Natural Minerals Coated by Biopolymer Chitosan: Synthesis, Physicochemical, and Adsorption Properties

Natural minerals are widely used in treatment technologies as mineral fertilizer, food additive in animal husbandry, and cosmetics because they combine valuable ion-exchanging and adsorption properties together with unique physicochemical and medical properties. Saponite (saponite clay) of the Ukrainian Podillya refers to the class of bentonites, a subclass of layered magnesium silicate montmorillonite. Clinoptilolits are aluminosilicates with carcase structure. In our work, we have coated biopolymer chitosan on the surfaces of natural minerals of Ukrainian origin — Podilsky saponite and Sokyrnitsky clinoptilolite. Chitosan mineral composites have been obtained by crosslinking of adsorbed biopolymer on saponite and clinoptilolite surface with glutaraldehyde. The obtained composites have been characterized by the physicochemical methods such as thermogravimetric/differential thermal analyses (DTA, DTG, TG), differential scanning calorimetry, mass analysis, nitrogen adsorption/desorption isotherms, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy to determine possible interactions between the silica and chitosan molecule. The adsorption of microquantities of cations Cu(II), Zn(II), Fe(III), Cd(II), and Pb(II) by the obtained composites and the initial natural minerals has been studied from aqueous solutions. The sorption capacities and kinetic adsorption characteristics of the adsorbents were estimated. It was found that the obtained results have shown that the ability of chitosan to coordinate heavy metal ions Zn(II), Cu(II), Cd(II), and Fe(III) is less or equal to the ability to retain ions of these metals in the pores of minerals without forming chemical bonds

Adsorption Properties of Bentonite with In Situ Immobilized Polyaniline Towards Anionic Forms of Cr(VI), Mo(VI), W(VI), V(V)

A new composite material bentonite-PANI was synthesized by in situ immobilization of polyaniline (PANI) on the surface of natural mineral bentonite. It was established as a result of the modification of bentonite a surface area and an interlayer distance of mineral decrease and particles of bentonite transformed of irregular shape with different porosity on irregularly shaped particles of smaller size. It has been found that the total Cr(VI) ions extraction took place under the acid conditions (pH=1 – 2) and W(VI) ions have been well adsorbed in the pH range from 1 to 8 by the composite bentonite-PANI unlike the initial mineral. Whereas adsorption of oxo anions of V(V) and Mo(VI) made up some 50%. It is proved that the in situ immobilization of bentonite by polyaniline leads to increasing the value of adsorption capacity towards the investigated ions compared with the initial mineral. It was established that the adsorption properties of the synthesized composite with respect to the studied oxo ions were worse than the adsorption properties of composite vermiculite-PANI, similar to the composite Sokyryntsyy clinoptilolite-PANI and better than composites of polyaniline with Podilskyy saponite and Karelian shungite.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.6976</p

Formation and Luminescent Properties of Al2O3:SiOC Nanocomposites on the Base of Alumina Nanoparticles Modified by Phenyltrimethoxysilane

Abstract Al2O3:SiOC nanocomposites were synthesized by thermal treatment of fumed alumina nanoparticles modified by phenyltrimethoxysilane. The effect of annealing temperature in inert ambient on structure and photoluminescence of modified alumina powder was studied by IR spectroscopy as well as photoluminescence spectroscopy with ultraviolet and X-ray excitation. It is demonstrated that increase of annealing temperature results in formation of silica precipitates on the surface of alumina particles that is accompanied by development and spectral evolution of visible photoluminescence. These observations are discussed in terms of structural transformation of the surface of Al2O3 particles