Investigation of Hydroxyapatite-Entrenched Cerium Organic Frameworks Incorporating Biopolymeric Beads for Efficient Fluoride Removal

Design of hydrotalcite and biopolymers entrapped tunable cerium organic cubic hybrid material for superior fluoride adsorption

The excess fluoride in drinking water is serious risk which leads to fluorosis. The adsorption method is facile route for defluoridation studies. Hybrid adsorbent possesses unique advantages like high surface area and high stability has been employed for water treatment. In the present work, hydrotalcite (HT) fabricated Ce-metal organic frameworks (MOFs) bridged with biopolymers (alginate and chitosan) namely HT-CeMOFs@Alg-CS cubic hybrid beads was developed and employed towards fluoride removal in batch mode. The fabricated HT-CeMOFs@Alg-CS beads were analyzed by DTA, FTIR, SEM, EDAX, TGA and XRD studies. Besides, FTIR and EDAX proved the affinity of HT-CeMOFs@Alg-CS cubic hybrid beads on fluoride was majorly attributed by electrostatic interaction, ion-exchange and complexation mechanism. To include detail insight into adsorption route; the kinetics, thermodynamic and isotherm studies were investigated for fluoride adsorption. The equilibrium data of HT-CeMOFs@Alg-CS cubic hybrid beads for fluoride adsorption was fitted with Langmuir isotherm model. Thermodynamic investigation results demonstrated that the fluoride adsorption was spontaneous with endothermic nature. The regeneration and field investigation results revealed that the developed HT-CeMOFs@Alg-CS cubic hybrid beads are reusable and more apt at field environment.

Construction of HAnW-based nanotwigs for removing inorganic fluorion in wastewater

The environmental pollution with fluoride compounds was currently being paid more and more attention as it threatens the safety of animal and human life in an ecosystem. In this study, an eco-friendly adsorbing material for removing fluoride ion (F^-) was prepared by hydroxyapatite nanowires (HAnWs), a typical biocompatible inorganic conjugates. UiO66, a typical zirconium-based metal-organic framework (MOF), was conjugated onto HAnW by a simple in situ hydrothermal reaction, which afforded a novel HAnW-based nanotwigs of conjugates like millet (UiO66@HAnWs). Being characterized by SEM, EDS, FT-IR, XRD, XPS, and TGA, the obtained UiO66@HAnWs were applied to removing F^- in wastewater, and its adsorption capacity was optimized. It was found that UiO66@HAnWs had a bigger specific surface area (115.310 m²/g), and its efficiency for removing F^- got to 99.3%, which was greatly improved than that of related materials. It was considered that the adsorption of F^- on UiO66@HAnWs was mainly multi-molecular layer adsorption, which fluoride ions aggregate on the Zr(IV) active sites to attain ligand switching, and the nanoconjugated structure like nanotwigs of millet greatly improved its adsorption capacity. In summary, a novel eco-friendly UiO66@HAnWs with nanoconjugated structure could be constructed by simple hydrothermal method, which the agglomeration defects of MOFs were not only ameliorated, but also its adsorption capacity was greatly improved.

Fluoride ion adsorption isotherms, kinetics, and thermodynamics on iron(III) oxyhydroxide powders containing cellulose nanofibrils

The adsorption isotherms, kinetics, and thermodynamics of fluoride ions (F^-) on FeOOH powders in water were investigated to obtain fundamental information on FeOOH powders, which are used as F^- adsorbents in drinking and industrial water, and industrial wastewater. FeOOH powders were prepared as precipitates by mixing aqueous FeCl₃ and NaOH solutions (1:3 mol/mol) in the presence of 2,2,6,6,-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibrils (TOCNs), carboxymethylcellulose (CMC), or TEMPO-oxidized cellulose (TOC) fibers (without nanofibrillation), and subsequent drying and pulverizing. The FeOOH:TOCN, FeOOH:CMC, and FeOOH:TOC dry mass ratios were controlled at 87:13. The amount of F^- adsorbed by the FeOOH/TOCN powder per FeOOH mass was higher than those adsorbed by FeOOH, FeOOH/CMC, or FeOOH/TOC. The F^- adsorption isotherms on the FeOOH-containing powders showed higher correlation coefficients with the Langmuir model than with the Freundlich model. This indicates that F^- adsorbed on FeOOH initially formed a monolayer, predominantly via physical adsorption. Pseudo-second-order kinetics fitted well to the time-dependent F^- adsorption behaviors on the FeOOH-containing powders. Thermodynamic analysis of F^- adsorption on the FeOOH-containing powders showed that the ΔG values were negative, which indicates that F^- adsorption on the FeOOH-containing powders proceeded spontaneously in water. The negative ΔG value for FeOOH/TOCN was higher than those for FeOOH, FeOOH/CMC, and FeOOH/TOC at the same temperature. This shows that the FeOOH/TOCN powder can be used as an excellent and efficient F^- adsorbent in water.