| Abstrakt: |
The sorption extraction of heavy metal (HM) ions Cu(II), Co(II), and Cd(II) from aqueous media with the use of Zn, Al- and Mg, Al-layered double hydroxides (LDHs) intercalated with citrate and trilonate ions and their composites with magnetic properties, such as Fe3O4/Zn,Al-Cit, Fe3O4/Mg,Al-Cit, and Fe3O4/Zn,Al-EDTA is studied. The mentioned organo-inorganic composite materials, which efficiently combine the advantages of each component, are synthesized via the ultrasonic treatment of a mixture of LDH intercalated with complexones and highly disperse magnetite intercalated with complexones to provide their high crystallinity. The HM extraction conditions (pH of aqueous medium, sorption kinetics, sorbent dose, effect of ionic strength and aqueous medium macrocomponents of organic and inorganic nature) are determined. It is established that a major fraction of HM ions is almost extracted for the first five minutes of contact between an aqueous solution and the solid phase of sorbents, and sorption equilibrium is attained on the studied LDH samples and their composites with magnetic properties in 1 h. Based on the parameters of kinetic models and the coefficients of linear correlation for these LDH forms, it is demonstrated that HM sorption can be most reliably described by the pseudo-second-order model throughout the entire range of sorption times in contrast to the pseudo-first-order model. This makes it possible to presume that the mechanism of metal ion extraction is predominantly implemented by means of chemosorption, and the equilibrium adsorption values calculated theoretically by the pseudo-second-order model are in good agreement with experimental data. The calculated forms of HM ions existing in aqueous solutions in the presence of Cit- and EDTA-ions at different pH of aqueous solution confirm the mechanism of HM removal from aqueous media within the studied pH range. The analysis of obtained data gives grounds to recommend the studied materials as efficient sorbents of complexing metals for the purification of contaminated surface water by the sorption technology with magnetic separation of sludges. [ABSTRACT FROM AUTHOR] |
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