Aqueous-Phase Catalytic Oxidation As
A Wastewater Treatment Technique
JAMES R. KATZER, Assistant Professor
AJIT SADANA, Research Assistant
HUNTER FICKE, Student
Department of Chemical Engineering
University of Delaware
Newark, Delaware 19711
INTRODUCTION
Many industrial wastewater streams contain high concentrations of dissolved and/or
suspended organics (1,2,3,4, 5). These are often phenolic organics (6, 7), and may even be
carcinogenic, e.g., 3,4-benzpyrene (3). Future, more severe wastewater treatment problems
will exist at large coal conversion and shale oil recovery plants located in arid or cold
regions.
Much improved physical-chemical treatment technology seems necessary to handle
such situations in the future. Aqueous-phase catalytic oxidation is a possible technique that
is insufficiently developed to evaluate its applicability.
Hamilton, et al (6) describe a process for catalytic oxidation of organic material
dissolved and suspended in aqueous media over manganese dioxide from 25 to 100 C, and at
25 C the rate is very slow. Moses and Smith (7) propose an aqueous-phase catalytic
oxidation process with a packed-bed reactor at elevated temperatures (125-300 C) and
pressures (27.2-136 atm). High degrees of removal were achievable. Krupp (8) announced a
commercial aqueous-phase catalytic oxidation process for liquid wastes (dyes, food
processing, wash and pickling liquors) which achieved greatly reduced retention times over
biological treatment. Sadana and Katzer (9) studied the aqueous-phase catalytic oxidation
of phenol over copper oxide and showed that at atmospheric pressure and 100 C rates are
too low but that moderate increases in system temperature and pressure result in rates of
practical interest.
These examples indicate that aqueous-phase catalytic oxidation has potential as a
pollutant removal technique in many industrial situations. Aqueous-phase oxidation
eliminates the need for the phase change of incineration and the frequent regenerations
required of adsorption at high organic concentrations. If compared with wet oxidation, the
application of a catalyst should result in sufficient rate enhancement to allow a significant
reduction in the severity of operation and thus reduction in operating costs. Yet the
literature provides Little quantitative information on aqueous-phase catalytic oxidation.
In this work the aqueous-phase oxidation of phenol to C02 and H20 over supported
copper oxide was studied, and the rate data obtained were used in the design of an aqueous-
phase catalytic oxidation process. The economic evaluation of the process was then
compared with that for other physical-chemical processes.
EXPERIMENTAL APPARATUS AND PROCEDURE
The apparatus used has been described in detail elsewhere (9). It consisted of a heated,
stirred, 1-liter autoclave with a glass liner, operated batchwise. A sparger introduced
oxygen immediately beneath a turbine stirrer, and a back-pressure regulator controlled the
system total pressure and oxygen flow through the system. The stirrer continually
redispersed gas into the liquid phase. Catalyst and distilled water (500 ml) were added, and
the autoclave brought to the desired conditions. Phenol was added, and the liquid and exit
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