N. Petrov

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.

Adsorption properties and microstructure of activated carbons produced from agricultural by-products by steam pyrolysis

A series of activated carbons has been prepared by steam pyrolysis of apricot and cherry stones, almond shells, and grape seeds at relatively low temperatures of 600, 650, and 700°C for 1–3 h at each temperature. The adsorption properties of the resulting activated carbons were studied as a function of the treatment temperature, soak time, and nature of the precursor. Activated carbons produced from various agricultural by-products showed different pore size distributions, depending on pyrolysis/activation conditions. Among the activation conditions used in this study, the treatment at 700°C for 2 h produced the highest N2 BET surface area and pore volume obtained from each precursor. The activated carbons were characterized by N2 adsorption, iodine, and methylene blue adsorption from solution. The microstructures of the carbons were examined by optical and scanning electron microscopy. The adsorption characteristics of the activated carbons produced from various agricultural by-products were found to be different and strongly dependent on the composition and structure of the raw materials.

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%.

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.

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.

Effect of water vapour on the porous structure of activated carbon from lignite

Abstract A Bulgarian lignite from the Chukurovo deposit was used to produce an activated carbon by one-step steam pyrolysis at 650 °C. The effects of the presence of water vapour on the yield and composition of the solid, liquid and gas products were investigated. The water vapour present during pyrolysis-activation contributes to distillation of low molecular weight products and reacts with the coal and the volatile products obtained during pyrolysis. These processes lead to an increase in the yield of liquid and gas products and a decrease in the solid yield. The resulting carbon is characterized by a more developed porous structure, a higher N 2 BET surface area and higher adsorption capacity for iodine and methylene blue compared to the solid product obtained after pyrolysis in an argon atmosphere. The concentration of the activated carbon surface functional groups is considerably higher than that of the char obtained by pyrolysis in an argon atmosphere under the same heating conditions.