- Thesis topic: The feasibility of oxygen plasma-modified membrane for azo dye wastewater treatment in air gap membrane distillation process

- Doi: 

- Abstract: 

        This study investigates the feasibility of enhancing air gap membrane distillation (AGMD) performance for azo dye wastewater treatment through oxygen plasma surface modification of hydrophobic polymer membranes. Commercial polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) membranes were treated with oxygen radio-frequency plasma under varying power and exposure times to optimize surface hydrophobicity and morphology. Characterization techniques including water contact angle (WCA) measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR-ATR), and zeta potential analysis revealed that oxygen plasma treatment increased membrane surface roughness and hydrophobicity, with WCA values reaching approximately 145° for PTFE and 135° for PVDF. Chemical modification was more pronounced in PVDF, evidenced by the introduction of carbonyl (C=O) groups, while PTFE underwent physical etching. AGMD performance tests using synthetic wastewater containing two azo dyes, Reactive Red 241 and Acid Yellow 79, demonstrated that plasma-modified PTFE membranes exhibited stable permeate flux (~9.53 kg/m².h for water), high color removal efficiency (>99%), and moderate fouling factors. Conversely, plasma-modified PVDF membranes showed a significant flux increase when treating Acid Yellow 79 but suffered from membrane wetting, leading to a drastic reduction in color removal efficiency (48.92%) and negative fouling factors. These outcomes highlight the critical influence of membrane-dyed chemical interactions on separation performance. The results highlight the importance of chemical interactions between the membrane and the dye in determining separation performance. The study concluded that oxygen plasma can effectively improve the AGMD performance of PTFE membranes, while PVDF membranes require further optimization to prevent wetting.

Keywords: Air gap membrane distillation (AGMD), Oxygen plasma modification, Membrane distillation, Azo dye wastewater, Wastewater treatment, Membrane Fouling