Studying the Fabrication of Electrically-conductive Nanocomposite Membranes for wastewater treatment

• Author / Creator

  Zandi, Zahra

• Membrane separation processes are crucial in separating various solutes from water sources, including ions, colloids, macromolecules, and organic matter. Among membrane technologies, ultrafiltration (UF) has emerged as a powerful method for effectively removing organic matter and macromolecules from wastewater treatment. Despite their efficacy, membrane fouling remains a significant challenge, impacting permeate flux, membrane lifespan, and energy consumption in widespread membrane technology applications for wastewater treatment. Surface modification is a crucial strategy in minimizing membrane fouling, offering a powerful technique to prevent fouling by altering membrane surface properties. This involves tuning the surface physicochemical properties (wettability, roughness, and charge) by various methods such as chemical grafting, coating, and plasma treatment. An innovative approach to mitigate fouling includes incorporating conductive elements like MXene nanosheets and silver nanoparticles onto the membrane surface. Applying electric potential to conductive membranes is an emerging electrochemical technique for fouling mitigation through various mechanisms, including electrochemical reactions, gas bubble generation, and electrostatic repulsive forces.
  In the project's first phase, Ti3C2 MXene was employed to produce electro-conductive antifouling polyamide-imide (PAI) membranes. The fabrication involved the phase inversion technique for the PAI membrane and a pressure-assisted filtration method to coat MXene on the PAI membrane surface. Different Ti3C2 MXene and carboxymethyl cellulose (CMC, as a binder) concentrations were used to tune the physicochemical properties of PAI membrane surfaces. A cathodic potential was applied in an experimental electrochemical membrane cell, and the Ti3C2 MXene-modified PAI membrane with the highest MXene content exhibited maximum conductivity. Evaluating the membrane performance in cathodic electro-reduction (CER), using various aqueous solutions of humic acid (HA), sodium alginate (SA)/calcium chloride (CaCl2), and bovine serum albumin (BSA) as model foulants, revealed significant improvement in flux decline ratio (FDR) and flux recovery ratio (FRR) with applied electric potential. For example, applying a 4V cathodic potential resulted in FDR and FRR less than 1% and 99.83%, respectively. Without voltage, the MXene-coated PAI membrane showed FDR and FRR of 45.56% and 92.51%, respectively.
  In the second phase of this study, a silver nanoparticle ink was applied to the surface of PAI membranes. The impact of the highly conductive silver coating layer was examined to produce electroconductive UF membranes with enhanced antifouling and dye rejection properties. Using 3 mL of silver nanoparticle ink to coat a 1000 cm2 area of a PAI membrane resulted in a membrane that demonstrated exceptional resistance to fouling when subjected to SA/CaCl2 as a model foulant. The modified Ag-coated PAI membrane exhibited a FDR of 42.94% and a high flux FRR of 80.41%, outperforming the pristine PAI membrane, which had a 59.58% FDR and a 49.14% FRR. This represents an improvement of approximately 16.6% in FDR and 31% in FRR. The enhanced antifouling properties of the modified Ag-coated membrane can be attributed to the high electrostatic repulsion between the Ag-coated PAI membrane and foulants facilitated by the high negative surface charge induced by the cathodic potential applied to the membrane surface.
  This study showcases the considerable potential of conductive elements in tackling antifouling challenges, improving dye removal, and generating value-added solutions for water treatment. It introduces a groundbreaking approach to developing high-performance membranes by integrating conductive materials, thus paving the way for innovative advancements in water treatment.

• Subjects / Keywords

  • Ti3C2 MXene
  • Silver nanoparticles
  • Electroconductive membranes
  • ultrafiltration
  • nanofiltration
  • surface modification
  • fouling
  • dye removal
  • wastewater treatment

• Graduation date

  Spring 2024

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-awx8-bx42

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.