Interactions of natural aminated polymers with different species of arsenic at low concentrations: Application in water treatment

In the present work, the interactions between the amine functionnal groups present in chitosan, a natural polysaccharide and different species of inorganic arsenic are studied. Depending of the N-deacetylation rate, chitosan provides amine functions that could be protonated and shows interesting affinities to adsorb oxyanions of arsenic in solution. Two species, arsenate (AsV) and arsenite (AsIII), have been tested at pH 5, and commercial chitosan and chitin were used. Kinetics have been carried out at two initial concentrations (50 and 500 μ g/L) and different temperatures fixed between 4 to 40°C. The results have shown the reaction is very fast, and consequently, the equilibrium times are short (30 min in the best case). Experimental data are well fitted with a first order kinetic model. In a second part, isotherms have been performed with an As concentration range of 10 to 500 μ g/L and 0.5 g/L of biosorbent. Maximum adsorption capacities, deduced from the Langmuir model, range between 260 μ g/g at 40°C and 730 μ g/g at 4°C. Finally the fixation mechanism could be described by an ion exchange reaction between the protonated amine moities of the chitosan and the arsenate anion in solution.