E-Waste: Recovery of Noble Metal
Rapid developments in Technology lead to increase in diversified production of electrical and electronic items, which is increasing day by day. With increasing population the consumption of such kind of items are also increasing rapidly. Electrical and electronic equipments have its significant impact in various fields in our society due to its higher capabilities, minimum error, and quite faster in operations. Massive use of computer, laptops, cellular phone, television, etc causes the generation of large quantity of e-waste which is a major global problem today. It is one of the fastest growing solid waste streams in the world. In 2005, in the EU, about 8.3 –9.1 million tonnes of waste of electrical and electronic equipments were estimated to be generated and this figure are forecast to reach 12.3 million tonnes by 2020 with an annual growth rate of 2.5–2. 7%. It was also reported that 20 - 50 million tons of waste of electrical and electronic equipments are generating globally in every year. The e-waste generation rate is increasing rapidly day by day.
Due to the inadequate recycling infrastructure only about
20% of the total ewaste is possible to recycle, whereas 80% either ending up in
land filling or being informally recycled. E-waste in land filling causes the
contamination in soil and groundwater. In the present time maximum e-wastes are
generating from waste mobile phones and computer parts. Quantitatively it will
not be surprised if we say that the existence of number of mobile phones is more than the number of people living on
the Earth at present.
On the basis of chemical
composition, the e-waste consists of various metals, metalloids, precious
metals, halogenated compounds and radioactive elements. Metals and metalloids
include aluminium, arsenic, antimony, barium, beryllium, cadmium, chromium,
copper, europium, lead, lithium, iron, manganese, mercury, nickel, selenium,
silica, tin, yttrium, zinc, etc. Precious metals include gold, indium, silver,
palladium, platinum, etc.
There is a research scope in this
area where the valuable materials (copper, gold, platinum) can be recovered
from the e-waste. Some important materials such as copper, gold, platinum,
aluminium, palladium, nickel, zinc, and so on are present in the e-waste in
different percentage. Recovery of this material from e-waste may be good
initiative in the reduction of the e-waste along with the reduction of
environmental pollution.
1. Huisman, J., Magalini, F., Kuehr, R., Maurer, C., Ogilvie, S., Poll, J., Delgado, C., Artim, E., Szlezak, J., Stevels, A., 2007. 2008 Review of Directive 2002/96 on Waste Electrical and Electronic Equipment. ENV.G.4/ETU/2006/0032. Unite d Nations University, Bonn, Germany 347.
2. UNEP, 2009. Sustainable innovation and technology transfer industri al sector studies, recycling from e-waste to resourc es. United Nations Environment Programme & United Nations University.
Related Article:
Waste Plastics: Production
of Oil
The global production of plastics is increasing rapidly because of their vital role in today’s daily activities. Plastics are widely used because of its advantages such as cheapness, endurance, lightness, hygiene and design adaptability. The sharp rise and mass consumption of plastics produce a great quantity of wastes, which poses a formidable challenge for waste management. Most plastics are not biodegradable and originate from the unsustainable fossil fuels. The disposal of waste plastics has become a major worldwide environmental problem in today’s world. Plastic disposal requires a large land area that otherwise could be used for other more useful purposes. Most of the plastic that is not disposed of properly eventually ends up in water. Some of this waste then accumulates in ocean gyres in the great lakes or in other large water bodies. This accumulated plastic can result in the death of animals and birds from their consumption of it. Thus, it is becoming increasingly challenging to manage and control the use of plastics due to their adverse environmental effects.
The major sources of plastic waste
include agricultural, household, automobile, packaging materials, toys, etc. At
present, the disposal processes of plastic wastes are mainly incineration and
landfill. The incineration and landfill deposition of municipal waste plastics
(MWP) may cause environmental problems and is becoming more expensive. Due to increasing volume of MWP and decreasing landfill capacity for disposal,
landfill becomes more challenging. In addition, landfill can release hazardous
sub-stances and plastic wastes take long time to degrade. In terms of
incineration, it causes hazardous releases such as nitrous oxide, sulphur
oxides, dusts, dioxins and other toxins. Especially, incineration of polyvinyl
chloride (PVC) plastic causes the environmental pollution and reduces the
service life of the incinerator by generating hazardous hydrogen chloride gas
and dioxins containing chlorine.
In this regard, the disposal of
plastic wastes has become an important issue all over the world, and recycling
is an effective way to solve this problem. Recycling of plastic wastes shows
numerous benefits, such as reducing consumption of energy; reducing the amount
of solid wastes that go to incineration and landfill and thus decreasing the
environmental pollutions; displacing partially virgin plastics produced from
refined fossil fuels.
Research can be focused on the
production of oil from the waste plastics, which is more reliable and
relatively inexpensive way for suitable applications.
1. Arena, U. Process and technological
aspects of municipal solid waste gasification. A review. Waste Manage. 2012, 32, 625–639.
2. Chiu, S.J.; Chen, S.H.; Tsai, C.T.
Effect of metal chlorides on thermal degradation of (waste) polycarbonate,
Waste Manage. 2006, 26, 252-259.
3. Wang,
C. –Q.; Wang, H.; Liu, Y.-N. Separation of polyethylene terephthalate from
municipal waste plastics by froth flotation for recycling industry. Waste Manage. 2015, 35, 42-47.
4. Wey, M.Y.; Yu, L. J.; Jou, S.I. The
influence of heavy metals on the formation of organics and HCl during incinerating
of PVC-containing waste. J. Hazard. Mater. 1998,
60, 259–270.
5. Saisinchai, S. Separation of PVC from
PET/PVC mixtures using flotation by calcium lignosulfonate depressant. Eng. J. 2013, 18, 45–54.
Related article:
Water Splitting: Hydrogen Production
One of the most used technologies for electrolytic hydrogen production is the alkaline water electrolysis. But in most industrial electrolysers the cost of production is high because of the high energy consumption. Zero-gap cell geometry, development of new electrocatalytic materials for electrodes and new diaphragm materials are the attempts made to overcome the problems. The conventional nickel electrodes experience extensive deactivation during electrolysis which results in huge current loss. Development of activator electrocatalysts increase the surface area of electrode and reduce hydrogen over potential. Such electrocatalyst toward hydrogen evolution research are cobalt-chrome, nickel-cobalt-molybednum, etc. From the literature it has been shown that electro-catalytic water splitting using solar light is a promising method for hydrogen generation because of high efficiency, purity of the product, large scale production, environmentally friendly and simple process.
Photocatalytic water splitting using
heterogeneous catalysts for hydrogen production attracted recent years because
of the material’s favorable electronic energy band structure. Different
catalysts, such as SrZrO3, Cu2O, NiW,
Nanoscale zero valent iron (nZVI), silver oxides, etc
have been used as the photocatalyst during water splitting.
However, development of highly
active and stable catalyst for the photocatalytic water splitting is still a
challenging job. Further development in catalyst and modification of method may
lead to large scale production of hydrogen for getting sustainable green energy
in near future.
1.
Huerta-Flores, A. M.; Torres-Martínez,
L. M.; Sánchez-Martínez, D.; Zarazúa-Morín, M. E. Fuel 2015, 158, 66–71.
2.
Chen, K.-F.; Li, S.; Zhang, W.-X. Chem.
Eng. J. 2011, 170, 562–567.
3.
Wang, W.; Zhao, Q.; Dong, J.; Li, J.
Int. J. hydrogen energy. 2011, 36,
7374 – 7380.
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