Removal of methyl orange and methylene blue from aqueous solution using dragon fruit foliage

The application of dragon fruit foliage (DFF) was investigated for decolourization of cationic and anionic dyes from aqueous solution. The effect of initial dye concentration, pH, amount of dragon fruit foliage, ion strength and contact time on adsorption capacity of DFF were investigated in batch and continues mode. A maximum adsorption capacity (maximum amount of dye in mg that can be adsorbed to 1.0 g of foliage) of 105 (mg/g) and 21.27 (mg/g) were obtained for removal of cationic dye (methylene blue,MB) and anionic dye (methyl orange, MO) respectively. Based on the obtained results for the tested cationic and anionic dyes, methylene blue was chosen to study the effect of modification on the dye removal ability of dragon fruit foliage. The results determined that the adsorption capacity of DFF increased from 105 to 133 (mg/g) after modification. Dye adsorption over the adsorbent was evaluated by the use of Freundlich and Langmuir adsorption isotherm models and it was found that the adsorption isotherm data of both mentioned dye in all three parts, best fitted the Freundlich model. The kinetic study data were well-represented by the pseudo-second-order kinetic model. The results suggest that dragon fruit foliage is more effective in removal of cationic dyes rather than anionic ones. In column test effect of flow rates and bed heights were the experimental parameters selected to obtain breakthrough curves. The maximum uptake of MB in a fixed bed adsorption column was 83 mg/g at pH 8, bed height 15 cm and flow rate 3 mL/min. The breakthrough time increased with a longer bed height and slower flow rate. Bohart–Adams and BDST models were applied to the data for predicting breakthrough curves and to determine the model,parameters. Results from the experiments revealed that, DFF may be useful as an alternative low cost and environmental friendly biosorbent for theremoval of cationic dyes from aqueous solutions.

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