Scholarly record

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

A. Eksilioglu, F. Karadag, A. Gul, M. Sipahi, T. Budinova, N. Petrov, D Savova

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.

Publication details

Back to publication list