MEMBRANE ULTRAFILTRATION OF NITROTOLUENES
FROM INDUSTRIAL WASTES
Dibakar Bhattacharyya, Research Associate
Kenneth A. Garrison, Research Assistant
Robert B. Grieves, Chairman
Department of Chemical Engineering
The University of Kentucky
Lexington, Kentucky 40506
INTRODUCTION
Membrane ultrafiltration with noncellulosic membranes is a promising technique for
the removal of various organic compounds present in aqueous solution, particularly for
waste treatment systems designed for in-plant water reuse.   Ultrafiltration is generally carried out at low pressures of 105 to 10 6 N/m2 and offers an attractive alternative in many
processing areas.   The process has been used successfully as an effective technique for the
treatment of a large number of industrial wastes.   Porter and Nelson [ 1 ] have reviewed
applications of ultrafiltration in the chemical, food processing and pharmaceutical industries.   The water reuse applications involving ultrafiltration include electrodeposition
primers [2], oil-water separation in metal cutting operations [3], color removal from
Kraft mill effluents [4] and laundry wastes [5].   The use of ultrafiltration for the separation of low-molecular-weight ionic solutes with charged membranes [6,7], modest-
molecular-weight (size) organic solutes [8,9], complex suspensions of a nonionic
surfactant, inorganics and particulates [5], and organic macromolecules and colloids [1],
has been reported in the literature.
The solute-rejection characteristics of a membrane depend on the relative diffusivities
and structures of the species of significance, on the ionic nature of the membrane, and
on the pore size distribution and frictional interaction between solute and pore wall in the
thin, anisotropic membrane skin.   In addition to selecting a membrane with the proper
intrinsic rejection characteristics, the well-known phenomenon of concentration polarization must be minimized to prevent water flux limitations.   The accumulation of solute(s)
on the membrane surface (concentration polarization) is caused by the rapid convection
to the surface of rejected solutes resulting from the high-flux nature of ultrafiltration
membranes.   Excellent discussions and mathematical formulations of the ultrafiltration
process, including considerable detail on concentration polarization, have been presented
by Michaels et al. [ 10], Porter [11] and Kozinski and Lightfoot [ 12].
The treatment of TNT manufacturing wastes by membrane processes for the purpose
of water reuse is a very promising application.   There are three kinds of wastewaters generated during TNT manufacture.   Highly acidic "red water" is the waste produced during
the selite (sodium sulfite) treatment; "pink water" is formed when partially purified TNT
is washed following the selite treatment; and "wash water" is produced during the TNT
finishing process involving drying, flaking and packaging.   The compounds o-TNT, dinitro-
toluenes and other trace nitrotoluenes are the organic constituents of the wastewaters.
No entirely successful treatment method for these wastes has been found.   Nay et al.
[13] have studied the possibility of neutralization and biological treatment, while Rosenblatt [14] and Spano et al. [15] have attempted the removal of nitrotoluenes by carbon
adsorption.   Carbon adsorption techniques suffer the disadvantage of the difficulty of
carbon regeneration by chemical means [15,16] and the hazard of thermal regeneration.
In the present study, the removal of nitrobodies from "pink water" is experimentally
investigated by continuous, thin-channel ultrafiltration of actual (obtained from the Radford Army Ammunition Plant) and synthetic wastes.   The objectives of this investigation
are to select an optimum membrane in terms of high organics (nitrotoluenes) rejection
and adequate water flux, to establish operating conditions to minimize concentration
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