Effects of process variable on synthesis and characterization of amorphous silica nanoparticles using sodium silicate solutions as precursor by sol–gel method

Abstract

The recent rapid urban growth has resulted into high demand for virgin materials thus causing more accumulation of solid wastes (urban mines). As a result, efforts are now geared towards urban mining approach based on re-using and recycling in order to ensure sustainability and environmental protection. In this regard, the present work synthesized pure amorphous silica nanoparticles using sodium silicate solutions produced from recycled glass powder under varying process parameter. In this work, the process variable used was NaOH concentration (3.0, 4.0 and 5.0 mol/L). 20 g of glass powder was reacted with 160 ml of 3.0, 4.0 and 5.0 mol/L NaOH solutions respectively in a 250 ml Erlenmeyer flask placed on a heating plate connected with a reflux condenser to maintain the volume of the mixture and stirred continuously at a speed of 60 rpm for 180 mins under reaction temperature of 200 °C. The solutions were filtered to obtain a sodium silicate solution (SSLS) samples. Hydrochloric acid (3 mol/L) was added gently into the respective SSLS while continuously stirred to obtain a white gel mixture. The gel was left to age for 18 h at room temperature (25 °C), then filtered and washed repeatedly using deionized water until a neutral pH is reached; then dried in an electric-powered oven at 80 °C for 12 h to obtain highly pure white silica powder. The results showed that the nano-size range between 0.025 μm (25 nm) to 0.067 μm (67 nm).