2D Nanomaterial-Assisted Nanocomposite Membranes for Removal of Contaminants From Wastewater

Abstract

This dissertation presents a comprehensive study on developing nano-engineered composite membranes that exhibited performance as nanofiltration membranes for water and wastewater treatment by synthesizing and incorporating 2D nanomaterials of molybdenum disulfide (MoS2) and graphene oxide (GO). The first study synthesized three unique MoS2 morphologies- nanospheres, nanoplatelets, and nanosheets- using a hydrothermal approach under different conditions. Each type of nanomaterial was individually incorporated into polymeric chitosan membranes to fabricate three different membranes. The membrane containing MoS2 nanoplatelets (P-CM) demonstrated superior performance and achieved the highest heavy metal ion removal efficiencies (93.0±0.5% for Mn2+ and 90.4±1.5% for Zn2+) and the highest water flux. This enhanced capability was attributed to the greater porosity provided by the embedded nanoplatelets across the composite membrane and their catalytic effect in generating reactive oxygen species (ROS) due to their morphology with thicker edges and higher surface-to-volume ratio.

The second study involved the fabrication of two nanocomposite membranes with different pore-forming polymer-to-nanomaterial ratios, CMG1 and CMG2, where MoS2 nanospheres and GO were incorporated into a chitosan polymer matrix. In the final step, MoS2 nanoplatelets were coated on the top surface of both CMG1 and CMG2 membranes to increase further the availability of the nano additives on the membrane surface. Both membranes exhibited combined catalytic and separation functionalities, leading to high efficiencies in color and total organic carbon (TOC) removal from wastewater. CMG2, with a higher pore-forming polymer-to-nanomaterials ratio, demonstrated better performance, likely due to the fact that the more porous CMG2 membrane better facilitated the synergistic catalytic effects of MoS2 nanospheres with H2O2 by generating reactive oxygen species. The GO nanosheets also introduced a stronger negative charge to enhance the separation and rejection of organic contaminants.

Lastly, the treatment application by the catalytic 2D nanocomposite membrane (CNC) of chitosan/MoS2/GO was extended to the simultaneous removal of dye compound and heavy metal ions from Wastewater. This membrane achieved over 99% removal efficiency for methylene blue (MB) and heavy metal Co2+, along with significant efficiencies for other heavy metals, including Cu2+, Pb2+, and Ni2+. The presence of MoS2 nanoparticles was vital to activating H2O2 to generate high ROS, as confirmed through terephthalic acid (TA) by fluorescence emission spectroscopy.

As explored in this research, the innovative use of 2D nanomaterials such as MoS2 and GO in membrane technology showcases positive progress in enhancing removal efficiencies, catalytic degradation capabilities, and robustness of treatment systems. Overall, this research contributes to developing next-generation water treatment technologies enhanced by 2D nanomaterials, offering promising strategies and solutions for addressing some of our time's most pressing environmental challenges.

Date of Award	20 Jul 2024
Original language	American English
Supervisor	Linda Zou (Supervisor)