Other affiliations: Shenzhen University
Bio: Huabo Duan is an academic researcher from Tsinghua University. The author has contributed to research in topics: Environmental pollution & Personal computer. The author has an hindex of 13, co-authored 16 publications receiving 1209 citations. Previous affiliations of Huabo Duan include Shenzhen University.
TL;DR: This study presents a combined recycling technology process on the basis of manual dismantling and chemical treatment of LCDs, showing that valuable materials and harmful substances could be efficiently recovered or separated through above-mentioned combined technology.
Abstract: Associated with the rapid development of the information and electronic industry, liquid crystal displays (LCDs) have been increasingly sold as displays. However, during the discarding at their end-of-life stage, significant environmental hazards, impacts on health and a loss of resources may occur, if the scraps are not managed in an appropriate way. In order to improve the efficiency of the recovery of valuable materials from waste LCDs panel in an environmentally sound manner, this study presents a combined recycling technology process on the basis of manual dismantling and chemical treatment of LCDs. Three key processes of this technology have been studied, including the separation of LCD polarizing film by thermal shock method the removal of liquid crystals between the glass substrates by the ultrasonic cleaning, and the recovery of indium metal from glass by dissolution. The results show that valuable materials (e.g. indium) and harmful substances (e.g. liquid crystals) could be efficiently recovered or separated through above-mentioned combined technology. The optimal conditions are: (1) the peak temperature of thermal shock to separate polarizing film, ranges from 230 to 240 degrees C, where pyrolysis could be avoided; (2) the ultrasonic-assisted cleaning was most efficient at a frequency of 40 KHz (P = 40 W) and the exposure of the substrate to industrial detergents for 10 min; and (3) indium separation from glass in a mix of concentrated hydrochloric acid at 38% and nitric acid at 69% (HCl:HNO(3):H(2)O = 45:5:50, volume ratio). The indium separation process was conducted with an exposure time of 30 min at a constant temperature of 60 degrees C.
TL;DR: The generation of discarded household hazardous waste (HHW) is another important source of hazardous waste and has come into being a huge challenge faced to Chinese environmental management.
Abstract: Associated with the rapid economic growth and tremendous industrial prosperity, continues to be the accelerated increase of hazardous waste generation in China. The reported generation of industrial hazardous waste (IHW) was 11.62 million tons in 2005, which accounted for 1.1% of industrial solid waste (ISW) volume. An average of 43.4% of IHW was recycled, 33.0% was stored, 23.0% was securely disposed, and 0.6% was discharged without pollution controlling. By the end of 2004, there were 177 formal treatment and disposal centers for IHW management. The reported quantity of IHW disposed in these centers was only 416,000 tons, 65% of which was landfilled, 35% was incinerated. The quantity of waste alkali and acid ranked the first among IHW categories, which accounted for 30.9%. And 39.0% of IHW was generated from the raw chemical materials and chemical products industry sectors. South west China had the maximum generation of IHW, accounted for 40.0%. In addition, it was extrapolated that 740,000 tons of medical wastes were generated per year, of which only 10% was soundly managed. The generation of discarded household hazardous waste (HHW) is another important source of hazardous waste. A great proportion of HHW was managed as municipal solid waste (MSW). Hazardous waste pollution controlling has come into being a huge challenge faced to Chinese environmental management.
TL;DR: The ingredients and conditions necessary to form PCDD/Fs or PBDD/Fs were definitely present, such as products of incomplete combustion, halogenides, an oxidizing atmosphere, and a catalyst-Cu salts being the most effective, significantly increasing the yields of PC DD/Fs and PBD dibenzofurans and decreasing the optimum temperature range.
Abstract: Many developing countries have not significantly changed their course with regard to electronic waste contamination, and they are still facing the specter of mountains of hazardous electronic waste, with serious consequences for both the environment and public health. An efficient and stable analytical method was developed to determine the inventory and emission factors of polybrominated dibenzo-p-dioxin and dibenzofurans (PBDD/Fs) and polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) formed from the incineration of scrap printed circuit boards (PCBs). Both PBDD/Fs and PCDD/Fs have been found in all experimental sections with a maximum formation rate at temperatures between 250 and 400 °C. The amounts tended first to increase and then began to decrease as the temperature rose. When subjected to a heating temperature of 325 °C, the total content of twelve 2,3,7,8-substituted PBDD/Fs congeners (tetra- through octabromo-) gathered from three outputs was the largest, at 19 000, 160 000, and 57 ng T...
TL;DR: The dismantling of printed circuit board assemblies and the recovery of their useful materials can lead to serious environmental impacts mainly due to their complicated physical structure and the variety of toxic elements contained in their material composition.
Abstract: The dismantling of printed circuit board assemblies (PCBAs) and the recovery of their useful materials can lead to serious environmental impacts mainly due to their complicated physical structure and the variety of toxic elements contained in their material composition. So far, less attention has been paid to their responsible recycling compared to that of bare printed circuit boards. Combined with other materials recovery process, proper dismantling of PCBAs is beneficial to conserve scarce resources, reuse the components, and eliminate or safely dispose of hazardous materials. In analyzing the generation, resources potential and hazardous risk of scrap PCBAs, technologies used for the dismantling of waste PCBAs have been widely investigated and reviewed from the aspects of both industrial application and laboratory-scale studies. In addition, the feasibility of PCBA dismantling has been discussed, the determinants of which, including the heating conditions and mechanical properties have been identified. Moreover, this paper evaluates the environmental consequences caused by the dismantling of PCBAs.
TL;DR: The application of life cycle assessment (LCA) is described to investigate the environmental performance of Chinese e-products from a global level and shows that the manufacturing and the use of such devices are of the highest environmental importance.
Abstract: Associated with the tremendous prosperity in world electronic information and telecommunication industry, there continues to be an increasing awareness of the environmental impacts related to the accelerating mass production, electricity use, and waste management of electronic and electric products (e-products). China's importance as both a consumer and supplier of e-products has grown at an unprecedented pace in recent decade. Hence, this paper aims to describe the application of life cycle assessment (LCA) to investigate the environmental performance of Chinese e-products from a global level. A desktop personal computer system has been selected to carry out a detailed and modular LCA which follows the ISO 14040 series. The LCA is constructed by SimaPro software version 7.0 and expressed with the Eco-indicator'99 life cycle impact assessment method. For a sensitivity analysis of the overall LCA results, the so-called CML method is used in order to estimate the influence of the choice of the assessment method on the result. Life cycle inventory information is complied by ecoinvent 1.3 databases, combined with literature and field investigations on the present Chinese situation. The established LCA study shows that that the manufacturing and the use of such devices are of the highest environmental importance. In the manufacturing of such devices, the integrated circuits (ICs) and the Liquid Crystal Display (LCD) are those parts contributing most to the impact. As no other aspects are taken into account during the use phase, the impact is due to the way how the electricity is produced. The final process steps--i.e. the end of life phase--lead to a clear environmental benefit if a formal and modern, up-to-date technical system is assumed, like here in this study.
TL;DR: Miniaturisation and the development of more efficient cloud computing networks, where computing services are delivered over the internet from remote locations, may offset the increase in E-waste production from global economic growth and theDevelopment of pervasive new technologies.
Abstract: E-waste comprises discarded electronic appliances, of which computers and mobile telephones are disproportionately abundant because of their short lifespan. The current global production of E-waste is estimated to be 20-25 million tonnes per year, with most E-waste being produced in Europe, the United States and Australasia. China, Eastern Europe and Latin America will become major E-waste producers in the next ten years. Miniaturisation and the development of more efficient cloud computing networks, where computing services are delivered over the internet from remote locations, may offset the increase in E-waste production from global economic growth and the development of pervasive new technologies. E-waste contains valuable metals (Cu, platinum group) as well as potential environmental contaminants, especially Pb, Sb, Hg, Cd, Ni, polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs). Burning E-waste may generate dioxins, furans, polycyclic aromatic hydrocarbons (PAHs), polyhalogenated aromatic hydrocarbons (PHAHs), and hydrogen chloride. The chemical composition of E-waste changes with the development of new technologies and pressure from environmental organisations on electronics companies to find alternatives to environmentally damaging materials. Most E-waste is disposed in landfills. Effective reprocessing technology, which recovers the valuable materials with minimal environmental impact, is expensive. Consequently, although illegal under the Basel Convention, rich countries export an unknown quantity of E-waste to poor countries, where recycling techniques include burning and dissolution in strong acids with few measures to protect human health and the environment. Such reprocessing initially results in extreme localised contamination followed by migration of the contaminants into receiving waters and food chains. E-waste workers suffer negative health effects through skin contact and inhalation, while the wider community are exposed to the contaminants through smoke, dust, drinking water and food. There is evidence that E-waste associated contaminants may be present in some agricultural or manufactured products for export.
TL;DR: An overview of toxic substances present in e-waste, their potential environmental and human health impacts together with management strategies currently being used in certain countries are presented.
Abstract: Electronic waste (e-waste) is one of the fastest-growing pollution problems worldwide given the presence if a variety of toxic substances which can contaminate the environment and threaten human health, if disposal protocols are not meticulously managed. This paper presents an overview of toxic substances present in e-waste, their potential environmental and human health impacts together with management strategies currently being used in certain countries. Several tools including Life Cycle Assessment (LCA), Material Flow Analysis (MFA), Multi Criteria Analysis (MCA) and Extended Producer Responsibility (EPR) have been developed to manage e-wastes especially in developed countries. The key to success in terms of e-waste management is to develop eco-design devices, properly collect e-waste, recover and recycle material by safe methods, dispose of e-waste by suitable techniques, forbid the transfer of used electronic devices to developing countries, and raise awareness of the impact of e-waste. No single tool is adequate but together they can complement each other to solve this issue. A national scheme such as EPR is a good policy in solving the growing e-waste problems.
TL;DR: In this article, an economic assessment of the potential revenues coming from the recovery of 14 e-products (e.g., LCD notebooks, LED notebooks, CRT TVs, LCD TVs, LED TVs, CRTs, LCD monitors, LED monitors, cell phones, smart phones, PV panels, HDDs, SSDs and tablets) on the base of current and future disposed volumes in Europe is presented.
Abstract: Waste from Electric and Electronic Equipments (WEEEs) is currently considered to be one of the fastest growing waste streams in the world, with an estimated growth rate going from 3% up to 5% per year. The recycling of Electric or electronic waste (E-waste) products could allow the diminishing use of virgin resources in manufacturing and, consequently, it could contribute in reducing the environmental pollution. Given that EU is trying, since the last two decades, to develop a circular economy based on the exploitation of resources recovered by wastes, a comprehensive framework supporting the decision-making process of multi-WEEE recycling centres will be analysed in this paper. An economic assessment will define the potential revenues coming from the recovery of 14 e-products (e.g. LCD notebooks, LED notebooks, CRT TVs, LCD TVs, LED TVs, CRT monitors, LCD monitors, LED monitors, cell phones, smart phones, PV panels, HDDs, SSDs and tablets) on the base of current and future disposed volumes in Europe. Moreover, a sensitivity analysis will be used to test the impact of some critical variables (e.g. price of recovered materials, input materials composition, degree of purity obtained by the recycling process, volumes generated, and percentage of collected waste) on specific economic indexes. A discussion of the economic assessment results shows the main challenges in the recycling sector and streamlines some concrete solutions.
TL;DR: The inputs of trace elements to agricultural soils via atmospheric deposition, livestock manures, fertilizers and agrochemicals, sewage irrigation and sewage sludge in China were analyzed and an annual inventory of trace element inputs was developed.
Abstract: It is important to understand the status and extent of soil contamination with trace elements to make sustainable management strategies for agricultural soils. The inputs of trace elements to agricultural soils via atmospheric deposition, livestock manures, fertilizers and agrochemicals, sewage irrigation and sewage sludge in China were analyzed and an annual inventory of trace element inputs was developed. The results showed that atmospheric deposition was responsible for 43-85% of the total As, Cr, Hg, Ni and Pb inputs, while livestock manures accounted for approximately 55%, 69% and 51% of the total Cd, Cu and Zn inputs, respectively. Among the elements concerned, Cd was a top priority in agricultural soils in China, with an average input rate of 0.004 mg/kg/yr in the plough layer (0-20 cm). Due to the spatial and temporal heterogeneity of the sources, the inventory as well as the environmental risks of trace elements in soils varies on a regional scale. For example, sewage sludge and fertilizers (mainly organic and phosphate-based inorganic fertilizers) can also be the predominant sources of trace elements where these materials were excessively applied. This work provides baseline information to develop policies to control and reduce toxic element inputs to and accumulation in agricultural soils.
TL;DR: It seems that hydrometallurgical route will be a key player in the base and precious metals recoveries from e-waste, along with purification and refining.
Abstract: This paper reviews the existing and state of art knowledge for electronic waste (e-waste) recycling. Electrical and/or electronic devices which are unwanted, broken or discarded by their original users are known as e-waste. The main purpose of this article is to provide a comprehensive review of e-waste problem, strategies of e-waste management and various physical, chemical and metallurgical e-waste recycling processes, their advantages and disadvantages towards achieving a cleaner process of waste utilization, with special attention towards extraction of both metallic values and nonmetallic substances. The hazards arise from the presence of heavy metals Hg, Cd, Pb, etc., brominated flame retardants (BFRs) and other potentially harmful substances in e-waste. Due to the presence of these substances, e-waste is generally considered as hazardous waste and, if improperly managed, may pose significant human and environmental health risks. This review describes the potential hazards and economic opportunities of e-waste. Firstly, an overview of e-waste/printed circuit board (PCB) components is given. Current status and future perspectives of e-waste/PCB recycling are described. E-waste characterization, dismantling methods, liberation and classification processes are also covered. Manual selective dismantling after desoldering and metal-nonmetal liberation at -150μm with two step crushing are seen to be the best techniques. After size reduction, mainly physical separation processes employing gravity, electrostatic, magnetic separators, froth floatation, etc. have been critically reviewed here for separation of metals and nonmetals, along with useful utilizations of the nonmetallic materials. The recovery of metals from e-waste material after physical separation through pyrometallurgical, hydrometallurgical or biohydrometallurgical routes is also discussed along with purification and refining. Suitable PCB recycling flowsheets for industrial applications are also given. It seems that hydrometallurgical route will be a key player in the base and precious metals recoveries from e-waste. E-waste recycling will be a very important sector in the near future from economic and environmental perspectives. Recycling technology aims to take today's waste and turn it into conflict-free, sustainable polymetallic secondary resources (i.e. Urban Mining) for tomorrow. Recycling technology must ensure that e-waste is processed in an environmentally friendly manner, with high efficiency and lowered carbon footprint, at a fraction of the costs involved with setting multibillion dollar smelting facilities. Taking into consideration our depleting natural resources, this Urban Mining approach offers quite a few benefits. This results in increased energy efficiency and lowers demand for mining of new raw materials.