07/26/2021
By Sokny Long

The Francis College of Engineering Department of Civil and Environmental Engineering invites you to attend a doctoral dissertation defense by Akarapan Rojjanapinun on “Functionalized Polymer Composite Membranes for Water Treatment.”

Ph.D. Candidate: Akarapan Rojjanapinun
Defense Date: Tuesday, August 3, 2021
Time: 1 to 3 p.m. EST
Location: This defense will be held via synchronous in-person (Southwick 240) and virtual (Zoom) meeting. Those interested in attending via Zoom should contact akarapan_rojjanapinun@student.uml.edu and committee advisor, sheree_pagsuyoin@uml.edu, at least 24 hours prior to the defense to request access to the meeting.

Committee Chair (Advisor): Sheree Pagsuyoin, Assistant Professor, Civil and Environmental Engineering, University of Massachusetts Lowell

Committee Members:

  • Weile Yan, Assistant Professor, Civil and Environmental Engineering, University of Massachusetts Lowell
  • Earl Ada, Director, Materials Characterization Lab, University of Massachusetts Lowell
  • Hongwei Sun, Professor, Mechanical Engineering, Northeastern University

Abstract:
Persistent organic micropollutants such as per- and polyfluoroalkyl substances (PFAS) and antibiotics are a threat to human and ecosystem health, and a big concern in water treatment. PFAS are carcinogenic and can bioaccumulate in wildlife while antibiotics can potentially induce antimicrobial resistance in pathogens. They are not fully removed during conventional water treatment although more advanced processes such as ozonation, advanced oxidation, and nanocarbon adsorption have been shown to be effective to varying degrees. The main disadvantages of existing treatment technologies include high cost, production of undesired by-products, and problems with disposal of spent materials.

The overarching goal of this study was to develop nanocomposite polymer membranes that can efficiently remove PFAS and antibiotics from water. Specifically, the study aimed to: (1) develop a hybrid nanolithography technique for manufacturing polyvinylidene fluoride (PVDF) nanomembranes; (2) manufacture nanocomposite PVDF membranes with enhanced durability and adsorptive properties; and (3) evaluate the performance of nanocomposite PVDF membranes in water treatment for 4 micropollutants: PFAS, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), and two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP).

Towards Aim 1, a 4-step hybrid technique involving nanosphere and soft lithography was developed for fabricating isoporous nanomembranes. In this technique, self-assembled nanosphere particles were used to create a master mask, the mask was used to create the mold, and the mold was used to cast thin-film PVDF with nominal pore sizes of 100 nm and 20 nm. The tensile strength, wettability, and flux through the membranes were comparable to those reported for high-performance membranes manufactured via phase inversion and electrospinning.

Towards Aim 2, novel and high performance PVDF nanocomposite membranes were developed. These membranes incorporated rice husk ash (RHA) and two superhydrophobic Zr-based metal-organic frameworks (OPA-UiO-66, MOF1; and OPA-UiO-66-SO3H, MOF2) nanoparticles to the PVDF. All new nanocomposite membranes demonstrated high permeability, durability, and antifouling properties due to the effect of the nanoparticles. Improved tensile strength was associated with increased crystalline formation of the PVDF, with the highest increase observed for PVDF/RHA (66% increase) due to the high silica content of the RHA.

Towards Aim 3, filtration tests were performed for high concentration aqueous solutions containing PFOA, PFOS, SMX, and TMP. High flux and rejection rates for these pollutants were achieved in PVDF/RHA and PVDF/MOF membranes in both dead-end and cross-flow filtration. These remarkable rejection rates can be attributed to several adsorption mechanisms including hydrogen bonding, π-π interactions, and electrostatic interactions between the chemicals and composite membranes. Furthermore, coupling UV treatment and ultrafiltration with PVDF/RHA and PVDF/MOFs membranes promoted degradation of the target pollutants, as confirmed from mass spectra analysis of the permeate and retentate streams.

This study demonstrates feasible and facile routes for controlling the rheology of polymer composites and manufacturing nanocomposite isoporous membranes with superior properties and performance characteristics for separation and purification applications. Study findings contribute to two key research areas: (i) development of rapid, low-cost, and more environment-friendly alternatives for manufacturing highly-structured nanocomposite membranes, and (ii) development of novel functionalized nanocomposite membranes for advanced water treatment.

All interested students and faculty members are invited to attend the online defense via remote access.