Characterization of Rice Husk and the Crystallization Process of Amorphous Silica from Rice Husk Ash

Abstract

Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies. Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies..

Properties of rice husk ash silica filled natural rubber and acrylonitrile-butadiene rubber blends

“…The characteristic narrow two theta (2θ) peak for silica at 21.6 degrees proved that the RHAS sample contained crystalline silica (SiO 2 ) structures. Almost the same result for rice husk silica has been observed by Rivas et al, (2016). According to their study, such crystallinity could occur in rice husk silica once it is heated in the muffle furnace at high temperatures beyond around 800 °C for a longer time.…”

Bio-Based Silica Reinforced Aliphatic Bio-Epoxy Composites

“…The top faces (not showed here) presented similar results. The amorphous peak around 2θ = 20-22º corresponds to silica in amorphous phase and its intercalation in the structure of the epoxy matrix [16][17][18]. No difference in the amorphous peak was observed, which implies a homogeneous structure in all samples with different concentrations of bio-silica.…”

“…Curing agents, Polyethylene Oxide diamine (PEO), Jeffamine EDR-148 (Mw~148 g/mol) and Polypropylene Oxide triamine (PPO), Jeffamine T-403 (Mw~403 g/mol) were used in this study. Bio-silica (BS) was Digital Object Identifier (DOI): http://dx.doi.org/10.18687/LACCEI2017.1.1.299 ISBN: 978-0-9993443-0-9 ISSN: 2414-6390 obtained from rice husk [16]. Fig.1 shows the chemical structure of epoxy resins and curing agents.…”

“…The rice husk was pretreated with 1N of hydrochloric acid (HCl) for 3 hours and then washed with distillated water and dried at 60 °C for 24 hours to finally be calcined in an electrical furnace at 640 °C for 3 hours. Such procedures have been efficient to obtain amorphous silica [16]. Table I shows a summary of the composites prepared by dispersing the different concentrations of silica in the epoxy resin using Flacktek DAC 400.1 FVZ speed mixer operated at 2,500 RPM for 2 minutes.…”