Study on the adsorption of Methylene blue by fly ash modified with activated sludge

Fly ash was modified with activated sludge, then the adsorption property on Methylene blue was studied. And the results indicated that fly ash modified with activated sludge showed very effective adsorption on Methylene blue compared with fly ash, and the adsorption capacity increased with the adding amount of activated sludge, achieving 9.08 mg/g when wt% of sludge was 50%, higher than the single additive of fly ash and activated sludge, presenting obvious synergy effects. The kinetics of methylene blue adsorption onto activated sludge/fly ash was determined by batch experiment, and the obtained data were analyzed by pseudo-second-order and intraparticle diffusion equation. The sorption processes were found to follow pseudo-second order kinetics. And when wt% of sludge was above 43%, intraparticle diffusion could be accepted as the primary rate determining step. The sorption processes and mechanism of Methylene blue onto the modified fly ash changed. SEM and EDS micrographs indicated that the introduction of sludge changed the surface property and metal kinds of fly ash. In addition, the parameters of dosage, initial pH value, initial concentration of Methylene blue and temperature influenced the sorption process were also investigated.