Comparison of the Adsorption Properties of the Mesoporous Sorbents Modified with Chelate Complexes of Rare-Earth Benzoyl Acetonates Studied by Gas Chromatography

Abstract

New sorption materials have been synthesized from mesoporous silicon dioxide modified with cerium, europium, and ytterbium benzoyl acetonates. The temperature at which the resulting sorbents are stable (260–320°C) was determined by thermal analysis. It was shown by low-temperature nitrogen adsorption/desorption that modification of the surface of the mesoporous SiO₂ layer leads to a decrease in the specific surface area from 133 to 100 m² g^–1. A gas chromatographic analysis revealed that the polarity of the samples with deposited cerium, europium, and ytterbium benzoyl acetonate complexes increases, the highest values being characteristic of organic compounds prone to donor-acceptor and proton-acceptor interactions. The effects of cerium, europium, and ytterbium benzoyl acetonates on the thermodynamic characteristics of adsorption of various classes of organic substances on the mesoporous SiO₂ surface were studied by gas chromatography. The differential molar heats of adsorption \({{\bar {q}}_{{{\text{dif,1}}}}}\), the change in the standard differential molar entropy of adsorption \(\Delta \bar {S}_{{1,{\text{C}}}}^{0}\), and the contributions of specific interactions to the total adsorption energy Δ\({{\bar {q}}_{{{\text{dif}},1({\text{sp}})}}}\) were calculated from the experimental data on the retention of the test adsorbate molecules.