Eco-friendly chitosan/κ-carrageenan membranes reinforced with activated bentonite for adsorption of methylene blue

In this work, the chitosan/κ-carrageenan/acid-activated bentonite composite membranes were prepared through blending method and used to adsorb methylene blue dye. The prepared composite membranes were characterized with several spectroscopic and microscopic techniques. The results revealed that the bentonite was homogeneously distributed in the membrane matrix, which means extensive porous structure was formed on the surface. The effects of initial concentration of methylene blue, adsorbent dosage, pH value, contact time, ionic strength, and temperature on methylene blue removal percentage the prepared membrane was investigated in detail. Adsorption kinetics and equilibrium adsorption isotherm fitted pseudo-second-order kinetic model and Freundlich isotherm model well, respectively. The thermodynamics analysis suggested that the adsorption process of methylene blue onto the chitosan/κ-carrageenan/acid-activated bentonite composite membrane was spontaneous and endothermic. The highest removal rate (98%) was achieved under the following conditions: adsorbent dose, 0.05 g; solution pH, 4; temperature, 50 °C; and time, 200 min. The maximum adsorption capacity for methylene blue was 18.80 mg/g at 50 °C. Moreover, the prepared composite membrane demonstrated the high reusability and adsorption rate (∼77%) without significant loss after sixth adsorption-desorption cycles. Considering of the above results, the prepared composite membrane can be a promising adsorbent candidate having low cost and high recyclability to remove methylene blue.