35 research outputs found
Recycling Metals from Wastes: A Novel Application of Mechanochemistry
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
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
<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
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
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
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
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.
<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.
<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.
<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