Abstract

Chlorine adsorption kinetics of activated carbons from Cattle bone, coconut-shell and wood as influenced by mode of activation (heat and acid) were studied using a commercial activated carbon (CAC) as control. Batch chlorine adsorption by each activated carbon was investigated by contacting with fixed amount of chlorine solution at 10, 15, 20, 25, and 30°C respectively at 10 min intervals. The residual chlorine data were fitted with Freundlinch, Langmuir isotherms, and first order kinetic model. The data were also fitted to Fick’s unsteady state mass transfer equation and chlorine diffusivities were calculated from the slopes. Heat (H) activation was at 950°C for 3 h to produce heat activated bone carbon (HCB), and 850°C for 2.5 h for heat activated coconut-shell and wood carbon (HCS and HWC) while concentrated phosphoric acid (A) (1:3-1:4) carbon: acid (w/w) was at 600°C for 2 h to produce acid activated wood (AWC), acid activated coconut-shell (ACS) and acid activated bone (ACB) samples. The rates of chlorine adsorption were faster within the first 10-30 min; follow first order kinetics and Freundlich models. Chlorine diffusivities ranged from 3.674 × 10^-6 m²/s for Acid activated cattle bone carbon to 5.017 × 10^-6 m²/s for Commercial activated carbon. Porosity characterization of the carbons shows a wide range of pore sizes for both gas and liquid phase applications. This study indicated that efficient activated carbons could be obtained from local raw materials by controlled activation with acid or heat for home and industrial purposes.

Key words:  Adsorption, kinetics, activations, isotherms, diffusivities, porosity.