Starch-clay based composites for water purification by filtration

Significant concerns have been raised due to increasing pollution of surface and ground waters. In the vast majority of water treatment plants, depth filtration is incorporated through the use of non-compressible filters made of granular activated carbon (GAC), but the efficiency of GAC for removal of pathogens is very poor. In addition, the removal of small organic polar molecules is not usually satisfactory. Therefore, there is a growing interest in the development of composites that improve the performance of GAC or even can be an alternative to its use. The current research describes the synthesis, characterization and potential use of clay-polymer composites for their use in water purification by filtration. The advantages of these clay-polymer composites are that they can be easily scaled for production at industrial levels; and they were formed by inexpensive materials, a day mineral (bentonite), and cationic starches which are widely used as additives in paper-making, textile and cosmetic industry. These starches are derivatized by the introduction of the cationic functional moiety 2-hydroxypropyltrimethylammonium. The interactions of three polymers with different degree of substitution with the surface of a commercial bentonite were examined. Sorption of the polymers and analysis of the surface charge of the complexes formed showed that charge neutralization at the external surface was observed at loadings lower than the CEC of this day. The lower values for the point of zero charge than the CEC of the clay can be explained by the high screening of the clay surface by non-charged segments of the polycation after sorption. The loading of polymer on the clay was highest for the polymer with the lowest charge density adopting a loop-and-train conformation on the clay surface, whereas a planar conformation was elucidated for the other two higher charged polymers. Several polymer-clay complexes were synthesized and tested for the inactivation and killing of the