Phase and granulometric composition, structural morphological and textural characteristics of the composite sorbent

Abstract

The purpose of this article is to determine the phase and granulometric composition, structural, morphological and textural characteristics of composite sorbents based on bentonite-like clay and hydroxylapatite synthesized by chemical precipitation.

X-ray phase analysis and IR spectroscopy revealed the formation of hydroxyaptite crystals in a composite sorbent. The method of the laser diffraction established that the experimental samples consist mainly particles with a size from 0.97 to 125 μm. The highest proportion of particles of bentonite-like clay is 68.40 wt%, hydroxylapatite 71.77 wt% and composite sorbent 74.76 wt% has a size of 1.0 to 10 μm.

The scanning electron microscopy was established that the bentonite-like clay consists to separate monocrystals of montmorillonite, to accompany minerals and their aggregates. Powders of hydroxylapatite consist of particles of elongated form. The surface of the particles composite of bentonite-like clay is covered in the composite sorbent by hydroxylapatite crystals.

The method of transmission electron microscopy established that montmorillonite monocrystal particles have the form of isometric films of 100-300 nm in size with twisting edges. Individual crystals of hydroxylapatite have an elongated form of 35 to 65 nm in length and 12 to 20 nm in width, respectively, and in the composite sorbent from 8 to 18 nm and from 5 to 8 nm, respectively.

The method of low-temperature nitrogen adsorption and desorption has established that bentonite-like clay, hydroxylapatite and composite sorbent have mesoporous structure and contain a small amount of micro- and macropores with an average size of 54.60, 228.18 and 121.93 Å, respectively. The specific surface area of ​​the composite sorbent is 96.81 m²/g, which is higher than the bentonite-like clay and hydroxylapatite by 85.78 and 12.85%, respectively. The obtained results allowed to predict the large sorption capacity of composite materials with heavy metal ions and organic compounds.