Effect of Washing Pretreatment with Aqueous Fraction of Bio-Oil on Pyrolysis Characteristic of Rice Husk and Preparation of Amorphous Silica

Abstract

Rice husk is an abundant agricultural by-product and the common disposal method of rice husk could cause serious environmental and human health problems. In this study, effects of washing with aqueous fraction of bio-oil on pyrolysis characteristic of rice husk and preparation of amorphous silica from combustion of biochar were investigated. Most metallic species in rice husk, especially alkali and alkaline earth metals (AAEMs), can be effectively removed by washing pretreatment with aqueous fraction of bio-oil. Thermogravimetric analysis indicated that aqueous fraction of bio-oil washing pretreatment prior to pyrolysis process obviously increased the value of pyrolysis characteristics parameters, such as the max decomposition rate, the temperature according to the max decomposition rate, and the mean decomposition rate. Meanwhile, the apparent activation energy was slightly increased after washing pretreatment. Furthermore, the high purity amorphous silica with a purity of 99.33% was obtained from combustion of biochar from pyrolysis of aqueous fraction of bio-oil washed rice husk. In addition, a novel method for utilization of rice husk via washing with aqueous fraction of bio-oil, pyrolysis and combustion of biochar was proposed. This method resolved the problem of pollution and waste aroused by rice husk and the whole process is known to be self-heating and environmentally friendly.