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Research article - Peer-reviewed, 2021

Organic dyes (acid red, fluorescein, methylene blue) and copper(II) adsorption on amino silica spherical particles with tailored surface hydrophobicity and porosity

Melnyk, Inna, V; Tomina, Veronika V.; Stolyarchuk, Nataliya, V; Seisenbaeva, Gulaim A.; Kessler, Vadim G.

Abstract

Organic dyes are common constituents in wastewater and contribute to accumulation of persistent organic pollutants in the environment. Common dyes are aromatic compounds, bearing a variety of hydrophilic functional groups. Their interaction with solid surfaces can thus involve both van-derWaals and hydrophobic interactions and electrostatic and/or hydrogen bonding. Aiming to tailor adsorbents with specific capacity for removal of dyes, silica microspheres were synthesized, combining aminopropyl functions as moderators of hydrophilic interaction and bridging aliphatic and aromatic functions as potential moderators of hydrophobic and p-stacking interactions. Two groups of samples were produced: non-porous silica spheres with amino or combined amino and hydrophobic residues; and porous polysilsesquioxane spheres incorporating aminopropyl components and organic bridges in the silica network. The hydrophilicity/hydrophobicity of the samples was studied by the absorption of water and benzene vapors. Bridged fragments, expected to promote the porosity of the samples, as well as hydrophobicity, did not contribute to the latter, because polysilsesquioxanes were bearing large numbers of residual silanol groups. Particles synthesized using tetraethoxysilane were up to 130 nm in size and held 1.6-1.8 mmol/g of amino groups, while, materials prepared from bridged silanes featured particle agglomerates up to 300 nm, 2.2-2.7 mmol/g amino groups content, and specific surface area of 540-620 m2/g. Interaction with Cu2+ was used to probe concentration and surface location of the amino functions, reaching 76-203 mg/g. Adsorption of anionic (acid red 88), neutral (fluorescein) and cationic (methylene blue) dyes was investigated revealing multiple interactions between the sorbent and sorbate. The dye sorption capacity values were 81-262 mg/g for acid red 88, 26-132 mg/g for fluorescein, and 55-146 mg/g for methylene blue. Produced silica microspheres have potential as high performance sorbents for the extraction of copper(II) ions and the dyes, and can act as fluorescent carriers after the dye adsorption. (C) 2021 Elsevier B.V. All rights reserved.

Keywords

Polysiloxane microspheres; Amino groups; Hydrophobicity; Dyes adsorption; Surface chemistry; Fluorescence

Published in

Journal of Molecular Liquids
2021, Volume: 336, article number: 116301
Publisher: ELSEVIER