Synthesis of SBA-16 mesoporous silica from rice husk ash for removal of Rhodamine B cationic dye: Effect of hydrothermal treatment time

Abstract

Recently, the use of silica-containing wastes has gained popularity as an excellent pathway to prepare mesoporous silica materials for applications of adsorption, catalysis and energy. Hence, this report aimed to prepare SBA-16 mesoporous silica samples derived from rice husk ash under varying times during hydrothermal treatment (viz., 24 and 48 h) and named as SBA-16–24 h and SBA-16–48 h. FE-SEM, TEM, XRD, FTIR, Raman and N2 gas adsorption at − 196°C tools were performed to explore the formation of SBA-16. Rhodamine B (RhB) dye uptake from aqueous solutions by both samples was determined by equilibrium isotherms and kinetics. Effects such as pH, dye initial concentration, temperature and contact time were investigated. Results revealed the successful preparation of SBA-16 with an amorphous, ordered mesoporous structure and a higher total surface area of 461 m2/g for SBA-16–48 h obtained during a longer time of hydrothermal treatment. Increasing the time of hydrothermal treatment to 48 h decreased the average particle sizes of SBA from 50–40 nm to 20–10 nm with enhancing the total surface area, mesopore volume and amount of Si-O-Si groups. Equilibrium adsorption isotherms were fitted better by the Langmuir model than the Freundlich Temkin and Dubinin-Radushkevich models. The maximum adsorption capacity calculated from Langmuir model showed that SBA-16–48 h featuring the larger capacity of about 166.7 mg/g at pH 6. Pseudo-second order kinetic is found to be more suitable to describe the adsorption. Negative values of ΔH0 and ΔS0 thermodynamic parameters affirmed that the adsorption of RhB dye is an exothermic and spontaneous process over prepared mesoporous silica. Conclusively, the investigated SBA-16–48 h is a promising adsorbent for effective removal of basic dyes from their aqueous stream.