Direct surface modification of a silica-based adsorbent for CO₂ capture from coir fibers dissolved in a sulfur-free alkali-urea system

The direct surface modification of silica using cellulose-based organosilane dissolved in a sulfur-free NaOH/urea solvent system was further investigated as a selective CO₂ adsorbent. Cellulose was dissolved at a low temperature of − 5°C, followed by mixing a silicate precursor as a silica source. Cellulose–carbamat complex grafting was carried out through a silica monomer condensation reaction using the sol–gel method. The anionic surfactant sodium lauryl sulfate (SLS) was added at various concentrations as a template to improve the particles’ physical characteristics. The process of particle formation and template removal was carried out in one stage in a spray drying system that followed the one droplet to one particle rule. Increasing the SLS concentration indicates a change in particle morphology from spherical to hollow, followed by an increase in particle size with a more uniform size distribution. The surface area and porosity of silica particles increased by up to fivefold when the SLS concentration was increased to 3 CMC. The physical characteristics that significantly increase show a linear influence on their ability to adsorb CO₂. At a pressure of 6 bar, the CO₂ gas adsorption capacity of the silica adsorbent with the SLS 3 CMC template was almost eight times greater than that with the SLS 3 CMC template, reaching 12.85 mmol/g silica.