New alginic acid derivatives ester for methylene blue dye adsorption: kinetic, isotherm, thermodynamic, and mechanism study

In this paper, the application of ester materials prepared by grafting different carbon chain lengths of diols in alginic acid (AA) by a simple, fast and efficient method for the adsorption of methylene blue (MB) is studied. The AA ester derivatives are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Zeta potential before and after MB adsorption. This study shows a significant improvement in the adsorption capacity of MB by AA after its esterification with a Qmax value up to 454.545 mg/g for the best adsorbent “Poly(AA-g-EG)”. The experimental data are studied according to two isothermal models (Langmuir and Freundlich) and two kinetic models (pseudo-second order and intra-particle diffusion). The adsorption of MB is also evaluated thermodynamically. An adsorption mechanism of MB is established. [Display omitted] •Four different ester derivatives based on alginic acid were prepared and applied to remove Methylene Blue from water.•The ester derivatives were characterized using FTIR, TGA/DTG, SEM, Zeta potential, AFM, and XPS.•Esterification of alginic acid improves its adsorption capacity for methylene blue.•Poly(AA-g-EG) showed a maximum capacity of more than 454 mg/g.•The kinetics, isotherm, and thermodynamics of the adsorption are studied in detail.