Interactions of the dye, CI direct orange 34 with natural clay

Clay minerals are efficient adsorbent for dyes due to their colloidal properties. Tunisian raw clay collected from mine of Tamra composed of two species of clay minerals (kaolinite and halloysite) has shown efficiency for removal of azo dye Direct orange 34 (DO34) from aqueous solutions. For this purpose, the adsorption of DO34 was studied in batch mode under various parameters such as: pH, contact time, adsorbent dose and temperature. The results showed that acid pH is favorable for the adsorption of dye and physisorption on broken edges of clay particles seemed to play a major role in the adsorption process. It was found that the rate of adsorption decreases with increasing temperature and the process is exothermic. The adsorption kinetics followed the pseudo-second-order equation. The intraparticle diffusion and film diffusion are the rate limiting steps. The raw halloysite-rich clay sample (HC) plays a major role in anionic dye adsorption due to mainly to its acidic surface sites. (C) 2015 Published by Elsevier B.V.