Performance evaluation of phosphate based new cellulose derivative as efficient biosorbent for methylene blue

Abstract Novel cellulose derivatives containing phosphate groups (phosphate@cellulose) have been synthesized for the first time for organic dyes adsorption. Dialdehyde cellulose was synthesized via selective oxidation with sodium periodate. O -phosphorylethanolamine was introduced to the cellulose backbone through the Schiff-base formation followed by reductive amination with 2-picoline borane. TGA analysis revealed that phosphate modification significantly improved the thermal stability of cellulose. SEM confirmed the morphological transformation, while EDX analysis verified the incorporation of nitrogen and phosphorus. XPS analysis confirmed the functionalization with phosphate groups, as evidenced by the appearance of distinct N1s and P2p peaks. Methylene blue adsorption revealed that phosphate@cellulose exhibited a maximum adsorption capacity of 399 mg/g. Chemisorption is implied by the adsorption kinetics, which follow a pseudo-second-order model, and the data aligned well with the Langmuir isotherm model. Thermodynamic evaluation exposed that the adsorption is spontaneous, endothermic, and accompanied by an increase in entropy, demonstrating favorable interactions between the phosphate@cellulose and MB molecules. Significantly, phosphate@cellulose demonstrated potential for regeneration and reusability over several cycles. Given the findings, phosphate@cellulose derivative could be considered as an efficient biosorbent for the elimination of cationic dyes from industrial wastewater and compelling alternative to conventional adsorbents. Graphical abstract