Abstract
ABSTRACTUse of waste or by-products from different industries and the agricultural sector has received increasing attention in the scientific, technology, ecological, economic and social spheres in recent years. Rice husk (RH) is a by-product of rice milling and rice husk ash (RHA) is generated by combustion in a separate boiler. Both RH and RHA are abundantly accessible in rice growing countries such as China, India, Brazil, the USA, and Southeast Asia. RH has therefore been recycled by burning it for energy production. This generates RHA, which contains a huge quantity (85–95%) of amorphous silica. Over the past two decades, RHA has been used extensively in numerous fields for manufacturing of different silicates, zeolites, catalysts, nanocomposite, cement, lightweight construction materials, insulators, and adsorbents. This paper presents a comprehensive overview on the processing of nano-silica from RH/RHA. It tries at the same time, to present a critical review of the application of RHA as an ingredient for the production of various ceramic materials, e.g. refractory, glass, whiteware, oxide and non-oxide ceramics, silica aerogel and SiO2/C composites. In summary, amorphous silica derived from RHA or RH provides a potential alternative to conventional silica sources (e.g. quartz) for the manufacture of value-added ceramics for practical applications.
Highlights
Today, the whole world is suffering from two types of problem, i.e. disappearance of virgin resources and the production of excess waste
Amorphous silica derived from rice husk ash (RHA) or Rice husk (RH) provides a potential alternative to conventional silica sources for the manufacture of value-added ceramics for practical applications
This review considers the numerous studies that have focused on the synthesis of silica from RH/RHA and its application for production of ceramics
Summary
The whole world is suffering from two types of problem, i.e. disappearance of virgin resources and the production of excess waste. Ceramics can be regarded as refractories, glass, tiles, sanitary ware, tableware, and ceramics for electrical applications [15] In all these industries, silica (SiO2) is the most important ingredient for production. Due to its high calorific value (16,720 kJ/kg), most can be used as fuel in boilers for energy production through direct combustion or by gasification [21] This burning generates new waste, designated as rice husk ash (RHA), which is roughly 25% of the initial husk weight and which causes environmental pollution as well as disposal problems [22]. The properties of RHA depend on the ecological circumstances of its origin as well as the process applied for burning the husk [23] It has a high silica content in the amorphous form, which has broad applicability in industries including ceramics, construction, chemicals and electronics among others [24].
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