High Fluoride Adsorption Capacity Research Articles

Fluoride removal by hydroxyapatite modified with anhydrous aluminum chloride

ABSTRACT Efficient and low-cost removal of fluoride from water has attracted wide attention. Here, aluminum-modified hydroxyapatite (Al-HAP) was prepared by a homogeneous hydrothermal co-precipitation method. The physicochemical properties of the Al-HAP surface were characterized by SEM, XRD, FT-IR, BET, and zeta potential, and the adsorption performances were evaluated. It showed that Al-HAP has a larger specific surface area (121.97 m2/g, which is 2.3 times larger than that of HAP), more surface-active hydroxyls and positively charged at pH less than 7, which indicate that Al-HAP is beneficial to the adsorption of negatively charged fluoride. Al-HAP had a higher fluoride adsorption capacity (56.44 mg/g) than that of HAP (28.36 mg/g), and not sensitive to the interference of coexisting ions except CO32-. Based on the adsorption kinetics and adsorption isotherm experiments, the proposed two-stage kinetic model and Freundlich isotherm model can better describe the adsorption process. From the results of XPS and FT-IR, it indicated that the ion exchange between hydroxyl group on the surface and fluoride ions is the main driven force for the adsorption, and electrostatic adsorption is also helpful. The present study provides an improved HAP to effectively remove fluoride from water.

Valorization of waste gypsum board as a green adsorbent for efficient fluoride removal in groundwater and wastewater treatment

The escalating generation of construction waste during building reconstruction and remodeling underscores the significance of recycling for environmental preservation and resource conservation. In this context, we propose the valorization of waste gypsum board (WGB), a common construction waste material, as a value-added environmental purification agent. WGB, composed primarily of CaSO4, displays the potential to react with fluoride to form CaF2, making it a promising adsorbent for fluoride removal. Through density functional theory analysis, we determined that WGB possesses mesoporous characteristics, with pore sizes ranging from 1 to 20 nm. While thermal treatment has been effective in enhancing fluoride adsorption on other adsorbents, our investigations revealed that the crystalline structure (CaSO4) of WGB remained unchanged under thermal treatment, limiting its impact on the fluoride adsorption capacity. Nevertheless, WGB exhibited a remarkably high fluoride adsorption capacity (285.90 mg/g), surpassing those of other reported adsorbents. Furthermore, the WGB demonstrated excellent fluoride removal performance, even at higher solution pH levels. In artificial wastewater, a dose of 3.33 g/L WGB achieved a remarkable removal efficiency (> 95%). The applicability of WGB was validated by successful fluoride removal in real wastewater and groundwater, with 94% of fluoride in groundwater removed using 0.33 g/L of WGB and 97% of the fluoride in the wastewater removed with 1.67 g/L WGB. This study opens a promising pathway, demonstrating the potential of WGB as a green adsorbent for the effective treatment of fluorine-contaminated wastewater and groundwater, transcending its traditional role in waste recycling.

Functional hBN decorated Ni(OH)2 nanosheets synthesized for remarkable adsorption performance for the elimination of fluoride ions.

Occurrence of fluoride in groundwater is a serious concern due to its fatal effects. Functionalized hexagonal boron nitride sheets have been combined with nickel hydroxide nanoparticles by a one step process and a hybrid adsorbent Ni(OH)2@hBN has been developed with an exceptionally high fluoride adsorption capacity of 365 mg g-1, higher than those of Ni(OH)2 and hBN. This maximum adsorption capacity is higher than those of most common adsorbents used for defluoridation including activated alumina, reported nickel oxide and carbon-based 2D material-supported alumina adsorbents. The presence of functionalized boron nitride significantly increased the surface area to 680 m2 g-1 with a pore volume of 0.33687 cm3 g-1 and provided rich hydroxyl group-containing surface sites for the removal of fluoride present in contaminated water. In addition, the adsorption of fluoride onto boron nitride-modified nickel hydroxide followed pseudo-second-order kinetics and the equilibrium data fitted well with the Langmuir adsorption isotherm, suggesting a monolayer adsorption mechanism. Furthermore, the material developed is tested with the water sample collected from a real affected area, from the Dhar district of India, and the material showed promising results in terms of fluoride removal efficacy.

Adsorption of fluoride from industrial wastewater using polymer adsorbents: a review

Fluoride pollution in ground and surface water originates from naturally occurring reactions and industrial activities such as the disposal of industrial wastewater. Amongst different fluoride removal technologies including chemical precipitation, membrane filtration, ion exchange processes, and electrodialysis, adsorption is an attractive method for fluoride removal from wastewater due to its low operational cost, simplicity, and good sustainability. Various adsorbents are used for fluoride removal including, metal oxides and hydroxide, carbonaceous adsorbents, zeolite, polysaccharides, and polyresin adsorbents. This review studies the application of modified polysaccharides and polyresin adsorbents for the removal of fluoride from wastewater. The relationship between the adsorption conditions and the resulting adsorption capacity is thoroughly discussed. Based on the reported studies, modified polysaccharides and polyresins adsorbents can effectively remove fluoride from wastewater achieving high adsorption capacity, the highest being 92.39 mg/g for aluminum impregnated amberlite at pH 3. Furthermore, aluminum impregnated adsorbents reported a higher fluoride adsorption capacity than other modification methods where the three adsorbents with the highest fluoride adsorption capacity are: aluminum impregnated amberlite 92.39 mg/g at pH 3> zirconium immobilized crossed linked chitosan 48.26 mg/g at pH 6 > chitosan/aluminum hydroxide beads 17.68 mg/g at pH 4. In addition, polymeric adsorbents are also highly sustainable as they can be regenerated multiple times to be reused. Therefore, the high adsorption capacity and good regeneration potential allow polymeric adsorbents to serve as promising and sustainable adsorbents to remove fluoride from industrial wastewater.

A novel alum impregnated CaO/ carbon composite for de-fluoridation of water

Excessive fluoride concentration (>1.5 mg/L) in water adversely affects human teeth and bones. The present study focuses on the development of a fluoride adsorbentvia wet chemical method, by treating activated carbon and CaO (derived from rice straw and egg shell respectively) with alum. The prepared adsorbents were characterized for various physico-chemical parameters and fluoride adsorption test. The optimized composite with highest fluoride adsorption capacity was further subjected to batch adsorption study. The adsorbent followed second order kinetic model with intra-particle diffusion revealing that the adsorption was controlled by pore diffusion along with the other process, i.e. electrostatic interaction between opposite charges. This has been explained by a mechanism which in turn is supported by XPS data. Langmuir isotherm fitted well with experimental data suggesting homogenous and monolayer adsorption of fluoride. The adsorption capacity obtained from Langmuir isotherm model is 48.78 mg/g. Thus the adsorbent is highly effective in removing fluoride from the initial concentration of 10 ppm to less than 0.2 ppm which is safe for drinking purpose.

A novel carboxylated polyacrylonitrile nanofibrous membrane with high adsorption capacity for fluoride removal from water

To deal with the drinking water safety caused by fluoride, a novel carboxylated polyacrylonitrile nanofibrous membrane (C-PAN NFM) is designed and fabricated massively for the first time by adopting synchronously biaxial stretching and carboxylation. The C-PAN NFM is composed of the layered stack structure by cross-linked nanofibers. Due to its high specific surface area, excellent hydrophilicity, a large amount of carboxyl and amine groups, C-PAN NFM owns high fluoride adsorption capacity and outstanding selectivity. Both the carboxylation and acid treatment of C-PAN NFM improved the fluoride adsorption capacity remarkably. Specifically, C-PAN NFM shows excellent reusability without secondary pollution. The fluoride adsorption behavior of C-PAN NFM is dominated by chemical adsorption, and the adsorption mechanism is mainly driven by hydrogen bonding and ion exchange. The mass-produced C-PAN NFM is a novel polyacrylonitrile-based porous membrane that shows a great application potential for fluoride removal with good efficiency and recyclability.

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.

Fluoride removal from water by ceramic oxides from cerium and manganese solutions

The excess of fluoride in water has given rise to serious health problems, reason why it is considered a priority pollutant to be removed from drinking water by the World Health Organization (WHO). Several investigations have shown that metal oxides possess a high fluoride adsorption capacity, and recent studies have shown that ceramic oxides are excellent adsorbent materials for various anions in aqueous solutions, which is attributed to their high content of OH– groups. Due to the above, in this research Ce and Mn ceramic oxides were synthesized by a solvothermal method in a microwave to obtain these crystalline oxides: octahedral CeO2, γ-MnOOH and Mn3O4 as rods and nanoparticles, and Ce(OH)SO4 as spherical and plates forms. These ceramic oxides were characterized by Fourier transform infrared spectroscopy (FTIR), potentiometric titrations, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to determine their morphology and composition, the oxides phases were identified by an X-ray diffraction, and their BET surface area was determined by Physisorption. In addition, adsorption and kinetic experiments were carried out to determine fluoride adsorption capacities and rate in aqueous solution. Among the oxides prepared, Ce(OH)SO4 was identified as the material with the highest fluoride adsorption capacity (≈16 mg g−1 at 10 ppm F− equilibrium concentration), although this material showed a low BET surface compared to the other oxides. Finally, the fluoride adsorption mechanism was proposed considering the compounds in the ceramic oxides.

Synthesis of bone char from cattle bones and its application for fluoride removal from the contaminated water

This study is focused on the synthesis of bone char (BC) and its application in adsorptive removal of fluoride from the water. The BC was synthesized by the thermal pyrolysis of used cattle bones. In preliminary stage, BC was synthesized at different temperatures ranging from 350 to 700 °C and due to the higher surface area and adsorption capacity, BC synthesized at 350 °C was selected for further experiments. The XRD pattern of BC found better in agreement with the standard pattern of hydroxyapatite. FTIR analysis also signified basic spectra of hydroxyapatite with specific bands at wavelength of 3429, 1639, 1453, 1037, 604 and 566 cm−1. Typical agglomerated structure of hydroxyapatite was witnessed in morphological examination with SEM. The specific surface area, total pore volume and the average pore diameter were found 79.34 m2 g−1, 0.041 cm3 g−1 and 2.09 nm, respectively. The elemental chemical analysis revealed 1.71 Ca/P ratio. About 10.56 mg of fluoride was adsorbed on 1 g of BC. The adsorption isotherm data was briefly illustrated by applying Langmuir isotherm model and Freundlich isotherm model. In conclusion, BC is successfully synthesized and the highest fluoride adsorption capacity was achieved as compared with earlier studies.

Organometallic Adsorbent for Mitigating Fluoride from Water: An Environment‐Friendly Approach

AbstractFluoride‐related health hazards are a serious environmental problem across the globe. Unavailability of an effective therapeutic agent to cure fluorosis creates an exigency to adopt preventive measures to curb excess fluoride intake. Herein, we report a zirconium‐based organometallic adsorbent (ZrVAc) for mitigating fluoride from water. The crosslinked, three dimensional and porous architecture of ZrVAc, composed of zirconyl methacrylate (ZrDMA) and vinyl acetate (VAc) have high porosity and excellent mechanical stability. The experimental factors such as effects of solution pH, coexisting anions, temperature, pHpzc, isotherm models and surface chemistry were investigated to verify the adsorption properties of ZrVAc. The equilibrium data were fitted well with Freundlich and Langmuir adsorption isotherms. The highest fluoride adsorption capacity (qm) was found to be 138 mg/g (at pH 7.0±0.2, initial F− concentration 100 mg/L, adsorbent dose 0.5 g/L for 6 h). The thermodynamic constants ΔG, ΔH, and ΔS were calculated as 45.158 KJ mol−1 (at 303 K), −37.64 KJ mol−1, and −0.161 KJ mol−1. ZrVAc showed efficient adsorption in pH range of pH 6.0‐8.0 which is preferable for field water application. Toxicity characteristics leaching procedure (TCLP) results suggested the ZrVAc was inert; does not leach out any contaminants (Zr, F−) and delivers safe and potable treated water.

The Extremely High Adsorption Capacity of Fluoride by Chicken Bone Char (CBC) in Defluoridation of Drinking Water in Relation to Its Finer Particle Size for Better Human Health.

The ingestion of fluoride-contaminated water causes serious health issues in people all over the world. In the current study, the adsorption of fluoride onto chicken bone char (CBC) was investigated as a defluoridation technique. Finer-sized CBC with a diameter of 106–212 µm was used to investigate the fluoride adsorption capacity onto CBC. Results revealed that finer-sized CBC yielded an unusually high fluoride adsorption capacity of 11.2 mg/g at the equilibrium fluoride concentration of 10 mg/L. The study shows that CBC can be utilized in the defluoridation of drinking water and that finer-sized CBC enhances ion exchange to perform a higher adsorption capacity.

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.

Electrically enhanced adsorption and green regeneration for fluoride removal using Ti(OH)4-loaded activated carbon electrodes

An electrically enhanced fluoride removal method was developed that blended the merits of electrosorption and adsorbent adsorption. This method has the advantages of high adsorption selectivity and capacity for fluoride. The saturated adsorption capacity of Ti(OH)4 for fluoride in the electrode of Ti(OH)4-loaded activated carbon reached 115.2 mg/g when a voltage of +1.2 V was applied to the electrode. The electrode was easily and cleanly regenerated in a short time in aqueous solution with high fluoride concentrations when a voltage of −1.6 V was applied. The adsorption capacity of the Ti(OH)4-loaded electrode for fluoride did not decrease after multiple cycles of electrically enhanced adsorption and regeneration. Excellent adsorption selectivity for fluoride was achieved. The electrically enhanced adsorption method showed potential for fluoride removal.

Hydrothermal synthesis of a mineral-substituted hydroxyapatite nanocomposite material for fluoride removal from drinking water

Mineral substituted hydroxyapatite (mHAp) nanocomposite was synthesized and it shows high fluoride adsorption capacity.

Synthesis and properties of a high-capacity iron oxide adsorbent for fluoride removal from drinking water

A novel iron oxide adsorbent with a high fluoride adsorption capacity was prepared by a facile wet-chemical precipitation method and ethanol treatment. The ethanol-treated adsorbent was amorphous and had a high specific surface area. The adsorption capacity of the treated adsorbent was much higher than that of untreated adsorbent. The Langmuir maximum adsorption capacity of the adsorbent prepared at a low final precipitation pH (≤9.0) and treated with ethanol reached 60.8mg/g. A fast adsorption rate was obtained, and 80% of the adsorption equilibrium capacity was achieved within 2min. The adsorbent had high fluoride-removal efficiency for water in a wide initial pH range of 3.5–10.3 and had a high affinity for fluoride in the presence of common co-anions. The ethanol treatment resulted in structure transformation of the adsorbent by inhibiting the crystallization of the nano-precipitates. The adsorption was confirmed to be ion exchange between fluoride ions and the hydroxyl groups on the adsorbent surface.

Removal of fluoride from drinking water using highly efficient nano-adsorbent, Al(III)-Fe(III)-La(III) trimetallic oxide prepared by chemical route

Al(III)-Fe(III)-La(III) trimetallic oxide was synthesized through chemical process. XRD revealed monoclinic phase when calcined at 800 °C, 4 h. IR study confirmed the formation of desired compound. A high surface area of 22.14 m2/g was observed with a pore volume 1.5 × 10−2 cc/g. The porosity and the microstructure were studied by SEM and TEM. F− adsorption capacity was studied varying the adsorbent dose in 100 ml: 0.05 g, 0.1 g, 0.2 g and 0.3 g and the contact time in minute: 15, 30, 45 and 60 taking 3 ppm, 5 ppm and 10 ppm fluoride solutions. Experimental observation revealed high fluoride adsorption capacity ∼99%.

Enhanced adsorption of fluoride from aqueous solutions by hierarchically structured Mg-Al LDHs/Al2O3 composites

Hierarchically structured layered double hydroxides (LDHs)/Al2O3 composites were fabricated from waste paper fibers using a two-step method. In the first step microscaled Al2O3 fibers were prepared by template-directed synthesis employing waste paper fibers as templates; and in the second step nanoscaled LDHs platelets were fabricated into hierarchical architectures based on crystal growth on Al2O3 fibers surface. The morphology and structure of asprepared samples were characterized by scanning electron microscopy (SEM), N2 adsorption/desorption analysis and X-ray diffraction (XRD) analysis. The SEM results revealed that the inorganic fibers were covered by LDHs platelets, forming the hierarchical structures with micro- to nanoscales. The BET analysis showed that the surface area was increased from 76.66m2/g (Al2O3 fibers) to 165.0m2/g (composites) by the growth of LDHs platelets on the surfaces of Al2O3 fibers. As compared to bare LDHs particles and Al2O3 fibers, the LDHs/Al2O3 composites show a high fluoride adsorption capacity, and the maximum adsorption capacity can reach up to 58.7mg/g. The Langmuir isotherm model was found to agree well with the equilibrium data, while the pseudo-second order model provided the highest correlation of the kinetic data for fluoride adsorption. The as-prepared LDHs/Al2O3 composites and corresponding design strategies developed herein are expected to be applicable to the synthesis of other LDHs based composites for the removal of pollutants from water.

Red Mud의 산처리 및 열처리가 불소 제거에 미치는 영향

Fluoride removal by acid and heat treated red mud were studied in batch and column system regarding contact time, initial concentration, pH, adsorbent dose, and filter depth. The results showed that acid treated with 0.8 M HCl, had highest adsorption capacity of fluoride and adsorption capacity decreased as heat treatment temperature increased. Sorption equilibrium reached in 30 min at a initial concentration of 50 mg-F/L but 1 h was required to reach the sorption equilibrium at the initial concentration of 500 mg-F/L by 0.8 M acid treated red mud (0.8 M-ATRM). Equilibrium adsorption data were fitted well to Langmuir isotherm model with maximum fluoride adsorption capacity of 23.162 mg/g. The fluoride adsorption decreased as pH increased due to the fluoride competition for favorable adsorption site with OH at higher pH. Removal percentage was increased but the amount of adsorption per unit mass decreased by adding the amount of 0.8 M-ATRM. It was concluded that the 0.8 MATRM could be used as a potential adsorbent for the fluoride removal from aqueous solutions because of its high fluoride adsorption capacity and low cost.

Comparing activated alumina with indigenous laterite and bauxite as potential sorbents for removing fluoride from drinking water in Ghana

Fluoride is considered beneficial to teeth and bones when consumed in low concentrations, but at elevated concentrations it can cause dental and skeletal fluorosis. Most fluoride-related health problems occur in poor, rural communities of the developing world where groundwater fluoride concentrations are high and the primary sources of drinking water are from community hand-pump borehole drilled wells. One solution to drinking high fluoride water is to attach a simple de-fluoridation filter to the hand-pump; and indigenous materials have been recommended as low-cost sorbents for use in these filters. In an effort to develop an effective, inexpensive, and low-maintenance de-fluoridation filter for a high fluoride region in rural northern Ghana, this study conducted batch fluoride adsorption experiments and potentiometric titrations to investigate the effectiveness of indigenous laterite and bauxite as sorbents for fluoride removal. It also determined the physical and chemical properties of each sorbent. Their properties and the experimental results, including fluoride adsorption capacity, were then compared to those of activated alumina, which has been identified as a good sorbent for removing fluoride from drinking water. The results indicate that, of the three sorbents, bauxite has the highest fluoride adsorption capacity per unit area, but is limited by a low specific surface area. When considering fluoride adsorption per unit weight, activated alumina has the highest fluoride adsorption capacity because of its high specific surface area. Activated alumina also adsorbs fluoride well in a wider pH range than bauxite, and particularly laterite. The differences in adsorption capacity are largely due to surface area, pore size, and mineralogy of the sorbent.

Adsorption of fluoride on Mg/Fe layered double hydroxides material prepared via hydrothermal process

A nitrate containing Mg/Fe-LDHs with ignorable leakage of metal ions and high fluoride adsorption capacity.