A composite microporous membrane made of
poly(N-benzyl-4-vinylpyridinium chloride) that
showed strong affinity with bacterial cells was prepared as a filter material
for removing
airborne bacteria. Thickness, pore diameter and porosity of the membrane
were 0·72 mm,
14·5 μm and 63%, respectively. Electron micrographic
analysis revealed that the membrane
consisted of a very large number of connected beads of 1·4 μm
in diameter made of the
pyridinium-type polymer. Filtration using the membrane was performed easily
at low flow rates
with insignificant pressure drop across the membrane. Filtration
at 63·7 cm/sec gave 99·98%
and 99·996% removal (3·7 and 4·4 log10-unit
reduction in concentration) of Escherichia coli and
Pseudomonas aeruginosa, respectively. Staphylococcus
aureus was not detected in filtrates. Since
pores of the membrane were much larger than these bacteria, the efficient
removal was best
explained in terms of the affinity of the polymer with bacterial cells.