Adsorption of Methylene Blue from Aqueous Solution - A Comparative Study for Colour Removal Efficiency of Bagasse Fly Ash and Brick Kiln Ash

Abstract

The excessive release of colour into the environment is a major concern worldwide. In this study, the use of low-cost adsorbents has been investigated as a replacement for the current conventional and often expensive methods of removing dyes from aqueous solutions. The adsorptive removal of Methylene blue dye was achieved using a packed bed column (down flow method), comparing Bagasse Fly Ash and Brick Kiln Ash as adsorbents. The effects of various factors such as influent concentration, flow rate and bed height were analysed. The column experiment showed that for the optimum influent concentration of 50 mg/l, the concentration dropped to 0.080 (99.83% reduction) and 0.097 (99.80% reduction) mg/l respectively after treatment by Bagasse Fly Ash and Brick Kiln Ash respectively. For 10cm bed height and 10ml/min flow rate, beyond 50mg/l concentration of dye, the capability for removing dye decreased. For the different bed heights, the percentage reduction increased with the increase in bed height due to the availability of more number of sorption sites. At optimum bed height (7.5cm), the percentage reduction achieved was 99.72% and 99.70% respectively. For the different flow rates, the percentage reduction decreased with the increase in flow rate because at higher flow rate, the contact time between adsorbate and adsorbent was minimized. At optimum flow rate (10ml/min.), the percentage reduction achieved was 99.62%, and 99.70%, respectively for Bagasse Fly Ash and Brick Kiln Ash. It is concluded that while Bagasse Fly Ash shows 0.03% higher efficiency than Brick Kiln Ash, this difference is too small to conclude that Bagasse Fly Ash is better than Brick Kiln Ash in terms of removing Methylene blue dye. However, Both Bagasse Fly Ash and Brick Kiln Ash can be deemed to be more effective than conventional methods. Also Freundlich isotherm was found to best fit for both of the adsorbents indicating that this study can be used for large scale treatment.