Phragmites australis: An alternative biosorbent for basic dye removal

• Phragmites australis, as a plant biomass, was experimentally tested for dye removal.
• Modification on OH groups resulted in an increase on the adsorption capacity about 2.2-fold.
• The reuse rate of the biomass was affected positively by modification, raising from 22% up to 65%.
• Temperature and pH ranges for maximum adsorption needed not much adjustment during practical applications.
• Equilibrium and thermodynamic studies showed that the adsorption process is physical.

This study is aimed at investigating the removal of methylene blue (MB) from aqueous solutions using a reed species, Phragmites australis as an adsorbent. P. australis was modified by means of a chemical treatment, assuring the alteration of hydroxyl groups to sulphonyl groups. Experiments were performed in the batch mode to determine the adsorption dynamics of the modified and untreated P. australis. The impact of several influential parameters such as initial pH, initial dye concentration and contact time on the adsorption capacity of P. australis was evaluated. The adsorption capacity of raw P. australis was found to improve significantly by modification reaction. The maximum sorption capacities of the raw and modified biomass were found to be 22.7 mg/g and 46.8 mg/g at initial MB concentration of 250 ppm, biosorbent dosage 0.25 g and initial dye solution of pH of 6.5, respectively. Dye adsorption equilibrium data were fitted well to the Langmuir isotherm rather than the others. The rate of adsorption followed the pseudo second-order kinetic model. Thermodynamic parameters for both raw and modified biomass showed that the adsorption of MB was favorable and spontaneous. Results showed that both P. australis and its modified form have a potential as an eco-friendly adsorbent for the removal of methylene blue from aqueous solution.