Extractions:
- In order to run analysis on the samples, the water must be absorbed (by MgSO4) and the contaminant must be transferred to tetrahydrofuran (THF)
- 0.5 mL of sample, 1 mL of THF, and 0.5 g of MgSO4 are added to a vial
- Remaining liquid is removed from the vial and moved to another vial containing 0.2 g of MgSO4
- Wait for 10 minutes to ensure complete adsorption of water
- The remaining liquid is removed using glass syringes into vials ready for gas chromatography mass spectrometry (GCMS) analysis
Development of a Biobased Carbon Adsorbent for Treating Emerging Contaminants in Recycled Water on the International Space Station
Savanna Vacek, Madeline Carroll, Gabson Baguma
Mentor: Dr. Erica Marti
Department of Civil and Environmental Engineering, University of Nevada - Las Vegas
This material is based upon work supported by the National Aeronautics and Space Administration under Cooperative Agreement No. 80NSSC20M0043.
I would also like to thank Dr. Erica Marti, Dr. Eakalak Khan, Gabson Baguma, and Madeline Carroll for their help and contributions.
- The International Space Station (ISS) operates as a closed system
- Water is recycled from humidity and urine and held in a wastewater tank; part of the Water Processing Assembly (WPA)
- Potable treated water is used indirectly in the Sabatier Reactor
- The Sabatier Reactor is a key component in the Environmental Control and Life Support System (ECLSS)
- Three main functions of ECLSS: water recovery, air revitalization, and oxygen generation
- Sabatier Reactor recently failed due to contamination of DMSO2, dimethyl sulfone, and DMSD, dimethylsilanediol
- DMSO2 and DMSD are emerging contaminants that are not removed by the media used in the WPA due to their low affinity
- DMSO2 and DMSD are introduced into the water system through personal hygiene products such as lotion, conditioner, and wipes, which all contain volatile methyl siloxanes (VMS)
- VMS are decomposed into DMSO2 or DMSD and are found in urine
Objectives:
- Synthesize at least 3 biobased ionic liquids
- Analyze and quantify how much DMSO2 is removed by the ionic liquids through liquid-liquid extractions
- Coat GAC with the most effective biobased ionic liquids
- Analyze and quantify how much DMSO2 is removed with uncoated GAC and ionic liquid coated GAC through batch adsorption testing
- The following ionic liquids were synthesized: a liquid result is successful, but any recrystallization is an unsuccessful result
Batch Adsorption Testing:
- 0 hours started with 756 ppb of DMSO2
- Over 24-96 hours, concentration stayed relatively the same around 515 ppb DMSO2
- 24 hours can be determined as the equilibrium time with only a 32% removal
- Demonstrates a need for ionic liquid coated GAC since uncoated GAC is not sufficient in removing DMSO2 from water
Extractions:
- Water was successfully absorbed by MgSO4, contaminant was transferred to THF phase for GCMS analysis
FTIR Characterization:
- Peaks show that all ionic liquid trials contained both a HBD and HBA
- X-axis location of peaks is consistent with ionic liquid formation across all thymol and decanoic acid liquids
- X-axis location of peaks is not consistent with ionic liquid formation across all thymol and dodecanoic acid liquids
- Analysis by GCMS will be completed to determine the DMSO2 adsorption by liquid-liquid extractions
- The best two ionic liquids, determined by analysis, will be coated onto biochar
- The two ionic liquid coated GACs will go through batch adsorption tests - equilibrium, isotherm, and kinetic testing
- The results of the adsorption experiments will be analyzed to determine the removal of DMSO2
- If removal was successful, the ionic liquid coated biochar would be a good recommendation to fix the Sabatier Reactor
International Space Station Water Processing Assembly - Graphic Credit: Dr. Khan’s Lab
Equilibrium Batch Adsorption Testing with Uncoated GAC:
- 100 mg of coconut granular activated carbon ranging in sizes from 400-595 microns is added to a 45 mL vial containing 800 ppb DMSO2
- Solution is shaken until reaching equilibrium
- Equilibrium time is determined by taking samples over time - 24, 48, 72, and 96 hours
- Samples are filtered to separate GAC from water
- Samples are analyzed by gas chromatography mass spectrometry (GCMS) to measure the concentration of DMSO2
Thymol and Decanoic Acid:
- Absorbance intensities differ at 2800 and 2900 peak (C-H stretching)
- Similar absorbance intensities at 1735 peak (C=O stretching)
- Small differences in intensity overall, 2:1 ratio more intense
Thymol and Dodecanoic Acid:
- Much higher absorbance for all compared to other ionic liquids
- 2:1 ratio shows the highest absorbance for every peak
- All synthesized ionic liquids were not successful
Thymol and Undecylenic Acid:
- Higher absorbance at 2800 and 2900 peak for 1:1 ratio (C-H stretching)
- 2:1 ratio shows very low to almost negative intensity, and was an unsuccessful ionic liquid
- Absorbance intensity is higher in 1:1 ratio than 2:1 ratio
Please view the PDF for references via QR code
- Ambersorb 4652, a styrenic polymer adsorbent that is not biobased or sustainable, is the current media used in the multifiltration beds in WPA on the ISS
- Costly and unsustainable, Ambersorb 4652 is challenged to remove DMSD and DMSO2 from recycled water
- Granular activated carbon (GAC) works similarly to a styrenic polymer adsorbent and can be made from biobased materials
- Ionic liquids are liquid molten salts at temperatures < 100 ℃ that are typically composed of large and unsymmetrical organic cations and organic or inorganic ions
- Composed of a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD)
- Remarkable solvation ability for a broad range of natural and synthetic materials and compounds
- The following ionic liquids were synthesized:
Granular Activated Carbon (GAC)
Synthesized Ionic Liquids
Synthesized Ionic Liquid Results
Uncoated GAC Equilibrium Batch Adsorption Test Results
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