Extraction and recovery of precious metals from electronic waste printed circuit boards by bioleaching acidophilic fungi

Printed circuit boards contain precious metals. They are produced in large volumes, rendering them an important component of the electronic waste. In view of the heterogeneity of the metals present, reprocessing of electronic waste is a heinous task. The present study focused on leaching of valuable metals from electronic waste printed circuit boards using Aspergillus niger DDNS1. The adaptation phases began at 0.1, 0.5 and 1.0% of fine powder of printed circuit boards with 10% inoculum and were optimized with three effective factors, viz. initial pH, particle size and pulp density, to achieve the maximum simultaneous recovery of the valuable metals. The interactions of these metals were also deciphered using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectrum and atomic absorption spectroscopy. The results indicated that extraction of the precious metals was accomplished mainly through the unique organic acids originating from A. niger DDNS1. The initial pH played an important role in the extraction of the precious metals and the metals precipitate formation. The leaching rate of the metals was generally higher at low powder dosage of printed circuit boards. The toxicity of the printed circuit boards had little effect on two-step bioleaching at the pulp density of 0.1% compared to one-step bioleaching. The two-step bioleaching process was followed under organic acid-forming conditions for the maximum mobilization of metals. Thus, the precious metals from printed circuit boards could be mobilized through fungal bioleaching which promises an important industrial application in recycling of electronic wastes.     

Electronic waste: present status and future perspectives of sustainable management practices in Malaysia

The ever-increasing and rapidly growing volume of waste electrical and electronic equipment has become a serious threat to the environment in many countries. The inevitability of e-waste management and the development of a holistic system to deal with it has become an indispensable socio-economic and environmental issue for the sustainable development of Malaysia. However, no comprehensive research has yet been carried out, and only a few works in a discreet manner have been begun. In view of the above, and as a small endeavor towards achieving the country’s Vision 2020, this study explores the present status and future perspectives of the management of waste electrical and electronic equipment in Malaysia. This article presents an overview of e-waste management practices around the world, including the generation of e-waste, the implementation of management strategies, and collection and recovery activities in Malaysia. It also presents the corresponding responses adopted so far with respect to legislation and other infrastructural development. Finally, through the use of structured and semi-structured interviews, it reveals the barriers and challenges, as well as future perspectives and sustainability issues related to the e-waste management system in this fast developing country.     

Legal geographies of e-waste legislation in Canada and the US: Jurisdiction,responsibility and the taboo of production

Electronic waste (e-waste) is thought to be the fastest growing segment of the overall solid waste stream in many countries. Between 2003 and 2010 more than half of all Canadian provinces and US states passed legislation specifically to govern the disposition of e-waste. The purpose of this research is to investigate the legal geographies of this legislation. The principle findings are that the work of jurisdiction around e-waste in Canada and the US places financial responsibility for waste management on consumers not producers. Thus, contra the explicit intent of e-waste legislation, a regime of extended consumer, rather than producer, responsibility is emerging and waste generated as a result of design and manufacturing decisions remains taboo. But the implications of the legislative governance of e-waste go beyond questions of regulatory success or failure. At stake in the legislative governance of e-waste is the assembling of the social in a legal way that generates distributions of action that are democratized only so long as they limit public decision making to waste already produced and marketized only so long as they extend the ability of manufacturers, e-waste recyclers, and paramarket organizations to appropriate value. The work of jurisdiction around e-waste suggests jurisdiction can be more multiple, distributed, and patchy than prevailing theory allows.     

Recovery of valuable materials from aluminium salt cakes

Salt cakes, which are nominally waste products derived from aluminium dross melting furnaces, are complex mixtures of some 20 different compounds made up of many different elements. Normally they are regarded as waste products and they are disposed of in toxic waste dumps. However, it is shown here that some components are readily recoverable as high-grade products for recycling or sale and that the residues thus generated can be non-toxic. Recoverable components include metallic aluminium, salt (halite (NaCl) and sylvite (KCl)), alumina-containing compounds, and possibly hydrogen gas.     

河南三门峡市实验室“三废”污染情况初探及思考

分析了实验室“三废”污染的现状、分布、数量、种类、;建议本着科学选择方法,节约使用试剂,适当处理和回收利用的原则来处理“三废”;强调“谁污染,谁治理”是化学工作者义不容辞的职责。     

开发水泥工业新技术，争创节能减排新水平

我国在国民经济持续高速发展的同时也承受着能源消耗和环境恶化的巨大压力,水泥行业是耗能、排污大户,面临技术升级和节能减排的重大课题和历史任务。天津水泥工业设计研究院有限公司一直致力于我国水泥工业开发和提供新技术和新装备,推动我国水泥工业走资源节约型、环境友好型的新型工业化道路。近年来的新成果主要在新一代烧成节能技术、无球磨粉磨节能技术、余热发电技术、水泥工业处置工业废弃物和城市生活垃圾以及减少水泥生产有害粉尘和气体的排放等方面,代表了我国新型干法水泥生产技术和装备的先进水平。     

淀粉废水资源化利用的现状和前景

阐述了近年来淀粉废水的资源化利用，着重列举了利用淀粉废水发展生态建设、从淀粉废水中回收蛋白以及利用淀粉废水生产新能源的方法，分析了淀粉废水资源化利用的前景。     

Rare earth elements:A review of applications,occurrence,exploration,analysis,recycling,and environmental impact

Rare earth elements(REE)include the lanthanide series elements(La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy.Ho,Er,Tm,Yb,and Lu)plus Sc and Y.Currently these metals have become very critical to several modern technologies ranging from cell phones and televisions to LED light bulbs and wind turbines.This article summarizes the occurrence of these metals in the Earth’s crust,their mineralogy,different types of deposits both on land and oceans from the standpoint of the new data with more examples from the Indian subcontinent.In addition to their utility to understand the formation of the major Earth reservoirs.multi-faceted updates on the applications of REE in agriculture and medicine including new emerging ones are presented.Environmental hazards including human health issues due to REE mining and large-scale dumping of e-waste containing significant concentrations of REE are summarized.New strategies for the future supply of REE including recent developments in the extraction of REE from coal fired ash and recycling from e-waste are presented.Recent developments in individual REE separation technologies in both metallurgical and recycling operations have been highlighted.An outline of the analytical methods for their precise and accurate determinations required in all these studies,such as,Xray fluorescence spectrometry(XRF),laser induced breakdown spectroscopy(LIBS),instrumental neutron activation analysis(INAA),inductively coupled plasma optical emission spectrometry(ICP-OES),glow discharge mass spectrometry(GD-MS),inductively coupled plasma mass spectrometry(including ICP-MS,ICP-TOF-MS,HR-ICP-MS with laser ablation as well as solution nebulization)and other instrumental techniques,in different types of materials are presented.     

Daily and seasonal stem radial activity of Populus euphratica and its association with hydroclimatic factors in the lower reaches of China’s Heihe River basin

The Vado Carranza dump, located in the Mexicali Valley, Baja California, northwest Mexico, was operated for more than 15 years receiving about 30 tons/day of solid wastes. The disposed wastes were periodically burned in open air. The presence of a shallow aquifer in the area makes the groundwater vulnerable to contamination processes. The purpose of this study was the evaluation of heavy metals content (Cu, Cd, Ni, Pb and Zn) in soil and groundwater in the vicinity of this dump. The results indicate high content of metals in soil, mainly at a superficial level, with the highest concentrations in the areas where burning of wastes occurred. Elevated concentrations of cadmium and copper were detected in groundwater with the highest concentrations occurring in monitoring wells located in the north side of the dump, downward of groundwater flow. Although the high content of metals in soil can be attributed to the burning of waste, other sources of pollution could be the agricultural irrigation in the vicinity of the dump. The program PHREEQC was used to model the geochemical evolution of groundwater. Results suggest that evaporation of the contaminated waters circulating below the landfill is one of the key processes that explain the increased concentration of contaminants in groundwater and its seasonal variations. As groundwater flows away from the dump, evaporation can concentrate the chemicals making the water more toxic. These results are important because they illustrate processes that are likely to occur in landfills located in other desert areas of the world.     

Multi-criteria analysis for the identification of waste disposal areas

The municipality of Cachoeiro de Itapemirim (ES) is currently the largest domestic producer and exporter of marble and granite in Brazil. The processing of the rock, especially the sawing results in a large volume of waste, including the abrasives used during sawing and the off-cut pieces. Presently these waste products are disposed of without proper environmental protection and cause pollution to surface water and groundwater resources, including silting, an increase in hardness and increased aluminium values in the groundwater. In order to minimize the harmful effects of these practices on the environment, a research project was undertaken to identify potential disposal sites for the generated waste. A multi-criteria approach was followed during which a database was compiled of all the companies generating waste products and also including a baseline environmental study of the region, integrated analysis (multi-criteria analysis) of the restriction factors and the preliminary identification of possible disposal sites. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of a master plan for industrial solid waste management

Rapid industrial growth in the province of Khuzestan in the south west of Iran has resulted in disposal of about 1750 tons of solid waste per day. Most of these industrial solid wastes including hazardous wastes are disposed without considering environmental issues. This has contributed considerably to the pollution of the environment. This paper introduces a framework in which to develop a master plan for industrial solid waste management. There are usually different criteria for evaluating the existing solid waste pollution loads and how effective the management schemes are. A multiple criteria decision making technique, namely Analytical Hierarchy Process (AHP), is used for ranking the industrial units based on their share in solid waste related environmental pollution and determining the share of each unit in total solid waste pollution load. In this framework, a comprehensive set of direct, indirect, and supporting projects are proposed for solid waste pollution control. The proposed framework is applied for industrial solid waste management in the province of Khuzestan in Iran and a databank including GIS based maps of the study area is also developed. The results have shown that the industries located near the capital city of the province, Ahwaz, produce more than 32 percent of the total solid waste pollution load of the province. Application of the methodology also has shown that it can be effectively used for development of the master plan and management of industrial solid wastes.     

High resolution X-ray fluorescence spectrometry for water analysis of metals in East China Sea

Within the last century, water pollution has become a major problem throughout the world. Aquatic systems are endangered by many different types of pollution but one of the most threatening is contamination by heavy metals, for example, Cd, etc. The presence of these metals is mainly due to industrial wastes or mining wastes being improperly treated and dumped into the water supply. The contamination may damage marine organisms or create changes in the aquatic environment. For these reasons, monitoring the concentrations of trace elements in rivers, coastal waters and open seawater is very important for environmental conservation. Like many countries in the world, China is facing the serious problem of water pollution in its aquatic system. Areas like the Yangtze River have been industrialized very quickly, and without proper waste control practices the pollution levels have increased with the economic growth. The Yangtze River covers thousands of square kilometers and crosses more than half of China before reaching the East China Sea.     

A novel approach to separation of waste printed circuit boards using dimethyl sulfoxide

Waste printed circuit boards are complex heterogeneous mixture consisting of organic material, metal and glass fiber, therefore, it is quite difficult for the recovery of valuable materials from waste printed circuit boards. In this study, waste printed circuit boards without electronic components (known as bare boards) are submerged into dimethyl sulfoxide solvent at 170 °C using refluxing process. Metallographic microscope shows that waste printed circuit boards produce the delamination after treated with dimethyl sulfoxide solvent for 15 min. When waste printed circuit boards are treated with dimethyl sulfoxide solvent for 30 min, the separation of waste printed circuit boards is complete to obtain metals and glass fibers. Moreover, the used dimethyl sulfoxide solvent is vaporized by the rotary decompression which obtains regenerative dimethyl sulfoxide and solid residues. Comparing two Fourier transform infrared spectroscopies, it is found that the regenerative dimethyl sulfoxide is the same as original dimethyl sulfoxide. Thermal analyses combined with Fourier transform infrared spectroscopy show that the solid residues are bromine epoxy resins. These findings suggest that this innovative technology offers an environmental friendly process with no pollution and high efficiency for separating valuable materials from waste printed circuit boards.     

Evaluation of water quality and protection strategies of water resources in arid–semiarid climates: a case study in the Yuxi River Valley of Northern Shaanxi Province, China

Water resource structure is one of the most important factors that constrain the economic development in arid–semiarid areas. Sustainable use of water requires a thorough understanding of the local geology and hydrology and developing of effective protection strategies. Discussed in this paper is a study on the phreatic water quality of the Yuxi River Valley of Shaanxi Province, China. The Yuxi River Valley passes through the Shaanbei energy base, which demands large quantities of high-quality water. A total of 129 water samples were collected in 4,938 km² in a recent study to delineate the areas with water suitable for drinking, industrial, and agricultural usage and areas with poor quality. The study indicates that the poor quality of water contains high concentrations of NH⁴⁺ and NO₂⁻¹, indicating possible contamination by waste disposal in the nearby cities and towns. A series of strategies are proposed to protect the water in the Yuxi River Valley, including proper treatment and recycling of the waste water in the cities and towns, strict control of the waste-water discharge from any new factories and mines, and prevention of groundwater contamination by wastes containing heavy metals.     

Extraction procedure testing of solid wastes generated at selected metal ore mines and mills

Solid waste samples from a reconnaissance study conducted at ore mining and milling sites were subjected to the U.S. Environmental Protection Agency extraction procedure (EP) leaching test Sites visited included mines and mills extracting ores of antimony (Sb), mercury (Hg), vanadium (V), tungsten (W), and nickel (Ni). Samples analyzed included mine wastes, treatment pond solids, tailings, low grade ore, and other solid wastes generated at these facilities Analysis of the leachate from these tests indicates that none of the samples generated leachate in which the concentration of any toxic metal parameter exceeded EPA criteria levels for those metals. By volume, tailings generally constitute the largest amount of solid wastes generated, but these data indicate that with proper management and monitoring, current EPA criteria can be met for tailings and for most solid wastes associated with mining and milling of these metal ores. Long-term studies are needed to determine if leachate characteristics change with time and to assist in development of closure plans and post closure monitoring programs.     

A critical review on waste paper sorting techniques

Efficient waste paper recycling has a significant role in the sustainable environment. Recyclable waste paper as a fundamental ingredient of municipal solid wastes (MSWs) is indeed an “urban ore”. Waste papers are considered as the solid recovered fuel which is recovered from MSW. Recyclable waste papers are segregated into various grades to produce high-quality products. Moreover, sorted paper streams save energy, chemicals, and water, as well as reduce sludge and rejects. Information technology is widely integrated with the waste management industry into its operations such as recycling, reuse, segregating based on categories and so on. This review article focuses on the life cycle of waste paper and existing waste paper sorting techniques. In the paper industry, many types of sensors are used in different mechanical and optical waste paper sorting systems. Such sensors include lignin, gloss, stiffness, mid-infrared, infrared, and color sensors. In this review, also described the effectiveness of different waste paper sorting systems, and finally, recommended appropriate waste paper sorting techniques based on effectiveness and low-cost implementation.     

Recycling of environmentally problematic plant wastes generated from greenhouse tomato crops through vermicomposting

The enormous quantity of plant waste produced from greenhouse tomato crops is an environmental problem that should be solved by recycling that waste into valuable organic products through low-cost technologies, such as vermicomposting. Feasibility of vermicomposting greenhouse tomato-plant waste (P) using paper-mill sludge (S) as complementary waste was investigated by this study. Earthworm development in P, S, and two mixtures of both wastes was monitored over 24 weeks and compared with that in cow dung (D), an optimum organic-waste to be vermicomposted. The effectiveness of vermicomposting to biostabilize those wastes was assessed by analysing phospholipid fatty acid composition, chemical features, plant-nutrient content, metal concentration, enzyme activities, and germination index (GI). A commercial vermicompost was also analyzed and taken as a reference of vermicompost quality. Earthworms did not survive in P alone, but a mixture of P with S at a ratio of 2:1 or 1:1 resulted in earthworm development similar to that observed in D. Phospholipid fatty acid analysis revealed that earthworm activity strongly transformed initial microbiota inhabiting the wastes, giving rise to vermicompost microbial communities which were similar to that of a commercial vermicompost. Both mixtures of P and S were properly biostabilized through vermicomposting, as indicated by decreases in their C:N ratio and enzyme activities together with increases in their degree of maturity (GI ~ 100 %) after the process. This study demonstrates that the vermicomposting of tomato-plant waste together with paper-mill sludge allows the recycling of both wastes, thereby improving the environmental sustainability of greenhouse crops.     

Adverse effects of coal mine waste dumps on the environment and their management

Waste dumps generated from mining that exposes sulfur-bearing overburden can be active sources of acid generation with the potential to severely contaminate soils, surface and groundwater, and endanger both local and downstream ecosystems. A waste rock management strategy ensure that disposal of such material is inert or at least stable and contained, and minimizes the surface footprint of the wastes, and explores options for alternate uses. Reclamation of waste dumps is another or parallel alternative to decrease the potential for adverse effects. At the coal mining area of Karmozd in Iran, large volumes of wastes have been produced and disposed of without any specific care for the environment. In this paper, the impacts of waste dumps on the environment were identified and this was followed by a research program to determine the characteristics of the wastes, their acid generation potential, the availability of hazardous contaminants, and a prediction of their environmental impacts on the site. Data was collected from the target site and by comparing several reclamation alternatives using a Multi-Attribute Decision-Making technique, forestry was selected as the post-mining land use for the waste dumps. Preliminary evaluations indicated that Zelkava could be a useful tree species for this region.     

Metal recovery from power plant ash: An ecological approach to coal utilization

The growing use of coal in electrical generation is resulting in power plant solid waste becoming a serious national problem. For 1977, approximately 62 million tonnes of utility ash was produced in the US. If oil and gas burning units that were originally designed to burn coal switch back to that fuel, utility ash will be the fourth largest solid material produced in the US. Disposing of such quantities of wastes poses siting and pollution problems which are becoming critical in areas experiencing increased land use competition.An alternative to disposal is to recover the constituent metals of the ash. Aluminium, iron, manganese, calcium, titanium, and magnesium are all present in fly ash, the utility waste that poses the major disposal problem. This paper indicates that metal recovery is an attractive alternative if national instead of special interest goals are maximized. Metal recovery from fly ash is attractive on environmental, self-sufficiency, and stragegic grounds although it may not be a wise decision for an individual entrepreneur. The geography of power plant location within the US is increasing the economical attractiveness of this potential resource since large, new facilities produce sufficient quantities of material that can be used in nearby metal smelters.     

极低放废物近地表处置的环境安全评价方法研究

放射性废物处置是当前严峻的环保问题之一,从经济、安全和高效角度出发,将极低放废物从中、低放废物中分离出来单独处置,对核废物的管理与处置具有重要意义。本文以我国西南某极低放废物备选处置场为研究对象,系统分析了处置的相关技术方法,重点研究了屏障技术和环境安全评价方法及其应用。针对拟建在古泥石流体山区山顶上的处置场,选取核素90Sr作为处置对象,选用盆状屏障式处置库,估算产生的核素90Sr的总活度和比活度。选用筛分的颗粒d<1 mm的介质作为屏障材料,厚度为0.5 m,批试验结果显示上述材料对90Sr的吸附效果明显;模拟计算结果显示核素90Sr在50 a内被完全阻滞在包气带中,可以达到安全处置废物的要求。