Synthesis and characterization of amorphous precipitated silica from alkaline dissolution of olivine

Abstract

The high worldwide demand for amorphous precipitated silica (APS) materials, millions of tons worth billions of dollars, makes it worthwhile to further expand the techniques for synthesizing new, cheap, and environmentally friendly resources. In this research, amorphous precipitated silica was synthesized from alkaline dissolution of olivine using a mixture of NaOH and KOH and characterized; this combination resulted in better kinetics than those of the separate components. Experimental parameters (concentration of alkali, liquid/solid ratio, reaction time, and temperature) were optimized to provide maximum recovery of APS from olivine dissolution, which was then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) N₂ adsorption–desorption measurements, and thermogravimetric analysis (TGA). The APS possessed suitable morphology for use as an additive in polymers and in catalysis: a particle size below 10 nm, pore width of 5.59 nm, BJH adsorption cumulative pore volume of 0.96 cm³ g⁻¹, BET surface area of 670.8 m² g⁻¹, and Langmuir surface area of 859.3 m² g⁻¹. The apparent activation energy of olivine dissolution with a mixture of NaOH/KOH was 43.6 kJ mol⁻¹. The steps involved in creation of APS from olivine resulted in opportunities for carbon dioxide absorption, which could contribute to the production of valuable materials through decarbonation of exhaust gases.