Efficient Removal Of Fluoride Research Articles

Efficient Removal of Fluoride by Complexation Extraction: Mechanism and Thermodynamics

A complexation extraction system was designed to develop a new process for the efficient removal of fluoride from solutions, such as zinc or copper electrolytes or wastewater derived from flue gas. The effects of the boron fluoride molar ratio, organic phase composition, initial pH, temperature, and phase volume ratio on the extraction efficiency were investigated. The extraction efficiency was found to increase with the increase in the boron fluoride molar ratio, Alamine336 concentration, and phase volume ratio, whereas it decreased with the increase in temperature. For the simulated electrolyte or wastewater derived from flue gas, the majority of metallic ions were insensitive to the extraction, with the exception of Al3+ and Fe3+. Fluoride decreased from 5 g/L to 0.05 g/L after two-stage cross-flow extraction alone; with an extraction efficiency of 99%. Both the stripping and cycling properties were excellent when sodium hydroxide was employed as the stripping reagent. Furthermore, the loading capacity was 43.4 g/L, and increased by four times, when boric acid was added. This novel process implies a wide range of potential applications, such as the removal of unwanted fluoride ions from various high-fluoride polluted solutions and the simplification of brine phase diagram.

Efficient Fluoride Removal and Dye Degradation of Contaminated Water Using Fe/Al/Ti Oxide Nanocomposite.

The trimetallic Fe/Al/Ti (1:1:1) nanocomposite (FAT), synthesized by an adaptable tuned chemical route, offers a new approach for water treatment, for example, the de-fluoridation and photodegradation soluble dye methylene blue (MB) at pH 7. FAT acted as a good fluoride scavenger in the presence of other co-ions and within a widespread pH range (pH 2–11). The photodegradation efficiencies were >90% for different concentrations of MB solutions. The characterization of FAT includes thermogravimetric analysis, X-ray diffraction, Fourier transform-infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and ζ-potential analysis. Furthermore, the regeneration efficiencies of both the water treatments were checked, where the removal efficiency was not hampered significantly even after five batches. Spectroscopic techniques were adopted to perform the kinetic studies and to propose the probable mechanistic paths.

Selective and Efficient Removal of Fluoride from Water: In Situ Engineered Amyloid Fibril/ZrO2 Hybrid Membranes.

We report a new strategy for efficient removal of F- from contaminated water streams, and it relies on carbon hybrid membranes made of amyloid fibril/ZrO2 nanoparticles (<10 nm). These membranes exhibit superior selectivity for F- against various competitive ions, with a distribution coefficient (Kd ) as high as 6820 mL g-1 , exceeding commercial ion-exchange resins (IRA-900) by 180 times and outdoing the performance of most commercial carbon-activated aluminum membranes. At both low and high (ca. 200 mg L-1 ) F- concentrations, the membrane efficiency exceeds 99.5 % removal. For real untreated municipal tap water (ca. 2.8 mg L-1 ) under continuous operating mode, data indicates that about 1750 kg water m-2 membrane can be treated while maintaining drinking water quality, and the saturated membranes can be regenerated and reused several times without decrease in performance. This technology is promising for mitigating the problem of fluoride water contamination worldwide.

Selective and Efficient Removal of Fluoride from Water: In Situ Engineered Amyloid Fibril/ZrO2 Hybrid Membranes

AbstractWe report a new strategy for efficient removal of F− from contaminated water streams, and it relies on carbon hybrid membranes made of amyloid fibril/ZrO2 nanoparticles (&lt;10 nm). These membranes exhibit superior selectivity for F− against various competitive ions, with a distribution coefficient (Kd) as high as 6820 mL g−1, exceeding commercial ion‐exchange resins (IRA‐900) by 180 times and outdoing the performance of most commercial carbon‐activated aluminum membranes. At both low and high (ca. 200 mg L−1) F− concentrations, the membrane efficiency exceeds 99.5 % removal. For real untreated municipal tap water (ca. 2.8 mg L−1) under continuous operating mode, data indicates that about 1750 kg water m−2 membrane can be treated while maintaining drinking water quality, and the saturated membranes can be regenerated and reused several times without decrease in performance. This technology is promising for mitigating the problem of fluoride water contamination worldwide.

Facile synthesis of Al/Fe bimetallic (oxyhydr)oxide-coated magnetite for efficient removal of fluoride from water

ABSTRACT In this work, we developed a novel magnetic bimetallic Al/Fe (oxyhydr)oxide adsorbent through a facile and cost-effective method and explored its potential to adsorb fluoride in water. Its synthesis involved corrosion of natural magnetite in aluminium chloride solution, followed by titration with NaOH solution for in-situ synthesis of Al/Fe (oxyhydr)oxide-coated magnetite (Mag@Al2Fe). Characterization data indicated a uniform coating of Al/Fe (oxyhydr)oxide on magnetite, and the resulting composite possessed large specific surface area (∼90 m2/g) and good magnetic property. In batch adsorption experiments, the isotherm and kinetic data fitted well to the Langmuir model and pseudo-second-order model, respectively. The maximum adsorption capacity of Mag@Al2Fe is 26.5 mg/g, which was much higher than natural magnetite (0.44 mg/g). Moreover, this material retained high adsorption capacity toward fluoride within a wide pH range (3.0–8.0) and offered facile magnetic separation from water. Influence of competing ions was also evaluated which showed that the presence of Cl− and NO3 − posed negligible interference, while HCO3 − and SO4 2− had negative effects on fluoride adsorption. Thermodynamic investigations revealed that fluoride adsorption was exothermic and spontaneous. The observed increase in solution pH and formation of Al–F and Fe–F bonds (as indicated by XPS analysis) after fluoride adsorption suggested the major adsorption mechanism of ligand exchange. Besides, the adsorption/desorption cycle studies demonstrated the well-retained performance of Mag@Al2Fe for repeated application after regeneration by 0.5 mol/L NaOH solution. Facile synthesis, high defluoridation, lower cost, and quick separation of Mag@Al2Fe indicates its promising potential for drinking water defluoridation.

Efficient fluoride removal by preparation, characterization of pyrolysis bone: Mixed level design experiment and Taguchi L8 orthogonal array optimization

Mixed level design experiment and Taguchi orthogonal array design L8 (4^1, 2^2) was applied to optimize pyrolysis process for preparing bone char in order to remove fluoride from real groundwater. Taguchi analysis is through selecting high signal-to-noise ratio as a better response. Estimated effects index based on the least squares approach indicated that the pyrolysis temperature had a main effect on bone char preparation using pyrolysis process. The bone char obtained at pyrolysis temperature = 550 °C had the highest adsorption capacity with maximum saturation experimental adsorption capacity of 12.05 mg/g. Specific surface area and Barrett-Joyner-Halenda area of the bone char obtained from pyrolysis of animal bones were 118 m2/g and 120 m2/g, respectively. The experimental adsorption results were better fitted to the Langmuir isotherm and the pseudo second-order kinetic model. Thermodynamic information indicated that fluoride adsorption process onto pyrolysis bone char followed spontaneously (∆Go = −4.972–4.296 kJ/mol), an endothermic (∆Ho = 5.59 kJ/mol) and nature randomness (∆So = 0.033 kJ/mol·K). Accordingly, the bone char obtained using pyrolysis process under optimum conditions demonstrated higher adsorption capacity compared to commercial bone chars applied for fluoride removal from groundwater.

Defluoridization of drinking water by electrocoagulation (EC): process optimization and kinetic study

In this work, removal of fluoride ions from drinking water using electrocoagulation (EC) was carried out using combination of different electrode materials in both monopolar and bipolar connections. The most effective pair of electrode for fluoride removal was found to be Al/Al in bipolar connection. Experiments were conducted to optimize the various operating parameters of EC such as pH, salt dose, stirring speed, inter electrode distance (IED) and current density for efficient removal of fluoride from water. Initial pH of 7.0, current density of 129.31 A/m2, IED of 1 cm, salt dose of 0.33 g/L, stirring speed of 500 and EC time of 40 minutes were found to be optimum conditions to reduce 10 mg/L fluoride ions from water below 1.5 mg/L, which is maximum contaminant level in drinking water as declared by WHO and Indian standard of drinking water. Efficacy of EC process on TDS and turbidity removal of the solution at different operating conditions had also been studied. First order kinetic model was found to fit for fluoride removal. Rate constant (k) increased from 0.02566 to 0.117 min−1 with increase in CD from 17.29 to 258.62 A/m2 due to availability of more aluminum hydroxide flocs in the solution.

Highly selective and efficient removal of fluoride from aqueous solution by Zr[sbnd]La dual-metal hydroxide anchored bio-sorbents

The pomelo peel was used as a bio-carrier for anchoring the dual-metal hydroxide (ZrLa), forming the ZrLa/PP composites. Morphology properties of the ZrLa/PP composites indicated that a large amount of ZrLa dual-metal hydroxides were self-aggregated on the virgin biomaterials, forming the different sizes (10–100 nm) of nano-structured aggregates on the ZrLa/PP composites. The Zr distribution corresponded well to the dispersed La in the ZrLa/PP composites. Fluoride capture by ZrLa/PP composites increased with the increase in temperature. The preferential fluoride adsorption by the ZrLa/PP composites can also be achieved in magnitudes of coexisting ions. The ZrLa/PP composites exhibited a promising fluoride adsorption capacity with a significantly excellent stability. Several column adsorption-desorption cycles exhibited that there were no significant loss in fluoride capacity; this indicated the high adsorption stability of ZrLa/PP composites. Based on all results above, it was suggested that the ZrLa/PP composites could be used as a promising adsorbent for fluoride removal in real application.

Highly efficient removal of fluoride from aqueous media through polymer composite membranes

Abstract Different aluminum and calcium based particles, montmorillonite (MMT), zeolites (NaY), bayerite (BAY) and hydroxyapatite (CaHAp), were compared and evaluated for water defluorination. The effect of parameters such as temperature of the medium, concentration (mass of adsorbent), reaction time and pH on the defluorination capacity were studied for the particles with best performance. MMT and CaHAp adsorbents showed increased fluoride rejections in batch experiments (≈45 and 100%). The defluorination capacity of MMT is influenced by the concentration and pH, while for CaHAp is independent of the evaluated parameters within the measured range. Further, polymer composite membranes based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and the adsorbents with higher defluorination capacity were prepared by thermally induced phase separation in order to produce active filters for fluoride removal from water. The composite membranes presented a homogeneous porous structure with degrees of porosity ranging between ≈20 and 76% and average pore size in the micron range. The permeability of the composite membranes ranged between 12,500 and 10,000 L/h·m2·bar. A maximum fluoride rejection of 68% was obtained after 6 filtrations for the CaHAp/P(VDF-HFP) composite membranes. Thus, the composite membranes of P(VDF-HFP) with MMT and CaHAp show suitable performance for defluorination in water purification systems.

Simultaneous and efficient removal of fluoride and phosphate by Fe-La composite: Adsorption kinetics and mechanism

We report the synthesis of a novel Fe-La composite adsorbent by one-pot hydrothermal method for removing fluoride and phosphate simultaneously. The as-obtained adsorbent shows rod-like morphology and large specific surface area of 113.13 m2/g. A series of adsorption experiments were carried out to investigate the influence of various factors on the simultaneous adsorption of fluoride and phosphate, such as different adsorbent dosage, pH, temperature and co-existing anion. The results demonstrate that the Fe-La adsorbent exhibited high adsorption capacity for fluoride and phosphate in a wide pH range (3.8–7.1). The adsorption kinetics of fluoride and phosphate by Fe-La composite could be well described by the Langmuir model and the pseudo-second-order model. The simultaneous removal of fluoride and phosphate by Fe-La composite could be ascribed to ion exchange between fluoride and La-OH groups, as well as the formation of metal phosphates precipitation, respectively. Our results may provide some insight to develop new adsorbents for removing fluoride and phosphate simultaneously.

Efficient fluoride removal from aqueous solution by synthetic Fe[sbnd]Mg[sbnd]La tri-metal nanocomposite and the analysis of its adsorption mechanism

La is highly electrically affinitive for fluoride ions, but it is costly. Therefore, it is reasonable to mix it with cheap metals to form hybrid materials. On the other hand, calciniation process is usually needed in preparation of many adsorbents based on metal elements, which is energy and time consuming and not environment-friendly. In the present study, a novel FeMgLa tri-metal nanocomposite was facilely prepared by co-precipitation without calcination. The role of individual metal in the tri-metal nanocomposite was illustrated. The samples were characterized by BET, SEM, TEM, Mapping EDS and XPS. Various influencing factors such as coexisting anions, pH and contacting time were studied in detail. Sorption isotherms showed that the sorption capacity of fluoride is 13.2 mg/g at the equilibrium fluoride concentration of 1 mg/L, and the maximum sorption capacity is 47.2 mg/g, indicating the high defluoridation performance of the adsorbent. The F− saturated adsorbent can be regenerated by alkaline and reused. Adsorption mechanism was analysized in detail, and the results indicated that F ions were able to substitute for all three metal-OH groups, and strong interactions happened between fluorion and the metals in the adsorption. The adsorption mechanism was speculated to be ligand exchange, which could be well supported by experimental results. The adsorbent is promising to treat fluoride polluted waters due to its high adsorption efficiency, low cost and easy operation.

Highly selective and efficient removal of fluoride from ground water by layered Al-Zr-La Tri-metal hydroxide

A novel layered Zr-Al-La tri-metal composite (AZL) was fabricated via co-precipitation method for fluoride removal. The as-prepared adsorbent was characterized by various technologies, and its adsorption behaviors to fluoride were thoroughly carried out to investigate the fluoride removal performance. The results showed that the layered structure existed and the AZL exhibited the maximum adsorption capacity of 90.48 mg g-1 at 308 K and pH 3.0 from the Langmuir isotherm model. The adsorption kinetics was well fitted by the pseudo-second-order equation, and the adsorption isotherms were well described by the Langmuir equation. Adsorption thermodynamics result was indicative of endothermic reaction in the process of adsorption of AZL to fluoride. The as-prepared AZL composite has excellent fluoride removal performance for the practical ground water and satisfies the permissible limit of fluoride in drinking water recommended by Chinese Standard. In addition, based on the characterization, the adsorption mechanism of fluoride on AZL was proposed, including electrostatic interaction between the protonated surface of AZL and fluoride, as well as ion-exchange by hydroxyl group and fluoride.

Metal-organic framework-801 for efficient removal of fluoride from water

Fluoride excess in water is harmful to human beings. Adsorption is an effective way to remove fluoride in water. Exploring novel and efficient sorbents for fluoride adsorption is very necessary and challenging. In this work, the fluoride adsorption behavior of zirconium fumarate metal-organic framework-801 (MOF-801) in water is studied through batch adsorption experiments. MOF-801 has high and stable adsorption efficiency at pH 2–10. The fluoride adsorption capacity on MOF-801 is neither affected by high ion strength nor other anions including Cl−, NO3− and SO42−. The fluoride adsorption on MOF-801 follows a pseudo-second-order model and the Langmuir equation. The fluoride adsorption capacity of MOF-801 is 40 mg g−1 at 303 K, changing little with temperature. The effective defluoridation of MOF-801 resulted from the ion exchange of fluoride ions and hydroxyl group in MOF-801. The practical use of MOF-801 for fluoride adsorption from real water sample reveals the potential of MOF-801 as an efficient adsorbent for the removal of fluoride from water.

Enhanced fluoride removal by La-doped Li/Al layered double hydroxides

In this study La intercalated Li/Al layered double hydroxide (LDH) was developed for efficient water defluoridation. The La-modified material, i.e., La doped Li/Al-LDH, exhibits more preferable fluoride adsorption than Li/Al-LDH in a broad pH range of 5–9, with the working capacity twice of the latter and seven times of magnitude higher than activated alumina. The fluoride removal kinetics is well fitted by pseudo-second order model, and the adsorption isotherm is well described by Freundlich model. Effect of pH and competing ions was examined during fluoride sequestration. The underlying mechanism for such enhanced adsorption of fluoride by La doped Li/Al-LDH was further revealed based on XPS and FTIR analysis. The presence of La and Al was found to be responsible for the satisfactory defluoridation of La doped Li/Al-LDH, and chloride replacement with fluoride occurred from both LDHs during fluoride adsorption. Also, the capacity of La doped Li/Al-LDH could be refreshed by alkaline solution (pH = 12) for cyclic runs. All the results implied that La doped Li/Al-LDH could serve asa potential adsorbent for efficient fluoride removal from water.

Development of Zr(IV)—Doped polypyrrole/zirconium (IV) iodate composite for efficient removal of fluoride from water environment

The present work reports the preparation of zirconium(IV)-doped polypyrrole/zirconium (IV) iodate composite for fluoride removal. The composite material was characterized by FTIR, XRD, TGA-DTA and SEM coupled with EDX. The effects of various experimental parameters such as pH, contact time, adsorbent dose and initial fluoride ion concentration on the fluoride removal were studied in batch mode and optimized for maximum removal of fluoride from water. The adsorption capacity was found to be 183.5mg/g at pH 6.8. The adsorption isotherm data were well described by Freundlich isotherm model. The results of kinetic studies indicated that the experimental data fitted well with the pseudo-second-order kinetic model. The activation energy for adsorption of fluoride on the adsorbent was found to be 37.04kJ/mol. The adsorbent has been successfully applied to remove fluoride from groundwater by column method.

Efficient Removal of Fluoride Using Polypyrrole-Modified Biochar Derived from Slow Pyrolysis of Pomelo Peel: Sorption Capacity and Mechanism

In this study, a novel adsorbent was developed by loading polypyrrole (PPy) onto biochar (BC) prepared by slow pyrolysis of pomelo peel. This PPy-grafted BC mainly exhibited anion-exchange behavior, which dramatically increased fluoride adsorption capacity. The effects of various factors (adsorbent dosage, pyrrole concentration, initial solution pH, co-existing anions and temperature) on the fluoride adsorption were investigated. The adsorbent was characterized by scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and automatic titration methods. Results showed that the optimized adsorbent (BP-0.1) performed excellently at pH 2.8–10.0, and possessed positive charge at pH < 8.6. The adsorption isotherm data were fitted well by the Langmuir model and the maximum adsorption capacity was 18.52 mg/g at 25 ± 2 °C. The adsorption kinetics followed the pseudo-second-order model and adsorption equilibrium was achieved at 24 h. Although both HCO3 − and CO3 2− had great influence on F− adsorption, there was no significant impact in the presence of Cl−, NO3 − and SO4 2−. Real groundwater study showed that 2.5 g/L of BP-0.1 could effectively reduce F− from 10.0 to 1.4 mg/L at pH 5.0. Thermodynamic parameters confirmed the spontaneous and endothermic nature of the adsorption process. Effect of pH, XPS analysis and the change of amount between Cl− and F− in the adsorption process revealed that ion exchange and electrostatic attraction were involved in the adsorption process and ion exchange was the main adsorption mechanism.

Seaweed-Derived Nontoxic Functionalized Graphene Sheets as Sustainable Materials for the Efficient Removal of Fluoride from High Fluoride Containing Drinking Water

Herein we present a sustainable and cost-effective approach for the preparation of functionalized graphene nanosheets (GNs) directly from seaweed and deep eutectic solvents (DESs). The seaweed granules remained after the recovery of juice from fresh brown seaweed, Sargassum tenerrimum, was utilized as a raw material and DESs generated by the complexation of choline chloride and metal salts were employed as solvent and catalyst for the large scale and facile production of metal oxide functionalized GNs. Moreover considering the biological application of such GNs, where nontoxic nature of substrates is desirable, we have also evaluated the cytotoxicity of the functionalized GNs (Fe3O4/Fe, SnO2/SnO/Sn, or ZnO/Zn-functionalized GNs), and most of them were found to be nontoxic against human lung carcinoma cells (A549). Thereafter, efficiency of these GNs was assessed for the removal of F– from fluoride contaminated groundwater (2.72–6.71 mg L–1) used for drinking purposes. After treatment with GNs, the concent...

Diseases Prevention by Water Defluoridation Using Hydrotalcites as Decontaminant Materials

Preventing diseases is deemed to be the major goal of our century especially when an excessive fluoride in drinking water can cause dental fluorosis, bone stiffness, rheumatism and skeletal fluorosis. Fluoride uptake from groundwater implies a worldwide multidisciplinary effort in order to develop renewable, cheap, human friendly materials. Among other materials, hydrotalcites could be good candidates for an efficient fluoride removal from water due to their adsorption, anion exchange and reconstruction properties. These nanostructured materials were synthesized using co-precipitation method in controlled conditions. Presence of anions in the interlayer structure and morphological aspects were performed by FTIR and SEM techniques. Thermal treatment of hydrotalcites showed good adsorption capacities for water defluoridation mostly due to their tendency to restore the original structure.

Efficient removal of fluoride from water using a paramagnetic adsorbent: FeAlOxHy combined with superconducting magnetic separation

ABSTRACTThe present study investigated fluoride removal by high-gradient superconducting magnetic separation (HGSMS) and paramagnetic adsorbents. FeAlOxHy adsorbents with different Fe/Al molar ratios were synthesized and characterized. The adsorption capacities of FeAlOxHy increased with increasing Al content. The FeAlOxHy were effectively separated in HGSMS, and approximately 87% of the fluoride was removed. Higher magnetic intensity, lower flow rate and finer steel wool are among the advantages of FeAlOxHy separated in HGSMS. The maximum desorption efficiency of fluoride adsorbed by FeAlOxHy was measured as 92.06%. A fluoride concentration time value of 40 was obtained using FeAlOxHy followed by the HGSMS process.

Synthesis, Characterization and Application of ZrCl4-Graphene Composite Supported on Activated Carbon for Efficient Removal of Fluoride to Obtain Drinking Water

The aim of this study is to evaluate the fluoride removal from contaminated water using a new adsorbent material of high efficiency to obtain drinking water. The ZrCl4-graphene supported on vegetal activated carbon composite (G-ZrCl4/VAC) was synthesized and characterized using transmission and scanning electron microscopy, N2 physisorption, energy dispersive X-ray spectrometry, Fourier transform-infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. Furthermore, the point of zero charge was determined. The G-ZrCl4/VAC was evaluated for fluoride adsorptive removal from water under several operating conditions in batch system. The results indicated that fluoride adsorption by G-ZrCl4/VAC is favored at low pH values with the maximum adsorption at pH 2, corresponding to 97.22% removal. Among the conditions of temperature and agitation evaluated, the best results were achieved at 30 °C and 130 rpm, with removal percentages equal to 47.78 and 48.48%, respectively. The equilibrium of the system was achieved in 5 h of operation. The pseudo-first order kinetic model was the one that best described the kinetic data, while the equilibrium data were best described by the Langmuir isotherm with maximum adsorption capacity equal to 3.89 mg g−1. Therefore, the results obtained show that the material synthesized has a great capacity for adsorption and demonstrate the viability of use of G-ZrCl4/VAC in the removal of fluoride to obtain drinking water.