Fatemeh nickkhoo shaldehi; Reza Ebrahimi Gaskarei
Abstract
Background and purpose: Gilan and Mazandaran produce about 84% of the country's rice. Gilan province has 1805 active rice mills that convert about 700,000 tons of paddy produced from ...
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Background and purpose: Gilan and Mazandaran produce about 84% of the country's rice. Gilan province has 1805 active rice mills that convert about 700,000 tons of paddy produced from 230,000 hectares of paddy fields into white rice every year. In this process, about 20% of the dry weight of paddy, i.e. 140,000 tons of the outer husk of rice remains as waste in the rice milling factories -about 20% of the dry weight of this husk is silica, so from a theoretical point of view, it is possibil to extract 28,000 tons silica from this waste.In the north of the country, the inner husk of rice paddy (soft husk) is used as livestock and poultry feed, but the outer husk of rice paddy (rough husk) contains 70% lignocellulose and 20% amorphous silica and has no nutritional value in livestock and poultry feed. For every ton of rice paddy, 0.2 ton of the outer shell of paddy is left in the rice mills factories. The outer shell of rice husk is the waste of rice mills and about twenty percent of its dry weight is silica in the form of SiO2, which can be extracted and returned to the production cycle espetially in paddy soils. In other words, the annual waste of rice mills can be used to extract silica. The necessity of this research is related to the insufficiency of silicon in the soil of some rice paddy fields in the north of Iran, returning silicon to the rice field and solving the problem of rice milling factory waste. The production of this element from organic waste is a demand-oriented, innovative and technological idea in line with sustainable agriculture. Due to the high price of imported silicon fertilizer and currency and vice versa, the cheap and annual availability of the outer shell of husk, as well as the many uses of silicon in agriculture, industry, medicine and pharmaceuticals, the production of granulated nano-organosilica from this waste with economic and environmental aspects is one of the goals of this applied research. Materials and methods: This research was done in the soil chemistry laboratory in University of Guilan. First, the outer shell of rice husk was obtained as a waste of rice mills from a rice mill factory in rural district of Jiredeh, Shaft city in Guilan and after boiling with hydrochloric acid, it was heated in an electric furnace at a temperature of 700 degrees Celsius so that amorphous nanosilica remains. From the interaction of amorphous nanosilica with potassium nitrate, semi-crystalline nanosilica was obtained. Field emission scanning electron microscopy (FESEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analyzes were used to identify amorphous nanosilica and semi-crystalline nanosilica. In addition, the production capacity of the outer shell of rice husk from the waste of rice mills in active mills was randomly estimated using a questionnaire.Result: Firstly it has been approved that the silica particles produced from rice husk are nanoparticles secondly the results showed that about 100 grams of nano-organosilica can be produced from every 1000 grams of outer shell of rice husk. Based on this result; the amount of silica that can be produced from rice husk in the country is estimated to be about 90 thousand tons. Conclusion: In line with sustainable agriculture, by extracting silica from the waste of rice mills, the soil silica needed of the rice fields in the north of the country can be supplied.
