Product Processing and Biomining Flashcards
What are the processes that can be used to obtain water?
Melting ice –> H20
Sabatier Reaction with CO2 – > H20
Ilmenite + H_2 Reduction – > H20
Reduction of glass with H2
Dissolving regolith with acidic liquids
What are the processes that can be used to obtain CO2?
- Mineral decomposition of regolith
- Direct extraction from atmosphere
- Direct extraction from CO2 ice
- Reduction of Ilmenite with CO
What are requirements for ISRU water?
- No chemical contamination
- No microbial contamination
- Specific pH range
- Avoiding electrode poisoning
What is Freeze Distillation?
A method for ISRU water capture and distillation.
What is the minimum potential difference for H20 Electrolysis
1.23 V
What are the most important types of H20 electrolysis?
- Alkaline Electrolysis
- Proton Exchange Membrane Electrolysis
- Solid Oxide Electrolysis
What are the contributing factors to cell voltage?
- Reversible potential
- Activation overpotential
- Ohmic overpotential
- Diffusion overpotential
- Bubble overpotential
What is the main problem of H20 electrolysis and some countermeasures?
- Reduced buoyancy and bubble detachment induces overpotential
Solutions:
- Nanopatterning
- UV radiation
- Pressure swings
- Vibration
What is the formula for CO2 electrolysis?
CO2 + 2e –> CO + O2
How can Electrolysis products be regulated?
Voltage adjustment
What is Biomining?
Microorganisms grown on ore forming leachate with dissolved metal ions
How can CO2 be obtained?
- Mineral Decomposition of Regolith
- Direct Extraction for Atmosphere
- CO2 Ice Deposit
- Reduction Ilmenite with CO
What are Important Points Regarding H20 Electrolysis?
- Minimum P.D of 1.23 V (external heat also required)
- Soluble Electrolyte is needed to provide ions for current flow
- Electrolyte ions must be harder to oxidize/reduce than water
What is Alkaline Electrolysis (AEL)?
- A method of H20 Electrolysis
- A membrane is used to ensure the separation of the reaction products
- Common membranes cannot tolerate extreme conditions
- Divide further into Classical, Zero Gap, and Dual Membrane
- OH- are charge carriers
What is Proton Exchange Membrane Electrolysis?
- Can be operated at higher pressure and with higher current densities compared to AEL
- Operate at lower temperature than AEL
- Acidic working environment (resistant electrodes required)
- Gas proof, proton conducting plastic membrane used to separate gas products
What is reversible potential?
Minimum potential required between electrodes to make water disassociation reaction occur
What is activation overpotential at anode and cathode?
Kinetics of the electronic charge transfer reactions.
(Extra potential required to overcome potential barrier.)
What is Ohmic overpotential?
Caused by non-infinite conductivity of the electrolysis cell.
Potential drop due to internal resistance.
What is diffusion overpotential?
for high current densities, the reaction is no longer controlled by electronic transfer but by matter transfer
Extra voltage required in a reaction due to the limited rate of mass transport
What is bubble overpotential?
Increased resistance due to non conductive bubbles covering parts of the electrodes
What is Solid Oxide Electrolysis (SOE)?
- Is basically a Solid Oxide Fuel Cell running in regenerative mode (reverse mode)
- Can operate at temperatures of up to 1000 C using superheated water vapor
- Can be up to 80 percent efficient
- Uses a porous cathode
- Delamination due to O2 pressure build up is a problem
What is a risk of CO2 electrolysis and how can it be counteracted?
- Electrode coking
- Electrodes coated, interferes with electrolysis process
- Nickel in cathode as catalyst, but also leads to structural damage
- Operate in safe voltage zone
What are the challenges of biomining?
- Survival of bacteria in space (radiation)
- Requires water
How good is regolith for plant growth?
- Terrestrial plants can grow with lunar regolith as primary support matrix
- Lunar regolith not a benign growth substrate (growth fail and oxidative stress)
- Immature regolith better than mature regolith
