Facile preparation of chitosan-coated biomass-based magsorbent beads for effective uptake of methylene blue from aqueous solution

The aim of this study was to develop a nFe(3)O(4)/citric acid-modified wheat straw (MWS)/chitosan (Cht) biocomposite adsorbent (nFe(3)O(4)@MWS/Cht) for removal of methylene blue (MB) from aqueous media. Experimental parameters such as dye concentration, contact time, amount of nFe(3)O(4)@MWS/Cht, solution pH, and temperature, which affect the adsorption process, were investigated. Isotherms and kinetics studies investigated the dye removal dynamics of the biocomposite system. The adsorption experimental data were analyzed with the Langmuir, Freundlich, Scathard, Temkin, and Dubinin-Radushkevich isotherms, widely used in aqueous solutions, and it was decided that the Langmuir is the most suitable isotherm. The maximum adsorption capacity of the monolayer was calculated to be 102.04 mg/g. The optimum contact time and adsorbent dose were determined as 2 h and 2 g/L. Adsorption experimental data were applied to pseudo-first-order and pseudo-second-order kinetic models and it was decided that the most suitable kinetic model was pseudo-second-order. In thermodynamic studies, it was determined that MB adsorption is a spontaneous and exothermic process. Possible interactions of the MB-biocomposite adsorbent were characterized by zeta potential, FTIR, XRD, and SEM analyses. The results showed that the developed biocomposite adsorbent could be an effective alternative for the removal of cationic dyestuffs from aqueous media because of its very high color removal capacity.