Effect of various solvents on the structure of silica nanocapsules synthesised for anionic and cationic dyes adsorption from aqueous solution

Abstract

Synthetic dyes were considered harmful due to their toxic, carcinogenic, and nonbiodegradable chemicals. Anionic (congo red (CR) and methyl orange (MO)) and cationic (methylene blue (MB) and Janus green B (JGB)) dyes are used in this study due to their ability to restrict oxygen and sunlight dispersion. The discharge of dyes can degrade aquatic systems. This study has investigated the potential of dyes' adsorption behaviour in silica nanocapsules (SiNCs) adsorbents. Silica nanocapsules (SiNCs) were synthesized using oil-in-water (o/w) emulsion by employing different solvents (ethanol (SiNCE), ethyl ether (SiNCEE), and toluene (SiNCT) to understand the effect of solvents on SINCs' structure and effective dye adsorption. Which found that toluene and ethyl ether were effective solvents to produce silica nanocapsules. SiNCT and SiNCEE were both hollow cores, while the SiNCE structure was spherical. SiNCT adsorbent had high selectivity removal of CR > MO and JGB > MB, in which the adsorption capacity was 0.102 mmol/g at pH 2, 0.029 mmol/g at pH 2, 0.0999 mmol/g at pH 10, and 0.0944 mmol/g at pH 12 for 24 h for CR, MO, JGB, and MB, respectively. The kinetic study shows that the adsorption of dyes follows pseudo-second-order. The experimental data followed the Langmuir isotherm model and gave maximum adsorption capacities of 0.0979 and 0.4147 mmol/g for CR and JGB, respectively. SiNCT was recycled and reused for six consecutive cycles. Developed adsorbents are low-cost, highly efficient, and viable materials to be used in wastewater treatment.