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

• Published in: Journal of molecular liquids 2021-08, Vol.336, p.116301, Article 116301
• Main Authors: Melnyk, Inna V., Tomina, Veronika V., Stolyarchuk, Nataliya V., Seisenbaeva, Gulaim A., Kessler, Vadim G.
• Format: Article
• Language: English
• Subjects: Amino groups; Dyes adsorption; Fluorescence; Fysikalisk kemi; Hydrophobicity; Physical Chemistry; Polysiloxane microspheres; Surface chemistry
• ISSN: 0167-7322; 1873-3166; 1873-3166
• DOI: 10.1016/j.molliq.2021.116301

[Display omitted] •Positively charged silica microspheres (SM) with controlled hydrophobicity were designed.•Porosity of SM was regulated by including bridged silanes in matrix structure.•Dyes adsorption occured better on porous surface via chemisorption.•SM hydrophilicity follows H2O interaction with th SiOH or amino groups.•SM exhibit luminescent properties due to adsorbed molecules. 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-der-Waals 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 π-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