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1.
Egyptian Journal of Chemistry. 2009; 52 (2): 179-191
em Inglês | IMEMR | ID: emr-135667

RESUMO

Good adsorbing carbon was obitained, for the first time in a pilot scale, from cotton stalks in a locally-designed rotary pyrolyzer. Activation was performed in absence of any purging gases by imprgnation with 50% H3P04 followed by heat treatment at 420°C. Mechanically cut short sticks were soaked in diluted H3PO4 for a short duration [Batch 1] and an extended period [Batch 2] prior to thermal treatment. The derived carbons contained both coarse and fine grains with acidic effect. Porosity was characterized by N2 adsorption at 77 [o]K and the isotherms analyzed by the alpha-method to estimate total and microporous surface areas in addition to total and microporous volumes. The produced carbons exhibited well-developed porosity that was essentially microporous in composition. Several key performance parameters were altered considerably as a result of impregnation with H3PO4 and the extended chemical activation period [Batch 2]. Most of the internal porosity of both carbons was accessible to adsorption of iodine, whereas the uptake of methylene blue dye was proportional to the average size of micropores which were larger for the batch with a longer acid soaking time. SEM and FTIR investigations revealed the presence of a developed honeycomb structure and different oxygen functionalities on surfaces of the activated products which are advantageous in liquid-phase applications. Preliminary laboratory-scale experiments with Pb[II] indicate that adsorption capacity of target heavy metals compares favorably with commercially-available activated carbons. The raw material, pre-processing, and activation process prove feasible for the production of activated carbon on a large scale, thereby providing a sustainable strategy for treatment of toxic waste streams


Assuntos
Fibra de Algodão/métodos , Estudos de Viabilidade , Fosfatos/química , Microscopia Eletrônica de Varredura/métodos
2.
Egyptian Journal of Chemistry. 2009; 52 (3): 381-393
em Inglês | IMEMR | ID: emr-135690

RESUMO

Nine carbon xerogels were synthesized from resorcinol formaldehyde resin [RF], under increasing resorcinol/catalyst, Na2CO3, [R/C] molar ratios [50, 500. 1000], followed by pyrolysis at temperatures of 500, 600 and 700°C, under no external flow of gases. One organic xerogel was included for the sake of comparison. Drying of the RF hydrogels was carried out by the conventional evaporation technique in static air to get the RF xerogel Obtained carbons were characterized by CHO content, TEM, and N2/77K adsorption. Porosity characteristics were calculated by applying the well established alpha s plots to get various textural parameters. It was found that an increase in surface area, and pore volume was associated with corresponding rise in the R/C molar ratios. Most porosity, mainly, existed within the micropore size range, particularly for xerogels developed at 600 or 700°C, Thus. well-developed porous activated carbons could be obtained from an organic RF-xerogel by pyrolysis at 700°C and at high R/C-precursor ratios [500 and 1000]. The described simple conditions of preparation might encourage the pilot-scale production of porous carbon xerogels, suitable as adsorbents in liquid-phase environmental treatment processes


Assuntos
Carbono/química , Formaldeído/química
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