Comparison of La3+ and mixed rare earths-loaded magnetic chitosan beads for fluoride adsorption

Zirconium‑cerium modified polyvinyl alcohol/NaCMC biocomposite film: Synthesis of films through high-speed shear assisted technique and removal fluoride from water

A new zirconium and cerium-modified polyvinyl alcohol (PVA) sodium carboxymethyl cellulose (NaCMC) film (PVA/CMC-Zr-Ce) was synthesized thru a high-speed shear-assisted method and its adsorption for the removal of fluoride was studied, in which the NaCMC provided -COONa for ion exchange between Na and Zr-Ce, thus the loading amount of Zr-Ce on films was accordingly increased. The morphology and structure of PVA/CMC-Zr-Ce were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Besides, the mechanical properties, water contact angle, and swelling ratio of film were also evaluated. The addition of high-speed shear improved the dispersion of the emulsion system, and PVA/CMC-Zr-Ce film with good adsorption performance and film stability was prepared. While, it was found that the adsorption capacity could reach 67.25 mg/g and equilibrium time could reach 20 min. The adsorption mechanism of PVA/CMC-Zr-Ce revealed that ion exchange between hydroxide and fluoride, electrostatic interactions and complexation were the dominating influencing factors. Based on these findings, it can be concluded that PVA/CMC-Zr-Ce film- synthesized with high-speed shear assistance technique is a promising adsorbent for fluoride removal from water.

Experimental and DFT calculation study on the efficient removal of high fluoride wastewater from metallurgical wastewater by kaolinite

Fluoride pollution and water scarcity are urgent issues. Reducing fluoride concentration in water is crucial. Kaolinite has been used to study adsorption and fluoride removal in water and to characterize material properties. The experimental results showed that the adsorption capacity of kaolinite decreased with increasing pH. The highest adsorption of fluoride occurred at pH 2, with a capacity of 11.1 mg/g. The fluoride removal efficiency remained high after four regeneration cycles. The fitting results with the Freundlich isotherm model and the external diffusion model showed that the non-homogeneous adsorption of kaolinite fit the adsorption behavior better. Finally, the adsorption mechanism was analyzed by FT-IR and XPS. The binding energies of various adsorption sites and the chemical adsorption properties of atomic states were discussed in relation to DFT calculations. The results showed that Al and H sites were the main binding sites, and the bonding stability for different forms of fluoride varies, with the size of Al-F (-7.498 eV) > H-F (-6.04 eV) > H-HF (-3.439 eV) > Al-HF (-3.283 eV). Furthermore, the density of states and Mulliken charge distribution revealed that the 2p orbital of F was found to be active in the adsorption process and was the main orbital for charge transfer.

Advances and future perspectives of water defluoridation by adsorption technology: A review

Fluoride contamination in water sources poses a significant challenge to human health and the environment. In recent years, adsorption technology has emerged as a promising approach for water defluoridation due to its efficiency and cost-effectiveness. This review article comprehensively explores the advances in water defluoridation through adsorption processes. Various adsorbents, including natural and synthetic materials, have been investigated for their efficacy in removing fluoride ions from water. The mechanisms underlying adsorption interactions are elucidated, shedding light on the factors influencing defluoridation efficiency. Moreover, the review outlines the current state of technology, highlighting successful case studies and field applications. Future perspectives in the field of water defluoridation by adsorption are discussed, emphasizing the need for sustainable and scalable solutions. The integration of novel materials, process optimization, and the development of hybrid technologies are proposed as pathways to address existing challenges and enhance the overall efficacy of water defluoridation. This comprehensive assessment of the advances and future directions in adsorption-based water defluoridation provides valuable insights for researchers, policymakers, and practitioners working towards ensuring safe and accessible drinking water for all.

Effective removal and adsorption mechanism of fluoride from water by biochar-based Ce(III)-La(III)-crosslinked sodium alginate hybrid hydrogel

An eco-friendly macroparticle biochar (BC)-based Ce(III)-La(III) crosslinked sodium alginate (SA) hybrid hydrogel (BC/Ce-SA-La) was synthesized by droplet polymerization and characterized by SEM-EDS, XRD, FTIR, UV-Vis and XPS. The effects of dosage, pH, contact time, temperature and coexisting ions on the F- ions removal by hybrid hydrogel, and the adsorption performance, interaction mechanism and reusability were investigated. The results demonstrate that the composite has a fancy wrinkle structure with a particle size of about 1.8 mm and abundant porosity on the surface. The removal rate of F- ions by BC/Ce-SA-La reached 90.2 % under the conditions of pH 2.0, 200 min of contact time and 298 K. The adsorption behavior was perfectly explained by Langmuir model, and the maximum adsorption capacity reached 129 mg/g. The adsorption process was an endothermic spontaneous reaction and followed Pseudo-second-order rate model. The strong adsorption was attributed to multi-interactions including complexation, hydrogen bonding and electrostatic adsorption between the composite and F- ions. Coexisting ions hardly interfered with the adsorption of F- ions by BC/Ce-SA-La except for a slight effect of phosphate. The composite after F- ion adsorption was easily separated and could be reused at least three times. BC/Ce-SA-La is a cost-effective and promising granular biosorbent.

Synthesis and characterization of functional calcium-phosphate-chitosan adsorbents for fluoride removal from water

Functional calcium-phosphate-chitosan adsorbents for fluoride (F-) removal from water with different proportions of calcium (0.7 or 1.4 % w/v) were synthesized by: i) ionotropic gelation technique followed by drying in a convection oven (IGA) or freeze drying (FDA); ii) freeze-gelation followed by drying in a convection oven (FGA). Adsorbents were analyzed by SEM-EDX and FTIR- ATR. F- removal percentages higher than 45 % were obtained with calcium-phosphate-chitosan adsorbents for an initial F- concentration of 9.6 mg L-1. Optimal conditions for F- removal were attained, using calcium-phosphate- chitosan adsorbents synthesized by ionotropic gelation with 0.7 % of Ca (IGA0.7). Under these conditions, initial F- concentration of 5 mg L-1, was reduced below the maximum limit of 1.5 mg L-1 established by WHO. Regeneration of IGA0.7 was achieved in acid media. The performance of IGA0.7 was slightly reduced in the presence of coexisting anions (nitrate, carbonate, arsenate). Adsorption kinetics was represented satisfactorily by the pseudo-second order equation; Langmuir isotherm provided the best fit to the equilibrium data and IGA0.7 exhibited a maximum F- adsorption capacity qL = 132.25 mg g-1. IGA0.7 particles were characterized by thermogravimetry coupled to FTIR, XRD, XPS and SEM-EDX. The calcium-phosphate-chitosan adsorbents constitute a suitable and emerging material for water defluorination.

Recent advances in removal of inorganic anions from water by chitosan-based composites: A comprehensive review

Chitosan is a modified natural carbohydrate polymer that has been found in the exoskeletons of crustaceans (e.g., lobsters, shrimps, krill, barnacles, crayfish, etc.), mollusks (octopus, oysters, squids, snails), algae (diatoms, brown algae, green algae), insects (silkworms, beetles, scorpions), and the cell walls of fungi (such as Ascomycetes, Basidiomycetes, and Phycomycetes; for example, Aspergillus niger and Penicillium notatum). However, it is mostly acquired from marine crustaceans such as shrimp shells. Chitosan-based composites often present superior chemical, physical, and mechanical properties compared to single chitosan by incorporating the benefits of both counterparts in the nanocomposites. The tunable surface chemistry, abundant surface-active sites, facilitation synthesize and functionalization, good recyclability, and economic viability make the chitosan-based materials potential adsorbents for effective and fast removal of a broad range of inorganic anions. This article reviews the different types of inorganic anions and their effects on the environment and human health. The development of the chitosan-based composites synthesis, the various parameters like initial concentration, pH, adsorbent dosage, temperature, the mechanism of adsorption, and regeneration of adsorbents are discussed in detail. Finally, the prospects and technical challenges are emphasized to improve the performance of chitosan-based composites in actual applications on a pilot or industrial scale.

The model and mechanism of adsorptive technologies for wastewater containing fluoride: A review

With the continuous development of society, industrialization, and human activities have been producing more and more pollutants. Fluoride discharge is one of the main causes of water pollution. This review summarizes various commonly used and effective fluoride removal technologies, including ion exchange technology, electrochemical technology, coagulation technology, membrane treatment, and adsorption technology, and points out the outstanding advantages of adsorption technology. Various commonly used fluoride removal techniques as well as typical adsorbent materials have been discussed in published papers, however, the relationship between different adsorbent materials and adsorption models has rarely been explored, therefore, this paper categorizes and summarizes the various models involved in static adsorption, dynamic adsorption, and electrosorption fluoride removal processes, such as pseudo-first-order and pseudo-second-order kinetic models, Langmuir and Freundlich isotherm models, Thomas and Clark dynamic adsorption models, including the mathematical equations of the corresponding models and the significance of the models are also comprehensively summarized. Furthermore, this comprehensive discussion delves into the fundamental adsorption mechanisms, quantification of maximum adsorption capacity, evaluation of resistance to anion interference, and assessment of adsorption regeneration performance exhibited by diverse adsorption materials. The selection of the best adsorption model not only predicts the adsorption performance of the adsorbent but also provides a better description and understanding of the details of each part of the adsorption process, which facilitates the adjustment of experimental conditions to optimize the adsorption process. This review may provide some guidance for the development of more cost-effective adsorbent materials and adsorption processes in the future.

Zirconium/lanthanum-modified chitosan/polyvinyl alcohol composite adsorbent for rapid removal of fluoride

A novel and easily separable adsorbent in the shape of a membrane for the rapid removal of fluoride from water was prepared after testing Zr, La and LaZr to modify a chitosan/polyvinyl alcohol composite adsorbent (CS/PVA-Zr, CS/PVA-La, CS/PVA-LA-Zr). The CS/PVA-La-Zr composite adsorbent can remove a large amount of fluoride within 1 min of contact time, and the adsorption equilibrium can be reached within 15 min. The fluoride adsorption behavior of the CS/PVA-La-Zr composite can be described by pseudo-second-order kinetics and Langmuir isotherms models. The morphology and structure of the adsorbents were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The adsorption mechanism was studied using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and which showed that ion exchange occurred mainly with hydroxide and fluoride ions. This study showed that an easily operable, low-cost and environmentally friendly CS/PVA-La-Zr has the potential to remove fluoride effectively from drinking water in a short time.

Synthesis of stable flowerlike MgAl-LDH@MIL-88A and its adsorption performance for fluoride

MgAl-LDH@MIL-88A as an effective adsorbent was successfully prepared by a simple stirring method in water bath through loading MIL-88A onto the surface of flowerlike MgAl-LDH, which was synthesized via solvothermal method. Interestingly, the results of characterizations showed that the MIL-88A could still grow, but extrude the brucite-like layers of MgAl-LDH. The influences of initial solution pH, contact time, temperature, and co-existing ions on the adsorption performance of MgAl-LDH@MIL-88A were studied systematically by batch static adsorption experiments. It was found that MgAl-LDH@MIL-88A represented the highest adsorption loading of fluoride (14.00 mg g−1) at initial pH 7.0 in 420 min. The uptake process was described appropriately by the pseudo-second-order, the Temkin and the Freundlich isotherm models. The thermodynamic parameters confirmed the endothermic and spontaneous nature of adsorption. MgAl-LDH@MIL-88A was the green adsorbent as the residual mental contents ([Mg2+] = 1.095 mg L−1, [Fe3+] = 0.007 mg L−1, [Al3+] = 0.076 mg L−1) after adsorption met the Chinese sanitary standard for drinking water (GB 5749-2006). The mechanism of fluoride removal by MgAl-LDH@MIL-88A involved the electrostatic interactions between Fe3+ of MIL-88A and fluoride, and ligand exchange among hydroxyl groups of MgAl-LDH, carboxylate groups of the C4H4O4 and fluoride.

Applications of biomass-based materials to remove fluoride from wastewater: A review

Fluoride is one of the essential trace elements for the human body, but excessive fluoride will cause serious environmental and health problems. This paper summarizes researches on the removal of fluoride from aqueous solutions using newly developed or improved biomass materials and biomass-like organic materials in recent years. These biomass materials are classified into chitosan, microorganisms, lignocellulose plant materials, animal attribute materials, biological carbonized materials and biomass-like organic materials, which are explained and analyzed. By comparing adsorption performance and mechanism of adsorbents for removing fluoride, it is found that carbonizing materials and modifying adsorbents with metal ions are more beneficial to improving adsorption efficiency and the adsorption mechanisms are various. The adsorption capacities are still considerable after regeneration. This paper not only reviews the properties of these materials for fluoride removal, but also focuses on the comparison of materials performance and fluoride removal mechanism. Herein, by discussing the improved adsorption performance and research technology development of biomass materials and biomass-like organic materials, various innovative ideas are provided for adsorbing and removing contaminants.

Applications of Nano Hydroxyapatite as Adsorbents: A Review

Nano hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) has aroused widespread attention as a green and environmentally friendly adsorbent due to its outstanding ability in removing heavy metal ions, radio nuclides, organic pollutants and fluoride ions for wastewater treatment. The hexagonal crystal structure of HAp supports the adsorption mechanisms including ionic exchange reaction, surface complexation, the co-precipitation of new partially soluble phases and physical adsorption such as electrostatic interaction and hydrogen bonding. However, nano HAp has some drawbacks such as agglomeration and a significant pressure drop during filtration when used in powder form. Therefore, instead of using nano HAp alone, researchers have worked on modificationsand composites of nano HAp to overcome these issues and enhance the adsorption capacity. The modification of cationic doping and organic molecule grafting for nano HAp can promote the immobilization of ions and then increase adsorption capacity. Developing nano HAp composite with biopolymers such as gelatin, chitosan and chitin has proven to obtain a synergetic effect for improving the adsorption capacity of composites, in which nano HAp fixed and dispersed in polymers can playmuch more of a role for adsorption. This review summarizes the adsorption properties and adsorbent applications of nano HAp as well as the methods to enhance the adsorption capacity of nano HAp.

Synergistic Fluoride Adsorption by Composite Adsorbents Synthesized From Different Types of Materials—A Review

The reduction of fluoride concentrations in water is one of many concerns. Adsorption is the most widely used technology for fluoride removal and the center to development of adsorption technology is the improvement of adsorbents. This review classifies the typical fluoride removal adsorbents into four types: metal oxides/hydroxides, biopolymers, carbon-based, and other adsorbents. The exploitation of new materials and the synthesis of composite materials are two ways of developing new adsorbents. In comparison to the discovery of novel adsorbents for fluoride adsorption, research into the composite synthesis of different types of conventional adsorbents has proliferated in recent years. The traditional adsorbents used the earliest, metal oxides, can act as active centers in a wide range of applications for modifying and compounding with other types of adsorbents. This study emphasizes reviewing the research on fluoride removal by composite adsorbents synthesized from different types of metal-modified materials. Seven factors were compared in terms of material characterization, initial fluoride concentration, adsorbent dose, pH, temperature, reaction time, and maximum adsorption capacity. The modification of composite adsorbents is facile and the synergistic effect of the different types of adsorbents significantly improves fluoride adsorption capacity. Metal composite adsorbents are synthesized by facile coprecipitation, hydrothermal, or impregnation modification methods. The adsorption mechanisms involve electrostatic attraction, ion exchange, complexation, and hydrogen bonding. The fluoride adsorption capacity of composite adsorbents has generally improved, indicating that most modifications are successful and have application prospects. However, to achieve significant breakthroughs in practical applications, numerous issues such as cost, separation/regeneration performance, and safety still need to be considered.

Cost-effective phosphorus removal from aqueous solution by a chitosan/lanthanum hydrogel bead: Material development, characterization of uptake process and investigation of mechanisms

Excessive phosphorus is one of the main reasons leading to eutrophication that causes severe ecosystem imbalance and negative human health impacts. In this study, several chitosan (CS)/lanthanum (La) hydrogel beads were first synthesized and tested for phosphorus removal. The stable cross-linked CS/La hydrogel bead prepared with the optimized conditions of 10 wt% La/CS and 1.5 mL of 5% glutaraldehyde demonstrated exceptional performance in the removal. It removed phosphate effectively from an aqueous solution in the pH range from 2 to 7. The complete phosphate uptake was achieved at contact time of 6 h under the completely mixing batch condition. The experimental maximum adsorption capacity of 107.7 mg g^-1 was observed at solution pH 4. The phosphate adsorption was well described by the Freundlich isotherm and the intraparticle surface diffusion model. Furthermore, the adsorbent was effectively regenerated and reused in a five-cycle adsorption-desorption operation. The removal of phosphate can be attributed to electrostatic attraction and ion exchange. Moreover, the bead was capable of removing heavy metals: copper, zinc and lead. This adsorbent may be served as a cost-effective material for the treatment of phosphorus-contaminated water so as to minimize the occurrence of eutrophication.

Enhanced fluoride adsorption from aqueous solution by zirconium (IV)-impregnated magnetic chitosan graphene oxide

In this study, zirconium (IV)-impregnated magnetic chitosan graphene oxide (Zr-MCGO) was synthesized for removing fluoride from aqueous solution in batch mode. Characterization approaches (pH_pzc, FTIR, SEM, XRD, VSM, Raman, BET, and XPS) proved the successful incorporation of Zr into the adsorbent. Zr-MCGO exhibited a relatively favorable and stable capacity of defluoridation at lower pH with a wide range of pH from 4.0 to 8.0, while there was slightly negative effect of ionic strength on adsorption. In addition, Elovich kinetic model and Koble-Corrigan isotherm model could describe the uptake of fluoride well. The adsorption capacity was 8.84 mg/g at 313 K and Zr-MCGO was easily separated from mixtures using external magnet. Based on the experiments and XPS, electrostatic force, ligand exchange, and Lewis acid-base interaction might be potential adsorption mechanisms. Pseudo-second-order model was more compatible with the desorption process by 0.01 mol/L NaHCO₃ solution. Therefore, Zr-MCGO was a promising candidate for defluoridation on wastewater pollution remediation.

Facile synthesis of Zr4+ incorporated chitosan/gelatin composite for the sequestration of Chromium(VI) and fluoride from water

The development of industrialization and agricultural activities have carried various negative impacts to living organisms in recent decades and also, the frequent problem of inorganic pollution have been environmental anxiety to the community. Among these, Cr⁶⁺ and F^- are priority poisonous pollutants from many industries. In this work, we present a low-cost synthesis procedure to obtain biocompatible zirconium incorporated chitosan-gelatin composite (CS-Zr-GEL) were fabricated and explored for the adsorptive removal of toxic Cr⁶⁺ and F^- from water. The adsorption mechanism of toxic Cr⁶⁺ and F^- was done by batch mode as a function of contact time, solution pH and co-existing ions. The obtained materials were extensively studied by several physico-chemical techniques to access their properties by X-ray diffraction (XRD), scanning electron microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) analysis. Additionally, the fabricated adsorbent is highly dependent on solution pH. The kinetic and isotherm data were fitted using pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity for CS-Zr-GEL is 138.89 and 12.13 mg/g at 323K for Cr⁶⁺ and F^- respectively. These findings demonstrate that the CS-Zr-GEL adsorbent represents a promising candidate that would have a practical influence on water/wastewater treatments.

Synthesis of Chitosan-Polyvinyl Alcohol Biopolymers to Eliminate Fluorides from Water

The fluoride content in groundwater varies depending on geological configuration. Fluoride problems tend to occur in places where these minerals are most abundant in rocks. The objective of the present work was to synthesize four biopolymers based on chitosan-polyvinyl alcohol (Ch-PVA) cross-linked with sodium tripolyphosphate pentabasic (TPP) and ethylene glycol diglycidyl ether (EGDE) and determine their ability to remove fluoride from water. The characterization of the Ch-PVA beads was performed by way of Scanning Electron Microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The percentage of humidity and the point of zero charge were determined. The Ch-PVA beads showed a surface area of 63.87 m² g⁻¹, a pore size of 7.6 nm, a point of zero charge of 7.4, and 98.6% humidity. The kinetic adsorption study was adjusted to the pseudo-second-order model and the adsorption equilibrium data were adjusted to the Freundlich adsorption isotherm, showing a maximum fluoride adsorption capacity of 12.64 mg g⁻¹ at pH 7 and 30 °C, for the beads of Ch-PVA-NaOH-TPP. According to the thermodynamic parameters: −∆G°, +∆H° and −∆S°, fluoride adsorption is spontaneous, endothermic in nature and there is no random energy change in the solid/liquid interface during the adsorption process.

Multiple bimetallic (Al-La or Fe-La) hydroxides embedded in cellulose/graphene hybrids for uptake of fluoride with phosphate surroundings

To insight into the selective adsorption mechanism of fluoride in the bimetallic system, Fe-La or Al-La composites were comparatively embedded onto the cellulose/graphene hybrids (CG hybrids) to fabricate the Fe-La@CG hybrids or Al-La@CG hybrids for fluoride uptake with existing phosphate. The results showed that Al-La@CG hybrids were mainly in the amorphous nature, while Fe-La@CG hybrids have the identical diffraction peaks as compared with those of hydrated lanthanum oxides (HLO) and hydrated iron oxides (HFO). Fluoride capture by Al-La@CG and Fe-La@CG hybrids followed the similar tendencies with the pH altering, but the adsorption performance of Al-La@CG hybrids was better than that of Fe-La@CG hybrids at the same pH levels. Adsorption of fluoride onto Al-La@CG hybrids exhibited less sensitivity and high selectivity with existing phosphate as compared with that of Fe-La@CG hybrids, which further indicated that the Al-La@CG hybrids were more preferable for fluoride adsorption. The fraction areas of La-F and Al-F accounted for 79.1 % and 20.9%, which indicated that the fluoride onto the Al-La@CG hybrids was mainly based on the La species. Similarly, La-F in exhausted Fe-La@CG hybrids accounted for 55.6%, higher than that (44.4%) of Fe-F.

Enhanced fluoride uptake by bimetallic hydroxides anchored in cotton cellulose/graphene oxide composites

A novel hybrid nanomaterial was synthesized by embedding the bimetallic Zr and La (hydro)xides onto the cotton cellulose/graphene oxide composites (CC/GO composites), forming the Zr-La-CC/GO nanocomposites. Selective uptake of fluoride onto the Zr-La /GO hybrids in multiple competitive environments were evaluated. Morphological characteristics of Zr-La-CC/GO nanocomposites reflected the well distributions of embedded Zr and La hydroxides in the nanocomposites. Results also indicated that the encapsulated bimetallic hydroxides in Zr-La-CC/GO hybrids exhibited extremely high fluoride adsorption capacity and stability. XPS investigation exhibited the strong ZrF and LaF bonds in spent Zr-La-CC/GO nanocomposites, and the bonds were weakened at higher pH, which was consistent with the adsorption results. In addition, CC/GO composites using as the host could also exert the strong shielding effect to improve the stability of embedded La and Zr species so as only a low La dissolution (<4.2%) and almost no Zr leaching (0.1%) were observed in high HA concentration. What's more, the Zr-La-CC/GO nanocomposites have also shown great potential application for defluoridation in field.

Enhanced removal of fluoride by zirconium modified tea waste with extrusion treatment: kinetics and mechanism

To improve the adsorption efficiency of tea-based biosorbents for removing fluoride in drinking water, the novel and effective adsorbent was formed by treating tea waste with extrusion technology. In this study, the extrusion technology was applied to the preparation of adsorbents for the first time. A low-priced and more efficient adsorbent was prepared by loading zirconium onto extruded tea waste (EXT-Zr). Extruded tea waste increased the surface pore size, which could provide more loading sites for zirconium. The EXT-Zr effectively removed fluoride from water in a pH range of 3.0–10.0, which is wider than the pH range of zirconium-loaded tea waste (Tea-Zr). The adsorption was fitted by a pseudo-second order kinetic model and the Langmuir adsorption model. The maximum adsorption capacity was 20.56 mg g⁻¹. The EXT-Zr adsorbent was characterized by Scanning electron microscopy (SEM), Energy-Dispersive Spectroscopy (EDS), X-ray diffraction (XRD), a Brunauer–Emmett–Teller (BET) method, Fourier-transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) to prove the mechanism of how EXT-Zr adsorbs fluoride. The results proved that EXT-based adsorbent will be effective for the enhanced removal of fluoride in drinking water.

Extruded tea waste (EXT) increased the pore size by extrusion technology. Extruded tea waste (EXT-Zr) modified by Zr performed well.