Material characterisation Flashcards
What is leaching?
a proces by which inorganic or organic contaminants are released from the solid phase inte the water phase
affected by:
- pH
- L/S ratio
- redox
- temperature
- shaking/stiring intensity
- particle properties
For what is leaching used?
- the environmental acceptability of materials used in construction
- remediation of contaminated soils
- disposal options for industrial, hazardous and nuclear wastes
what is ASE?
accelerated solvent extraction
- used for organic contaminents
- technique for extracting solid and semisolid samples with liquid solvents
- elevated temperature (up to 200 grader)
- high pressure (upp to 200 atm)
What are some of the limitations to leaching tests?
- a simplified system
- time aspect
- mainly performed at room temperature
- dificult to control (microbial activity, redox)
- poor correlation with bioavalability
What is bioavailability?
the degree to which a contaminant or nutrient in an environment media can be absorbed, transported and utilized physiologically
a process of physical, chemical and biological interaction
- if a nutrient or contaminant can be taken up by a organism it is “bioavailable”
How can bioavailible fraction of contaminants be assessed?
chemical methods: assessment outside a cell, contaminanat release
bioassays: determination inside a cell, uptake across a physiological membrane
When does chemical methods work?
- weak extractions
- reductive extractants
- weak acids
- strong complexing agents
- combination of salt-acid extractants
- diluted strong acids
- concentrated strong acids
When does bioassays work?
Main groups of tests:
- whole -cell bacterial biosensors
- microbial
- plant
- invertebrate
