Adsorption of basic dyes from aqueous solution by natural adsorbent

Abstract

The capability of the Sagaun sawdust for removing basic dyes (crystal violet, methylene blue, malachite green and rhodamine B) from aqueous solutions has been investigated. The effect of system variables such as concentration, temperature, <i>p</i>H and particle size have been studied to understand equilibrium and kinetics of adsorption process. The maximum removal was found to be 89% at concentration 6.0 mgL^-1, temperature 30⁰C and <i>p</i>H 7.5 . The amount of the dye(crystal violet and methylene blue) adsorbed, decreases from 2.773 mg g^-1 (86.68%) to 2.310 mg g^-1 (72.19%) and 2.672 mg g^-1 (83.52%)<i> </i>to 2.205 mg g^-1 (68.93%) with the rise of temperature of dye solutions from 25 to 45⁰C<i> </i>indicating the process to be exothermic. The value of k_ad of crystal violet at 25 , 35 and 45⁰C were found to be 9.72x10^{- 2}, 9.57x 10^-2 and 9.25x10^-2 min^-1 ,respectively. The adsorption capacity for dye-adsorbent system has been determined. The dye adsorption follows the Langmuir isotherm. On the basis of isotherm studies, various thermodynamic parameters such as Δ<i>G</i>⁰, Δ<i>H⁰ </i>and Δ<i>S</i>⁰ have been calculated.