In Situ Ring-Opening Polymerization of L-lactide on the Surface of Pristine and Aminated Silica: Synthesis and Metal Ions Extraction

Liliia M Polishchuk; Roman B Kozakevych; Andrii P Kusyak; Valentin A Tertykh; Oleg Tkachenko; Maria Strømme; Tetyana M Budnyak

doi:10.3390/polym14224995

In Situ Ring-Opening Polymerization of L-lactide on the Surface of Pristine and Aminated Silica: Synthesis and Metal Ions Extraction

Polymers (Basel). 2022 Nov 18;14(22):4995. doi: 10.3390/polym14224995.

Authors

Liliia M Polishchuk¹, Roman B Kozakevych¹, Andrii P Kusyak¹, Valentin A Tertykh¹, Oleg Tkachenko², Maria Strømme², Tetyana M Budnyak²

Affiliations

¹ Chuiko Institute of Surface Chemistry, 17 General Naumov Street, 03164 Kyiv, Ukraine.
² The Ångström Laboratory, Division of Nanotechnology and Functional Materials, Department of Materials Science and Engineering, Uppsala University, Lägerhyddsvägen 1, 751 03 Uppsala, Sweden.

Abstract

The development of functional materials from food waste sources and minerals is currently of high importance. In the present work, polylactic acid (PLA)/silica composites were prepared by in situ ring-opening polymerizations of L-lactide onto the surface of pristine (Silochrom) and amine-functionalized (Silochrom-NH₂) silica. The characteristics of the ring-opening polymerization onto the surface of modified and unmodified silica were identified and discussed. Fourier transform infrared spectroscopy was used to confirm the polymerization of lactide onto the silica surface, and thermogravimetric analysis determined that PLA constituted 5.9% and 7.5% of the composite mass for Silochrom/PLA and Silochrom-NH₂/PLA, respectively. The sorption properties of the composites with respect to Pb(II), Co(II), and Cu(II) ions were investigated, and the effect of contact time, initial metal ion concentration, and initial pH were evaluated. Silochrom-NH₂/PLA composites were found to have a higher adsorption capacity than Silochrom/PLA for all chosen ions, with the highest adsorption value occurring for Pb²⁺ at 1.5 mmol/g (90% removal efficiency). The composites showed the highest performance in the neutral or near-neutral pH (created by distilled water or buffer pH 6.86) during the first 15 min of phase contact. The equilibrium characteristics of adsorption were found to follow the Langmuir isotherm model rather than the Freundlich and Temkin models. Perspective applications for these PLA/silicas include remediation of industrial wastewater or leaching solutions from spent lead-acid and Li-ion batteries.

Keywords: L-lactide; adsorption; polylactic acid; polylactide-silica composites; ring-opening polymerization; toxic metal ions.

Grants and funding

Oleg Tkachenko is thankful for the funding from Carl Trygger’s Foundation for Scientific Research (CTS 21:1701). Tetyana M. Budnyak acknowledges financial support from Formas—a Swedish Research Council for Sustainable Development (project: 2020-02321).