Development and characterization of composite membranes for use in countercurrent solvent extraction

Author

• Lydia Neves Rodrigues, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

8-31-2021

Degree Name

Doctor of Philosophy in Chemical Engineering - (Ph.D.)

Department

Chemical and Materials Engineering

First Advisor

Kamalesh K. Sirkar

Second Advisor

Roman S. Voronov

Third Advisor

Boris Khusid

Fourth Advisor

Kathleen McEnnis

Fifth Advisor

S. Mitra

Abstract

Porous membranes having a particular wetting characteristic, hydrophobic or hydrophilic, are used for nondispersive membrane solvent extraction (MSX) where two immiscible phases flow on two sides of the membrane. The aqueous-organic phase interface across which solvent extraction/back extraction occurs remains immobilized on one surface of the membrane. This process requires the pressure of the phase not present in membrane pores to be either equal to or higher than that of the phase present in membrane pores; the excess phase pressure should not exceed a breakthrough pressure. In countercurrent MSX with significant flow pressure drop in each phase, this often poses a problem. In this dissertation, new Janus membranes are developed in order to overcome this problem. The Janus membrane consists of one membrane with two unique sides, one being hydrophobic and one being hydrophilic. Several materials are studied to this end: polyvinylidene fluoride (PVDF), polyamide (Nylon 6,6), polyether ether ketone (PEEK), polypropylene (PP), and polytetrafluoroethylene (PTFE). Two different treatment methods are employed to create the opposite wetting characteristics on each side: a plasma-polymerization treatment and a 2-part treatment of a caustic-potassium hydroxide (KOH) solution followed by an acrylic acid (AA) solution treatment. Both flat membranes and hollow fibers are studied. The Janus membranes are characterized using the contact angle, liquid entry pressure (LEP) and the droplet breakthrough pressure from each side of the membrane along with characterizations via scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Nondispersive solvent extractions are carried out successfully for two systems, octanol-phenol (solute)-water, toluene-acetone (solute)-water, with either flowing phase at a pressure higher than that of the other phase. The phenol extraction system has a high solute distribution coefficient whereas acetone prefers both phases almost identically. The Wilson-plot method is used to characterize the membrane resistances as well as the individual-phase boundary layer resistances for each extraction system. The potential practical utility of the MSX technique will be substantially enhanced via Janus MSX membranes.

Recommended Citation

Rodrigues, Lydia Neves, "Development and characterization of composite membranes for use in countercurrent solvent extraction" (2021). Dissertations. 1913.
https://digitalcommons.njit.edu/dissertations/1913