Purity Of Silica Research Articles

Palm Ash as an Alternative Source for Silica Production

Agricultural wastes such as palm ash and rice husk have a possibility to be used as a useful renewable source for the production of silica (SiO2). Extensive researches have been carried out to extract silica from agricultural wastes such as rice husk, due to silica as a useful raw material for industrial application. In this study, the environmentally benign and economically effective process to produce SiO2 materials from palm ash has been established by using citric acid leaching, not the conventional strong acids. Results showed that silica can be extracted from palm ash using the citric acid leaching method under the optimum extracting conditions with 700 °C of solution temperature, 60 minutes of reaction time and concentration of citric acid of more than 2 %. The purity of silica extracted is more than 90 %.

Characterisation of bio-silica synthesised from cogon grass (Imperata cylindrica)

Amorphous silica has many applications due to the material's high surface area and pozzolanic properties. In this work, amorphous silica was synthesised from cogon grass (Imperata cylindrica) by combustion at 650°C. Kinetic parameters of the combustion were determined by fitting thermogravimetric analysis (TGA) data to the Flynn–Wall–Ozawa model, where the corresponding activation energy and frequency factor are 202.5±5.1kJmol−1 and (7.9±6.7)×1015s−1. Energy-dispersive X-ray (EDX) analysis revealed that cogon grass has a relatively low silica content (2.9wt.%). In addition, X-ray diffraction (XRD) data showed that the purity and amorphicity of silica obtained are significantly affected by the potassium content in the weed. However, the process of acid leaching removed the impurities and increased the purity of silica from 31.4wt.% to 83.4wt.%. The primary particle size (a) and the mass fractal dimension (D) of silica particles determined by small-angle X-ray scattering (SAXS) were 19.8nm and 2.4, respectively.

Extraction of Silica from Palm Ash Using Organic Acid Leaching Treatment

Agricultural wastes such as palm ash and rice husk have a possibility to be used as a usefully renewable source for production of energy and silica (SiO2). Extensive researches have been carried out to extract silica from agricultural wastes such as rice husk, due to silica as a useful raw material for industrial application. In the previous studies, the strong acid leaching treatment was carried out to remove metallic impurities and organics contained in rice husk. A strong acid leaching treatment, however, is significantly hazardous to the environment and people [. In this study, the environmentally benign and economically effective process to produce SiO2 materials from palm ash has been established by using citric acid leaching, not the conventional strong acids. Results showed that silica can be extracted from palm ash using citric acid leaching treatment under the optimum extracting conditions with 70°C of solution temperature, 60 minutes of reaction time and concentration of citric acid of more than 2%. The purity of silica extracted is more than 90%.

Extraction of Silica from Palm Ash Using Citric Acid Leaching Treatment: Preliminary Result

Large quantities of agricultural wastes such as palm ash and rice husk are found throughout Malaysia, have a possibility to be used as a usefully renewable source for production of energy and silica (SiO2). Extensive researches have been carried out to extract silica from agricultural wastes such as rice husk, due to silica as a useful raw material for industrial application. In the previous studies, the strong acid leaching treatment was carried out to remove metallic impurities and organics contained in rice husk. Since leaching treatment is a proper route to extract the silica, sulphuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3) solutions are currently used in leaching treatment to prepare silica materials [. A strong acid leaching treatment, however, is significantly hazardous to the environment and people. In this study, the weaker acid, citric acid solutions were used to replace strong acid in leaching processes. Preliminary results showed that silica can be extracted from palm ash using citric acid leaching treatment under the optimum extracting conditions with 70°C of solution temperature, 60 minutes of reaction time and concentration of citric acid of more than 2%. The purity of silica extracted is more than 90%.

Nano-Porous Structure of a Porous Ceramics from Rice Husk

A porous ceramics is obtained using rice husk as the source of silica. The modification of mesoscopic structure under different sintering conditions has been investigated using neutron scattering techniques and scanning electron microscopy. X-ray diffraction confirmed the purity of silica by comparing the diffraction pattern from pure silica. Thermogravimetry data show that a phase transition occurs at 750°C. X-ray data confirms that sodium calcium silicate is formed after the latter transition. Small angle neutron scattering measurements reveal the presence of nanopores of two distinct size ranges; viz. 162 and 30 nm. Porosity of the compact by bulk density measurement has been found to be ∼50%.

Tronoh Silica Sand Nanoparticle Production and Applications Design for Composites

Tronoh silica sand was ground to nanoparticles using a ball mill and it was observed that the milling process increased the percentage purity of silica in silica sand. The size of the nanoparticles of silica sand was verified by using a ZetaSizer nanoparticles analyzer and FESEM analysis. The silica sand nanoparticles were used to develop and study the characterization and properties of metal, ceramic and polymer based composites. The powder metallurgy and powder processing techniques were used to develop MMC and CMC composites. Compression moulding was used to develop polymer matrix (HDPE) composites. An increased hardness in the case of MMC and CMC was observed. The tensile strength and flexural strength exhibited an increasing trend in the case of PMC with up to 15wt.% of silica sand nanoparticles.

High-purity nano silica powder from rice husk using a simple chemical method

A highly pure, small particle-sized and high surface area nano silica powder was prepared from rice husk using alkali extraction, followed by an acid precipitation method. The composition, phase, morphology, size and surface area of the as-synthesised nano silica powder was investigated by energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, particle size analyser and BET surface area analyser. High-purity nano silica powder was obtained by sodium hydroxide (NaOH) purification treatment (0.5, 1, 1.5, 2 and 2.5 N). The high purity of silica (∼99.9%) was obtained at 2.5 N NaOH treatment. The pure nano silica powder that is obtained shows an average particle size of ∼25 nm with a high-specific surface area (SSA) of 274 m2 g−1, with an average pore diameter of 1.46 nm.

Effects of Different Treatments on Purity of Silica from Soluble Sodium Silicate1

Noncrystalline silica was obtained with lows iron, sodium, and nitrate ions concentrations from soluble sodium silicate (water glass) and nitric acid solution. Extractions with nitric acid solution and/or deionized water and/or dialysis were carried out to eliminate soluble metal ions. Products were dried in a microwave oven and characterized by chemical analysis, XRD, and IR. Dialysis seems to be the best treatment for the elimination of sodium and nitrate ions. Silica purified by nitric acid and water extractions followed by dialysis yields the purest silica sample.

Effect of Cryolite on the Growth of SiC Whiskers

Recently, SiC and Si3N4 whiskers have been synthesized using natural sources. However the yield is usually low. In the present study, having an eye to the fact that cryolite was often used to advance the purity of silica, in order to estimate an available possibility to natural sources, the mixture powder of silica and cryolite were used as a starting material and the effect of cryolite on the growth of SiC whiskers was investigated. As a result, SiC whiskers and Na2Si2O5 were generated through the reaction of silica and cryolite under the existence of graphite in the stream of CH4 mixture gas. Thus, the available possibility was suggested since SiC formed as a whisker through the reaction.

Method of high-purity silica production from hexafluorosilicic acid

The method elaborated allows to create a no-waste technology for obtaining two marketable products-high silica purity, which is the raw material for glass surface treatment, and fluorite qith CaF2 cintents of not less than 92%.