MANTRA

Every year, huge quantities of organic and inorganic compounds are released in the environment as a consequence of human activities. Current water treatment technologies are designed for the removal of most metals, sulfates and phosphates but are not efficient regarding other classes of pollutants (such as organic pollutants, including pesticides or pharmaceutical compounds). As an alternative, we are investigating here a new process based on new materials: green hybrid composite materials made of biorefinery by-products and biopolymers. To these materials, we have added a magnetic iron oxide. The physical processes of removal are then, firstly, entrapment (adsorption) of the pollutant compounds onto the magnetic biobased nanocomposites, and secondly, recovery of the adsorbed pollutant by application of an external magnetic field; the later attracts and isolates the magnetic nanocomposite, and with it, the pollutant it carries. We chose dyes as models for hydrophilic organic pollutants and cesium as an example of radioactive pollutant (produced for instance in the Fukushima accident). Adsorption processes were studied as a function of parameters such as pH (i.e., acidity of the water), contact time between pollutant and composite surface, and initial concentration of pollutants.

Among the major results, the magnetization of biorefinery by-products and biopolymers has been successful. We could determine the optimal external magnetic field to be applied for a complete removal of the pollutants. Adsorption of pollutants was revealed to be dependent on pH (in range of 2-6) and on contact time. The adsorption process was found to operate even at low pollutant concentrations (lower than 10^-4 mol/L). For example, 100% of the dye was removed after 24h, at pH 6. The use of magnetic biopolymer and biorefinery by-product nanocomposites might thus be a powerful way to depollute water at low cost and with minimal operational management.