engleski

EFFECT OF NaX ZEOLITE MASS AND BAFFLE PRESENCE ON COPPER SORPTION

Copper sorption on NaX zeolite using a pitched blade turbine (PBT) was carried out in a baffled and unbaffled batch laboratory reactor. The impeller to reactor diameter ratio (D/dT=0.32), the impeller clearance to impeller diameter ratio (C/D=1.03) and the impeller off-bottom clearance (C/H=0.33) were kept constant. Impeller speed was equal to the lowest impeller speed for complete off-bottom suspension i.e. just suspended impeller speed (NJS) which was determined according to Zwietering 1s criterion for three different zeolite masses in both, baffled and unbaffled, batch reactors. Sorption is regularly carried out in stirred batch reactors without evaluating which mixing speed is necessary to avoid compromises in yield and cost. Mixing in the batch reactor at the NJS is a compromise between these conflicting objectives. Besides kinetic sorption experiments and kinetic analyses of gained data, to get insight into the hydrodynamic behaviour of the system, transient multiphase computational fluid dynamics simulations were performed. The NJS speed is related to the particle settling speed, i.e. the suspension mass concentration, and for that reason it changes depending on the zeolite suspension mass concentration. At higher zeolite suspension mass concentration, a higher NJS speed must be applied to ensure a complete suspension state, i.e. more energy must be applied. The differences in NJS speeds for the zeolite suspension mass concentrations investigated are not substantial, and for this reason, the increase in mixing intensity for the tested systems is not significant. From the results can be concluded that the hydrodynamic conditions used do not significantly affect the maximum amount of copper sorbed, but it is significantly affected by zeolite mass. The results also showed that the reaction is generally faster in the unbaffled reactor, and that the values of NJS and PJS were higher in an unbaffled reactor regardless of the zeolite mass used.

Zeolite mass, Copper, Sorption, PBT impeller, CFD

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