New Membrane for Desalination

Reverse-osmosis desalination uses high pressure to force polluted water through the pores of a membrane. Water molecules pass through the pores of the membrane, but mineral salt ions, bacteria and other impurities do not. Over time, the pores become clogged and the membrane damaged, requiring expensive cleanup and membrane replacement.

UCLA scientists have produced a new membrane which could increase membrane life and reduce desalination plant operational costs. The new membrane is synthesized in a three step process:

1. synthesis of a polyamide thin-film composite
2. activation of the polyamide surface with atmospheric pressure plasma to create active sites on the surface
3. initiation of a graft polymerization reaction on the activation sites using a monomer solution to create a polymer "brush layer"

The polymer chains of the brush layer, which are chemically anchored to the polyamide surface, are in constant motion, much like seaweed that is in constant motion but anchored to the sea floor. This motion makes it difficult for bacteria and other colloidal matter to anchor to the surface of the membrane increasing the life expectancy of the membrane.

References:

1. Nancy H. Lin, Myung-man Kim, Gregory T. Lewis, Yoram Cohen. Polymer surface nano-structuring of reverse osmosis membranes for fouling resistance and improved flux performance. Journal of Materials Chemistry, 2010; DOI: 10.1039/b926918e
2. Myung-man Kim, Nancy H. Lin, Gregory T. Lewis, Yoram Cohen. Surface nano-structuring of reverse osmosis membranes via atmospheric pressure plasma-induced graft polymerization for reduction of mineral scaling propensity. Journal of Membrane Science, 2010; DOI: 10.1016/j.memsci.2010.02.053

Study Questions:

1. What is osmosis?
2. Name some mineral salt ions you would expect to find in seawater.
3. What is a monomer?
4. What is a polymer?
5. What is meant by the term polymerization?
6. Describe a polyamide.
7. Draw a table listing some polymers, their respective monomers, and the properties and uses of the polymers