Title
Efficient process of deashing straw cellulose
Authors
LIYUAN XUE YUHU CUI LIANGCONG YAN SHIMENG LIU MAN JIANG and ZUOWAN ZHOU

Received January 18, 2016
Published Volume 51 Issue 9-10 September-December
Keywords deashing, rice straw cellulose, NaF-HCl aqueous solution, HF-HCl aqueous solution, recyclable, H₂SiF₆

Abstract
Crop straw cellulose always contains a high percentage of ash, which seriously restricts its high-value-added applications. In this study, two dilute mixed aqueous solutions (NaF-HCl and HF-HCl) have been used to treat raw rice straw cellulose and the optimized conditions have been determined as: temperature of 60 °C, treatment time of 2 h with 34.0 wt% NaF in 2.0 wt% HCl aqueous solution, and temperature of 60 °C, treatment time of 6 h with 1.5 wt% HF in 2.0 wt% HCl aqueous solution. Under the optimal conditions, 96.15% and 99.93% ash could be removed, respectively. It was demonstrated that such deashing processes had no obvious impact on the chemical properties of cellulose, while the crystallinity was relatively improved. The results of ICP analysis proved that HCl, NaF and HF had different effects on ash elements. After deashing, the solution can be recycled to obtain H2SiF6, which is a useful preservative and a raw material for production of fluosilicate and silicon tetrafluoride.