Abstract:
This research investigated the ozonation of dye solutions by membrane contacting process. The first
part studied the effect of operating parameters and dyeing auxiliary reagents on ozone mass transfer
efficiency. The membranes used in this work were Polyvinylidenefluoride (PVDF) and
Polytetrafluoroethylene (PTFE). The experiments were carried out at 40 mg/L ozone concentration,
0.12-0.22 m/s gas phase velocity, 0.46-0.89 m/s liquid phase velocity (Re = 354-687) and 28-50?C
liquid phase temperature. Pure water (physical absorption), 100 mg/L dye solution of Acid blue 113
and Direct red 23 (chemical absorption) were used as feeds. Dyeing auxiliary reagents were NaCl
and Na2C03 It was found that, in both physical absorption and chemical absorption, the ozone flux
increased with increasing liquid phase velocity. Change in gas phase velocity did not influence the
ozone flux. The ozone flux of PVDF membrane was higher than that of PTFE membrane. However,
it was found that, after 16 hours operation, ozone flux of PVDF and PTFE decreased by
approximately 31.13 and 9.44 percent, respectively. In chemical absorption, ozone flux increased
with increasing temperature. But ozone flux decreased with increasing temperature in physical
absorption. The presence of Na2C03 in the dye solution resulted in increasing the ozone flux.
Conversely, when NaCI was added, ozone flux decreased. The second part studied the effect of
operating parameters and dyeing auxiliary reagents on the treating performance of dye solutions and
ozonation kinetics. The operating conditions applied were 300 mg/L initial dye solution, 500 mL
volume, 40 mg/L ozone concentration, 0.12 m/s ozone velocity and 60 minutes ozonation time. It
was found that the removal of dye color increased with increasing dyes solution velocity. The
removal of dye color increased slightly with increasing dye solution temperature. The presence of
Na2C03 and NaCI in dye solution resulted in decreasing the removal of dye color. At 0.46 m/s dye
solution velocity, 28?C temperature and PVDF membrane, the removal of dye color and COD of
Acid blue 113 dye solution were 97.11 and 44.44 percent, respectively. In case of Direct red 23, the
removal of dye color and COD were 72.83 and 41.51 percent, respectively. BOD/COD values
increased with operation time. It was found that kinetics of ozonation between dye and ozone was
pseudo-first order reaction. Ozonation rate constants of Direct red 23 and Acid blue 113 were 0.065
min'l and 0.023 min'l, respectively.