Nanocomposites and nanomaterials
Nanoscale complexes based on natural polymers as effective flocculants

A.F. Tymchuk, V.V. Tymchuk
Faculty of Chemistry, Odessa National University, Dvoryanskaya str. 2, Odessa, Ukraine,65026, Tymchuk@onu.edu.ua.
Natural polymers (chitosan and sodium alginate) can be used in sorption and flocculation processes. They have a complex of properties: biodegradability, playback of the raw material base, compatibility with living tissues without toxicity. 
The aim of our researches was to study the flocculation ability of the complexes based on chitosan, sodium alginate and surfactants. 
As a model system, we used an aqueous suspension of kaolin, in which the surface layer of the particle has a negative charge due to the silanol groups. Kaolin was dried to constant weight. The concentration of the dispersed phase in the suspensions was 0,3-7,0 %. Polyacrylamide-kaolin systems were used as a comparison system. The process of formation nanoscale complexes based on polymers in solution with the addition of sodium alkylsulfates was study previously. The formation of complexes in solution was confirmed by a change in the rheological, surfactant and electrokinetic properties of systems.
Studies have shown that the range of effective concentrations of polymers for flocculation is (0.5 - 5.0) mg / l. In this interval there is a change in the hydrodynamic properties of macromolecules is observed. An optimal correlation is established between the charge density and the flexibility of the macromolecule. High flocculation ability is explained by changes in the conformation of macromolecules. The mean-square radius of the macromolecules increases to 11 and 15 nm for sodium alginate and chitosan, respectively. The root-mean-square distance between the ends of the macromolecular chain is 28 and 37 nm, respectively. The macromolecule changes the conformation in such a way that the number of segments available for interaction increases. Microscopic analysis confirms that bulk flocculs are formed in solutions containing chitosan and sodium alginate. This leads to a sharp destabilization of systems. In the case of chitosan flocculation proceeds through a neutralization mechanism.
Our studies have confirmed that nanocomplexes formed by chitosan and sodium alginate can be used as effective flocculants, because they show a high flocculating effect.

1. Tymchuk A.F.,Grubnyak A.E. Influence natural and synthetic flocculants on the sedimentation stability of suspensions/Issues of Chemistry and Chemical Technology. – 2017. – V.22-2 (63), p. 71-81