of water flow. There are also several other techniques available for the generation of
pores in the membranes which include ion irradiation, electron beam lithography,
oxidative etching, electron beam irradiation, and helium ion drilling (Fig. 4.9).
4.5 Surface Modification (Fig. 4.10)
4.5.1 Macromolecule Immobilization
Macromolecule immobilization is a method for introducing a functional layer onto
the synthesized membrane surface. The reaction between the macromolecules and
the membrane surfaces is classified into three categories as follows: (a) direct
reaction between the membrane and the functional groups of the macromolecules,
Nano membrane
Synthesis
Top down approach
Bottom up approach
Chemical Vapor
Deposition (CVD)
Low temperature and
low pressure CVD
Plasma-enhanced
CVD (PECVD)
Thermal CVD
synthesis
Types
Development of Nanopores
Techniques involved
Etching
Lithography
Irradiation
Sputtering
Ion bombardment
Oxidation, Diblock
copolymer templating,
Helium ion drilling,
Doping, focused electron
beam ablation
etching
Types
Types
Defectselective recoil
sputtering
Fig. 4.9 Various methods available for the synthesis of nanoporous membrane
4 Functional Properties of Nanoporous Membranes for the Desalination of Water
141