Environmental Engineering Reference
In-Depth Information
9
Dye Adsorption on Expanding
hree-Layer Clays
Tolga Depci 1 and Mehmet S. Çelik* ,2
1 Faculty of Engineering, Department of Mining Engineering, Inonu University,
Malatya, Turkey
2 Faculty of Mining, Mineral Processing Department, Istanbul, Turkey
Abstract
Many dyes that are used in the textile industry are toxic and tend to accumulate
in living organisms directly or indirectly, causing various diseases and disorders.
Clay minerals have recently been shown to be good candidates as dye adsor-
bents for wastewater treatment. This review discusses the use of both natural and
modified three-layer clays such as bentonite, montmorillonite, and vermiculite to
remove both cationic and anionic dyes. The most important parameters governing
adsorption capacities are pH, ionic strength, and modification processes. Specific
surface area is somewhat less important. Modification processes include thermal
activation, acid activation, surfactant addition, and combinations of these, all of
which increase adsorption capacities. Adjusting the pH changes both adsorbent
surface properties and adsorbate dye ionization.
Keywords: Bentonite, montmorillonite, cationic dyes, anionic dyes, adsorption,
dye removal
9.1 Introduction
Dye-containing wastewaters from the textile industry are one of the main
pollutant sources worldwide. There are over 100,000 different textile dyes
with an estimated annual production of 7.10 5 metric tons. Of these dyes,
30% are used in excess of 1,000 tons per annum and 90% are used at the
level of 100 tons per annum [1-5]. In addition to the textile industry, the
 
 
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