Surface Functionalizations of Water Filters: a Moringa oleifera Sand Filter and Metal-Organic Nanofiltration Membranes

Open Access
Author:
Uliana, Adam Andrew
Area of Honors:
Environmental Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Stephanie Velegol, Thesis Supervisor
  • John Regan, Honors Advisor
Keywords:
  • Moringa oleifera
  • water purification
  • global water crisis
  • nanofiltration membranes
  • metal-organic frameworks
  • surface functionalization
Abstract:
This thesis reports two novel technologies that use material surface functionalizations for improved water purification: Moringa oleifera-coated sand (f-sand) filters and nanofiltration membranes with metal-organic interfaces. Moringa oleifera seeds contain an antimicrobial, cationic protein that can adhere to sand. This cationic f-sand strongly adsorbs waterborne pathogens and is particularly advantageous for use in developing global regions. Tests on miniature f-sand columns reported here attained over 5 log-removal of pathogens and lasted in effectiveness at least 10 times longer than regular sand filters. In order to be scaled up to practical sizes, three different clean-bed filtration models were applied to model the f-sand filter based on biocolloid transport through the filter. Two additional strategies (two-step deposition and co-deposition) were also designed that use mussel-inspired polydopamine (PDA) to strongly immobilize copper nanoparticles (CuNPs) onto a porous polymeric membrane for chemical wastewater treatment. To confirm the optimization of membrane surface properties, a series of materials characterizations (e.g., water contact angle) was executed. The enhanced surface charge, hydrophilicity, and pore size promoted an outstanding salt permeation (82% Na2SO4, 98% NaCl), water permeability (18.2 LMH/bar), and textile dye rejection (600-800 Da, >99.0% rejection), respectively. Furthermore, the functionalized membranes displayed a distinct bactericidal activity with a reduction of 93.7% in the number of live Escherichia coli (E. coli) bacteria. The nanofiltration membrane studies highlight fast, facile surface modification strategies to assemble multifunctional coatings onto membranes for chemical wastewater treatment.