V. Minkova

Biomass conversion to carbon adsorbents and gas

Abstract A process is created for the utilization of biomass by producing carbon adsorbents and gas. Carbon adsorbents with alkaline character of the surface, tar and gas products are obtained by steam pyrolysis of biomass (almond shells, nut shells, apricot stones, cherry stones, grape seeds). Mixtures of tar obtained during this process and furfural are used for obtaining carbon adsorbents with low ash and sulphur contents and different chemical character of the surface. The chemical character of oxygen functional groups on their surface reveals that they are polyfunctional cationites. Carbon adsorbents obtained have a hydrophilic surface and are suitable for removing metal ions and other pollutants from water. The gas products can be used as energy source.

Removal of mercury (II) from aqueous solution by activated carbon obtained from furfural

The adsorption of Hg(II) from aqueous solution at 293 K by activated carbon obtained from furfural is studied. The carbon is prepared by polymerization of furfural following carbonization and activation of the obtained polymer material with water vapor at 800 degrees C. Adsorption studies of Hg(II) are carried out varying some conditions: treatment time, metal ion concentration, adsorbent amount and pH. It is determined that Hg(II) adsorption follows both Langmuir and Freundlich isotherms. The adsorption capacity of the carbon is 174 mg/g. It is determined that Hg(II) uptake increases with increasing pH. Desorption studies are performed with hot water. The percent recovery of Hg(II) is 6%.

Effect of water vapour on the pyrolysis of solid fuels: 1. Effect of water vapour during the pyrolysis of solid fuels on the yield and composition of the liquid products

Abstract The effect of water vapour on the yield and composition of the products obtained by low temperature thermal destruction of solid fuels at atmospheric pressure, before and after complete extraction with ethanol-benzene, is investigated. The liquid products and extractables are studied by infra-red and 1 H nuclear magnetic resonance spectroscopy, gas chromatography and gas chromatography-mass spectrometry. The results obtained enable us to distinguish the processes of distillation and desorption of low molecular components of the organic mass from the reactions of thermal destruction of the non-distilled part. The pyrolysis in a stream of water vapour is suggested as an appropriate procedure for structural studies of solid fuels since a large quantity of informative products are obtained.

PURIFICATION OF WATER BY ACTIVATED CARBONS FROM APRICOT STONES, LIGNITES AND ANTHRACITE

High efficiency activated carbons with various chemical characteristics, appropriate for the purification of waste and potable water with different pollutions (trihalomethanes, metal ions) were prepared. A suitable selection of both raw materials and activating agents as well as an additional modification were used for this purpose. It is established that activated carbon obtained from apricot stones by pyrolysis in a flow of water vapour (PWV method) can be used for removal of trihalomethanes from water treated with chlorine. Activated carbons obtained from apricot stones and lignites by the same method as well as oxidized anthracite can be used for removal of Pb2+ and Zn2+ ions from potable water. The chemical character of these carbon surfaces favours to a larger extent hemosorption of metal ions. Carbon obtained by steam-activation when used for water purification promotes the formation of nitrites. This hindrance can be eliminated by a suitable oxidation treatment of the carbon.

Removal of mercury ion from aqueous solution by activated carbons obtained from biomass and coals

Abstract The adsorption of Hg(II) from aqueous solution at 293 K by activated carbons obtained from apricot stones, furfural and coals was studied. Adsorption studies were performed under the varying conditions of time of treatment, metal ion concentration and pH. The process of adsorption followed Langmuir isotherm. The removal of Hg(II) increased with the increase of pH of the solution from 2 to 5 and remained constant up to pH 10. Desorption studies were preformed.

The influence of the texture and surface properties of carbon adsorbents obtained from biomass products on the adsorption of manganese ions from aqueous solution

Studies on the adsorption of manganese ions from aqueous solution on carbon obtained from a mixture of biomass products indicate the importance of acidic surface oxides for manganese ion adsorption that is predominantly site specific. 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 of the carbon surface by appropriate selection of the precursor composition and surface properties modification. The surface functionalities of oxidized carbon from a mixture of biomass products resembles the behavior of an ion-exchange resin. Oxidized carbon obtained from a 50:50 mixture of tar from steam pyrolysis of apricot stones and furfural contains a balance of surface area and high surface concentration of functional groups favorable for adsorption of positively charged manganese ions.

Preparation and characterization of carbon adsorbents from furfural

Abstract Carbon adsorbents with different properties were obtained from furfural with variations in the activation reagents and conditions of treatment. They possess insignificant ash and sulfur contents. Pore volume, pore size distribution and the chemical character of the surface of the obtained carbon adsorbent depend on the activation reagent and temperature of treatment. Various oxygen-containing groups of acidic character (carboxyl groups, carboxyl groups in lactone-like binding, phenolic hydroxyl and carbonyl groups) and different chemical properties are present on the surface of carbon oxidized with air. The sample activated with water vapour contains predominantly oxygen-containing groups with basic character.

Effect of water vapour on the pyrolysis of solid fuels: 2. Effect of water vapour during the pyrolysis of solid fuels on the formation of the porous structure of semicoke

Abstract The effect of the yield and composition of the liquid products on the formation of the porous structure of semicoke is examined. The more complete desorption of the low molecular weight components in a stream of water vapour up to 300 °C leads to a considerable increase in the total pore volume and the specific surface area of the solid residue as compared with that of the standard carbonization.

Formation of porous structure of semicokes from pyrolysis of Turkish coals in different atmospheres

Activated carbons were obtained from Turkish coals by one-step steam pyrolysis process. The effect of the water vapor on the yield of the solid, liquid and gas products was studied. The presence of steam during pyrolysis-activation process contributes to distillation of low molecular weight products and reacts with the coal and the volatile products obtained during the pyrolysis. These processes lead to an increase in the yield of liquid and gas products and a decrease in the solid yield. The resulting carbons are determined to have good adsorption characteristics.

Characterization of liquid products from pyrolysis of subbituminous coals

Abstract Liquid products obtained during the process of steam pyrolysis and pyrolysis in inert atmosphere of four samples of subbituminous coals were the focus of interest in this work. The composition of aliphatic and aromatic fractions from silica gel chromatography of maltenes obtained both by steam pyrolysis and nitrogen pyrolysis was characterized by GC and GC–MS. Conclusions are drawn about the structure and utilization of the investigated coals.