Supercritical carbon dioxide fiber opening: a new paradigm for cleaner leather manufacture

Industrial research generally focuses on developing sustainable processes through environmentally friendly processes and chemicals. The leather sector receives a lot of attention on account of being intensive in the use of water and chemicals. The liming/fiber opening process in the pre-tanning stage consume a high amount of water and chemicals. Eventually, this process results in generation of wastewater with high biological oxygen demand (BOD), chemical oxygen demand (COD), and total dissolved solids (TDS). The present study focuses on the sustainable fiber opening process using supercritical carbon dioxide (SCCO₂) to reduce pollution by minimizing chemical and water usage. The designed SCCO₂ fiber opening process is entirely free of chemical additives and water. And, the process condition is optimized at 75 bar for 30 mins, where the conventional liming process serves as a control. The CO₂ diffuses into the skin matrix and opens the fiber bundles through physical modification. Hence, the SCCO₂ fiber opening process does not require chemicals and water, thus results in zero pollution loads. Further, the experimental fiber opened samples exhibited enhanced porosity compared to control, where the control and experimental sample mean value was 20.58 cm³/s and 54.04 cm³/s, respectively, at a maximum 75 psi pressure. Fiber opening efficacy of SCCO₂ experimental trials was further substantiated based on the scanning electron microscopic analysis. Additionally, processed leather has improved organoleptic and physical strength characteristics. According to the study, using SCCO₂ in the fiber opening process can result in an environmentally friendly process by reducing pollution, chemical use, and time.