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The adsorption equilibria of methane, ethane, and nitrogen on BDH-activated carbon was measured using a volumetric adsorption apparatus in the temperature range of (30 to 60) °C for nitrogen and methane and (40 to 60) °C for ethane. The absolute pressures covered in the measurements were in the range of (0 to 5) atm for methane and ethane and (0 to 8) atm for nitrogen. Overall, the adsorption isotherms showed a standard Langmuirtype isotherm behavior and were fitted favorably to the Langmuir equation in a predictive form. The isosteric heats of adsorption for each component on BDH-activated carbon were estimated based on these fittings. The experimental data were also fitted collectively to the Dubinin-Radushkevich equation. The fitting was satisfactory, and the fitting parameters were consistent with the adsorption affinities and total pore volume obtained from the experimental data.

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ABSTRACT:Date pits, i.e. agricultural wastes, were converted into activated carbon by air and phosphoric acid activation. The surfaces of some of the prepared activated carbons were modified chemically using 8-hydroxyquinoline. The carbons prepared by both air and phosphoric acid activation showed surface areas of 864.8 m 2 /g and 502.2 m 2 /g, respectively, and micropore volumes of 0.298 cm 3 /g and 0.126 cm 3 /g, respectively.The adsorption of Methylene Blue onto the prepared activated carbon demonstrated its very high adsorption capacity. The adsorption of lead ions on both carbons, i.e. activated and chemically-modified, was studied under different conditions. The experimental results showed that both types of carbon gave a relatively large maximum lead ion uptake, the increase in the uptake as a result of chemical modification being insignificant. Lead ion uptake was found to increase by increasing the solution pH -whereby the maximum adsorption of lead ions was obtained at pH 5.2 -and by increasing the initial lead ion concentration. Equilibrium studies showed that the adsorption of lead ions on both adsorbents could be described by the Langmuir and Freundlich isotherm models. Kinetic studies showed that the adsorption of lead ions on the prepared activated carbons followed pseudo-second-order kinetics. The presence of EDTA, acetic acid or citric acid led to a significant decrease of lead ion uptake by the activated carbons.

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