Development of the Miniature Robotic Electrodialysis (MR ED) System for
Small-Scale Desalting of Liquid Samples with Recovery of Organics
Abstract
While liquid environments with high salt content are of broad interest
to the Earth and Planetary Science communities, instruments face
challenges in detecting organics in hypersaline samples due to the
effects of salts. Therefore, technology to desalt samples before
analysis by these instruments would be enabling for liquid sampling on
missions to Mars or ocean worlds. Electrodialysis (ED) removes salt from
aqueous solutions by applying an electric potential across a series of
ion-selective membranes, and is demonstrated to retain a significant
percentage of dissolved organic molecules (DOM) in marine samples.
However, current electrodialysis systems used for DOM recovery are too
large for deployment on missions or for use in terrestrial fieldwork.
Here we present the design and evaluation of the Minature Robotic
Electrodialysis (MR ED) system, which is approximately 1/20th the size
of heritage instruments and processes as little as 50 mL of sample at a
time. We present tests of the instrument efficiency and DOM recovery
using lab-created solutions as well as natural samples taken from an
estuary of the Skidaway River (Savannah, GA) and from South Bay
Saltworks (San Diego, CA). Our results show that the MR ED system
removed 97-99% of the salts in most samples, with an average DOC
recovery range from 53 to 77%, achieving similar capability to tabletop
instruments. This work both demonstrates MR ED as a possible field
instrument and increases the technology readiness level of miniaturized
electrodialysis systems for future missions.