Development of magnetic La doped AlO core-shell nanoparticle loaded hydrogel for selective recovery of fluoride from aquatic medium.

The selective removal of pollutants from water bodies is regarded as a conciliation between the rapid expansion of industrial activities and need of clean water for sustainability. Fluoride is one such geogenic pollutant, and various materials have already been reported. Developing an efficient field employable material is however a challenge. Herein, we report the synthesis and competencies of strategically designed magnetic La-doped AlO core-shell nanoparticle loaded polymeric nanohybrid as a benchmark fluoride sorbent. A facile synthesis strategy involved fabrication of FeO magnetic core followed by growth of La doped AlO shell using sol-gel method. Doping of LaO into AlO structure was optimised (6%), resulting in FeO-Al LaO core-shell particles which provided exceptional fluoride affinity. The obtained magnetic FeO-AlLaO core-shell nanoparticles were then loaded (22%) into alginate to form cross-linked hydrogel beads (FeO-Al La O-Ca-ALG). These prepared hydrogel beads were characterised and utilized for selective recovery of fluoride under different ambient conditions. Driving forces for enhanced fluoride uptake by La doped AlO were investigated and explained with the help of both experimental observation and theoretical simulation. Density functional theory calculations indicated significant expansion in the cell volume of AlO due to La doping which favoured the fluoride sorption. The calculated defect formation energy for the incorporation of F into AlO was found to decrease in the presence of La. XPS analysis suggested direct interaction of fluoride with Al, forming Al-F bond and breaking Al-O bond. Different vital parameters for uptake were optimised. Also, kinetics, isotherm and diffusion models were evaluated. Developed hydrogel beads attained record sorption capacity of 132.3 mgg for fluoride. Overall, excellent stability, no leaching of constituents, effectiveness for selective fluoride recovery from groundwater, brand it a perfect epitome of sustainable water treatment application.