Plasma of Nonpolymerizable Gases

FIGURE 3.5 Membrane surface modification via O2 plasma treatment. (Reprinted from Desalination, 189, Tyszler, D., et al., 119-129, Copyright (2006), with permission from Elsevier.) 

Treatment with N2 plasma introduces various chemical groups, such as amine, imine, amide, or nitrile, on the membrane surface, making it more hydrophilic and less liable to fouling (Kull et al. 2005). For example, after continuous operation in an SMBR for about 90 h, flux recoveries for plasma-treated PP membranes for 8 min were 62.9% and 67.8% higher than those for the virgin membrane after water and NaOH cleaning (Yu et al. 2007). 

The hydrophilicity of the NH3 plasma-treated PP membranes increased with the increase in plasma treatment time and decreased with the increase in storage time (Yan et al. 2008). The adsorption of BSA on the modified membranes was lower than that on the unmodified-membrane surface and the flux recoveries after water and caustic cleaning for the NH3 plasma-treated membranes for 1 min were 51.1% and 60.7% higher than those for the unmodified membrane. However, the mechanical properties of the membranes decreased after prolonged plasma treatment, thus the optimal plasma treatment time for membrane modification was taken as 1 min. 

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