Встановлено закономірності адсорбції урану (VI) з сульфатних розчинів частинками
парафіну, модифікованими триалкіламіном, у рівноважних умовах. Здійснено моделювання експериментальних ізотерм адсорбції з використанням моделей Ленгмюра,
Фрейндліха, Тьомкіна і Дубініна-Радушкевича. Доведено, що ізотерми адсорбції урану краще описуються моделлю Ленгмюра (рН 4) та моделями Фрейндліха і ДубінінаРадушкевича (рН 8). Розраховано адсорбційну ємність адсорбенту і константи зазначених моделей залежно від рН розчинів адсорбату та температури. Встановлено, що
процес адсорбції урану частинками парафіну, модифікованими триалкіламіном, є самочинним (ΔG
адс.
< 0), екзотермічним (ΔH
адс.
< 0), супроводжується упорядкуванням системи (ΔS
адс.
< 0)
Paraffin particles modified with surfactants, in particular the technical product trialkylamine,
are affordable, effective adsorbents and flotation carriers of lanthanides and actinides.
Such adsorbents are easily regenerated, which is accompanied by the concentration of
the solution to be purified. Their use also does not lead to secondary contamination of the
treated water. The regularities of uranium (VI) adsorption from sulfate solutions by paraffin
particles modified with trialkylamine under equilibrium conditions depending on the pH of
the adsorbate solutions and temperature have been established. Solutions similar to those
studied are formed during the sulfuric acid stripping of uranium ores, which is the main
technological scheme for processing uranium-containing raw materials at the Eastern Mining
and Processing Plant (Zhovty Vody, Kirovohrad Oblast, Ukraine). The analysis of the effect
of temperature on uranium adsorption from solutions with pH 4 showed that the adsorption
mechanism changes with an increase in the equilibrium concentration of the adsorbate -
physical adsorption changes to chemisorption and then to a mixed adsorption. Increasing
the pH of uranium-containing solutions from 4 to 8 leads to a decrease in the adsorption
capacity of the adsorbent. The adsorption capacity of the adsorbent has been proved, mg
U/g: 110.9 (pH 4, 298 K), 173.3 (pH 4, 303 K), 196.1 (pH 4, 313 K), 57.4 (pH 6, 298 K),
14.8 (pH 8, 298 K), 132.8 (pH 10, 298 K). A comparative study of the possibility of using a
number of models (Langmuir, Freundlich, Dubinin-Radushkevich, and Tеmkin) to describe
adsorption isotherms was carried out by determining the parameters characterizing the
adsorption process. It was proved that uranium adsorption isotherms from solutions with pH 4
are better described by the Langmuir model, and from solutions with pH 8 – by the Freundlich
and Dubinin-Radushkevich models. It was found that the process of uranium adsorption by
paraffin particles modified with trialkylamine is spontaneous (ΔGads. < 0, ranges from -21.24
to -32.29 kJ/mol), exothermic (ΔHads. = -36.96 kJ/mol), and is accompanied by the ordering of
the system (ΔSads.< 0, ranges from -25.5 to -27.3 J/(mol∙K)). The values of the characteristic
energy of adsorption (Dubinin-Radushkevich model) lie in the range of 7.7–16.4 kJ/mol,
which is characteristic of the ion exchange mechanism of adsorption.
