Tailoring the surface functionality of ukrainian kaolin via deep eutectic solvent immobilization: A potential hybrid material for dye adsorption

A deep eutectic solvent-functionalized kaolin adsorbent was developed for the first time. • DES treatment reconstructed the kaolin surface and modified its pore architecture. • Surface functionalization altered polarity, zeta potential, and colloidal behavior of kaolin. • The hybrid adsorbent delivered 96–99% methylene blue removal from water. • Green metrics confirmed the sustainability of both DES synthesis and adsorbent preparation. A new deep eutectic solvent (DES)-modified kaolin-based adsorbent was synthesized for the first time as material for adsorption of organic pollutants. A ternary DES Choline chloride – Urea – Glycerol (1:1:1) was used to modify kaolin. Quantum-chemical calculations are applied to predict the properties of DES, particularly the reactivity of hydrogen bond donors (HBDs) and the nature of their hydrogen-bond interactions. The successful preparation of DES was confirmed by proton nuclear magnetic resonance ( 1 Н NMR) and Fourier transform infrared spectrometry (FTIR). The physicochemical properties of DES, including electrical conductivity (0.273 mS·cm −1 ), surface tension (66.25 mN·m −1 ), pH (3.22), and polarity (205.9 kJ∙mol −1 ), were determined. The FTIR, low-temperature N 2 adsorption-desorption, particle size characterization via DLS, and zeta-potential analyses confirmed the successful DES functionalization of kaolin, resulting in surface restructuring, pore blocking, altered electrokinetic behavior, increased surface polarity, and formation of hydrated organo-mineral agglomerates. It has been established that modification of kaolin with DES contributes to increasing the efficiency of removal of the model dye MB from the aqueous medium, providing a removal efficiency of over 96–99%. The environmental friendliness of the developed sorbent modification and adsorption procedure was assessed using the AGREEprep and AGREE metrics. The sustainability of the synthesized DES was assessed using DES Ecoscale. Download: Download high-res image (241KB) Download: Download full-size image