Fluoride Removal Research Articles

Ethanol Treated Mn–Zr Compound for Fluoride Removal and its Adsorption Mechanism

Ethanol Treated Mn–Zr Compound for Fluoride Removal and its Adsorption Mechanism

Zero-waste approach to fluoride removal by contact precipitation using Hyriopsis cumingii shells with value-added products

We propose a zero-waste approach using Hyriopsis cumingii shells for fluoride (F) removal via contact precipitation with value-added products. H3PO4 was used as the precipitant for F removal. The F concentration could be reduced from 9.5 mg/L to 0.09–0.91 mg/L for over 900 BV with running-backwashing cycle. The precipitates formed during contact precipitation were easily stripped from the shell matrix by periodic backwashing, thus supporting the continuous dissolution of calcium (Ca) from the shell particles. X-ray diffraction (XRD)-Rietveld analysis showed that the backwashing residue was fluorapatite (FAP) with a small amount of hydroxy substitution. Therefore, FAP can be used as a raw material in phosphate fertilizer manufacturing. Economic analysis and sustainability evaluation showed that the contact precipitation process with H. cumingii shells as the substrate not only reduces chemical costs but also generates value-added products; thus, this process is environmentally friendly compared to traditional methods of F removal. The proposed approach for F elimination, waste shell utilization, and F and Ca resource recovery in the contact precipitation process represents a novel sustainable water treatment technology.

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.

Facile construction of graphene oxide and iron organic frameworks decorated biopolymeric hybrid materials for fluoride uptake from water

The widespread excess level of fluoride in water causes a possible risk to human health. Herein, graphene oxide (GO) and iron-type metal–organic frameworks namely iron-benzene-1,4-dicarboxylate (Fe-BDC) namely GO/Fe-BDC was employed to remove fluoride in water. Because of powder form, GO/Fe-BDC creates pressure drop during filtration. To overcome such troubles and improve adsorption capacity, GO/Fe-BDC integrated alginate (Alg) and chitosan (CS) biopolymer-based hybrid material namely GO/Fe-BDC/Alg-CS beads was developed for fluoride removal. Defluoridation properties of GO/Fe-BDC and GO/Fe-BDC/Alg-CS beads were evaluated under numerous influencing conditions namely pH, contact time, variable fluoride concentration, co-ions, dosage and temperature studies. The GO/Fe-BDC and GO/Fe-BDC/Alg-CS beads revealed finer fluoride adsorption ability and also had high fluoride selectivity in complexed atmosphere with several co-ions. The element composition, crystal morphology and material morphology of GO/Fe-BDC and GO/Fe-BDC/Alg-CS beads were characterized using SEM, XRD, FTIR and EDAX analysis. The order and nature of defluoridation was examined with kinetics, thermodynamic and isotherm analysis. The highest r values and lowest sd values exhibit that Langmuir adsorption isotherm and pseudo-second-order models were consider as best fit models for fluoride adsorption process onto GO/Fe-BDC and GO/Fe-BDC/Alg-CS beads. The thermodynamic results illustrate that fluoride adsorption was spontaneous, chemical adsorption with endothermic nature involved. Electrostatic interaction and complexation were found as the primary defluoridation mechanism of GO/Fe-BDC and GO/Fe-BDC/Alg-CS beads. The renewal and field investigations of GO/Fe-BDC and GO/Fe-BDC/Alg-CS beads were explored to check their regeneration ability and field suitability nature.

Electrochemical characterization of binder effect in natural magnetite electrodes for fluoride removal of well water

This work presents the study of the behavior of magnetite in fluoride electroadsorption. A concern in the fluoride electroadsorption is related to the type of binder, fluoride concentration, pH, and coexisting ions. A graphite/Nafion/magnetite electrode increases the specific capacitance of the surface favoring the surface complexation of anions due to the increase in the effective adsorption surface in this system. There is a tendency to increase the specific capacitance when the concentration and pH increase. The anionic affinity of the system is directly related to the nature of the ions and the hydrated ionic radius, in ions with the same charge, a lower hydrated radius results in a greater possibility of surface complexation. Excess OH− groups increase the accumulation of charge in the double layer, making the surface complexation of the anionic species towards the surface difficult. The selectivity trend is: CO32− > SO42− > F− > Cl− > NO3−.

Carbon doping enhances the fluoride removal performance of aluminum-based adsorbents.

Excessive fluoride presence in water poses significant environmental and public health risks, necessitating the development of effective remediation techniques. Conventional aluminum-based adsorbents face inherent limitations such as limited pH range and low adsorption capacity. To overcome these challenges, we present a facile solvent-thermal method for synthesizing a carbon-doped aluminum-based adsorbent (CDAA). Extensive characterization of CDAA reveals remarkable features including substantial carbon-containing groups, unsaturated aluminum sites, and a high pH at point of zero charge (pHpzc). CDAA demonstrates superior efficiency and selectivity in removing fluoride contaminants, surpassing other adsorbents. It exhibits exceptional adaptability across a broad pH spectrum from 3 to 12, with a maximum adsorption capacity of 637.4mg/g, more than 110 times higher than alumina. The applicability of the Langmuir isotherm and pseudo-second-order models effectively supports these findings. Notably, CDAA exhibits rapid kinetics, achieving near-equilibrium within just 5min. Comprehensive analyses utilizing Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) offer detailed insights into the mechanisms involving electrostatic attraction, ion exchange, and ligand exchange. Carbon-based groups play a role in ligand exchange processes, synergistically interacting with the unsaturated aluminum structure to provide a multitude of adsorption sites. The exceptional attributes of CDAA establish its immense potential as a transformative solution for the pressing challenge of fluoride removal from water sources.

High-Level Disordered Metal-Organic Frameworks Synthesized by Interference-Oriented Attachment for Electrochemical Anion Sieve.

Disordered MOFs seamlessly amalgamate the robust stability and pore tunability inherent in crystalline MOFs with the advantages derived from abundant defects and active sites present in amorphous structures. This study pioneers the use of the interference-oriented attachment (IOA) mechanism to meticulously craft the morphology and crystal growth of MIL-101(Cr) (Cr-MOF), resulting in the successful synthesis of a high-level disordered Cr-MOF boasting an enhanced array of active sites and exceptional electrochemical properties. The correlation between disordered structures and the electrochemical properties of MOFs are elucidated using the lattice distortion index and fractal dimension. The high-level disordered MOF electrode showcases a remarkable fluoride sieving effect, outperforming conventional fluoride removal materials with a remarkable fluoride adsorption capacity of 41.04 mgNaF gelectrodes -1. First-principles calculations, in conjunction with relevant experiments, provided further validation that the disordered structure significantly enhances the defluorination performance of the material. This study introduces a novel approach for the direct bottom-up synthesis of high-level disordered MOFs, showcasing their potential for applications in electrochemical water treatment.

Process Intensification for Enhanced Fluoride Removal and Recovery as Calcium Fluoride Using a Fluidized Bed Reactor.

This study explored the feasibility of fluoride removal from simulated semiconductor industry wastewater and its recovery as calcium fluoride using fluidized bed crystallization. The continuous reactor showed the best performance (>90% fluoride removal and >95% crystallization efficiency) at a calcium-to-fluoride ratio of 0.6 within the first 40 days of continuous operation. The resulting particle size increased by more than double during this time, along with a 36% increase in the seed bed height, indicating the deposition of CaF2 onto the silica seed. The SEM-EDX analysis showed the size and shape of the crystals formed, along with the presence of a high amount of Ca-F ions. The purity of the CaF2 crystals was determined to be 91.1% though ICP-OES analysis. Following the continuous experiment, different process improvement strategies were explored. The addition of an excess amount of calcium resulted in the removal of an additional 6% of the fluoride; however, compared to this single-stage process, a two-stage approach was found to be a better strategy to achieve a low effluent concentration of fluoride. The fluoride removal reached 94% with this two-stage approach under the optimum conditions of 4 + 1 h HRT combinations and a [Ca2+]/[F-] ratio of 0.55 and 0.7 for the two reactors, respectively. CFD simulation showed the impact of the inlet diameter, bottom-angle shape, and width-to-height ratio of the reactor on the mixing inside the reactor and the possibility of further improvement in the reactor performance by optimizing the FBR configuration.

Enhanced fluoride removal using Mg-Zr binary metal oxide nanoparticles confined in a strong-base anion exchanger

Generally, the pH of fluorinated groundwater or many industrial wastewater is neutral, while the majority of metal-modified adsorbents can work efficiently only under acidic conditions. In this study, we synthesized a novel hybrid adsorbent, Mg–Zr-D213, by loading nano-Mg/Zr binary metal (hydrogen) oxides in a strong-base anion exchanger, D213, to enhance the adsorption of fluoride from neutral water. Mg–Zr-D213 exhibited a better fluoride-removal capacity in neutral water than monometallic modified resins. Under the interference of competing anions and coexisting organic acids, Mg–Zr-D213 exhibited superior selectivity. The Langmuir model indicated that the fitted maximum sorption capacity of Mg–Zr-D213 was 41.38 mg/g. The results of column experiments showed that the effective treatment volume of Mg–Zr-D213 was 8–16-times higher than that of D213 for both synthetic groundwater and actual industrial wastewater, and that NaOH–NaCl eluent could effectively recover more than 95% of fluoride. Adsorption experiments with Mg/Zr metal (hydrogen) oxide particles and D213 separately demonstrated a synergistic effect between –N+(CH3)3 and Mg/Zr metal (hydrogen) oxide particles. The ligand exchange or metal-ligand interaction of Mg/Zr metal (hydrogen) oxide particles on fluoride was further demonstrated via X-ray photoelectron spectroscopy. Overall, Mg–Zr-D213 has great potential for enhanced fluoride removal in neutral water.

Approaches for the Efficient Removal of Fluoride from Groundwater: A Comprehensive Review

Contamination of groundwater with fluoride represents a significant global issue, with high concentrations posing serious public health threats. While fluoride is a critical element in water, excessive levels can be detrimental to human health and potentially life-threatening. Addressing the challenge of removing fluoride from underground water sources via nanotechnological approaches is a pressing concern in environmental science. To collate relevant information, extensive literature searches were conducted across multiple databases, including Google Scholar, PubMed, Scopus, Web of Science, the American Chemical Society, Elsevier, Springer, and the Royal Society of Chemistry. VOS Viewer software version 1.6.20 was employed for a systematic review. This article delivers an exhaustive evaluation of various groundwater fluoride removal techniques, such as adsorption, membrane filtration, electrocoagulation, photocatalysis, and ion exchange. Among these, the application of nanoparticles emerges as a notable method. The article delves into nano-compounds, optimizing conditions for the fluoride removal process and benchmarking their efficacy against other techniques. Studies demonstrate that advanced nanotechnologies—owing to their rapid reaction times and potent oxidation capabilities—can remove fluoride effectively. The implementation of nanotechnologies in fluoride removal not only enhances water quality but also contributes to the safeguarding of human health.

Fluoride removal from wastewater and potential for resource recovery: Comparative studies between different treatment technologies

Fluoride removal from wastewater and potential for resource recovery: Comparative studies between different treatment technologies

Fluoride removal using tartaric acid-modified rice husk biochar: Comprehensive batch and column studies

Tartaric Acid-modified Rice Husk biochar (TARH) was evaluated as an efficient and cost-effective adsorbent to eliminate Fluoride (F¯) ions from aqueous solutions. F¯ is a major contaminant in groundwater, and current conventional treatment methods have certain drawbacks in treating higher concentrations of fluoride. The adsorption efficiency of TARH was improved by pre-treating rice husk biochar using tartaric acid (organic acid), which was confirmed by FT-IR measurement, indicating the presence of carboxylic acids, hydroxyl groups, and amine surface functional groups. The study optimized fluoride batch adsorption experiments by considering the parameters affecting adsorption, including pH, contact time, initial concentration, and adsorbent dosage using the Central Composite Design (CCD) from Response Surface Methodology (RSM). Maximum fluoride adsorption of 74.73% was attained by TARH under ideal circumstances (an initial fluoride concentration of 32 mg/L, a pH of 7, 0.25 g/100 mL of adsorbent dosage, and 180 minutes contact duration). The CCD models showed an exceptional R2 value of 0.988 for fluoride adsorption, illustrating their efficacy. Three-dimensional response surface plots were visualized to analyse the effects of control parameters on %adsorption, and statistical analysis supported the validity of the CCD model. Isotherm models and adsorption kinetics were investigated. The adsorption exhibited monolayer adsorption according to the Langmuir isotherm model and a pseudo-second-order rate-limiting phase due to chemisorption. The column adsorption studies were performed for various experimental factors such as influent fluoride concentration (4–16 ppm), influent flow rate (4–8 mL/min), and fixed-bed depth (4–8 cm). The experimental data were examined using the Yoon-Nelson, Thomas, and BDST models, which revealed a substantial correlation between the experimental findings and model predictions. The effectiveness of TARH was examined by regeneration study and case study was performed to evaluate the fluoride removal from actual water samples.

Capacitive deionization chloride and fluoride removal by amine and titania-modified biochar electrodes

Capacitive deionization chloride and fluoride removal by amine and titania-modified biochar electrodes

Defluoridation of tap water by electrocoagulation and fluoride adsorption on aluminum hydroxide flocs

Abstract Overload of fluoride ions in water is observed in several regions of southern Tunisia, mainly the regions close to the mining basin of Gafsa: Metlaoui, Omlarayes and Redayef. This study concerns fluoride removal from Metlaoui's tap water by electrocoagulation (EC) using aluminum electrodes in a batch reactor. This water contains 3.5 mg·L−1 of fluoride, the highest concentration observed in these basins. The effect of the operating conditions of EC treatment on tap water defluoridation was analyzed, namely, current density, temperature and interelectrode distance. Hydroxide aluminum flocs, formed with different durations of EC, were used as sorbents in fluorinated deionized water ([F−] = 3.5 mg·L−1) and Metlaoui's tap water. Flocs formed after 30 min of EC, produced by dissolving (79 ± 1) mg·L−1 of aluminum and adjusted at pH = 6.5, allowed the adsorption of (98 ± 1)% of fluoride ions from deionized fluorinated water. Flocs adjusted at different pH, from 5 to 9, were used as sorbents in fluorinated deionized water and Metlaoui's tap water. Acidic and neutral flocs allowed the best yields of fluoride adsorption. Contrary to the literature, this work highlighted the absence of ion exchange of hydroxide anion by fluoride anion in water, highlighting a mechanism of physical adsorption on aluminum hydroxide flocs.

Synthesis of a Ce–La Adsorbent with Large Adsorption Capacity for Efficient Fluoride Removal from Leaching Solution of Spent Lithium-Ion Batteries

Synthesis of a Ce–La Adsorbent with Large Adsorption Capacity for Efficient Fluoride Removal from Leaching Solution of Spent Lithium-Ion Batteries

Optimization of Calcium Fluoride Crystallization Process for Treatment of High-Concentration Fluoride-Containing Semiconductor Industry Wastewater.

This study utilized a fluidized bed reactor (FBR) for fluoride removal from high-concentration fluoride-ion-containing simulated semiconductor industry wastewater and recovered high-purity CaF2 crystals. The effects of hydraulic retention time (HRT), pH, Ca2+ to F- ratio, upflow velocity, seed size and seed bed height were investigated by performing lab-scale batch experiments. Considering fluoride removal and CaF2 crystallization efficiency, 5 h HRT, pH 6, seed height of 50 cm and [Ca2+]/[F-] ratio of 0.55 (mol/mol) were found to be optimum. The effect of the interaction between the important process parameters on fluoride removal was further analyzed using response surface methodology (RSM) experimental design. The results showed that all the individual parameters have a significant impact (p = 0.0001) on fluoride removal. SEM-EDX and FTIR analysis showed the composition of the crystals formed inside FBR. HR-XRD analysis confirmed that the crystalline structure of samples was mainly CaF2. The results clearly demonstrated the feasibility of silica seed material containing FBR for efficient removal and recovery of fluoride as high-purity calcium fluoride crystals.

Application of Nanoclay in the Removal of Fluoride from Water: A Review

Water contamination with fluoride poses a significant threat to public health, leading to various adverse effects such as dental and skeletal fluorosis. Traditional methods for fluoride removal often involve the use of expensive and complex technologies. Nanotechnology offers a promising avenue for the development of efficient and cost-effective solutions. This research paper provides a comprehensive review of the current state of knowledge regarding the removal of fluoride from water using nanoclay adsorbents. It explores the synthesis, characteristic properties, performance mechanism and application of nanoclay adsorbents, along with their performance efficiency and potential challenges. Keywords: Dental and skeletal fluorosis, Nanotechnology, Fluoride, Nanoclay adsorbents

Redox transformation of bismuth active units encapsulated on carbon nanorods for efficient fluoride Electrosorption: Synergistic roles of Faradaic effect and EDL capacitance

Remediation of fluoride in groundwater through electrosorption to cope with its high charge density and the smallest anion radius remains a promising strategy. Composite carbon materials obtained by calcining metal–organic frameworks contribute to the performance of conventional fluoride electrosorption systems. This study provides a redox-active electrode (MBiC@tE) that incorporates the Faradaic ion trapping effect for fluoride removal. Under potential control, MBiC@tE reversibly traps/releases fluoride anions from the aqueous solution through the combined roles of Faradaic pseudocapacitance and electrical double layer capacitance, with an electrosorption capacity of approximately 37.9 mgF- gelectrode-1. The target contaminant anions are directly involved in the Faradaic reaction on the bismuth sites, with the formation of Bi-F bond excited by an electric field, thus resulting in the removal of fluoride as a consequence of the generation of insoluble substance (BiF3). Furthermore, as expected (Bi0 + 3F- ⇌ BiF3 + 3e-), the working electrode exhibits good reversibility and maintains a high fluoride removal capacity even after multiple cycles. This study presents a comprehensive elucidation on the synergistic roles of Faradaic effect and electrical double layer capacitance induced by the electric field, and offers profound insights into the phase transition of bismuth and its affinity for fluoride during the electrosorption.

Low operating pressure hydrophilic MOF-801/Biopolymer interfacial membrane for defluoridation and Co-Organic pollutant remediation

In the context of the energy-water nexus, where the demand for clean water intersects with the imperative for energy-efficient water treatment solutions, this research is dedicated to achieving low-pressure-driven membrane solution. Herein, study uses new class of active MOF-801 fillers materials that are in to stable biopolymers matrix to address the pervasive issue of fluoride contamination in drinking water. By harnessing the synergistic potentials of biogenic chitosan-sodium alginate (CS:SA) multilayers combined with MOF-801 fillers on the polyether sulfone (PES) porous support matrix. This study not only achieves significant improvements in fluoride removal but also enhances with exceptional resistance to fouling. Target specific designed membranes also exhibit versatility in effectively removing various emerging pollutants including fouling agents (BSA, TA, HA) and organic dyes (CR, MO, MB, CV), with a flux of > 40 L·m−2·h−1. The optimized membrane showed exceptional stability under different pH condition showed great separation performance and regeneration capabilities, as well as its effectiveness in defluoridation of groundwater feed. Large scale testing of defluoridation abilities tested for ∼ 5000 L of feed with a fluoride ion distribution coefficient (Kd) of 45621 mL/g at 4 bars of pressure. Therefore, the optimized membrane stands as an ideal candidate for applications within the energy-water nexus, where sustainability and resource efficiency are of paramount importance.

Stratified control of chemical crystallization in a pellet fluidized bed for pH-Adjusted fluoride and phosphate reduction: An experimental study

Chemical crystallization granulation in a fluidized bed offers an environmentally friendly technology with significant promise for fluoride removal. This study investigates the impact of stratified pH control in a crystallization granulation fluidized bed for the removal of fluoride and phosphate on a pilot scale. The results indicate that using dolomite as a seed crystal, employing sodium dihydrogen phosphate (SDP) and calcium chloride as crystallizing agents, and controlling the molar ratio n(F):n(P):n(Ca) = 1:5:10 with an upflow velocity of 7.52 m/h, effectively removes fluoride and phosphate. Stratified pH control—maintaining weakly acidic conditions (pH = 6–7) at the bottom and weakly alkaline conditions (pH = 7–8) at the top—facilitates the induction of fluoroapatite (FAP) and calcium phosphate crystallization. This approach reduces groundwater fluoride levels from 9.5 mg/L to 0.2–0.6 mg/L and phosphate levels to 0.1–0.2 mg/L. Particle size analysis, scanning electron microscopy–energy-dispersive X-ray spectroscopy, and X-ray diffraction physical characterizations reveal significant differences in crystal morphology between the top and bottom layers, with the lower layer primarily generating high-purity FAP crystals. Further analysis shows that dolomite-induced FAP crystallization offers distinct advantages. SDP not only dissolves on the dolomite surface to provide active sites for crystallization but also, under weakly acidic conditions, renders both dolomite and FAP surfaces negatively charged. This allows for the effective adsorption of PO43−, HPO42−, and F− anions onto the crystal surfaces. This study provides supporting data for the removal of fluoride from groundwater through induced FAP crystallization in a chemical crystallization pellet fluidized bed.