ABSTRACT
Polymer membranes employed in gas separation play a pivotal role in advancing environmental sustainability, energy production, and gas purification technologies. Despite their significance, the current design and manufacturing of these membranes lack cradle-to-cradle approaches, contributing to plastic waste pollution. This study explores emerging solutions, including the use of biodegradable biopolymers such as polyhydroxybutyrate (PHB) and membrane recycling, with a focus on the specific impact of mechanical recycling on the performance of biodegradable gas separation membranes. This research represents the first systematic exploration of recycling biodegradable membranes for gas separation. Demonstrating that PHB membranes can be recycled and remanufactured without solvents using hot-melt extrusion and 3D printing, the research highlights PHB's promising performance in developing more sustainable CO2 separations, despite an increase in gas permeability with successive recycling steps due to reduced polymer molecular weight. The study emphasizes the excellent thermal, chemical, and mechanical stability of PHB membranes, albeit with a marginal reduction in gas selectivity upon recycling. However, limitations in PHB's molecular weight affecting extrudability and processability restrict the recycling to three cycles. Anticipating that this study will serve as a foundational exploration, we foresee more sophisticated recycling studies for gas separation membranes, paving the way for a circular economy in future membrane technologies.
ABSTRACT
BACKGROUND: Tissue engineering and biomaterials have made it possible to innovate bone treatments for orthopedic and spine problems. The aim of this study is to develop a novel polyethylene oxide (PEO)/silicon-substituted hydroxyapatite (Si-HA) composite to be used as a scaffold for hard tissue engineering in orthopedic and spine procedures. MATERIALS AND METHODS: The composite was fabricated through the electrospinning technique. The applied voltage (5 kV) and PEO concentration (5%) were fixed. Processing parameters such as the flow rates (20 µl/min and 50 µl/min), distances from capillary tube to the collector (130 mm and 180 mm), spinning time (10 min and 20 min), and concentration of Si-HA (0.2% and 0.6%) were explored to find the optimum conditions to produce fine composite fibers. RESULTS: Scanning electron microscope images showed that 5% PEO, 5% PEO/0.2% Si-HA, and 5% PEO/0.6% Si-HA fibers were successively produced. Flow rates and working distances showed significant influence on the morphology of the polymeric and composite fibers. A high flow rate (50 µl/min) and a larger working distance (180 mm) resulted in larger fibers. The comparison between the mean fiber diameter of 5% PEO/0.2% Si-HA and 5% PEO/0.6% Si-HA showed to be significantly different. As the Si-HA concentration increased, certain fibers were having particles of Si-HA that were not properly integrated into the polymer matrix. CONCLUSIONS: Synthesis of a novel biomaterial for hard tissue scaffold through electrospinning was successful. In general, PEO/Si-HA fibers produced have the desired characteristics to mimic the extracellular matrix of bone.
