Effect Of Pretreatments On Structure And Hydrolysis Of Recycled Fibers

As increasing recycled plant fibers from waste papers are discarded, solid waste contamination problem has become more serious. Recycled plant fibers from nature cellulosic materials that can be converted into bioethanol fuels have attracted considerable attentions.In this paper, the recycling process of plant fibers was performed to investigate the effects of recycling process on hydrolysis of recycled plant fibers, including recycled numbers, dry conditions and removal of hemicellulose and lignin. The impact mechanism and the effect of ultrasonic pretreatment on hydrolysis results of recycled fibers were studied, through analyzing the effects of ultrasonic pretreatment on morphology and super molecular structure changes of recycled plant fibers.The effects of NaOH, 1,2-Ethanediamine, zinc chloride solutions chemical pretreatment on crystalline structure of cellulose and hydrolysis efficiency of recycled plant fibers were also studied by using FT-IR and XRD. The results obtained in this paper are as follow:After several recycling, concentrations of glucose and xylose were decreased by 33% and 15.8%, respectively, which indicated that the recycling of plant fibers had an adverse effects on fiber hydrolysis. The drying process also had negative effects on fiber hydrolysis. In addition, comparative study of the removal of hemicelluloses and lignin on hydrolysis of fibers had showed that the removal of hemicelluloses had more significant enhancements on hydrolysis of recycled fibers with low lignin.Ultrasonic pretreatment led to fibrillation and the improvement of swelling ability of recycled plant fibers. The water retention value of recycled fibers after ultrasound pretreatment has arisen by 54.2%, and the reduced sugars content ascended by 31.3% with increasing ultrasonic time, compared to the control sample. The efficiency of hydrolysis of recycled plant fibers had been enhanced. Furthermore, the results indicated that ultrasonic pretreatment could not change the crystalline structure of fibers, but improved the accessibility and reactivity of hydrolysis and resulted in more production of reduced sugars. Moreover, the ultrasonic treatment time is the major factor influencing the ultrasonic pretreatment.FT-IR and XRD analysis demonstrated crystallinity and N.O'-KI index of cellulose decreased and cellulose and hemicellulose contents also decreased. The three cellulose solvents not only to some extent changed the crystalline structure and destroyed the hydrogen-boned structures of fiber cellulose, but also dissolved or decomposed cellulose and hemicelulose partially, and resulted in the loss of plant fibers. When recycled fibers were pretreated by using NaOH and EDA chemical pretreatments, glucose content was increased by 101% and 17.2%, respectively, which indicated the efficiency of hydrolysis was enhanced. NaOH pretreatment obtained the best efficiency of hydrolysis.