Abstract:
Huge consumption of water and low biodegradability of textile dye wastes calls for a
combination of biological, chemical, physico-chemical and physical processes along with
a complementary treatment process to remove more of the dyes. Persistent aromatic
structure and recalcitrant nature of various dyes and textile chemicals makes the
biological treatment not always successful in the treatment of cotton textile wastewater.
Chemical methods also have limitations. No universally accepted and efficient method is
yet developed for dye removal.
In the present study water-soluble reactive azo dyes , fast red RC salt and solar yellow
BG were removed from water using locally available industrial by product, a waste
residue generated from the manufacture of alum from kaolin by the sulfuric acid process.
Batch experiments are carried out for the sorption of fast red salt RC and solar yellow
BG onto the adsorbent. The operating variables studied for that of FR-RC salt are
adsorbent dose, contact time, system pH, initial dye concentration, and kinetics and
adsorption isotherms. And for SY-BG the operating variables studied are adsorbent dose
and contact time. The mechanism of dye adsorption for FR-RC salt onto the media is
investigated by using the experimental results. The adsorption process is slow for FR-RC
salt; requiring 30 hours to reach equilibrium and an adsorbent dose of 19g/L is optimum
for this equilibrium contact time for 77.4 % removal efficiency. For SY-BG the
equilibrium contact time and optimum dose are 12 minutes and 0.3g/L respectively for
99.3 removal efficiency. When the pH of the system is 7to9 the dye removal efficiency for
FR-RC salt is greater than 90%. For the given concentration range the removal of dye
from water was not depend on initial dye concentration for FR-RC salt. The adsorption
process was found to undergo via a pseudo-second-order adsorption kinetics with a rate
constant of 3.81X10-3(g mg-1min-1). The equilibrium data are fitted to Freundlich
isotherm equations for that of FR-RC salt. From these the adsorption efficiency,
adsorption capacity and intensity of adsorption are calculated. The overall result shows
the adsorbent is efficient decolorizing material.
Key Words: Textile dye, Batch decolorization, an industrial by product; Dye removal
efficiency, Adsorption capacity, equilibrium time.