Synthesis and characterization of mesoporous bio-silica nanoparticles developed from rice husks for oil spillage remediation

Abstract

• Optimized amorphous mesoporous bio-silica nanoparticles were synthesized from rice husks • The developed bio-silica nanoparticles had an oil removal efficiency of 44.57% • Adsorption of oil was by both physisorption and chemisorption process • Rice husk bio-silica nanoparticles are a potential alternative to conventional synthetic sorbents Paddy rice production in Uganda was 125,000 tons in 2021/2022, corresponding to about 25,000 tons of rice husks as agro-industrial waste. This study focused on the synthesis of bio-silica nanoparticles from rice husks and their application in petroleum oil spill remediation. The Box-Behnken design was used to optimize the effect of HCl concentration, calcination temperature, and calcination time on ash yield. Synthesis was done at optimal conditions of 1 M HCl leaching and calcination at 600°C for 3 h. The characterization techniques used were FTIR, XRD, DLS and SEM. HCl treated RH exhibited increased ash content (6.84%db) and reduced volatile matter and fixed carbon compared to raw RH. From FTIR, the dominant silica peaks at 1058 cm −1 and 791 cm −1 confirmed the formation of a siloxane network (Si–O–Si). The broad peak of 22.77 o was observed through XRD, typical of amorphous silica nanoparticles with a monomodal distribution and size ranges of 60-80 nm. Morphology of bio-silica revealed that nanoparticles appeared to be clustered or agglomerated into larger, dense masses, typical for silica nanoparticles. The nanoparticles had an approximate specific surface area of 294 m 2 /g and pore diameter of 15.3 nm. ANOVA confirmed the statistical significance of the ash yield model (F = 393.17, p = 0.0001). In application, bio-silica nanoparticles demonstrated petroleum oil removal efficiency of 44.57% for initial concentrations of 18.24 mg/L, decreasing slightly to 43.35% at higher initial concentrations of 25.26 mg/L. Adsorption followed Langmuir isotherm (R² = 0.9963) and pseudo-first order kinetics (R² = 0.9998), suggesting a physisorption mechanism. These findings demonstrate the potential of RH-derived bio-silica as a sustainable material for petroleum oil pollution mitigation.