Adsorptive removal of chlorophenols from water by bituminous shale

Chlorophenols are among priority water pollutants which are taken up by aquatic fauna and flora and enriched in the food chains. Acid-activated bituminous shale has been used as an adsorbent for the removal of 2-chlorophenol (MCP) and 2,4-dichlorophenol (DCP) from water and the related process parameters were investigated. Kinetic analysis showed that the adsorption reaction could be approximated by a first-order rate equation for which pore-diffusion was the essential rate-controlling step. Adsorption was endothermic and basically of a physical character. Equilibrium modelling by linearized adsorption isotherms revealed that a Langmuir equation could well represent the observed data. The entropy change of adsorption was more positive for DCP due to its higher polarity. The saturation capacity of the sorbent for both chlorophenols were determined by dynamic column tests, this experimental capacity being lower than the theoretical monolayer capacity envisaged by the Langmuir equation. Adsorption was completely reversible as the retained DCP could be completely desorbed from the column with distilled water as eluant. The results were evaluated within the scope of utilization of cost-effective unconventional sorbents to remove chlorinated organics as possible substitutes for activated carbon. (C) 1998 Elsevier Science Ltd. All rights reserved.