Decolorization of Dye RB-19 Solution in a Continuous Ozone Process

Abstract

This work studied the decolorization of dye C.I. Reactive Blue 19 (RB-19) solution in a new gas-inducing reactor under continuous process. The decolorization behavior, decolorization kinetic, ozone utilization rate and Chemical Oxygen Demand (COD) are examined under various operation conditions, such as input ADMI color values (ADMI _o ), input liquid flow rates (Q _L ), input ozone gas concentrations , input gas flow rates (Q _g ), and agitation speeds (N). Experimental results of decolorization behavior indicate that the American Dye Manufactures Institute (ADMI) removal percentage ( R _ADMI) decreases with increasing ADMI color value input rate or decreasing ozone input rate. For the study of ozone utilization rate, increases with increasing ADMI color value input rate or decreasing ozone input rate. The 70% ADMI removal percentage can be regarded as the index of the competition of dye and its unknown intermediates for ozone. In addition, the increase of the agitation speed can improve the ADMI removal percentage as well as the ozone utilization rate. A pseudo-first order kinetic model is adopted to describe the decolorization behavior. At steady state, the overall decolorization rate constant, k _ADMIs.s., can be expressed as a function of liquid flow rate, input ADMI color value, input ozone gas concentration, gas flow rate, and agitation speed. This correlation can be used to predict the ADMI color value at steady state (ADMI_s.s.) and the reactor size in the continuous process. The ΔO₃/ΔCOD is dependent on the liquid composition. The higher the dye concentration in the liquid, the higher the ΔO₃/ΔCOD. The COD removal percentage ( R _COD) and the ozone utilization rate can be further improved by using the continuous operation with two reactors in series.

Keywords:

• Decolorization
• ADMI color value
• COD
• Ozone utilization rate
• Gas-inducing reactor

Acknowledgment

The authors thank the National Science Council of R.O.C. for the financial support. (Project no.: NSC88-2211-E-011-012).