Applied Mechanics and Materials Vol. 768

Abstract: This paper mainly introduces a novel route for copper recovery from waste printed circuit boards (WPCBs) via mechanochemistry. Copper in the crust is most commonly present as copper-iron-sulfide and copper-sulfide minerals (about 80%) and there exist many methods to extract copper from cooper ores in mineral engineering. It seems an alternative to transform the metallic components in obsolete materials to their corresponding compounds common in nature. By means of mechanochemistry, copper and sulfur were verified to form into copper sulfide in the model experiment, where, meanwhile, the optimal ball milling time was determined (20 minutes). In the real experiment, WPCB fragments and sulfur were mixed and ground for 20 minutes, no copper was detected by XRD analysis but copper sulfide was left. After leaching in sulfuric acid (3M) and hydrogen peroxide (30 wt%), the yield of copper reached nearly 95% and, also, resin was conserved for further utilization. This paper, for the first time, reports the green recovery route combining mechanical activation and sulfurization and may provide an alternative in other studies of metal recovery.

Abstract: Printed circuit boards (PCBs) are the typical and fundamental components of almost all electric and electronic equipments. The mechanical and physical treatment of PCBs generates a large amount of non-metallic materials and thus there is an urgent need to develop alternative treatment methods for them. In this study, the characteristics and environmental risk of non-metallic materials were analyzed. The current recycling methods were investigated as well. The results showed that their chemical components were distinct for the glass fiber/epoxy laminated boards and paper/phenolic laminated boards. The presence of bromine, chlorine, copper, chromium and lead would pose a threat to the environment during its recycling. The current recycling methods included landfill, preparing composites and building materials, pyrolysis and combustion. These methods had their own distinct advantages and disadvantages. The comparative analysis indicated that preparing composites may be an alternative recycling method. Molten salt oxidation (MSO) technology is prospective and need be further studied.

Abstract: Treatment technology of brominated epoxy resin (BER) is still a big challenge to waste printed circuit boards (PCBs) recycling. In order to make full use of the materials, ionic liquid 1-butyl-3-methyl imidazole chloride ([Bmim]Cl) was used to dissolve BER to separate glass fibers from PCB nonmetallic powders. The effects of dissolving parameters including temperature, time and solid/ liquid ratio on the dissolution rate of BER were investigated. The dissolved BER were regenerated and were characterized by FTIR and thermal analysis. Results showed that [Bmim]Cl was a good direct solvent for BER dissolution and at a suitable condition of 170°Cfor 6 hours with solid/liquid ratio of 1: 20 (g/g), nearly 90% of BER in original powders were dissolved. The possible dissolution mechanism was also discussed.

Abstract: Waste organic solvents have been classified as hazardous waste in many countries because of their toxicity, high volatility and Ignitability. Waste organic solvents are produced in a lot of industries including of the electronics industry. In this industry, organic solvents are used as cleaning agent and developer, which would generate a lot of waste organic solvents. In China, in the management and re-use of waste organic solvents, the current management systems are not completely. So it is need to learn the laws and regulations, treatment and disposal technologies, control standards of waste organic solvents generated in electronics industry in the developed countries. In this paper, based on an organic solvent waste for feature analysis and risk assessment, which generated by the electronics industry, Therefore, the waste organic solvent has a more serious environmental risk and human health risk through the soil and underwater than the air. Forbid the waste organic solvents produced company casual dump, in order to avoid the waste pollution. The evaluation result of the waste organic solvents produced by China's electronics industry is the data basis to obtain relevant management regulations On this basis, put forward the suggestion and management specifications of waste organic solvents, provide strong supports for the revise of the " National Catalogue of Hazardous Wastes ".

Abstract: Electronic waste is widespread across the globe comprises wide range of elements, growing exponential recent years and even categorized as hazardous if the elements like lead, mercury, arsenic, cadmium, selenium, and hexavalent chromium etc. are present beyond the permissible quantities. They may also be important secondary resources if processed in eco-friendly manner for secured supply of contained metals. Bio-extraction of metals from E-waste with microbes such as bacteria and fungi is being increasingly explored to meet the twin objectives of resource recycling and pollution mitigation. This review focuses on the biological extraction techniques including an assessment has been made to quantify the different E-waste and their metal compositions, microbes used, metal leaching efficiency etc. and proposes that the biological recovery allows the cycling of metals by a process close to natural biogeochemical cycles reducing the demand for resources such as ores, energy, or landfill space.

Abstract: Tetrabromobisphenol A (TBBPA) is widely used as a flame retardant and relatively persistent in the environment. There has been increasing interest in the developing alternative approach for its degradation and debromination. In this study, we explored the debromination of TBBPA by alkaline hydrothermal treatment with reactive minerals, namely iron powder, layered double hydroxide (LDH) and gibbsite. The effects of hydrothermal temperatures and time, the initial TBBPA concentrations, and additive amounts of reactive minerals on debromination were investigated. As a comparison, the conventional hydrothermal treatment with no additive as the control group was included. The UV-vis absorption spectra of TBBPA before and after debromination were studied as well. The results showed that increasing temperature was helpful for the improvement of debromination. It significantly increased by 223.5, 54.3 and 78.1% with increasing temperature from 140 to 160 °C for the control, iron power and LDH groups, respectively. When the hydrothermal time was shorter than a critical value, the debromination rate increased with time rising. A maximum rate of 79.9% was achieved for iron powder group after reaction for 8 h. The preferred initial TBBPA concentration was determined as 60 ppm for all groups. The optimum amounts of reactive minerals were not consistent and determined as 0.08 g for iron powder, 0.32 g for LDH and 0.16 g for gibbsite, respectively. The maximum absorption bands of TBBPA increased as the pH was raised. They were located at 209 and 308 nm for neutral TBBPA and increased to 211 and 311 nm for TBBPA-Na₂CO₃. New absorption bands in the wavelength region of 225-275 and 300-350 nm were observed, when TBBPA was subjected to hydrothermal treatment. Keywords: Brominated flame retardants (BFRs); tetrabromobisphenol A (TBBPA); debromination; hydrothermal treatment; UV-vis absorption spectra

Abstract: Lithium-ion battery (LIB) is significantly changing the landscape of human life. The feasibility of recycling and disposal of spent LIBs was proposed based on the study of their forecasted demand and distribution characteristics in China. The yearly processing capacity of recycling and disposal facilities of spent LIBs on a nationwide scale were estimated to be at least 50 kilotons. The recycling and disposal facilities should be established in the southeastern coast areas of China, which generated high-density spent LIBs. Beijing was chosen as a city case study to discuss the demand forecasting and present one detailed construction planning of spent LIBs recycling. The obtained thoughts and results can contribute to the recycling and disposal facilities of other Chinese megacities.

Abstract: The Copper Clad Laminate (CCL) residue recycling technologies are important to improve the recycling of waste circuit boards and reducing the environmental impact during its life cycle. However, there has not yet been able to have the technical evaluation criteria for CCL residue. This study demonstrates the feasibility of one recycling technology from the technical, economic, social, environmental and political, and then determinates CCL residue recycling technologies evaluation index system by Delphi Method, AHP, expert panel and Questionnaire and etc., which provides a tool for CCL residue recycling technologies assessment.

Abstract: Container houses have exhibited huge advantages in such aspects as building efficiency, environmental protection and sustainability. The theoretical basis of the recycling design of waste container is formed based on the idea of reuse design and the idea modular design and the idea of energy-saving design and the idea of improving design combination. This article also obtained the inventive principle of the reuse design of waste containers from the theory of TRIZ. This article will provides certain references for the future transformation design of the containers.

Abstract: Along with the process of economic growth and urbanization, China has entered a peak period of electronic appliances and automotive industry products obsolescence. On one hand, municipal waste disposal is increasing and causing environmental pollution and damage; on the other hand, native mineral resources’ exhaustion has increased year by year along with exploitation difficulty and mineral resources import growth. Meanwhile, urban industrial scrap, aka "urban mines", does contain abundant of renewable resources, such as copper, iron, and aluminum. Therefore, based on the theory of circular economy, the exploitation of these "urban mines" is the key strategic industry of China’s "12th five-year plan". This paper is based on the survey of Chengdu city regeneration resources industry situation. We analyzed the current status of regeneration resources recycling industry in Chengdu city, finding problems such as the number of existing garbage collection stations inadequate for renewable resources, and processing technology out of date. Generally speaking, the renewable resources industry in Chengdu is under developed.