Trimetallic oxide entrapped in alginate polymeric matrix employed for adsorption studies of fluoride

A biopolymer-based adsorbent synthesized by entrapping trimetallic oxide into the polymer matrix was employed for the adsorption of health hazardous (F-) from aqueous systems. Adsorption techniques were utilized to study the adsorption behavior of F- onto Fe-La-Ni oxide entrapped calcium alginate beads (Ca@FLN). To prove the adsorption mechanism, nine different adsorption isotherms were utilized for the study of adsorption-Langmuir, Freundlich, Temkin, Dubinin - Radushkevich (DR), Halsey, Sips, Elovich, Harkins-Jura, and Redlich Peterson, of which Freundlich isotherm model was the best fit. The adsorption involved anion exchanges and electrostatic interactions which were confirmed by XPS and IR studies. The kinetic study of F- adsorption showed that the pseudo-second-order (PSO) model is a better fit as compared to other kinetic models. The feasibility and spontaneity of endothermic adsorption process were confirmed by the thermodynamic study. The synthesized novel Ca@FLN entrapped in the polymeric matrix shows a very high adsorption capacity i.e. 333 mg/g due to a very high surface area (257 m(2)/g). The Ca@FLN could be developed into a very viable technology for highly effective adsorption of F- from polluted water to make it suitable for drinking with a permissible F- content of 1.5 mg/L as per World Health Organization (WHO).