Biosorption of Acid Dyes Using Spent Brewery Grains: Characterization and Modeling

In the present work the brewery industry waste is taken as a low cost biosorbent for the removal of acid dyes from the aqueous solution. Biosorption of acid dyes (Acid Yellow - AY 17 and Acid Blue - AB 25) onto spent brewery grains (SBG) was investigated. The biosorbent material is characterized using scanning electron microscopy, FT-IR spectroscopy, XRD and BET surface area. The dye binding capacity of biosorbent was shown as a function of initial pH, initial dye concentration, biosorbent dosage, contact time and temperature. Equilibrium uptake was found to be pH dependent and maximum uptake was observed at a pH of 2 for both the dyes. Colour removal was found to decrease with initial dye concentration, temperature and increase with biosorbent dosage and time. The equilibrium data fitted very well to Freundlich adsorption model. The results showed that both the dyes uptake processes followed the second-order rate expression. The study confirms that the spent brewery grains can be used as biosorbent for the removal of acid dyes from its aqueous solution.