Reuse of Activated Sludge Biomass: Equilibrium Studies for the Absorption of Basic Dyes on Biomass

Abstract

The absorption equilibriums of Basic Yellow 24 and Basic Blue 54 dye by an activated sludge biomass (empirical formula, C₆₀H₁₁₀O₂₇N₈S) are studied. The optimum equilibra tion parameters investigated are 12 hours' equilibration time, 0.8 g L^-1 biomass dose, 150-300 μm biomass particle size, 300 ppm initial dye concentration, and 30°C dye solution temperature. The experimental results indicate that for two basic dyes with the same chemical class (thiazole azo) and nearly the same molecular weight, the optimum absorption equilibria are the same but the maximum absorption capacities are different. These absorptive differences could exist because the more hydrophobic residues a dye molecule contains, the more basic dyes the biomass absorbs. The results of analyzing equilibration data show that for the absorption equilibria of two basic dyes absorbed by biomass, the Langmuir absorption isotherm is a better fit than the Freundlich isotherm. The absorption process is exothermic in nature and the absorption type is chemisorption.