Ph.D. Thesis Defense Announcement

NANO-STRUCTURED MEMBRANES FOR CLEAN ENERGY HARVESTING FROM SALINITY GRADIENT AND LOW-GRADE WASTE HEAT

By

Xin Tong

Advisor:

Dr. Yongsheng Chen

Committee Members:

Dr. John Crittenden (CEE); Dr. Ching-Hua Huang (CEE); Dr. Xing Xie (CEE); Dr. Ryan Lively (ChBE)

Date & Time: Thursday, August 9th, 2018, 2:00PM

Location: Sustainable Education Building

Salinity gradient power (SGP) is a new type of sustainable energy that can be generated from the mixing of two solutions with different salinities. Despite the great potential for energy generation globally, significant technological progress is needed before the type of energy can be utilized on a large scale. This study focuses on the synthesis of new types of membranes for the application in reverse electrodialysis (RED) and pressure retarded osmosis (PRO) to harvest the SGP. In addition, the mechanisms of transport property improvement of the new membranes are explored and discussed.

pecifically, a RED-specific nanocomposite cation exchange membrane (CEM) is synthesized for the application in RED. Due to the decreased ionic resistance and increased permselectivity, the nanocomposite CEM can achieve higher power density in the RED system than the pristine polymeric CEMs. Next, by combining experimental work and theoretical modeling, the origin of property enhancement of the nanocomposite CEM is explored. The interaction between the nanomaterial and the polymeric material can alter the micro-structure of the nanocomposite CEM, which makes the ion transport across the membrane more efficient. Freestanding graphene oxide membranes (GOMs) are synthesized in this study. Since no membrane support layer is needed, internal concentration polarization is minimized and effective driving force across the membrane is increased in osmotic-driven processes. As a result, when the freestanding GOM is used in the PRO and the osmotic heat engine, the power density of those systems increases. The conclusions of this study can guide the future design of new membranes for renewable energy harvesting from salinity gradient.