Abstract
Abstract Magnetite particles are prepared from a mixed aqueous solution of FeCl2 and FeCl3, and magnetite−bentonite composite particles are obtained from a mixed dispersion of magnetite and bentonite by precipitation with ammonia. The dispersions are examined by the X-ray diffraction, transmission electron microscopy, IR spectroscopy, dynamic light scattering, and electrophoresis methods. In the presence of magnetite, the basal reflection at 2θ = 6.06° in the X-ray diffraction pattern of bentonite shifts to 7.14° due to the replacement of K+, Na+, and Mg2+ ions by Fe3+ ions. Moreover, peaks corresponding to iron compounds arise in the diffraction pattern, while an absorption band at 1405 cm–1 assigned to Fe–O bonds appears in the IR spectrum of the composite particles, thereby probably indicating the formation of small magnetite particles between bentonite layers. Along with the indicated changes, the passage from original bentonite to the magnetite−bentonite composite is accompanied by an increase in the ζ-potential of the particles from –35.1 to –25.7 mV and a decrease in their sizes from 300 to 220 nm. The latter phenomenon is explained by ion exchange, water removal from the interlayer space, and the contribution of smaller particles of magnetite. To test the functional potential of the obtained composite particles, the adsorption of a drug, kazcaine, on them is studied, and the maximum kazcaine adsorption value is found to be as large as 74.65 mg/g. The analysis of kazcaine adsorption kinetics at different temperatures is carried out to determine the thermodynamic parameters of the process. The results obtained show that the process can be described by a pseudo-second-order kinetic equation. The Langmuir model appears to be most suitable for describing the adsorption mechanism.