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.

Road Marking Glass Microspheres Fabricated from Rice Husk Ash

“…For RHA, it is observed that, in addition to the presence of a high silica content, which makes it a suitable material for the production of silicabased glasses, other oxides are present. In particular, it was observed in another work that small amounts of manganese ions can cause an absorption around 480 nm, leaving the glass with a reddish color 21,31 . Actually, the absorbance at 480nm is an effect of the manganese 3+ oxidation state 21 .…”

“…In particular, it was observed in another work that small amounts of manganese ions can cause an absorption around 480 nm, leaving the glass with a reddish color 21,31 . Actually, the absorbance at 480nm is an effect of the manganese 3+ oxidation state 21 . According to the literature, antimony trioxide can react with the metallic ions of manganese at high temperatures, by the following redox reaction 32 : Sb 3+ + 2Mn 3+ → 2Mn 2+ + Sb 5+ , reducing Mn 3+ to Mn 2+ inside the glass matrix, enabling to obtain transparent glasses in the visible region.…”

“…where Boron trioxide was inserted in the composition in order to lower the melting temperature of the glass 21 . Antimony trioxide was added in the amount of 0.01 mol% in order to produce colorless glasses, just in the case of rice husk ash as source of silica 21 . The mixture was homogenized, with the aid of a pestle and mortar, and placed in a 30 ml gold/platinum crucible.…”

“…The molds were kept at a temperature of 400 °C for 1 h. Finally, the glass was naturally cooled to room temperature. More details of the glass fabrication process can be seen in reference 21 . In the case of UV-Vis analysis, the samples were cut, sanded and polished using a metallographic polisher up to a thickness of 3 mm.…”

Adsorption study of micropollutants by biosorbents from different rice harvest residues for large scale applications

“…and rice straw ashes (RSA). Other works demonstrated that RHA can be reused in the manufacture of innovative materials, such as glass (Gonçalves, 2020), ceramic and cement materials (Hossain, 2018) mainly due to its silica composition, and as an adsorbent for water purification (Abaide, 2019;Ahmaruzzaman, 2011).…”