Novel dye adsorbent materials based on ionic liquid-derived natural wool/silica composites: preparation, characterization, and adsorption capacity

Natural polymers/silica composite materials are increasingly being advocated for water treatment. The goal of this work is the preparation of new adsorbent materials using regenerated wool/silica structured composites. Imidazole-based ionic liquid (IL) was used to develop the regenerated wool, which was then enriched with silica particles using two different silica procurers including tetraethyl orthosilicate (TEOS) and aminopropyltriethoxysilanes (APTS). The microstructure features and adsorption capacity wool/silica (WO/SiO₂) and wool/silica with amine groups (WO/SiO₂-NH₂) using methyl orange (MO) were studied under different conditions. Scanning electron microscope (SEM) study demonstrates the formation of particle reinforced composite materials of regenerated WO functionalized with SiO₂ particles of average diameter around 730 ± 380 nm for WO/SiO₂ and 911 ± 293 nm for the WO/SiO₂-NH₂ samples. The adsorption results indicated that the equilibrium data are well fitted into the Langmuir isotherm model, proposing monolayer adsorption and Langmuir isotherm with maximum adsorption capacity of 182 mg/g for WO/SiO₂-NH₂ sample. The surface of WO/SiO2-NH2 composite samples provides a great amount of silanol and amino groups that interact with the N atom on MO dye, resulting in dipole–dipole H-bonding interactions. Therefore, the adsorption efficiency of WO/SiO₂-NH₂ sample is mostly retained even after five consecutive cycles of adsorption and desorption suggesting its potential as an advanced generation of sustainable material for organic dye removal.