12-06-2014, 03:11 PM
Membrane separation
Membrane separation.ppt (Size: 117 KB / Downloads: 34)
Membrane separation processes: Introduction
Definition: A membrane is a thin barrier which allows selective passage of different species through it.
This selectivity is utilized for separation.
The selectivity is due to:
Size
Shape
Electrostatic charge
Diffusivity
Physicochemical interactions
Volatility
Polarity/solubility
Membrane separation processes: Applications
Product concentration, i.e. removal of solvent from solute/s
Clarification, i.e. removal of particles from fluids, a special case being sterilization which refers to removal of microorganisms from fluids
Removal of solute from solvent, e.g. desalting, desalination, demineralization, dialysis
Fractionation, i.e. separation of one solute from another
Gas separation, i.e. separation of one gas from another
Pervaporation, i.e. removal of volatiles from non volatiles (usually solvents)
Driving force in membrane processes
Transmembrane pressure (TMP)
Concentration gradient
Chemical potential
Osmotic pressure
Electric field
Magnetic field
Partial pressure
pH gradient
Membrane processes based on principles other than species size
Pervaporation (PV)
Driven by partial pressure
Selectivity depends on volatility and solubility of species in membrane
Gas separation
Driven by partial pressure
Selectivity depends on solubility of species in membrane
Electrodialysis (ED)
Driven by electric field
Selectivity depends of charge exclusion