Date of Award

Spring 1997

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemical Engineering - (Ph.D.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Kamalesh K. Sirkar

Second Advisor

Gordon Lewandowski

Third Advisor

Basil Baltzis

Fourth Advisor

Dana E. Knox

Fifth Advisor

Robert J. Farrauto

Abstract

Many gaseous and aqueous waste streams contain multiple organic pollutants at low concentration levels. It is not economical to recover and reuse these compounds; it would be advantageous to destroy them efficiently within the waste stream. This work employed ozone, a powerful oxidizing agent, in concert with a compact membrane-based phase-contacting device. Three types of membrane devices were studied: two of them (the single-phase membrane ozonator and the two-phase membrane ozonator) treated organic pollutants in wastewater, while the third (the integrated absorption-oxidation membrane ozonator) removed volatile organic compounds (VOCs) from a gaseous waste stream.

In the single-phase membrane ozonator, the polluted wastewater stream was exposed to O3/O2 by means of a nonporous silicone capillary membrane. Experiments conducted to ascertain the effect of long-term exposure of O3 on the membranes measured the permeability of O2/N2 across the membrane before and after exposure to O3; the permeability of O3 across the nonporous membrane was also experimentally measured and found to be four times that of oxygen. The removal of organic pollutants (phenol, acrylonitrile and nitrobenzene, feed concentrations -100ppm) from wastewater was studied experimentally. A mathematical model was proposed; numerical simulations of the model successfully predicted the performance of this membrane reactor. The two-phase membrane ozonator and the integrated absorption-oxidation membrane ozonator used an inert fluorocarbon (FQ medium as a liquid membrane and a reaction medium. Ozone has a very high solubility in this FC phase compared to that in water. The performance of the two-phase membrane ozonator was studied experimentally for the following compounds: phenol, nitrobenzene, acrylonitrile, toluene and trichloroethylene (TCE). A mathematical model was developed; the model predictions were close to the experimentally observed reactor performance.

The two-phase membrane reactor showed higher rates of pollutant degradation than the singlephase membrane ozonator for nitrobenzene as a model pollutant (feed concentration ~120 ppm). Experimentally observed ozone utilization in the two-phase membrane ozonator for nitrobenzene as a model pollutant showed an ozone utilization rate > 15 for a feed concentration of ~120 ppm; and 0.1 for a feed concentration of 1400 ppm. The performance of the integrated absorption- oxidation membrane ozonator was studied for trichloroethylene (TCE) and toluene as representative VOCs. This reactor demonstrated that the two-phase ozonation concept can be successfully extended (with little modification to the membrane reactor) to treat gaseous waste streams with VOCs.

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