IIT Kharagpur researchers develop industry-grade silica from rice biomass & curb rice husk ash pollution

New Delhi: Rice husk is one of the most widely available agricultural wastes. The process of disposal of rice husks looks more crucial as burning the material each year during the winters has been creating a severe environmental challenge. While the husk is often used to meet energy requirements for rice milling, this process produces an enormous amount of ash (approx. 20%) which is a hazardous material to the environment. Researchers at IIT Kharagpur have devised an economic and eco-friendly way to dispose of this biowaste.

A team of researchers from IIT Kharagpur’s Dept. of Agricultural and Food Engineering have developed a chemical treatment that will separate the silica content in the husk ash residue which is about 90 – 95% and neutralize the remaining biomass for disposal in water bodies.

“The silica extracted on purification has the potential of commercial-grade silica which can further be used for the production of metallurgical and solar grade silicon, confirmed the researchers,” said lead researcher Prof. A K Datta.

Four different alkalis, namely, KOH, K₂CO₃, NaOH, and Na₂CO₃, and two different solvents, namely, water and alcohol (ethanol) were selected to accomplish the extraction process. The physical and chemical characterizations of the extracted silica were evaluated using a field-emission scanning electron microscope attached with an energy dispersive X-ray spectrometer, X-ray diffractometer, Fourier-transform infrared spectrometer, and atomic absorption spectrophotometer.

To make the process eco-friendly and pollution-free, the rice husk ash was initially dispersed into the water and then Na₂CO₃ was added to it. As a result, carbonic acid was produced instead of CO₂, which is harmless for the environment.

“The results of the study suggested that the morphological, microstructural and compositional characteristics of the extracted silica nanoparticles (SiO₂-NPs) are at par with the market available silica” explained Prof. Datta.

The researchers have conducted a cost analysis of the treatment of silica samples to compare the costs with market grade silica. The result of the study suggested that the silica nanoparticle obtained from rice husk ash can be a suitable low-cost precursor for Magnesium silicide.