The adsorption of catechol onto "waste" Fe(III)/Cr(III) hydroxide was investigated to assess the possible use of this adsorbent. The influence of various parameters such as agitation time, catechol concentration, adsorbent dose, pH, and temperature has been studied. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. Adsorption followed second-order rate kinetics. The Langmuir adsorption capacity (Q(o)) was found to be 4.0 mg/g of the adsorbent. Acidic pH was favorable for the adsorption of catechol. Desorption studies showed that chemisorption seems to be the major mode of the adsorption process. Thermodynamic parameters such as DeltaGdegrees, DeltaHdegrees, and DeltaSdegrees for the adsorption were evaluated.