Improving textile circular economy through banana fibers from the leaves central rib: effect of different extraction methods

In the last decades, the use of agricultural wastes as a source of natural cellulosic fibers has become urgent, given the growing demand for natural and synthetic fiberss. Cellulose is a renewable natural resource and the most abundant in nature, being obtained from biomass such as wood, cotton and vegetables. Banana fiber is of great interest as bananas are one of the most consumed fruits in the world. Banana fiber is extracted from the banana pseudo-stems and leaves that remain after the fruit is harvested. Added value products based on banana fiber are an innovative material with strong potential in the market. The extraction of fibers from the banana plant can be carried out mechanically, chemically, or biologically. A combination of these methods is also possible, meaning that mechanical extraction can be followed by other treatments. In this work, the extraction of banana fibers was carried out using different methods, namely, manual extraction, chemical extraction (sodium hydroxide (NaOH)), biological extraction (retting in water at room temperature and 35 ºC) and boiling water. All the extracted fibers were analyzed using Optical Microscopy, Fourier-Transform Infrared Spectroscopy coupled with an Attenuated Total Reflectance accessory (ATR-FTIR), Thermogravimetric Analysis (TGA), Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD) and their mechanical properties were also evaluated. Fibers with diameters between 27.46 and 240.89 µm were obtained. Chemical extraction increased the tensile strength of the fibers by effectively removing non-cellulosic components, but some cellulose degradation was observed. Biological extractions removed lignin and hemicellulose, resulting in increased fiber individualization and homogeneous fiber surfaces with improved thermal properties.