Silica Retention by the Addition of Sodium Metaaluminate During the Impregnation Stage of Bamboo Kraft Pulping

Bamboo is the most utilized non-wood biomass in China. One of its most important applications is in the pulp and paper industry. In such an application, one of the significant challenges is decreasing the silica dissolution in the pulping process. In this study, the use of sodium metaaluminate (NaAlO2) to decrease the silica dissolution into liquor was investigated. The results showed that an alkali-resistant Si–Al coating layer was formed onto the silica particles by the addition of NaAlO2. Under the impregnation conditions, NaAlO2 reacted with Na2SiO3 and produced poly-condensated Si/Al compounds, which are insoluble under kraft pulping conditions. It was found that the silicon retention in bamboo chips was 90% with the addition of NaAlO2 under the conditions studied. This novel silica-retaining technology has a great potential for industrial applications.