Highly reusable plant-based biosorbent for the selective methylene blue biosorption from dye mixture in aqueous media

Abstract

The natural Polygonum cognatum (P. cognatum) was utilized as a selective biosorbent for the biosorption of methylene blue (MB) from dye mixtures (MB/RhB and MB/MO), separately. P. cognatum was characterized by using SEM–EDX, FT-IR, TGA, BET surface area and zeta measurement techniques. The effects of diverse parameters on the biosorption were investigated, and the kinetic and isotherm models were applied to obtain data to exhibit the biosorption mechanism. The characterization results showed that P. cognatum had various functional groups and also roughness, irregularity and cavities on the structure with the BET surface area of 57.65 m2/g. P. cognatum biosorbed the MB selectively with an attractive efficiency from MB/RhB and MB/MO mixtures and the maximum biosorption capacity of P. cognatum was calculated as 426.39 mg g−1 for MB at pH ~ 5. The selective biosorption could be ascribed to the electrostatic and weak interactions between smaller cationic dye (MB) and negatively charged biosorbent surface with a zeta potential value of − 26.30 mV at pH 5. The pseudo-second order kinetic and Langmuir isotherm models have well-defined the biosorption process. Moreover, P. cognatum showed high biosorption (97.54%) and desorption (100%) efficiencies after ten repeated cycles for MB biosorption. P. cognatum with a high biosorption capacity could be a reusable biosorbent for the selective MB biosorption from dye mixtures. Polygonum cognatum (P. cognatum) selectively biosorbed MB over RhB and MO from the dye mixtures with the maximum biosorption capacity of 426.39 mg g−1. The selective biosorption could be attributed to the electrostatic and weak interactions between smaller cationic dye (MB) and negatively charged biosorbent surface. P. cognatum showed highly reusability after ten repeated cycles for MB biosorption.