Enhanced adsorption properties of Algerian bentonite modified by starch and glycerol for methylene blue and red methyl retention

This paper describes the preparation of novel bentonite-starch composites and assesses their effectiveness as adsorbents for removing methylene blue (MB) and methyl red (MR) dyes from aqueous solutions. The adsorbents were characterized using X-ray diffraction and FTIR spectroscopy. This study is aimed to optimize the removal process by investigating the effect of pH, adsorbent dose, contact time and initial concentration. The sorption kinetics of MB and MR dyes were analysed using the pseudo-first order and pseudosecond order models. The experimental results indicate that the pseudo-second order kinetic model provides the best fit. The composite adsorbents exhibited a sorption capacity for MB, ranging from 146.21 to 157.58 mg g-1 for bentonite? ?starch (Bt@star) and bentonite?starch?glycerol (Bt@star@gly), respectively. The sorption capacity for MR dye was 426.38 mg g-1 for Bt@star and 309.82 mg g-1 for Bt@star@gly. Furthermore, the correlation coefficient values indicate that the adsorption of MB and MR by Bt@star@gly is best described by the Langmuir model, which unequivocally implies that the adsorbent surface is homogeneous, resulting in monolayer adsorption. The Langmuir model also accurately describes the adsorption of MB onto Bt@Star. However, the Freundlich isotherm model is the best fit for the adsorption of MR, indicating the existence of multilayer adsorption. Finally, this study demonstrates that the composite adsorbents prepared herewith exhibit excellent adsorption performance and can be a cost-effective alternative for treating coloured wastewater.