Synthesis of Glutaraldehyde Cross-Linked Magnetic Alginate/Banana Peel Biocomposite for the Removal of Methylene Blue: Kinetic, Thermodynamic and Equilibrium Studies

Abstract

One of the specific pollutants worldwide is dyes. These must be removed from wastewater before being discharged into receiving environments. In this study, the adsorption of methylene blue (MB), used in many industries, from its aqueous solution onto glutaraldehyde cross-linked nano Fe3O4/banana peel/alginate beads (g-BP/ALG@Fe3O4) was examined. Biocomposite beads were prepared by incorporating nano Fe3O4 powder and banana peel powder into a calcium alginate gel using a simple 'mix and drop' synthesis. Characterization of the synthesized g-BP/ALG@Fe3O4 was carried out by FTIR, SEM, EDX-mapping and XRD. In the study, for MB adsorption in the batch system with g-BP/ALG@Fe3O4, adsorbent amount (1-8g/L), pH (3-9), contact time (5-360min), temperature (25-55 degrees C), initial dye concentration (10-300mg/L) optimum removal conditions were examined. The optimum conditions obtained were determined as pH6 (original solution pH), temperature 25 degrees C, amount of adsorbent 4 g/L, and contact time 180 min. To calculate isotherm parameters and examine adsorption kinetics, Langmuir, Freundlich, Tempkin, Scarthard, D-R adsorption isotherm models and pseudo-I-order kinetic, pseudo-II-order kinetic, elovich, intraparticle diffusion kinetic models equations were applied. It was determined that the adsorption process conformed more to Langmuir isotherm model and adsorption capacity was determined as 75.76 mg/g. The adsorption process followed the pseudo-II-order kinetic model, thermodynamic studies revealed that it was an exothermic and spontaneous process. This new adsorbent, synthesized for reasons such as the high removal capacity of waste banana peels, cheap, environmentally friendly, recyclable, and the fact that alginate as a biopolymer does not harm the environment, has been found to be an effective and alternative material when compared to different adsorbents in the removal of MB dye from aqueous media.