Adsorptive removal of methylene blue from aqueous solution using prepared chitosan-furfural Schiff base

Abstract

This study was aimed at preparing chitosan-furfural Schiff base (CFSB) as an effective adsorbent for the removal of methylene blue from aqueous solution. The research demonstrates the formation of Schiff base by the reaction of chitosan and furfural, resulting in a material with remarkable adsorption efficiency, capable of removing methylene blue from aqueous solution. The structural and morphological characteristics of the adsorbent were evaluated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET) and Energy dispersive X-ray microanalysis (EDS). For FTIR, it was observed that chitosan furfural Schiff base showed characteristic absorption peaks at 3290.35cm^-1 which is attributed to OH, N-H in NH₂, 1644.47cm^-1 , 1552.69cm^-1 , 1150.38cm^-1 and 1022.02cm^-1 are attributed to C=N (Imine linkage), the presence of the C=C cyclic alkene, C-O ether stretch and C-O stretch of primary alcohol in –CHO of furfural respectively. The SEM analysis, showed a rough large pore surface, the BET analysis showed that it had a large surface area 339.85 m² /g, a pore diameter of 2.94nm and a pore volume of 0.194 cm³ / g. The result of EDS confirms the percentage of silicon, oxygen, carbon, magnesium, calcium, iron and aluminium as major elements alongside trace of potassium, sodium and sulphur. The prepared material was used to adsorb aqueous methylene blue. It was observed that percentage removal of methylene blue increase steadily from 33.450% to 59.934% with a corresponding increase in the initial concentration from 10 mgL^-1 to 50 mgL^-1 . The results obtained were evaluated with Langmuir and Freundlich adsorption isotherm. It was observed that the Freundlich isotherm adsorption data with R² value of 0.934 was found to be best fit when compared to that of Langmuir isotherm, R² value of 0.930. The R² values are regarded as a measure of the best fit of experimental data on the isotherm model. It is more suitable to describe the relationship between the amounts of methylene blue adsorbed by the chitosan-furfural Schiff base and this indicates the material proved uptake onto heterogeneous adsorbent surfaces.