Adsorptive Behavior of Dispersed and
Basic Textile Dyes on Activated Carbon
WILLIAM H. FRYE, Graduate Student
FRANCIS A. DiGIANO, Assistant Professor
Department of Civil Engineering
University of Massachusetts
Amherst, Massachusetts 01002
INTRODUCTION
Carbon Adsorption has been demonstrated as being an effective method for improving
the effluent quality of textile dyeing wastes (1,2, 3). With the recent issuance of effluent
guidelines for the textile industry (4), adsorption may be considered as best available
control technology for meeting the 1983 requirements. Moreover, in anticipation of these
more stringent guidelines, it may be reasonable, and ultimately more economical, to
integrate adsorption into control technology for meeting the 1977 guidelines.
One major difficulty in applying carbon adsorption to the treatment of textile dyeing
wastes is the wide variability in adsorptivity of different dye types. Because a particular
dyeing operation may employ many dye types, efficient treatment requires that the
adsorptive behavior of each dyebath be known. Presently, such information is gained
through on-site pilot scale testing of the dyebath. Such a procedure is not only time
consuming, but must be repeated if the dyebath is changed significantly. Considerable time
and effort could be saved if the adsorptive behavior of various dye types were characterized
with respect to other dye types with which they are often combined.
This paper presents the results of a project designed to characterize the adsorptive
behavior of two widely used dye types: dispersed and basic. An attempt has been made to
illustrate the causitive factors which differentiate adsorptive behavior between these
different dye types, and also between different chemical classes of dyes within each group.
FACTORS INFLUENCING ADSORPTION OF DYES
Adsorption is influenced, in part, by the physical and chemical properties of the
sorbate, the surface characteristics of the sorbent, and by solute-solvent and sorbent-
solvent interactions. Environmental conditions such as pH and temperature will also
influence the sorptive behavior exhibited by a particular sorbate-sorbent system. In column
operations, sorptive behavior is dependent largely upon the hydraulics of the system, i.e.,
contact time. Although all of the factors described above are of importance, many such as
pH, temperature and contact time, can be considered to be fixed either by the nature of the
waste or by design specification. Of the factors which cannot be easily controlled, sorbate
properties and solute-solvent and sorbent-solvent interactions are certain to affect
adsorptive behavior to a large extent.
Because of the high degree of variability in dyebath formulations, the properties of
various dye types, or sorbates, demands closer attention. Dispersed and basic dyes differ
primarily in ionic character which in turn causes their degree of solubility in aqueous
solution to differ markedly. Dispersed dyes are nonionic, organic compounds which are
only slightly water-soluble, while the basic dyes (also referred to as cationic dyes) are
characterized by the presence of a cation within their primary (or chromophore) group.
These latter dyes exhibit high solubility in aqueous solution. Particular dyes contained
within each of these general groupings may be derived from a wide variety of starting
materials. Chemically, dyes are classified by the structure of their primary color rendering,
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