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Abstract
High purity nano-silica xerogel was synthesized from rice straw ash that is a residue materials from agriculture. To obtain the rice straw ash for preparing of sodium silicate that is then used as silica source, pretreated rice straw was burned at 600-900 oC. Rice straw ash was reacted with 0.5 M NaOH for 3-12 h and filtrated by a no.41 filter to prepare sodium silicate. Afterwards, sodium silicate was mixed with 0.5 M HCl for 6 h to produce the nano-silica. In this study, nano-silica was synthesized by using a template, as well. Characteristics of nano-silica synthesized with and without template were compared. In order to get the pure nano-silica xerogels, as-synthesized silica was filtrated and clean with deionized water for 3 times, dried in electric oven at 85 oC overnight and calcined at 500 oC. To confirm the quality of particles, nano-silica was characterized by various analytical techniques like SEM, TEM, XRD, FTIR-ATR, BET, % whiteness and measurement of water contact angle. First experimental results showed that nano-silica xerogels with purity up to 99 wt% were completely synthesized by a facile method. Nano-silica with intermediate specific surface area and pore volume was obtained. Experimental results also showed silica-xerogels with good absorption properties.
Keywords: Rice straw ash; Nano-silica; Xerogel; Facile-method; Surface area.