In the concrete business, rice husk ash silica is a viable alternative to conventional sand, particularly in areas where sand is scarce. Silica is extracted from rice husk ash using high-temperature calcination and carbonization procedures to produce silicon dioxide, which can be used to concrete mixes to improve qualities like as strength, density, air entrainment, and freeze-thaw resistance.
The husk formed during milling is usually used as a fuel in the boilers for processing paddy, providing energy through direct combustion and/or gasification. This RHA poses a significant environmental risk by causing harm to the ground and surrounding area where it is dumped. Many options for disposing of them through commercial use of this RHA are being considered.
Every year, India generates 12 million tonnes of rice husks. The global husk output is projected to be 80 million tonnes per year. Rice husk is considered a waste product of the rice milling process, and it is frequently allowed to rot in the field or burned in the open. In some underdeveloped countries, rice husk has been used as a fuel for cooking and parboiling paddy rice to some extent.
Different types of silica area given below:-
The high silica content of rice husk ash has sparked interest in finding commercial applications for it. Although silica is found in practically all arial sections of the rice plant as a component of cells or cell walls, it is most plentiful in the husk. One of the most precious inorganic chemical substances is silica. Gel, crystalline, and amorphous forms are all possible.
Precipitated Silica (also known as particulate silica) is made up of aggregates of colloidal-size ultimate particles that haven't formed a large gel network throughout the preparation process.
Three types of amorphous silica can be distinguished. Silica made indicating either amorphous or crystalline silica with high speed neutrons & Micro amorphous silica are examples of vitreous silica or glass made by fusing quartz.
Gynogenic silicas are generated by condensation of SiO2 from the vapour phase at high temperatures, or by chemical reaction in the vapour phase followed by condensation at low temperatures. Silica can form as sols, gels, or particles in an aqueous solution.
Amorphous silica is produced by concentrating an under saturated solution into a heated saturated solution, or by producing Si(OH)4 of the silica ester SiH4, SiS2, SiCl4, or Si.
Precipitated Silica soluble silicate solutions are porous and have finely regulated particle sizes. Dried pulverised gels have a more open structure with less volume than precipitated silica powders.
Silica is used in toothpastes and cosmetics as a filler for paper and rubber, as a carrier and diluent for agricultural chemicals, as an anti-caking agent, to control viscosity and thickness, and as a cleansing agent.
1. Adhesive: Silica is used as a reinforcing and thickening agent, as well as to improve bond strength. When a liquid adhesive comes into touch with a solid surface, the dispersed silica particles within it solidify quickly. Adhesive based on natural and synthetic rubber.
2. Chappals: Silica is utilised in shoe soles because of its wear and tear durability, non-scuffing properties, and the ability to create compounds with light colours or even transparent materials.
3. Conveyor Belt & Transmission Belt: Due to its small particle size and complex aggregate structure, silica is employed to improve tear strength.
4. PVC Sheets: Silica improves pigment dispersion, acts as a separating agent and an absorbent to increase flow, and gives the compound a dry feel.
5. Railway Pads: Silica is utilised in railway pads for the following reasons:
7. Rubber Products and Rubber Hoses: In industrial rubber, silica gives higher strength and durability, as well as improved heat resistance and tear strength, to industrial Rubber Belts and Rubber Hoses.
8. Silicon Tubes: Silicone rubber is utilised in a variety of applications where its distinct qualities are advantageous. Many of these characteristics are heavily influenced by the type and amount of filler used in the compound.
In 2019-20, the India silica market was worth USD 46.8 million. It is expected to grow at a CAGR of 6.5 percent in the next years. Because of its anti-caking and super absorption qualities, strong product demand in the food industry has helped the market gain traction in recent years.
The rubber industry's increased usage of silica in the production of micro sheets, rice rollers, thermoplastic rubber, PVC sheets, and shoe soles is expected to move the market forward. Over the forecast period, the market is expected to develop due to increased use of the product in transmission and conveyor belts, particularly for improved tear strength and elastomer compound reinforcement.
Rising vehicle manufacturing, particularly in India, China, Indonesia, South Korea, Japan, Malaysia, Taiwan, Mexico, the United States, and Germany, is driving up tyre demand. Rapid economic growth, more government expenditure, improvements in road infrastructure, and a growing preference for personal transportation are likely to stimulate demand for automobiles, pushing market expansion.
The global silica market was valued at USD 5.22 billion in 2018 and is expected to grow at an annual rate of 8.6% over the next five years. Precipitated, fumed, gels and sols, as well as microsilica, are all included in the market's scope (fumes). The key driver of the market is rising demand for the product from the rubber industry. Rubber goods with silica have better abrasion resistance, tensile strength, and flex fatigue qualities. Because of its capacity to strengthen the binding and tear resistance between rubber tyres and metallic reinforcements, it is frequently employed in tyre applications.
