Adsorptive removal of phenols by Fe(III)/Cr(III) hydroxide, an industrial solid waste

Phenolics have recently been of great concern because of the extreme toxicity and persistency in the environment. Laboratory investigations of the potential use of Fe(III)/Cr(III) hydroxide as an adsorbent for the removal of bisphenol A and 2-aminophenol from aqueous solution were conducted. The operating variables studied are agitation time, initial concentration, adsorbent dose, pH and temperature. Equilibrium data follow Langmuir, Freundlich and Dubinin-Radushkevich isotherms. The Langmuir adsorption capacity of untreated and pretreated adsorbent was found to be 3.47 and 3.67 mg g(-1), respectively, for bisphenol A; and 2.94 and 6.03 mg g(-1) for 2-aminophenol. Adsorption was analyzed using first order, second order and Elovich kinetic models and the data were found to follow second order and Elovich kinetic models for the adsorption of bisphenol A by untreated adsorbent and first order and Elovich kinetic models for the adsorption of 2-aminophenol by untreated adsorbent. Thermodynamic parameters such as Delta G(0), Delta H-0 and Delta S-0 for the adsorption were evaluated.