Use 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 SiO 2 /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.

No abstract

Wastes from different manufacturing processes and energy generation unite are attributed to the ecological and health issues. Instead of land-filling, the waste can be recycled or reused to convert marketable value-added products with high ecologic and economic interest. Ceramics are attracting particularly in waste recycling perceptions. From this eco-friendly propensity, in the last two decades, an increasing number of studies have demonstrated the possibility to use alternative ingredients in the place of conventional raw materials (e.g., most common ternary clay-quartz-feldspar system) for the fabrication of ceramics. Researchers are trying to incorporate the wastes and industrial by-products like fly ash (FA), rice husk ash (RHA), blast furnace slag (BFS), sludge, glass waste, polished tile waste, eggshell and others for making different ceramics. The present review is aimed to provide an up-to-date overview of the recent wastederived ceramics including refractories, glasses, whitewares, oxide and non-oxide ceramics with the correlation of waste incorporation limits, manufacturing routes, and properties of the ceramics. The investigation reveals that ceramic industries have huge potential to utilize the wastes as substitution of the natural raw materials. The waste to value-added ceramics conversion not only solves the disposal problems but also conserves the natural resources.

The aim of the study was to investigate the effect of amorphous silica on the phase formation and study the physical characteristics of forsterite refractory prepared from quartz and MgO powder. Various samples were subjected to sintering temperature around 1100 • C and development of forsterite phase was characterized using Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The result indicate that the addition of rice husk ash (RHA) significantly affect the formation of forsterite phase. As the amount of RHA increased, it led to a better reaction between amorphous silica and periclase, later that will transform into forsterite phase at a temperature around 1100 • C. Formation of forsterite resulted in decrease of density, porosity, and thermal conductivity, while the opposite was observed for Cold Crushing Strength. Formation of forsterite phase was identified by XRD analysis of the sample. Based on the characteristics, the samples were considered as an insulator and of the potential use as refractory devices.

No abstract