Biosorption of Methylene Blue from Aqueous Solution Using Lawny Grass Modified with Citric Acid

Using the low cost of lawny grass to remove methylene blue (MB) from aqueous solution was evaluated in the batch process and the fixed-bed column. The MB adsorption capacity onto CG (grass modified with citric acid) was 301.1 mg . g(-1) biomass, which was almost three times than that of RG (raw grass). The equilibrium could be explained as pseudofirst-order kinetic processes, and equilibrium time was shortened to 20 min (CG) from 40 min (RG). The adsorption equilibrium followed the Langmuir isotherm model. The desorption rate with 0.1 mol . L-1 HCl was almost 90 %. Regenerated CG was reusable with a little decrease (only about 3.38%) in its adsorption capacity during six repeated cycles. In the fixed-bed column, the breakthrough point of CG begins at 183 BV, which was much higher than that of RG (56 By). The elution process was achieved in a very small HCl volume.