Structure-Property Relationships in Intercalated Graphene Oxide Membranes for Separation of Salts and Hydrocarbons from Petroleum-Containing Wastewaters

Graphene oxide (GO) membranes are emerging as a viable new technology for separation of complex aqueous streams. Prior work by the Nair group and collaborators has developed scalable GO membranes that a robust in a variety of harsh operating environments. Additionally, they demonstrated that GO membranes intercalated by conjugated polyaromatic molecules showed enhanced rejection of salts as well as excellent rejection of organics (including hydrocarbons). However, the mechanisms underlying these findings are not well understood. The aims of my work are threefold: (1) Determine the key aspects of the microstructure-separation property relations of GO nanofiltration membranes that are intercalated/functionalized by a representative p-conjugated polyaromatic intercalant toluidine blue O (TBO). A combination of experimental techniques will be used for this purpose. (2) Based on initial insights from aim 1, synthesize an expanded set of “GO-X” membranes intercalated with a systematically chosen set of polyaromatic intercalants (“X”), and refine the structure-property relationships with a focus on enhanced rejection of monovalent salts such as NaCl. (3) Apply these fundamental advances to develop GO membranes for petroleum wastewater recycling. Large amounts of wastewater are generated in petroleum refineries from crude oil desalting operations (~80 million metric tons in the US). This wastewater contains significant amounts of crude oil, as well as salts such as NaCl (which is extracted from crude oil by washing with water). These wastewaters are commonly sent for biological wastewater treatment and are not reused. Detailed separation measurements on these wastewaters with the engineered GO-X membranes, and use of the process data in conjunction with ASPEN flow sheeting, will allow the development of a membrane-based process for production of reusable water and recovery of valuable crude oil from the desalter effluent. Preliminary work on all three aims shows encouraging results that set the stage for achieving the aims of this research.