Controlling the synthesis conditions for silica nanosphere from semi-burned rice straw

Silica nanoparticles have been prepared through dissolution–precipitation process from rice straw ash (RSA) for different electronic applications. The dissolution of silica from RSA was carried out using alkali leaching process by sodium hydroxide. The precipitation of silica from the produced sodium silicate solution was carried out using sulphuric acid at pH 7. The factors affecting the precipitation process of the sodium silicate solution of dissociated RSA; such as; sodium silicate concentration, sulfuric acid concentration and addition of anionic surfactant (sodium dodecyl sulfate, SDS) on the particle size of the precipitated silica were studied. X-ray diffraction (XRD), X-ray fluorescence (XRF), specific surface area SBET and transmission electron microscope (TEM) have been used for the characterization of the produced nano-silica. The results showed that the optimum conditions of the dissolution efficiency of the silica of about 99% was achieved at 100 °C for 4 h, and NaOH/SiO2 molar ratio three. The particle size of the precipitated silica gel was decreased with increasing Na2SiO3 and SDS concentrations, while H2SO4 concentration had insignificant effect. Particle size of about 16 nm can be achieved at 30% Na2SiO3, 4% H2SO4 and 200 ppm SDS. The produced silica had 99.93% purity, amorphous and nanosphere particles with narrow size distribution. The produced silica can be used in many applications especially for chemical mechanical polishing (CMP) slurries for semiconductors industries.