Huabo Duan

Recovery of valuable materials from waste liquid crystal display panel

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.

Characterization and Inventory of PCDD/Fs and PBDD/Fs Emissions from the Incineration of Waste Printed Circuit Board

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 19u2009000, 160u2009000, and 57 ng TEQ/kg in solid, liquid, and gaseous fractions, respectively; the total content of seventeen 2,3,7,8-substituted PCDD/Fs congeners (tetra- through octachloro-) was 820, 550, and 1.4 ng TEQ/kg. The formation of PCDD/Fs was remarkably less than that of PBDD/Fs because bromine concentrations considerably exceeded chlorine concentrations. 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 PCDD/Fs and PBDD/Fs and decreasing the optimum temperature range.

Examining the technology acceptance for dismantling of waste printed circuit boards in light of recycling and environmental concerns.

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.

Hazardous waste generation and management in China: A review

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.

Life cycle assessment study of a Chinese desktop personal computer.

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). Chinas 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-indicator99 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.

Behavior of urban residents toward the discarding of waste electrical and electronic equipment: a case study in Baoding, China

The volume of waste electrical and electronic equipment (WEEE) is growing rapidly worldwide, making its management difficult; therefore, this should be improved as a matter of urgency. WEEE includes both essential household appliances [including televisions, refrigerators, and washing machines; but not air conditioners, where the consumption mode is more like information, communication and technology (ICT)] ICT equipment (also called high-tech household appliances). In the present study, Baoding, a medium-sized, prefecture-level city in north central China with a population of 11 million, including 1.1 million urban residents, was selected as a representative city for an investigation of recycling behaviors. A valid sample size of 346 households in Baoding was investigated, and categorized into various income and educational levels. The results showed that the major reason for discarding WEEE was malfunction of the appliance, accounting for 52% of disposals. Surveyed households with either high income or good education were more likely to consume high-tech household appliances, attracted by advanced technology, versatile functions or flexibility of use. Personal computer ownership rates were highest in households with a high income and good education—1.2 and 0.9 per home respectively. WEEE was most often sold to peddlers or hawkers from where the WEEE flowed into the second-hand market to be refurbished or repaired, and then re-sold. However, 56.3% of residents in the college community were in support of charging consumers for disposal and 61.7% were in support of including a disposal surcharge in the purchase price of new products—a percentage approximately three times that for high-income residents. Thus, high educational level appears to be currently the most important factor in raising the potential of a household’s willingness to pay for WEEE treatment cost. The findings of this study can be used to develop sound recycling systems for WEEE in mainland China.

Systematic characterization of generation and management of e-waste in China.

Over the last decade, there has been much effort to promote the management of e-waste in China. Policies have been affected to prohibit imports and to control pollution. Research has been conducted in laboratories and on large-scale industrial operations. A subsidy system to support sound e-waste recycling has been put in place. However, the handling of e-waste is still a concern in China and the issue remains unresolved. There has been relatively little work to follow up this issue or to interpret continuing problems from the perspective of sustainable development. This paper first provides a brief overview of conventional and emerging environmental pollution in Chinese “famous” e-waste dismantling areas, including Guiyu in Guangdong and Wenling in Zhejiang. Environmentalists have repeatedly proven that these areas are significantly polluted. Importing and backyard recycling are decreasing but are ongoing. Most importantly, no work is being done to treat or remediate the contaminated environmental media. The situation is exacerbated by the rising tide of e-waste generated by domestic update of various electronics. This study, therefore, employs a Sales Obsolescence Model approach to predict the generation of e-waste. When accounting for weight, approximately 8 million tons of e-waste will be generated domestically in 2015, of which around 50xa0% is ferrous metals, followed by miscellaneous plastic (30xa0%), copper metal and cables (8xa0%), aluminum (5xa0%), and others (7xa0%). Of this, 3.6xa0% will come from scrap PCBs and 0.2xa0% from lead CRT glass. While more and more end-of-life electronics have been collected and treated by formal or licensed recyclers in China in terms of our analysis, many of them only have dismantling and separation activities. Hazardous e-wastes, including those from PCBs, CRT glass, and brominated flame retardant (BFR) plastics, have become problematic and probably flow to small or backyard recyclers without environmentally sound management. Traditional technologies are still being used to recover precious metals—such as cyanide method of gold hydrometallurgy—from e-waste. While recovery rates of precious metals from e-waste are above 50xa0%, it has encountered some challenges from environmental considerations. Worse, many critical metals contained in e-waste are lost because the recovery rates are less than 1xa0%. On the other hand, this implies that there is opportunity to develop the urban mine of the critical metals from e-waste.

Quantifying Export Flows of Used Electronics: Advanced Methods to Resolve Used Goods within Trade Data

There is limited convincing quantitative data on the export of used electronics from the United States (U.S.). Thus, we advance a methodology to quantify the export flows of whole units of used electronics from the U.S. using detailed export trade data, and demonstrate the methodology using laptops. Since used electronics are not explicitly identified in export trade data, we hypothesize that exports with a low unit value below a used-new threshold specific to a destination world region are used. The importance of using the most disaggregated trade data set available when resolving used and new goods is illustrated. Two detailed U.S. export trade data sets were combined to arrive at quantities and unit values for each port, mode of transport, month, trade partner country, and trade code. We add rigor to the determination of the used-new threshold by utilizing both the Neighborhood valley-emphasis method (NVEM) and published sales prices. This analysis found that 748 to 1199 thousand units of used laptops were exported from the U.S. in 2010, of which 78-81% are destined for non-OECD countries. Asia was found to be the largest destination of used laptop exports across all used-new threshold methods. Latin American and the Caribbean was the second largest recipient of these exports. North America and Europe also received used laptops from the U.S. Only a small fraction of used laptops was exported to Africa. However, these quantities are lower bound estimates because not all shipments of used laptops may be shipped using the proper laptop trade code. Still, this approach has the potential to give insight into the quantity and destinations of the exports if applied to all used electronics product types across a series of years.

Environmental risk assessment of CRT and PCB workshops in a mobile e-waste recycling plant

The mobile e-waste recycling equipment was chosen as the object of this study, including manual dismantling, mechanical separation of cathode ray tubes (CRTs), and printed circuit boards (PCBs) in the two independent workshops. To determine the potential environmental contamination, the noise, the heavy metals (Cu, Cd, Pb), and the environmental impacts of the e-waste recycling processes in the two workshops of the mobile plant have been evaluated in this paper. This study determined that when control measures are employed, the noise within the two workshops (<80xa0dB) will meet the national standards. In the CRT workshop, Pb was the most polluting metal, with 2.3xa0μg/m3 and 10.53xa0mg/g in the air and floor dust, respectively. The result of a health risk assessment shows that noncancerous effects are possible for Pb (hazard index (HI)u2009=u20093.54 in the CRT workshop and HIu2009=u20091.27 in the PCB workshop). The carcinogenic risks to workers for Cd are relatively light in both the workshops. From the results of life cycle assessment (LCA), it can be seen that there was an environmental benefit from the e-waste recycling process as a whole.

Characterization of brominated flame retardants in construction and demolition waste components: HBCD and PBDEs.

The vast majority of construction material is inert and can be managed as nonhazardous. However, structures may have either been built with some environmentally unfriendly substances such as brominated flame retardants (BFRs), or have absorbed harmful elements such as heavy metals. This study focuses on end-of-life construction materials, i.e. construction and demolition (C&D) waste components. The aim was to characterize the concentration of extremely harmful substances, primarily BFRs, including hexabromocyclododecane (HBCD) and polybrominateddiphenyl ethers (PBDEs). Results revealed extremely high contents of HBCD and PBDEs in typical C&D waste components, particularly polyurethane foam materials. Policies should therefore be developed for the proper management of C&D waste, with priority for POP-containing debris. The first priority is to develop a classification system and procedures to separate out the harmful materials for more extensive processing. Additionally, identification and quantification of the environmental implications associated with dumping-dominated disposal of these wastes are required. Finally, more sustainable materials should be selected for use in the construction industry.