Bleaching processes of pineapple fibers assisted with sustainable technologies: Microwave, ultrasound and ozonation

Abstract

In this study, various bleaching processes, including conventional hydrogen peroxide bleaching, microwave-assisted hydrogen peroxide bleaching, ozone bleaching, and ultrasound-assisted ozone (Ozone/UH) bleaching, were applied to pineapple fiber woven fabrics to assess their effectiveness in enhancing fabric whiteness and reducing environmental impact. The effects of these treatments on fabric properties, including colorimetric values, tear strength, stiffness, wrinkle recovery, thickness, water absorption, chemical oxygen demand (COD) of wastewater, and fiber structural changes (via FTIR-ATR), were systematically analyzed. The optimal conditions for conventional hydrogen peroxide bleaching were determined as 10 g/l hydrogen peroxide at 95 degrees C for 60 min. Ozone bleaching for 120 min resulted in comparable whiteness values to conventional bleaching while reducing COD, indicating a more environmentally sustainable alternative. Microwave-assisted hydrogen peroxide bleaching did not significantly enhance whiteness compared to conventional methods. Meanwhile, ultrasound-assisted ozone bleaching achieved high whiteness levels in a shorter time (20 min), but resulted in greater fabric strength loss. FTIR-ATR analysis confirmed chemical modifications in the fiber structure following bleaching, particularly the reduction of lignin and hemicellulose content. The highest water absorption capacity was observed in Ozone/UH-treated fabrics, while the lowest COD values were recorded for ultrasound-assisted ozone bleaching, highlighting its eco-friendly potential. Overall, the results suggest that ozone bleaching, particularly when combined with ultrasound, offers a promising alternative to conventional peroxide bleaching by reducing chemical consumption and environmental impact. However, the balance between bleaching efficiency and fabric integrity must be carefully considered when selecting the optimal treatment for industrial applications.