Adsorption modification of the zeolite surface with chitosan

Abstract

In order to modify the surface, thermal acid activation of the zeolite of the Chankanai deposit was conducted. It was found that the treatment of the mineral with acid at high temperature leads to a decrease in the content of Ca, Al and Sr in its composition. Adsorption of chitosan on the surface of thermoacid-activated zeolite was also studied. Processing of the adsorption isotherms according to Langmuir and Freundlich models showed that the maximum adsorption of chitosan on the zeolite surface is 30.1 mg/g and the Freundlich constant 1/n is 0.75. On the IR-spectra of chitosan-modified zeolite, a certain shift to the higher frequencies of the peak was found at the oscillation frequency of 1638 cm^-1, which can be explained by the contribution of amino groups adsorbed on the surface of the mineral. The shift to the left of the peak at 581 cm^-1, typical for aluminosilicate groups, is also an evidence of their interactions with chitosan. When studying the effect of chitosan concentration on the wetting of the modified zeolite powder, it was found that at concentration of 2^.10^-3 base mol/L, an increase in the wetting angle from 10° to 47° occurs due to surface overcharging. According to the data of adsorption, IR spectroscopy and wetting of the surface, the main mechanism for binding chitosan to the zeolite surface was due to the electrostatic interaction of polymer amino groups with silicate and aluminosilicate groups of the mineral, stabilized by hydrogen bonds between the OH-groups of the polymer and ≡Si-O-groups of the solid phase.