Abstract

HERNANDEZ-VELAZQUEZ, Pedro Iván et al. Hybrid functionalized phosphonate silica: insight into chromium removal chemistry from aqueous solutions. J. Mex. Chem. Soc [online]. 2019, vol.63, n.2, pp.130-153.  Epub Apr 20, 2020. ISSN 1870-249X.  https://doi.org/10.29356/jmcs.v63i2.793.

Insight into Cr(III) ions removal chemistry from aqueous solutions was gained by using hybrid phosphonate-functionalized silica adsorbents synthesized through a modified route of sol-gel processing (SPMF). Evaluation of the degree of metal removal was obtained from kinetics and batch experiments. Elemental analysis, FTIR, NMR and XPS techniques were used to study the nature of surface complex formed on adsorbent. Adsorption equilibrium results showed a maximum Cr(III) removal of 78.639 mg g-1Cr(III) at pH 3.6 on adsorbent SPMF04; kinetics measurements indicated that equilibrium was reached in 80 min contact time. The achievement of 2.923 mmol P/g as phosphonate groups was obtained. A Langmuir-type mechanism explained the adsorption equilibrium results whereas kinetic measurements were explained through a pseudo-second order mechanism. FTIR measurements indicated a strong influence of Cr(III) adsorbed on surficial functional groups. 29Si CP MAS NMR results indicated that Cr(III) interacted not only with phosphonate surface groups but also with a large of amount of geminal OH surface groups. XPS studies suggested that Cr(III) was removed through the formation of the surface complex R as monovalent chromium acetate and/or divalent. The adsorbent SPMF04 can be potentially employed in industrial applications.

Keywords : amorphous silica; sol-gel process; Cr(III) ions; NMR; XPS.

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