Enhancing the adsorption capacity of modified biopolymer thorugh anionic hydration effects for dye removal from water

In this study, a pyridinium modified based biopolymeric adsorbent has been prepared and its adsorption capacity towards methylene blue was investigated. The polymer extracted from flax seed was modified via furfural, resulting in an insoluble adsorbent containing furfuryl and pyridinium moieties. The characterization was performed via spectroscopic methods (¹³C solids NMR, FT-IR, Raman), thermogravimetric analysis (TGA), and ζ-potential (DLS). The presence of furfuryl and pyridinium moieties was evidenced via ¹³C NMR. The material presents a negative surface charge above pH 4.5. To enhance the adsorption capacity, the material was pretreated in various salt solutions and compared to only water soaked adsorbent. The application of sulfate and phosphate resulted in a small increase of dye uptake (ca. 36 % removal), compared to the chloride ion (ca. 50-60 % removal) or perchlorate and thiocyanate (94-97 % removal). The pretreatment of adsorbent material with various sodium salts showed that the adsorption capacity towards model dye was tripled, compared to non-pretreated adsorbent. Further, adsorption capacity increased based on using perchlorate and thiocyanate salts. The regeneration experiments showed that the salt application (compared to no salt pretreatment) can further increase the % removal of the model dye (methylene blue) from solution for the first three cycles and remains high up to 6 cycles.