant of competitivity in this sector). On the other hand, the controlled incineration of wastes allows the cement industry to present an 'environmentally friendly' image (savings of primary energy inputs, reductions in solid waste disposal requirements). Commercial decisions to invest in waste incineration options therefore must take account of a variety of supply cost, regulatory, and social factors that render uncertain the economic viability and social legitimacy of the choice.     

含重金属水处理污泥的固化和浸出毒性研究

工业危险固体废物在进行安全填埋前需要进行固化稳定处理。针对电镀厂和皮革厂含重金属的水处理污泥 ,用不同比例的水泥、粉煤灰进行固化稳定处理。考虑酸雨环境 ,浸出实验采用TCLP标准。电镀厂污泥单独固化时 ,其浸出液中铜离子浓度由 78 0mg/L下降到 1 5mg/L ;镍离子浓度由 2 2 4 5mg/L下降到 2 2 2mg/L ,高于危险废物允许进入填埋区 15mg/L的控制限值。电镀厂污泥与皮革厂污泥混合后固化 ,浸出液毒性明显降低。铜离子的浸出浓度降低到1 98mg/L ,镍离子降低到 4 10mg/L ,总铬降低到 0 4 0mg/L ,各项指标均低于国家危险废物允许进入填埋区的控制限值 ,可安全填埋。     

Chemical Manufacturers Association 1984 Hazardous Waste Survey

This paper discusses the Chemical Manufacturers Association's 1984 survey of the chemical industry's hazardous waste management practices. The survey data include a breakdown of how the industry's hazardous wastes are managed, detailing generation, treatment and disposal, and cover 725 plants in 81 companies. The 1984 survey is the third CM A hazardous waste survey, and the paper discusses resultant waste treatment trends from 1981- 1984, the period covered by previous surveys. A total of 278.5 million tons of hazardous waste was treated and disposed by survey respondents. Of this, 276.8 million tons was hazardous wastewater and 1.7 million tons was solid hazardous waste. The survey solid hazardous waste total was projected to the entire industry (Standard Industrial Code 2800) and is estimated at 6.9 million tons. The survey showed continued decreasing trends in hazardous waste generation in the chemical industry. It demonstrated changes in hazardous waste management practices, with decreased use of landfills and increased incineration of the solid wastes that are generated.     

宝应县工业固体废物污染现状及防治对策

近年来,随着宝应县大力实施工业强县战略,规模企业群体加快壮大,固体废物的产生量也随之不断增加,构成类别逐步呈现多样化,尤其是工业固废污染环境状况由此变得严峻起来。本文在近年来环境统计及2007年度污染源普查数据的基础上,对宝应县工业固体废物的产生、构成、处置现状进行了分析,并针对该县在处置利用工业固体废物过程中存在的问题,提出了相应的对策和建议。     

苏州市生活垃圾两种处置方法的生命周期影响评价

采用生命周期评价的方法，比较了苏州市垃圾填埋和垃圾焚烧2种处置方法对环境的影响。研究的系统范围主要包括垃圾收集、垃圾运输、垃圾填埋或焚烧以及发电等几个部分。采用收集的垃圾组分数据，利用IPCC推荐的模型等，计算了垃圾填埋和垃圾焚烧时CO₂等气体污染物的排放量。根据对垃圾渗滤液的实测数据，计算了水污染物的排放量。环境影响评价采用日本开发的AIST-LCA Ver4计算机软件进行。计算结果表明：垃圾填埋的生态币值要大得多，可见垃圾焚烧对环境的影响比垃圾填埋的影响要小。所获得的结论较为客观地反映了对环境的影响，可以作为中国城市垃圾处置决策的参考依据。     

Waste Streams,Technology, and State Requirements

Biomedical wastes are generated by hospitals, laboratories, animal research facilities, and by other institutional sources. The disposal of these wastes is coming under critical public scrutiny, and regulations are being promulgated to control their disposal. Incineration is not a final disposal method since it generates a solid residue (ash) which must be buried or otherwise disposed. The incineration process, however, renders the waste non-toxic, non-hazardous, and non-putrescible, and reduces the volume of material for ultimate disposal by an order of magnitude. In some instances, the residue may have high levels of heavy metals; however, this is the exception rather than the rule.     

典型建筑固体废弃物再生骨料对环保砖性能的影响

随着我国城市化和工业化进程的快速推进,城市建设产生大量的建筑废弃物,燃煤电厂产生大量炉底渣,建筑固废的处置在城市可持续发展过程中备受关注。以建筑垃圾再生骨料、炉底渣和石粉等区域特色的骨料制备环保砖,系统考察了骨料对环保砖力学性能的影响。实验结果表明,再生骨料的种类对环保砖抗压强度的影响显著。再生骨料中混凝土的增加,环保砖抗压强度逐渐增加;而再生骨料中粘土砖含量的增加,环保砖抗压强度明显降低。环保砖抗压强度随炉底渣的含量增加而降低,石粉对环保砖抗压强度有提升作用。     

Occurrences and inventories of heavy metals and brominated flame retardants in wastes from printed circuit board production

Pollutants including heavy metals and brominated flame retardant were detected in 10 types of production wastes from a typical printed circuit board manufacturing plant, and their inventories were estimated. Rinsing water from etching process had the highest concentrations of copper (665.51 mg/L), lead (1.02 mg/L), nickel (3.60 mg/L), chromium (0.97 mg/L), and tin (1.79 mg/L). Powdered solid waste (SW) from the cut lamination process contained the highest tetrabromobisphenol-A (TBBPA) levels (49.86 mg/kg). Polybrominated diphenyl ethers (PBDEs) were absent in this plant, in agreement with the international regulations of PBDE phase out. The pollutant inventories in the wastes exhibited in the order of copper >?>?zinc?>?tin?≈?nickel?>?lead?>?chromium >?>?TBBPA. The potential environmental impact of pollutants in SW during production and disposal were further investigated. A high partitioning of pollutant concentration between the total suspended particle and SW (?0.10?K _TS?相似文献   

Burning Chemical Wastes as Fuels in Cement Kilns

Hazardous wastes in the environment represent one of our most serious problems. Ever increasing quantities of toxic wastes have contaminated our land, air, and water. Lack of adequate hazardous waste disposal facilities is a critical problem. Landfilling toxic wastes is no longer considered safe. The tragedy of the Love Canal has demonstrated the need for proper hazardous waste disposal facilities. The best organic chemical waste disposal method is process incineration. Cement kilns have been used for burning toxic chemical industrial wastes in Canada, Michigan, New York, Sweden, etc. Existing cement kilns, when properly operated, can destroy most organic chemical wastes. Even the most complex chlorinated hydrocarbons, including PCB can be completely destroyed during normal cement kiln operations, with minimal emissions to the environment. Burning toxic chemical wastes in cement kilns, and other mineral industries, is mutually beneficial to both industry, who generates such wastes, and to society and government, who want to dispose properly of such wastes in a safe, environmentally acceptable manner. The added benefit of energy conservation is important, since large quantities of valuable fuel can be saved in the manufacture of cement when such techniques are employed.     

Treatment Technologies For Hazardous Wastes: Part IV A Review of Alternative Treatment Processes for Metal Bearing Hazardous Waste Streams

The U.S. Congress and the U.S. Environmental Protection Agency believe that treatment and recovery techniques should be given maximum priority when considering methods for managing the nation's generated hazardous waste. A prohibition for the disposal of certain categories of hazardous wastes either directly onto or into the land without being treated to an accepted degree prior to such disposal practice has been promulgated.¹ Wastes containing toxic metals and cyanide complexes have been selected as a group to be restricted. Due to the high generation rate associated with this category, a large capacity of waste treatment processing will be required. Existing and emerging treatment alternatives which are or have the potential to be employed for waste treatment of metal bearing wastes are presented in this paper.     

Waste Analysis Plan Review Advisor: An Intelligent Database to Assist RCRA Permit Reviewers

The Waste Analysis Plan Review Advisor (WAPRA) system assists in the review of the Waste Analysis Plan Section of RCRA Part B facility permit applications. Specifically, this program automates two functions of the waste analysis plan review. First, the system checks all wastes which will be processed in the same treatment or disposal unit to identify possible chemical interactions which might pose a health threat to unit operators or degrade the performance of the waste processing unit. Second, sampling methods are analyzed and judged for appropriateness based on guidelines in EPA Reference SW-846. WAPRA is best classified as an intelligent database. It contains the expertise of a chemist in a menu-driven user-friendly interface.