Synthesis and characterization of lanthanum impregnated chitosan flakes for fluoride removal in water

In the present research work, biopolymer chitosan has been modified by impregnation of lanthanum to enhance the fluoride removal capacity of chitosan. The effect of various synthesis parameters like lanthanum loading, stirring time and drying temperature, on fluoride removal has been studied. It was observed that the synthesis parameters have significant influence on development of LCF and in turn on fluoride removal capacity. The adsorbent has been characterized with XRD, SEM and FTIR studies. The optimal condition for synthesis of LCF includes lanthanum loading: 20 wt.%, stirring time: 6 h, drying temperature: 75 °C for 2 h with maximum adsorption capacity of 1.27 mg/g. XRD Pattern of LCF was compared with bare chitosan which shows that chitosan structure is retained after lanthanum impregnation. SEM of LCF shows the presence of spherical particles spread over the chitosan matrix. The experimental data fitted well in Freundlich isotherm and follows pseudo-second order kinetics and governed by intra-particle diffusion and it is a complex process. Effect of pH and effect of presence of interfering ions on adsorption of fluoride were studied. The performance of LCF was compared with many other reported adsorbent for fluoride removal. Reuse and regeneration capacity of LCF was also explored.

Graphical AbstractFigure optionsDownload as PowerPoint slideResearch Highlights
► Lanthanum impregnation on chitosan enhanced the fluoride adsorption capacity and selectivity for fluoride.
► SEM images show the lanthanum impregnation on chitosan where small spherical particles of lanthanum are observed on chitosan surface.
► Synthesis parameters like lanthanum loading and stirring time during synthesis has significant effect on fluoride adsorption.
► Synthesis of LCF has been optimized for defluoridation.