School of Civil and Environmental Engineering

Ph.D. Thesis Defense Announcement

Ion exchange membrane systems: modeling and optimization for salinity gradient energy generation

By

Bopeng Zhang

Advisor:

Dr. Yongsheng Chen (CEE)

Committee Members:

Dr. Yongsheng Chen (Advisor, CEE); Dr. John Crittenden (CEE); Dr. Sotira Yiacoumi (CEE); Dr. Shuman Xia (Mechanical Engineering); Dr. Xing Xie (CEE)

Date & Time: Wednesday, May 2nd, 2018 , 10:00AM

Location: Sustainable Education Building, 122

Energy can be sustainably generated by harnessing natural salinity gradients in coastal environments. Power derived

from the mixing of freshwater and seawater can be recovered as electrical energy by regulated ion transport in reverse

electrodialysis (RED) systems. Cation exchange membranes and anion exchange membranes, known together as ion

exchange membranes (IEMs), are crucial components to the energy generation efficiency in RED stacks. Considering

the fundamental nature of electrochemical systems, it is conceivable that membrane functional properties, including

ionic conductivity and permselectivity, have significant effects on RED energy performance. A better understanding

of these determining factors is therefore critical to advance commercialization feasibility.

This study focused on advancing the understanding of IEMs through modeling, simulation and experimental

validation in addition to novel approaches for RED energy performance improvement. Specifically, conductivity

gains were realized through implementation of ion exchange resin in low-concentration compartments. Mathematical

modeling and experimental validation were leveraged to infer crucial factors in membrane conductivity and other

physical property determinations. In addition, this framework was extended to illuminate the role of nanoparticle

introduction during the synthesis process.

Modeling and simulation results were successful in revealing the underlying dependencies of IEM characterization

and improving the system energy performance. A majority of these theories and simulations are generalized -

potentially yielding broad impacts to similar membrane-based systems and processes (e.g., electrodialysis).