Adsorption of dyes on sawdust phosphate: Kinetics and equilibrium studies

Abstract

The distribution coefficients, Kd, for navy brown 3REL, direct red, procion red H8B, methylene blue, metamega chrome yellow and lanasyn green 5 GL, solar violet and procion blue H5G from their aqueous solutions, at pH 3.2 and 7.5 on saw-dust phosphate (SDP) have been reported. Effect of pH and added surfactant concentration on the percent removal of lanasyn green 5 GL has been studied. Percent dye removal increases with the decrease in pH. The applicability of the Freundlich and Langmuir equation has been tested for equilibrium data of which Langmuir isotherm model is found to be most appropriate. The values of Langmuir and Freundlich constants as well as the distribution constants show that SDP is a good adsorbent for all dyes, being better for basic dyes. The kinetics of adsorption of lanasyn green 5 GL on SDP was investigated at pH 3.2 and temperatures 25, 30, 35 and 40ºC. It is first order with respect to the dye and less than unity with respect to SDP. The values of kad, kp and kք at 30º was found to be 2.18 x 10⁻⁴ s⁻¹, 15.33 x 10⁻⁵ s⁻¹ and 20.72 x 10⁻⁴ s⁻¹ respectively.