METHOD FOR RECYCLING RICE HUSK ASH USING POTASSIUM HYDROXIDE SOLUTION TO CO-RECOVER NANOSILICIDE HYDROGEL, RICE HUSK CHARCOAL, SLOW-RELEASE POTASSIUM RICE HUSK ASH FERTILIZER, AND POTASSIUM FOLIAR FERTILIZER SOLUTION

Abstract

The invention relates to a method for recycling rice husk ash using a potassium hydroxide solution to co-recover silicon dioxide nanohydrogel, rice husk charcoal, slow-release potassium rice husk ash fertilizer, and potassium foliar fertilizer solution.This method includes the following steps: supplying rice husk ash from the boiler and crushing and sieving to obtain fine rice husk ash; treating the fine rice husk ash in a potassium hydroxide solution to create a potassium silicate solution and a solid phase containing rice husk charcoal; separating, washing, and drying the solid phase to obtain rice husk charcoal; neutralizing the potassium silicate solution with acetic acid to create a precipitate of nano silicate; filtering and washing the precipitate but not completely drying it to obtain a high-water content nano silicate hydrogel with a limited hardening layer of hydrated water; collecting wastewater containing potassium hydroxide, potassium silicate, and / or potassium acetate; treating the wastewater with rice husk ash-derived materials and adjusting the pH to separate it into a solid phase of rice husk ash containing potassium and silica dioxide, and a liquid phase containing dissolved potassium; pressing the solid phase into slow-release potassium rice husk ash fertilizer pellets with a cross-sectional size of not less than 5 mm. and collect the liquid phase with a total dissolved solids content of 4000 ppm to 8000 ppm to use as the stock solution for potassium foliar fertilizer.This invention helps to simultaneously recover silicon, carbon, and potassium streams from rice husk ash, reducing potassium loss in wastewater and creating a value chain of products from agricultural by-products.