Removal of textile dyes from aqueous solutions using low cost Moroccan clay

Abstract

This study aims to evaluate the technical feasibility to apply natural clay from Fez area as a low cost alternative adsorbent to remove dyes from contaminated waters. Methylene blue (MB) and congo red (CR) are used here as representatives of cationic and anionic dyes normally present in wastewater from textile industry. This material was characterised by different physical-chemical methods, including BET, X-ray fluorescence and pHPZC. Additionally, the influence of operating conditions such as contact time, adsorbent dosages and pH were evaluated. Experimental results show that the adsorption processes takes place very rapid, reaching the equilibrium at 30 and 45 min for MB and CR, respectively. Maximum adsorption capacities result to be pH-depends. Hence, MB adsorption is favoured under basic pH conditions, whereas CR does it at acid pH. A pseudo-second-order kinetic model provides the best fit to the experimental data of MB and CR adsorption. Adsorption data are better described by Langmuir and Toth isotherm models. Adsorption occurs with a maximum monolayer adsorption capacity of 195 and 185 mg g-1 for MB and CR, respectively. Experimental results indicate that the Moroccan clay could be used as a potential adsorbent for the elimination of dyes from contaminated waters, at a lower cost.