4. Conclusion
Activated charcoal is efficiently utilized as an adsorbent for
the removal of hazardous dyes from the aqueous solutions. The
adsorption isotherms for all the dyes investigated here are of
L-type however for tertiary mixture of dyes the isotherms are Stype.
The adsorption of all the dyes was found to decrease with
the increase in temperature. The BET isotherm was not obeyed
by all the dyes, suggesting that the adsorption on activated charcoal
is chemisorption and the value of −H between 26 and
55 kJ mol−1 also confirm this. The adsorption also decreased
with the pH except in case of methylene blue and malachite
green. The negativeGandHvalues showthat the adsorption
of dyes on activated charcoal is spontaneous and exothermic.