Biosorption of Methylene Blue Dye onto Three Different Marine Macroalgae: Effects of Different Parameters on Isotherm, Kinetic and Thermodynamic

In the present study, the removal of a cationic dye, methylene blue (MB) with brown (Nizamuddinia zanardinii), red (Gracilaria parvispora) and green (Ulva fasciata) macroalgae was studied. The effects of different parameters such as initial solution pH, initial dye concentration, biomass dosage and contact time were investigated on the biosorption of MB by algae. Biosorption isotherm was modeled using the Langmuir, Freundlich and Temkin models. The highest MB dye removal efficiency onto algae was observed in the range of 5–11. Increasing biosorbent dosage from 80 to 240 mg/L, significantly increased the removal efficiency of MB dye; however, increasing the biosorbent dosage above 240 mg/L up to 400 mg/L did not significantly increase the dye removal efficiency. The biosorption of MB dye onto macroalgae reached equilibrium after about 90 min. Based on the Langmuir model, the uptake of MB by brown, red and green algae was determined as 863.4, 83.08 and 1514 mg/g, respectively. The biosorption kinetic data were successfully described with pseudo-second-order model for three biosorbents. FT-IR spectrum analysis suggested amido or hydroxyl, C=C and C–H groups present on algae surface could take part in MB dye biosorption.