Synthesis of Biodegradable Plastics from Dyeing Wastewater and Optimization of Continuous Poly(3-Hydroxybutyrate) Fibrous Membranes via Electrospinning Process

The Polyhydroxyalkanoates (PHAs) are promising biodegradable materials exhibit similar thermal and mechanical properties as conventional plastics. However, the current production cost for PHAs is high and less application examples were found. In addition, the development of electrospun nanofibrous membrane has attracted more attention in recent years. This study aims to investigate the production of PHAs using dyeing wastewater as the carbon source to reduce the major operation cost and prepare Poly(3-hydroxybutyrate) (PHB)-based fibrous membrane with controlled surface microstructure through electrospinning technique. At the optimal Carbon to Nitrogen (C:N) ratio (100:1) by using dyeing wastewater, the reactor achieved 0.2562 g PHAs from unit mass of activated sludge and 0.0571 g PHAs from unit mass of COD consumed. By using industrial glucose as carbon source adjustment, 1.180 g polymer per 1 RMB could be synthesized at the optimal C:N ratio. As a feasible study, the industrial PHB was used for electropining. The influence of the process parameters (applied electric field, solution flow rate and polymer concentration) on the electrospun fiber microstructure was investigated and optimized in order to achieve smooth, bead-free fibers with diameter range of 1 - 10 mm. The morphological transition from bead-like microstructure to smooth fiber was investigated under control of three major process parameters: applied voltage increased from 9 kV to 20 kV, flow rate de-creased from 5 mL.hr-1 to 0.5 mL.hr-1 and polymer concentration increased from 9 wt% to 15 wt%. It was observed that well-defined fibrous film was achieved at applied electric field of 12 kV, flow rate of 1 mL.hr-1 and solution concentration of 14 wt%. The optimally processed electrospun fibers exhibited large area, continuous network with good distribution of fiber diameter distribution. Fibrous membrane fabricated by well-developed electrospinning technique has potentially offered application interest in the design of barrier coatings, adhesive interlayers for biological materials, and membranes for filtration of particulate matters and fiber-based food packaging materials.