REMOVAL OF DYES FROM WASTE WATER

Abstract

Adsorption has received great attention in the recent years as an efficient process for wastewater treatment. Besides dyes several other substances like phenolic compounds and heavy metals can be effectively removed from the wastewater by adsorption. Among the various adsorbents employed for the purpose, activated carbon has found wide acceptance by virtue of its high removal capacity and adaptability for a wide range of dyes. Adsorption of Metanil Yellow and Methyl Blue Onto granular activated carbon was studied in batch and continuous systems using synthetic wastewater. The effect of dye concentration, particle size of the activated carbon and the solution pH was studied in batch experiments. The effect of bed height was examined in adsorption columns. Removal to the tune of 97% and 99% respectively for Metanil Yellow and Methyl Blue is achieved for a dye solution concentration of 20 mg/1 in a batch reactor. Batch studies further reveal that the dye removal decreases with increasing initial dye concentration and large particle size of the activated carbon. The equilibrium behaviour corresponds to the Freundlich equation for both the dyes. The equilibrium is favourable at a higher pH range.Lagergren plots for the two dyes suggest a first order rate kinetics. Adsorption in a downflow fixed bed column gives effective dye removal. The effect of bed height on the breakthrough time for the two dyes is examined based on the Bohart - Adams model and the constants are evaluated.