Zdrojový dokument:Scientific papers of the University of Pardubice. Series A, Faculty of Chemical Technology. 21/2015
ISSN:1211-5541
Abstrakt:
The influence of a coagulant type and operating parameters on crossflow
microfiltration of aqueous dispersions of titanium dioxide has been examined. The
experiments were carried out with a tubular ceramic microfiltration membrane
of nominal pore size 0.1 μm at various operating parameters. Three chosen types
of organic coagulants were used for a series of crossflow microfiltration
experiments: polyacrylamide (PAM), poly(diallyldimethylammonium chloride)
(pDADMAC) and poly(acrylamide-co-acrylic acid) partial sodium salt (PACA).
The value of steady-state permeate flux has been experimentally evaluated for the
crossflow microfiltration with and without pretreatment.
The results of the experiments without coagulants have shown that initial
flux declines rapidly, but after an initial decline, the flux is stabilised. The results
also suggest that pDADMAC is a better coagulant for this system and its optimum concentration is 30 mg l–1. Finally, it is shown that the feed pretreated by
pDADMAC has resulted in more than three-times higher permeate flux than that
without any pretreatment. Moreover, there was a very positive effect of this
coagulant on the particle size. Pretreatment by 30 mg l–1 pDADMAC has led to
almost eighteen-times higher average particle size compared to the average
particle size without pretreatment. The other two coagulants did not show such
improvements as pDADMAC; pretreatment of the feed by PAM giving only a 10 %
higher permeate flux whilst the pretreatment of the feed by PACA causing even
lower permeate flux than those without any pretreatment. Thus, the individual
experiments have suggested us the need for careful selection of coagulants,
because of their different impact upon the permeate flux.