Alginic Acid Foams with Hierarchical Porosity: Promising Materials for Dyes Adsorption

Alginic acid foams with hierarchical porosity: Promising materials for dyes adsorption

Nathalie Tanchoux^1*, Asja Pettignano^1,2, Luca Bernardi², Thierry Vincent³, Eric Guibal³, Françoise Quignard¹

¹ Institut Charles Gerhardt, CNRS-UM2-ENSC-UM1, 8 Rue Ecole Normale, 34090, Montpellier, France. nathalie.tanchoux@enscm.fr

² Department of Industrial Chemistry, UNIBO, V. Risorgimento, 4, 40136, Bologna, Italy.

³ Ecole des Mines d’Alès, C2MA/MPA, 6 Avenue de Clavières, 30319, Alès, France.

Keywords: foams, hierarchical porosity, biopolymers, alginic acid, biocompatible adsorbent

Water pollution due to organic dyes is a serious environmental problem. Their release, even in low quantities, is highly undesirable because of their high visibility, low biodegradability and toxic effects on humans and marine organisms. Among the treatments proposed for water decontamination, adsorption is a popular method, because of its high efficiency and low operating cost. Therefore, the development of low-cost adsorbents is becoming extremely attractive and natural biopolymers are often presented as abundant, renewable and biodegradable resources for this application.[1] In our study, alginic acid, a biopolymer derived from brown algae, has been studied as a cost-effective replacement for conventional adsorbents. The presence of hydroxyl and carboxylic groups in its polymeric backbone confers: (a) the ability to associate, by physical and chemical interactions, with a wide variety of molecules [2] and (b) an excellent selectivity towards cationic dyes. Employing the tremendous manipulability of this polysaccharide, alginate foams with macro-meso pores have been developed with a simple procedure. The influence of preparation parameters (alginate composition, temperature, concentration, acidification procedure) on the final texture have been studied by SEM microscopy and N₂ adsorption, which confirmed the presence of a hierarchical porosity. The applicability of the newly developed material have been tested by examining its sorption behavior towards cationic dyes (such as methylene blue), by equilibrium and kinetic experiments, proving that alginic acid foams can be employed as biocompatible, green and low-cost adsorbents for wastewater remediation.

[1].  G. Crini, Prog. Polym. Sci. 2005, 30, 38-70.

[2].  F. Quignard, F. Di Renzo, E. Guibal, Top. Curr. Chem. 2010, 294, 165-197.