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PURIFICATION OF WATER FROM METAL IONS BY ACTIVATED CARBONS OBTAINED FROM COALS AND AGRICULTURAL BYPRODUCTS

AUTHOR/S: EKSILIOGLU, A., KARADAG, F.,GUL, A.,SIPAHI,M., BUDINOVA, T., PETROV, N.,SAVOVA,D
Sunday 1 August 2010 by Libadmin2005

5th International Scientific Conference - SGEM2005, www.sgem.org, SGEM2005 Conference Proceedings/ ISBN: 954-918181-2, June 13-17, 2005, 379- 386pp

ABSTRACT

The problems for the protection of the environment from various pollutants are
considered worldwide as fundamental for mankind. A large number of people are nowadays
exposed to the different pollutions in waste and potable water. The pollutions have a harmful
effect on the biological system. Some regions in Bulgaria and Turkey have serious problems
with water contaminated with metal ions. The heavy metals (Hg, As, Cd, Mn, etc.) have a
harmful effect on human physiology and other biological system when they are found above
the tolerance level.
Bulgarian and Turkish coals of different origin and agricultural by-products: olive
stones, apricot stones, coconut shells, birch wood, furfural, mixtures from biomass tar and
furfural are used for obtaining of activated carbons. After physical activation with water
vapour and air and chemical activation with H3PO4 and K2CO3, carbon adsorbents with
basic and acidic characters are prepared. They are characterized with well developed
porous structures, surface area from 1000 to 1600 m2/g) and higher adsorption capacity
towards iodine (800-1300mg/g).
The adsorption of Hg (II), Mn(II), As(III), Pb(II), Zn(II) , Cu(II), Cd(II) from aqueous
solution by obtained activated carbons was studied. The results from the study showed that
all modifications of the adsorbents (with alkaline and acidic character) are efficient
adsorbent for metal removal from water. The process of adsorption followed Langmuir
isotherm. The influence of the solution pH on the adsorption process has been studied. The
acidic character of the carbon surfaces favors to a larger extent chemisorptions of metal ions. The results show that oxygen remaining from the raw material participates in the formation
of surface oxides and indicates the possibility of controlling the content of acidic surface sites
on the carbon surface by appropriate selection of the precursor composition and the surface
properties modification.
All activated carbons exhibited an ability to adsorb different metal ions from water.
Activated carbons from anthracite and lignite show an ability to adsorb metal ions with the
capacities increasing in the order Cd2+Zn2+Cu2+Pb2+.
The maximum sorption capacity for mercury ion is in the following order: steam
activated furfural adsorbent -174mg/g; steam-activated adsorbent from mixture of furfural
and tar from apricot stones-154mg/g; air-oxidized furfural adsorbent 134mg/g, birch-wood
adsorbent-154mg/g; turkish colas(Somma and Mengen) – 105 and 92 mg/g.
The results for As(III) removal are found to be highly promising from 2.87 to 9.54 mg/g
for different modification of adsorbents, obtained from olive pulp and olive stones.
The adsorption of manganese ions on carbon obtained from mixtures tar from apricot
stones and furfural depends on the concentration of surface oxides. This determines the
higher adsorption capacity of the oxidized carbon (10.20 mg/g)) in comparison with the
carbon activated with water vapor (3.89 mg/g). The investigations indicate the possibilities to
remove metal ions from water by carbon adsorbents obtained from coals, agricultural byproducts
and their treatment products.