Sonochemical treatment of fly ash for dye removal from wastewater.

Fly ash samples modified by NaOH solution and sonochemical treatment were tested for a basic dye (methylene blue) adsorption in aqueous solution. It is found that sonochemical treatment of fly ash can significantly increase the adsorption capacity depending on the concentration of NaOH and treatment time. The untreated FA and the sonochemically treated sample exhibits adsorption capacity at 6 x 10(-6)mol/g and 1.2 x 10(-5)mol/g at 30 degrees C, respectively. The adsorption tests show that solution pH and adsorption temperature also influence the adsorption behaviour. The adsorption isotherms can be fitted by Langmuir and Freudlich models, while the two-site Langmuir heterogeneous model will present the best result.