Adsorption Properties of Activated Carbons Prepared from Olive Stones by Chemical and Physical Activation

Abstract

Activated carbons were prepared from olive stones either by the addition of zinc chloride (25-50 wt%) or by gasifying non-activated carbon with steam to burn-offs between 25% and 49%. The adsorption of nitrogen at 77 K was investigated and the adsorption data interpreted by the application of the Langmuir equation, the BET equation and the a S -method. The adsorption of carbon dioxide at 273 K was also followed and the data analyzed using the DR and DA equations. The adsorption of iodine from aqueous potassium iodide solution, and of Methylene Blue and p-nitrophenol from aqueous solutions at 298 K was also determined.Activation with zinc chloride produced physical and chemical changes which modified the thermal degradation process. Carbonization with zinc chloride restricted the formation of tars with the subsequent formation of solid carbon, the amount of zinc chloride incorporated in the precursor governing the porosity of the resulting carbon. The atmosphere under which activation of samples containing zinc chloride was undertaken was another factor in determining the texture of the carbon. Activation with steam to low burn-offs created new micropores by burning off the more reactive carbon atoms, but at high burn-offs erosion of the pore walls occurred leading to pore widening.Adsorption from solution was determined by the solubility of the solute in the solvent and by competition for this solute between the solvent and the adsorbent. The pore size of the carbon adsorbent and the molecular size of the adsorbate molecule were prominent factors in determining the extent of adsorption from solution.

Estimation of surface area and pore volume of activated carbons by methylene blue and iodine numbers

“…Indeed, the methylene blue molecule has an area 15 of 2.08 nm 2 and can only enter in large micropores and mesopores. 5 The iodine molecule is relatively small with an area 15 of 0.4 nm 2 and can enter in the smaller micropores.…”

“…To test the accuracy of the method, we used experimental and literature data. The literature data were obtained from activated carbons produced from olive-waste cakes, 5 tree seed husks, 8 bituminous coal, wood, 9 Eucalyptus bark, 10 rubberwood sawdust, 11 waste newsprint, 12 sugarcane bagasse, 13,14 babassu, coconut shells, 14 sugarcane residues, 7 olive stones, 15 petroleum pitch, 16 shells and fruit pits, 17,18 fruit seeds 18 and knitted fabrics, 19 besides commercial activated carbon. 20 The experimental data were obtained using activated carbons produced in our laboratory from spent coffee grounds, 21 bean husks 22 and a commercial sample.…”

Thermogravimetric and spectroscopic study (TG–DTA/FT–IR) of activated carbon from the renewable biomass source Babassu

“…Many discussions in this respect have been generated, and the agreed pore diameter for MB adsorption averages 1.3 nm. 29,30 Thus, it would be interesting that small deviations from the mathematical equations used could also be considered in the pore size determination.…”

Adsorption of heavy metals by activated carbon synthesized from solid wastes

“…This ability to arrest the different pollutant molecules is mainly attributed to its higher specific surface area [21]. The recent trend is the preparation of activated carbons from various kinds of wastes [22][23][24][25][26], e.g. wood, coconut shell, nutshells, cotton stalks and wastes rubber.…”