SCOPE OF THE PROJECT
What is the problem?
The
president of Ukraine L. Kuchma, acting on XIX express session to
General Assembly of United Nation in July, 1997, has noted presence on
Ukraine of ecological crisis, which by the begining of the accident has
served Chernobyl catastrophe. The technogenic pressure in territory of
Ukraine in 6-7 times exceeds a level of the developed countries. For a
period " of the advanced socialism " on Ukraine is saved more than 25
billion tons of a waste, which occupy 13 thousand km2
of plough-lands. Agrees to "The National report on a state of
environmental natural medium in Ukraine " (Ministry of ecology and
natural resources, 1999), 40 % of territory of Ukraine is polluted, 30
% - is very much polluted, and 1,7 % of territories are territories of
ecological disaster. First of all, it is a band of alienation about
Chernobyl nuclear power plant and series of terrains in the
Dnepropetrovsk, Donetsk, Lugansk, Zaporozhye, Lvov regions. On the data
of the same source, in 1999 volume of return water has made 10988
million m3, from which 3172 million м3 were unsufficiently cleaned, and 746 million м3
were not cleaned at all. And 68 % of unpurified waters is a share
industries. The majority of these waters is dumped in the rivers of
Dnieper basin, which make 80 % of water resources of Ukraine and serve
a radiant of water supply 32 million people and 2/3 facilities of
Ukraine. Last years the excess in waters of the rivers of this basin of
the permissible content of such metals, as copper, iron, manganese,
chrome is observed. Besides in a spring period in river Pripyat`
(region of Kyiv) the content of radioactive strontium (90Sr) grows up to 34 Bk/l3 (at norm - 2 Bk/l3). As a whole, in 1999 - in comparison with 1998 - the average annual exponent of the content 90Sr in water of reservoirs of Dnieper stage has grown in 2 times.
The
singular alarm is caused by a state of ground waters in region
Chernobyl nuclear power plant, for which characteristicly boosted
content 90Sr and 137Cs.
Besides causes an alarm and increase of a fluid radioactive wastage
from atomic power stations (so, last years volume of this wastage was
incremented on 11-13 %).
In
connection with the usual situation the Government of Ukraine was
developed the Concept and Basic directions of state ecological
politics. The considerable place in this document is given to questions
of monitoring, clearing of sewage, clearing of potable water etc.
measures. The search of new methods, materials, repaying of
technologies is provided. The speech goes and about expansion of gauges
of production of sorbents, first of all of zeolites, including zeolites
on the basis of mineral natural raw material. The development of
technologies of extraction from industrial wastes of gold, silver and
other nouble metals is provided also, that will promote pinch of
currency reserves of the country. In this connection it becomes clear,
that the search of new high performance sorbents, which on the order
would surpass already existing, becomes an essential problem.
How to Solve the Problems?
In summary we shall add, that many nuclear power plants in the Ukraine
and around the world use process water that becomes contaminated with
radioactive metal ions, such as caesium, that have long half-lives.
Presently, this contaminated water is stored in large vessels until a
technology can be used to separate selectively only those metal ions
that present the greatest danger and to concentrate these ions into a
solid form that can be placed in stable underground storage facilities.
We can imagine a technology for the removal of toxic/radioactive metal
ions from water using beads of solids specially designed to address
each problem. This technology can be successful if one can synthesize
an irreversible adsorbent that will selectively adsorb from aqueous
solutions only the desired metal ions, such as caesium, from a mixture
of similar ions, such as sodium.
Thus, we propose to use the functionalized polysiloxane superadsorbents
as a potential solution to the following basic problems facing the
Ukraine in particular and other countries around the world -
remediation of water contaminated with radioactive metal ions (caesium,
strontium). Several questions come to mind in applying this technology
to the basic problems at hand.
Why use polyoxosilanes instead of zeolites and instead of
functionalizing the surface with silica with vapor deposition of active
agents?
- Zeolites bind metal
ions by ion exchange only, this interaction is reversible making
removal of these ions from low concentrations very difficult.
Polyoxosilanes use functional groups on the surface that form
coordination compounds with the desired metal ion.
- Polyoxosilanes
can be formed in a one-step synthesis at room temperature using
inexpensive materials. This point is very important for industry.
- No solvent is needed to make the solids as opposed to zeolite. This is very important from ecology point of view.
- No dangerous byproducts are generated as is common to functionalization of silica using vapor phase reaction.
- Larger
concentrations of functional groups can be developed on surface of
polyoxosilanes than can be developed using surface modification of
silica.
These
advantages of the polyoxysilanes are augmented by the following
properties: 1) a controllable, porous structure and 2) a
multifunctional surface layer, that confer upon polyoxosilanes
irreversible binding of selected metal ions to the sorbent and and high
binding capacity, hence the term: superadsorbents. Taken together, all
of these attributes of the superadsorbents make them an attractive
choice for remediation of waters contaminated with low-level
radioactive wastes.
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