Seawater Modification of Lignocellulosic Fibers from Wheat Straw: Effects of Temperature, Ultrasonic, and Microwave Fields

In this study, the effects of physical fields on the seawater modification of lignocellulosic fibers obtained from wheat straw were investigated by incorporating three types of physical fields, namely temperature, ultrasonic, and microwave fields, into seawater based on the response surface methodology. The results obtained herein suggests that the optimum parameters of temperature, ultrasonic, and microwave fields were 82.2°C + 53 min, 80 W + 49 min, and 420 W + 28.3 min, respectively. Seawater/physical field modification resulted in lesser hydroxyl groups, hemicellulose content, and silicon content, as well as higher crystallinity, surface roughness, and thermal stability. From the viewpoint of surface, chemical, and thermal properties, seawater/microwave field exhibited the best modification effect, followed by those of seawater/temperature field and seawater/ultrasonic field. The silicon content was decreased from 29.9 to 10.1 wt.% after seawater/microwave field modification. Moreover, the crystallinity and degradation temperature at 5% weight loss increased from 48.5 to 55.2% and 96 to 175°C, respectively.