Constant pressure microfiltration of solutions of the protein bovine s
erum albumin (BSA) has been studied in a batch filtration cell without
stirring. Row resistance increased dramatically with time compared wi
th the initial membrane resistance while most of the solutes passed th
rough the membrane. The variation of the filtration flux rate with tim
e during extended filtration periods could not be analysed by a unique
blocking filtration law. The long-term decline in the filtration rate
was accurately described by considering the variation of the value of
the exponent i in the general characteristic form of the blocking fil
tration laws. It was found that the value of i continued to decrease w
ith the progress of filtration. In addition, the effects on the filtra
tion rate due to the solution pH, the filtration pressure, the fluid s
olute concentration, and the membrane type were described based on the
general characteristic form of the blocking filtration laws.