Production of transparent soda-lime glass from rice husk containing iron and manganese impurities

Abstract

Glass is a familiar material that requires abundant mineral sources, with devastating consequences for the environment. Rice husk ash (RHA) presents a very high silica content (>95%) and it can be a very promising alternative source for silica in silica-based glass. However, impurities like manganese and iron, which depend on the rice harvest, might limit RHA use, particularly in the production of optical transparent glasses. In this work, we discussed how Mn and Fe can affect the coloring of the produced glass, and how the effect of these impurities can be removed. First, the RHA was treated with acid solutions, leading to the production of a soda-lime glass with similar transparency to commercial glass (>70%). Secondly, another simpler approach was studied: a small amount of antimony oxide was added in the composition of the glass, obtaining a transparent glass (>80%, same thickness) with RHA.