Copper and nitrophenol removal by low cost alginate/Mauritanian clay composite beads

The aim of the present work concerns the feasibility of using Mauritanian clays through encapsulation with alginate for the removal of water pollutants e.g. copper and 4-nitrophenol. Results were compared to those obtained with commercial Volclay bentonite and activated carbon. Four raw clays were selected from sites around Rosso and Nouakchott (Mauritania) with kaolinite and illite as main minerals. A Mauritanian clay (ZS 26) was selected from its higher rate of smectite and gel-like beads were obtained as a result of the cross-linking between sodium alginate and this clay. In agreement with previous works, the pseudo-second order equation fits well with the kinetic data and the diffusion coefficients obtained (4-8 x 10(-7) cm(2)/s) are within the ranges reported in other works. Adsorption isotherms were analyzed using Langmuir model and non-linear regression. Adsorption of Cu2+ was in the following order SA > composite microbeads > clays, activated carbon; adsorption of 4-NP was favourized onto activated carbon and the order was AC > AC/SA > Na-mont > Na-ZS26/SA, Na-mont/SA. The sorption capacities of Cu2+ and 4-NP by Na-ZS 26/SA microbeads are in the range reported in a previous work for the commercial clay. Further insights were provided and the removal of 4-NP by encapsulated clays or clays (ZS 26 or commercial bentonite) was greatly affected by the presence of Cu2+. In conclusion, this work has developed a simple, eco-friendly and practical method for the production of a low cost composite Mauritanian clay/alginate beads which can be used for the removal of inorganic and organic pollutants. (C) 2011 Elsevier B.V. All rights reserved.