Large quantities of agricultural wastes such as palm ash and rice husk are found throughout Malaysia, have a possibility to be used as a usefully renewable source for production of energy and silica (SiO2). Extensive researches have been carried out to extract silica from agricultural wastes such as rice husk, due to silica as a useful raw material for industrial application. In the previous studies, the strong acid leaching treatment was carried out to remove metallic impurities and organics contained in rice husk. Since leaching treatment is a proper route to extract the silica, sulphuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3) solutions are currently used in leaching treatment to prepare silica materials [. A strong acid leaching treatment, however, is significantly hazardous to the environment and people. In this study, the weaker acid, citric acid solutions were used to replace strong acid in leaching processes. Preliminary results showed that silica can be extracted from palm ash using citric acid leaching treatment under the optimum extracting conditions with 70°C of solution temperature, 60 minutes of reaction time and concentration of citric acid of more than 2%. The purity of silica extracted is more than 90%.

Large quantities of agricultural wastes such as palm ash and rice husk are found in Malaysia, have a large possibility to be employed as usefully renewable to produce energy and silica (SiO2). Extensive researches have been carried out to extract silica from agricultural wastes such rice husk, because silica is useful raw material for industrial application. In the previous studies, the strong acid leaching treatment was carried out on rice husk to remove metallic impurities and organics contained in them. Leaching treatment is a proper route to extract the silica. Sulphuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3) solutions are conventionally used in leaching treatment to prepare silica materials [. A strong acid leaching treatment, however, is significantly hazardous to the environment and humans. This paper reviews the common extraction method used and the latest research trends in extraction of silica.

No abstract

No abstract

No abstract