Cellulose Fibers Extraction from Cotton Stalk via One-Step Acid Bleachable Pretreatment for Fiber-Optic Humidity Sensor Fabrication

摘要

Abstract In this study, cellulose fibers was extracted from cotton stalks via one-step acid bleachable pretreatment under mild conditions (≤?80?°C). 75.24% of hemicellulose and 83.02% of lignin were dissolved out at a p-TsOH concentration of 80 wt%, a pretreatment temperature of 80?°C, and a pretreatment time of 45?min. Subsequently, cellulose fibers (pulp) were obtained from the pretreated cotton stalks matrix via subsequent 10?s ultrasonic treatment. The obtained fibers displayed a high whiteness of 47.5% ISO and a length range between 0.20 and 0.84?mm. After dissolving the fibers in lithium bromide solution (LiBr·3H2O) and coating the cellulose hydrogel on the end-face of optical fiber, a fiber-optic relative humidity sensor (FORHS) was prepared. The fabricated FORHS displayed a relatively high humidity response (0.15?dB/RH%), small humidity hysteresis error (rH?=?±?0.07%), and a high stability (R2?=?0.98) in a humidity monitoring range from RH 40% to RH 80% and a temperature range between 25 and 40?°C. The novelty of this study is to successfully fabricate a FORHS using cotton stalks cellulose hydrogel as moisture-sensitive material. Thus, the research provided a sustainable strategy for preparation of FORHS and value-added utilization of cotton stalk.Graphical Abstract