Kinetic and equilibrium adsorption of methylene blue and remazol dyes onto steam-activated carbons developed from date pits

Steam-activated carbons DS2 and DS5 were prepared by gasifying 600 degrees C-date pits carbonization products with steam at 950 degrees C to burn-off = 20 and 50%, respectively. The textural properties of these carbons were determined from the nitrogen adsorption at -196 degrees C. The chemistry of the carbon surface was determined from the surface pH and from neutralization of the surface carbon-oxygen groups of basic and acidic type. The kinetic and equilibrium adsorption of MB and RY on DS2 and DS5 was determined at 27 and 37 degrees C and at initial sorption solution pH 3-7. DS2 and DS5 have expanded surface area, large total pore volume and contain both micro and mesoporosity. They have on their surface basic and acidic groups of different strength and functionality. This enhanced the sorption of the cationic dye (MB) and of the anionic dye (RY). The adsorption of MB and RY on DS2 and DS5 involves intraparticle diffusion and followed pseudo-second order kinetics. The adsorption isotherms were applicable to the Langmuir isotherm and high monolayer capacities for MB and RY dyes were evaluated indicating the high efficiencies of the carbons for dye adsorption. (C) 2009 King Saud University. All rights reserved.