35 research outputs found

    Recycling Metals from Wastes: A Novel Application of Mechanochemistry

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    Recycling metals from wastes is essential to a resource-efficient economy, and increasing attention from researchers has been devoted to this process in recent years, with emphasis on mechanochemistry technology. The mechanochemical method can make technically feasible the recycling of metals from some specific wastes, such as cathode ray tube (CRT) funnel glass and tungsten carbide waste, while significantly improving recycling efficiency. Particle size reduction, specific surface area increase, crystalline structure decomposition and bond breakage have been identified as the main processes occurring during the mechanochemical operations in the studies. The activation energy required decreases and reaction activity increases, after these changes with activation progress. This study presents an overall review of the applications of mechanochemistry to metal recycling from wastes. The reaction mechanisms, equipment used, method procedures, and optimized operating parameters of each case, as well as methods enhancing the activation process are discussed in detail. The issues to be addressed and perspectives on the future development of mechanochemistry applied for metal recycling are also presented

    Urban Mining of E‑Waste is Becoming More Cost-Effective Than Virgin Mining

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    Stocks of virgin-mined materials utilized in linear economic flows continue to present enormous challenges. E-waste is one of the fastest growing waste streams, and threatens to grow into a global problem of unmanageable proportions. An effective form of management of resource recycling and environmental improvement is available, in the form of extraction and purification of precious metals taken from waste streams, in a process known as urban mining. In this work, we demonstrate utilizing real cost data from e-waste processors in China that ingots of pure copper and gold could be recovered from e-waste streams at costs that are comparable to those encountered in virgin mining of ores. Our results are confined to the cases of copper and gold extracted and processed from e-waste streams made up of recycled TV sets, but these results indicate a trend and potential if applied across a broader range of e-waste sources and metals extracted. If these results can be extended to other metals and countries, they promise to have positive impact on waste disposal and mining activities globally, as the circular economy comes to displace linear economic pathways

    Adapting to new policy environment – past pattern and future trend in us-sino waste plastic trade flow

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    <p>Plastics are one of the most used materials in human activities, where consumer consumption and industrial production together has imposed vast rise in demand for this material in last century. While plastic is ideally derived from crude oil as a primary source from manufacturers’ perspective, varying crude oil prices are driving manufacturers economically to seek for alternative sources for plastics production. Waste plastic recovered from obsolete consumer products thus becomes an economic substitution for virgin plastics, which is further intensified with the possibility of international waste plastic trading. This study focuses on waste plastic trade between the US and mainland China by performing a correlation analysis of trade data. It is suggested in this study that although waste plastics are traded from the US to mainland China in general, as many of us believes, the route is gradually shifting in the past years. With tightening Chinese customs regulations, waste plastic from the US now tends to take a transit in a third destination (Hong Kong SAR for instance) for preliminary treatment to bypass Chinese customs inspection. Such phenomenon is worth noting, as a complication in waste plastic trading route hinders waste plastic transboundary movement monitoring. Furthermore, it will have adverse consequent consumer, industrial, and environmental impacts. It is thus necessary for national competent authorities to strengthen cooperative study and communication capacity in the future as a response to the changing waste plastic trade pattern.</p

    Innovated Application of Mechanical Activation To Separate Lead from Scrap Cathode Ray Tube Funnel Glass

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    The disposal of scrap cathode ray tube (CRT) funnel glass has become a global environmental problem due to the rapid shrinkage of new CRT monitor demand, which greatly reduces the reuse for remanufacturing. To detoxificate CRT funnel glass by lead recovery with traditional metallurgical methods, mechanical activation by ball milling was introduced to pretreat the funnel glass. As a result, substantial physicochemical changes have been observed after mechanical activation including chemical breakage and defects formation in glass inner structure. These changes contribute to the easy dissolution of the activated sample in solution. High yield of 92.5% of lead from activated CRT funnel glass by diluted nitric acid leaching and successful formation of lead sulfide by sulfur sulfidization in water have also been achieved. All the results indicate that the application of mechanical activation on recovering lead from CRT funnel glass is efficient and promising, which is also probably appropriate to detoxificate any other kind of leaded glass

    Na<sub>2</sub>ZrO<sub>3</sub> as an Effective Bifunctional Catalyst–Sorbent during Cellulose Pyrolysis

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    Na<sub>2</sub>ZrO<sub>3</sub> was tested as bifunctional catalyst sorbent using cellulose as model biomass under pyrolytic conditions. Thermogravimetric analyzer connected to a mass spectrometer (TG-MS) was used to study the influence of Na<sub>2</sub>ZrO<sub>3</sub> on the gas evolution from cellulose pyrolysis. The weight loss data and gas evolution was analyzed over a temperature range of 200–800 °C. Na<sub>2</sub>ZrO<sub>3</sub> showed a clear catalytic influence during cellulose pyrolysis, and it was actively catalyzing tar cracking and reforming reactions at elevated temperatures. A comparison with CaO was conducted under identical conditions and results showed that Na<sub>2</sub>ZrO<sub>3</sub> mixed samples were able to produce higher yield of hydrogen from cellulose, mainly due to participating in tar-cracking and reforming reactions at lower temperatures than CaO (500 °C for Na<sub>2</sub>ZrO<sub>3</sub>, compared to 600 °C for CaO). The study showed that Na<sub>2</sub>ZrO<sub>3</sub> can act as catalyst for pyrolysis reactions of cracking and reforming, and subsequently remove CO<sub>2</sub> produced <i>in situ</i>. The results suggest that Na<sub>2</sub>ZrO<sub>3</sub> has potential to participate in the gasification of biomass as an effective bifunctional catalyst–sorbent, which may enhance hydrogen yield

    Green Process of Metal Recycling: Coprocessing Waste Printed Circuit Boards and Spent Tin Stripping Solution

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    Electronic waste (e-waste), including waste printed circuit boards (PCBs), has caused global concern owing to its potential environmental pollution and rich resource content. Previous studies have indicated that urban mining for metals recycling can decrease energy consumption and pollutants emission compared to the extraction of metals from natural minerals. During the production of PCBs, a large amount of spent tin stripping solution (TSS) is simultaneously generated, containing the significant amounts of metal ions and residue nitric acid. In this study, the coprocessing of waste PCBs and spent TSS at room temperature was proposed and investigated, with the aim of developing an environmentally sound process to address these problems. This coprocessing approach proved to be effective. 87% of the Sn–Pb solder, 30% of the Cu, 29% of the Fe, and 78% of the Zn was leached from waste PCBs with spent TSS after 2 h, at room temperature. Moreover, approximately 87% of the electronic components were dismantled from waste PCBs. About 99% of the Sn, Pb, Fe, Cu, and Zn were recovered from the leaching solutions by chemical precipitation. The proposed green process has substantial advantages over traditional recovery methods of heating waste PCBs, in terms of both material and energy efficiency

    Ultrafast Self-Healing Nanocomposites via Infrared Laser and Their Application in Flexible Electronics

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    The continuous evolution toward flexible electronics with mechanical robust property and restoring structure simultaneously places high demand on a set of polymeric material substrate. Herein, we describe a composite material composed of a polyurethane based on Diels–Alder chemistry (PU-DA) covalently linked with functionalized graphene nanosheets (FGNS), which shows mechanical robust and infrared (IR) laser self-healing properties at ambient conditions and is therefore suitable for flexible substrate applications. The mechanical strength can be tuned by varying the amount of FGNS and breaking strength can reach as high as 36 MPa with only 0.5 wt % FGNS loading. On rupture, the initial mechanical properties are restored with more than 96% healing efficiency after 1 min irradiation time by 980 nm IR laser. Especially, this is the highest value of healing efficiency reported in the self-healable materials based on DA chemistry systems until now, and the composite exhibits a high volume resistivity up to 5.6 × 10<sup>11</sup> Ω·cm even the loading of FGNS increased to 1.0 wt %. Moreover, the conductivity of the broken electric circuit which was fabricated by silver paste drop-cast on the healable composite substrate was completely recovered via IR laser irradiating bottom substrate mimicking human skin. These results demonstrate that the FGNS-PU-DA nanocomposite can be used as self-healing flexible substrate for the next generation of intelligent flexible electronics

    Hyperthermia induces apoptosis in 786-O cells.

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    <p>Cells were exposed to 37°C and 42°C for the indicated amount of time. Apoptotic cells were measured by flow cytometry immediately after heat treatment. <b>A:</b> Images showing flow cytometric analysis of apoptosis. <b>B:</b> The histogram shows the result from A (%). *P<0.05 compared to control. Results are representative of three independent experiments.</p

    Ku expression was detected in 786-O cells exposed to 37°C or 42°C for the indicated amount of time.

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    <p><b>A</b> and <b>B:</b> Ku70 and Ku80 mRNA expression was analysed by RT-PCR. <b>C</b> and <b>D:</b> Ku70 and Ku80 protein expression was detected by Western blot. *P<0.05 compared to control.</p

    Effect of Ku80 expression on cell cycle distribution under hyperthermia.

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    <p>786-O-shKu80 and 786-O-scramble cells were subjected to 42°C for the indicated amount of time. Then the cell cycle distribution was measured immediately after hyperthermia. Images showing flow cytometric analysis of cell cycle distribution.</p
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