Adsorptive removal of fluoride from water samples using Zr–Mn composite material

Utilization of organic waste from Chinar leaves as sustainable and eco-friendly adsorbent for fluoride removal

Due to concerns about high water fluoride concentrations and their detrimental consequences on health, particularly dental and skeletal fluorosis, dependable and cost-effective defluoridation techniques are needed. Chinar leaves (Platanus orientalis), a common waste, might be utilized for the production of activated carbon. For Chinar leaf activated carbon (CLAC) manufacturing, two pre-pyrolysis chemical modification procedures were used: acidic HCl (H-activation) and alkaline NaOH (OH-activation). The success of fluoride removal suggests further research and implementation in locations with fluoride-related water quality issues. This study examines how CLAC dosage, fluoride concentration, temperature, pH, and contact exposure effect defluoridation efficiency. The pseudo-second-order non-linear kinetic model and Freundlich non-linear isotherm model with R2 = 0.99 fit the data, resulting in a peak adsorption capacity of 30.3 mg/g for 0.3 g CLAC. In the present work, the adsorption mechanism was regulated by more than intraparticle diffusion. Adsorption occurred spontaneously as exothermic monolayer chemisorption, according to thermodynamic studies. Adsorbent activated with HCl (H-activated) showed promising results, with 73% F- removal efficiency for OH-activated and 91% for H-activated CLAC.

Highly efficient adsorption of ciprofloxacin from aqueous solutions by waste cation exchange resin-based activated carbons: Performance, mechanism, and theoretical calculation

This study focused on the preparation of a highly efficient activated carbon adsorbent from waste cation exchange resins through one-step carbonization to remove ciprofloxacin (CIP) from aqueous solutions. Scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectrometry, and X-ray photoelectron spectroscopy were used to characterize the physicochemical properties of the carbonized materials. The CIP removal efficiency, influencing factors, and adsorption mechanisms of CIP on the carbonized resins were investigated. Density functional theory (DFT) computations were performed to elucidate the adsorption mechanisms. The CIP removal reached 93 % when the adsorbent dosage was 300 mg/L at 25 °C. The adsorption capacity of the carbonized resins to CIP gradually decreased with an increasing pH from 3.0 to 7.0 and sharply declined with a pH from 7.0 to 11.0. The adsorption process better fitted by the pseudo second-order kinetic and Langmuir models, indicating that the interaction between CIP and the carbonized resins was monolayer adsorption. The maximum adsorption capacity fitted by the Langmuir model was 384.4 mg/g at 25 °C. Microstructural analysis showed that the adsorption of CIP on the carbonized resins was a joint effect of H-bonding, ion exchange, and graphite-N adsorption. Computational results signified the strong H-bonding and ion exchange interactions existed between CIP and carbonized resins. The high adsorption and reusability suggest that waste cation exchange resin-based activated carbons can be used as an effective and reusable adsorbent for removing CIP from aqueous solutions.

One-pot synthesis of versatile sphere-like nano adsorbent MnAl2O4 (MAO): an optical and magnetic material for efficient fluoride removal and latent finger print detection

Spherically shaped trimetallic MnAl2O4 (MAO) nanoadsorbent was prepared in an one-pot synthesis process for the removal of excess fluoride from water. The adsorbent was characterized by thermogravimetric analysis (TGA), X-ray diffraction study (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), etc. The adsorption property for fluoride on the MAO was analyzed by batch experiments varying the adsorbent dose, pH, contact time, and initial fluoride concentration. The results showed that the fluoride uptake behavior of the samples could precisely be fitted by the Freundlich model, and the maximum adsorption capacity was estimated to be 39.21 mg/g at room temperature. The pseudo-second-order models accurately described the adsorption kinetics data. The regenerated sample showed excellent reusability along with high removal capacity on real water sample also. The underlying fluoride adsorption mechanism via ion-exchange and electrostatic interaction was established from X-ray photoelectron spectroscopy (XPS) and zeta potential studies. The sample showed excellent luminescence with blue emission with a band gap of 2.6 eV. The materials also showed good elastic behavior exhibiting the Poisson's ratio (σ) 0.32 and excellent latent figure print detection capacity distinguishing the clearly the ridge and furrow regions under UV light. The magnetic behavior was also found to be in long range with antiferromagnetic characteristics.

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

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

Rationally designed and hierarchically structured functionalized aluminium organic frameworks incorporated chitosan hybrid beads for defluoridation of water

In this present investigation, aluminium (Al³⁺) fabricated 2-aminobenzene-1,4-dicarboxylic acid (ABDC) namely Al@ABDC metal organic frameworks (MOFs) was developed for defluoridation studies. The unique advantages of developed MOFs possess high selectivity, high porosity and enhanced surface area but the developed powder form of Al@ABDC MOFs has several limitations in field applications like slow filtration and column blockage. To prevail over these troubles, biopolymer namely chitosan (CS) supported Al@ABDC MOFs namely Al@ABDC-CS beads were developed for effective fluoride adsorption from water. The synthesized Al@ABDC-CS beads were employed for the retention of fluoride in batch level. The defluoridation capacities (DCs) of Al@ABDC MOFs and Al@ABDC-CS beads were found to be 4880 and 4900 mgF^- kg^-1 respectively. The influencing parameters of adsorption method namely agitation time, adsorbent dosage, initial fluoride concentration, pH, co-existing anions and temperature were exploit to get utmost defluoridation capacity (DC) of Al@ABDC-CS beads. The experimental data of Al@ABDC-CS beads have been evaluated utilizing Langmuir, Fruendlich and Dubinin-Radushkevich (D-R) isotherms. The defluoridation nature of Al@ABDC-CS beads was determined by the thermodynamic parameters. The order of reaction of Al@ABDC-CS beads was studied using various kinetic models. The regeneration and field water studies of Al@ABDC-CS beads were also carried out to check their reusability and suitability at field conditions.

Defluoridation using hydroxyapatite implanted lanthanum organic framework-based bio-hybrid beads

The present study reports on biopolymer based material namely HAp–La-BTC MOFs@Alg–CS hybrid beads were developed and it was potentially employed for fluoride removal.

Design and synthesis of amine grafted graphene oxide encapsulated chitosan hybrid beads for defluoridation of water

The promising adsorbent like graphene oxide (GO), chitosan (CS) and amine functionalized graphene oxide (AGO) decorated chitosan (CS) namely AGO@CS composite beads was efficiently prepared for defluoridation studies. The prepared AGO@CS composite beads possess enriched defluoridation capacity (DC) of 4650 mgF^- kg^-1. Batch method was used to optimize the maximum DC of AGO@CS composite beads. The physicochemical properties of AGO@CS composite beads were explored by numerous instrumental techniques viz., FTIR, Raman, XPS, SEM and TGA investigation. The experimental values of AGO@CS composite beads for fluoride removal at various temperature conditions were assessed with adsorption isotherms, kinetic and thermodynamic studies. The possible defluoridation mechanism of AGO@CS beads was mostly proposed that electrostatic attraction. The reusability and field investigation results of AGO@CS beads shows they are regenerable and applicable at field circumstances.

Development of adsorbent from Mentha plant ash and its application in fluoride adsorption from aqueous solution: a mechanism, isotherm, thermodynamic, and kinetics studies

In the present study, Mentha plant ash was modified by Na and Al for the synthesis of adsorbent and applied for the removal of Fluoride from an aqueous solution. Mixture of acid washed Mentha plant ash (MPA) and NaOH (in the ratio 1:1.3) thermally treated at 600°C in a muffle furnace then treated with aqueous solution of sodium aluminate. The characterization of sodium aluminum modified ash (Na-Al-MA) powder was done such as SEM (Scanning Electron Microscopy), Particle Size Analysis (PSA), Fourier transformed spectroscopy (FTIR), Zeta Potential, XRD (X-ray Diffraction) analysis, and Brunauer-Emmett-Teller (BET) analysis. The removal of fluoride from an aqueous solution carried out with Na-Al-MA by batch adsorption process. The Na-Al-MA was found to be very effective as adsorbent. The maximum removal of fluoride was achieved ̴ 86% at neutral pH and at room temperature. It was investigated that Langmuir adsorption isotherm and pseudo-second-order kinetic was best fitted for fluoride adsorption. The fluoride adsorption on Na-Al-MA was an exothermic process. A possible mechanism including electrostatic attraction, hydrogen bonding, and metal-fluoride interaction for fluoride adsorption on Na-Al-MA have described in this study. Novelty statement: Utilization of Mentha plant ash for the development of adsorbent and its application in adsorptive removal of fluoride from aqueous solution is the novelty of this work. Adsorbent preparation may be the better way of waste biomass management.

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

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.

Application of statistical response surface methodology for optimization of fluoride removal efficiency by Padina sp. alga

Human exposure to fluoride in drink water at a level above 1.5 mg/L causes a lot of health problems. The present study was carried out to assess the fluoride biosorption capability of Padina sp. alga as biosorbent material using conventional one-factor-at-a-time (OFAT) and Box-Behnken design to optimize the process. By OFAT, fluoride uptake was significantly affected by pH, time, fluoride concentration, and biosorbent dose (p-value < 0.05) and the highest fluoride biosorption (85.95%) was recorded at pH 7, time 60 min, fluoride concentration 2 g/L, and an adsorbent dose 30 g/L. Based on the Box-Behnken design, the quadratic model was developed to correlate the variables to the response. By Analysis of Variance (ANOVA), the model was statistically significant (p-value < 0.05). It was suggested that optimal values of pH, time, fluoride concentration, and biosorbent dose were 5, 90 min, 3 mg/L, and 30 g/L, respectively, and fluoride removal at these optimum conditions was 94.57%. For application, Padina sp. was removed from 67.79% to 78.78% of fluoride in collected groundwater samples. It was concluded that the Padina sp. could be used as eco-friendly biosorbent for fluoride and response surface methodology was more applicable and effective in optimization to obtain the highest removal efficiency of fluoride by Padina sp. PRACTITIONER POINTS: The fluoride biosorption was studied using Padina sp. alga as an eco-friendly biosorbent. By one-factor-at-a-time (OFAT), the highest fluoride biosorption rate was 85.95%. Response surface methodology was suggested that maximum Fluoride removal at optimum condition was 94.57%. Statistical response surface methodology was more applicable, effective in optimization and considered the interaction between factors.

A review of bismuth-based sorptive materials for the removal of major contaminants from drinking water

In recent years, bismuth has gained attention of many researchers because of its sorptive properties. Sorptive properties of bismuth compounds are used for removal of ionic contaminants from aqueous solution. In this paper, an attempt is made to review the recent developments in the area of contaminant removal from aqueous solutions using bismuth-based media. List of various bismuth-based adsorbents are collected from published literature and their adsorption capacities are also compared. The methods of characterization of some of the synthesized bismuth-based materials have also been discussed. Hydrous bismuth oxides (HBOs) have sorptive potential for nitrate and fluoride removal from aqueous solution with maximum capacity of 0.508-0.512 mg/g and 0.60-1.93 mg/g respectively. Thus, it can be beneficially used for treatment of drinking water treatment, particularly in small scale household applications.

One-pot synthesis of β-cyclodextrin amended mesoporous cerium(IV) incorporated ferric oxide surface towards the evaluation of fluoride removal efficiency from contaminated water for point of use

Surface modified Cerium(IV)-incorporated hydrous Fe(III) oxide (CIHFO) with β-cyclodextrin (β-CD) nanocomposite (βC-CIHFO) has been developed by in-situ wet chemical deposition method and characterized by means of some analytical tools such as FTIR, XRD,OM, SEM-EDX, TEM-EDX, AFM, TG-DTA and BET surface area analyses, resembled the irregular and undulated surface morphology consisting of microcrystals (∼2-3 nm) and mesoporous (∼6.022 nm) structure confirm surface amended CIHFO with β-CD. Enhanced fluoride adsorption capacity of βC-CIHFO (107.62 mg g^-1) than pure CIHFO (32.62 mg g^-1) at pH 7.0 is due to the plenty of surface -OH groups of β-CD, which plays a crucial role in enhancing fluoride adsorption capacity of CIHFO. Kinetic studies obeyed pseudo-second order kinetics and multilayer adsorption process, respectively. The adsorption process is reasonably spontaneous and endothermic in nature. Minute amount of βC-CIHFO (1.8 g L^-1) can effectively treat fluoride containing natural groundwater samples (9.05 mg L^-1) and achieved desirable permissible level in a while. The adsorbent was magnificently regenerated up to 75.19% with a solution of pH 13.0, and can be reused up to five cycles ensures sustainable use of proposed adsorbent for fluoride removal from aqueous media.

Properties of multifunctional composite materials based on nanomaterials: a review

Composite materials are being used for high-end applications such as aviation technology, space ships, and heavy equipment manufacturing. The use of composite materials has been observed in recent advancements in the field of multifunctional composite materials (MFCMs). There is continuous progress related to improvements, innovations, and replacement of metals inspite of rigorous destructive and non-destructive testing, proving the toughness and lifelong durability of such materials. The present study aims to review the topics relevant to modern multifunctional composite materials. The reviewed articles mostly cover the field of MFCMs based on nanomaterials. The structural functions emphasize on the mechanical properties such as fracture toughness, strength, thermal stability, damping, stiffness, and tensile strength. The non-structural properties include biodegradability, thermal conductivity, electrical conductivity, and electromagnetic interference (EMI) shielding. The study has concluded that the applications of multifunctional nanoparticle-based composite materials and structures include durable but light-weight aircraft wings, components and structures of electric self-driving vehicles, and biomedical composite materials for drug delivery.

Composite materials are being used for high-end applications such as aviation technology, space ships, and heavy equipment manufacturing.

Enhanced capacity of fluoride scavenging from contaminated water by nano-architectural reorientation of cerium-incorporated hydrous iron oxide with graphene oxide

An in situ wet chemical deposition method has been applied for the successful surface modification of Ce (IV)-incorporated hydrous Fe(III) oxide (CIHFO) with a hydrophilic graphene precursor, graphene oxide (GO). The surface area of as-prepared composite (GO-CIHFO) has enhanced (189.57 m² g^-1) compared with that of pristine CIHFO (140.711 m² g^-1) and has irregular surface morphology consisting of microcrystals (~ 2-3 nm) and mesoporous (3.5486 nm) structure. The GO-CIHFO composite shows enhanced fluoride scavenging capacity (136.24 mg F g^-1) than GO (3 mg F g^-1) and pristine CIHFO (32.62 mg F g^-1) at pH 7.0. Also, in acidic pH range and at 323 K temperature, the Langmuir capacity of as-prepared composite is 190.61 mg F g^-1. It has been observed that fluoride removal by GO-CIHFO occurs from solutions obeying pseudo-second-order kinetics and multilayer adsorption process. The film/boundary layer diffusion process is also the rate-determining step. The nature of the adsorption reaction is reasonably spontaneous and endothermic in thermodynamic sense. It was observed that 1.2 g.L^-1 of GO-CIHFO dosage can effectively optimise the fluoride level of natural groundwater samples (9.05 mg L^-1) to the desirable permissible limit. Reactivation of used material up to a level of 73.77% with a solution of alkaline pH has proposed reusability of nanocomposites ensuring sustainability of the proposed material as fluoride scavenger in future.

Adsorption capacity of kelp-like electrospun nanofibers immobilized with bayberry tannin for uranium(vi) extraction from seawater

The extraction of uranium(vi) from seawater is of paramount interest to meet the rapid expansion of global energy needs. A novel gelatin/PVA composite nanofiber band loaded with bayberry tannin (GPNB-BT) was used to extract uranium(vi) from simulated seawater in this study. It was fabricated by electrostatic spinning and crosslinking, and characterized by SEM, EDX, FTIR, and XPS. Batch experiments were carried out to investigate the adsorption of uranium(vi) onto GPNB-BT. Simultaneously, the regeneration-reuse process of the GPNB-BT was determined and illustrated here. The GPNB-BT exhibited excellent adsorption and regeneration performance, and a maximum adsorption capacity of 254.8 mg g-1 toward uranium(vi) was obtained at 298.15 K, pH = 5.5. Further, the regeneration rate for uranium did not decrease significantly after five cycles. Moreover, even at an extremely low initial concentration of 3 μg L-1 in the simulated seawater for 24 h, GPNB-BT showed an ultrahigh adsorption rate of more than 90% and adsorption capacity of 7.2 μg g-1 for uranium. The high density of adjacent phenolic hydroxyl groups and the specific surface area of GPNB-BT improved the adsorption ability of GPNB-BT for uranium. Therefore, the GPNB-BT was shown to have an application prospect for the effective extraction of uranium(vi) from seawater.

Defluoridation investigation of Yttrium by laminated Y-Zr-Al tri-metal nanocomposite and analysis of the fluoride sorption mechanism

In this study, a laminated nanocomposite of Y-Zr-Al with significantly high surface area of 256.6 m²/g was successfully prepared, and was used to investigate the defluoridation performance of sorbent based on Yttrium. The composite showed high fluoride sorption performance, especially at low F^- concentration conditions. SEM, BET, Elemental Mapping and XPS were used to characterize physicochemical properties of the composite in detail. Several influence factors including pH, presence of coexisting anions and contacting time were detailly investigated. The sorption course was studied by equilibrium sorption isotherm and sorption kinetics. Based on experimental results, a mechanism for fluoride sorption onto Y-Zr-Al composite was proposed, which revealed that there were three main sorption models, including mesoporous diffusion sorption, electronic interaction sorption and ion exchange, in the sorption course. The composite was considered to be highly potential in treating fluoride polluted waste water due to its high efficiency, high anti-interference ability and easy operation, and the discovery of fluoride highly attractive rare earth element was important to further understand and develop defluoridation sorbents based on rare earth.

Ultrasound assisted synthesis of Mg-Mn-Zr impregnated activated carbon for effective fluoride adsorption from water

High fluoride content in the natural water sources is a serious matter of concern and adsorption is recommended as one of the most convenient, affordable and widely applied defluorination technologies. In this study, a novel composite was synthesized by impregnating magnesium (Mg), manganese (Mn) and zirconium (Zr) on powdered activated carbon (AC) for effective fluoride adsorption and the synthesis was made using sonochemical method. The characterization of the prepared adsorbent AC-Mg-Mn-Zr along with individual metal composites AC-Zr, AC-Mg and AC-Mn were done by SEM, EDX, FTIR, XRD and BET analysis to understand the major functional bonds, and changes in surface chemistry after adsorption. The mechanism of the process was discussed through major reactions involved for individual metals. Due to high point of zero charge (pH_PZC = 11.9), the adsorbent was able to remove more than 96% of fluoride consistently with only 1 g/L of optimum adsorbent dosage for a wide pH range (2 to 10). The maximum adsorption capacity obtained was 26.27 mg/g within an equilibrium time of 3 h. More than 96% energy saving was achieved in the sonochemical synthesis route compared to conventional precipitation method of synthesis.

Acoustic cavitation induced synthesis of zirconium impregnated activated carbon for effective fluoride scavenging from water by adsorption

Environmental concern associated with the side effects of high fluoride content in ground water and surface water has prompted the researchers to look for an efficient, convenient and easy method. Considering the potential of a good adsorbent, present study reports the synthesis of a composite by impregnating zirconium on powdered activated carbon (AC) using ultrasound as the tool for synthesis and applying it for fluoride adsorption from water. The nature of the composite was determined through characterization by scanning electron microscopy (SEM), energy dispersive Xray (EDX), Xray diffraction (XRD), N₂ adsorption analysis (BET) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The pH_pzc (point of zero charge) of the adsorbent was found to be 5.03; with the optimum pH obtained at 4 for adsorption of strong electronegative fluoride ions. The initial fluoride concentration was varied from 2.5 up to 20 mg.L^-1 and the maximum adsorption capacity of 5 mg.g^-1 was obtained. A maximum fluoride removal of 94.4% was obtained for an initial concentration of 2.5 mg.L^-1 within an equilibrium time of 180 min. The adsorption isotherm followed the Langmuir isotherm model indicating a monolayer adsorption process and the adsorption kinetics followed pseudo second order model. The effects of various coexisting ions (HCO₃^-, NO₃^-, SO₄^2-, Cl^-) commonly present in the water were found to have negligible impact on the process performance. Conducting the adsorption-desorption studies for five consecutive cycles for an initial fluoride concentration of 10 mg.L^-1, the removal efficiency reduced from 86.2 to 32.6%. The ultrasonic method provided an easy route to synthesize the composite in less time and significantly reduced energy consumption by more than 96% compared to the conventional method.

The removal of fluoride from aqueous solution by a lateritic soil adsorption: Kinetic and equilibrium studies

The use of natural sorbents to remove fluoride from drinking water is a promising alternative because of its low-cost and easy implementation. In this article, fluoride adsorption on a latosol soil from Misiones province (Argentina) was studied regarding kinetic and equilibrium aspects. Experiments were conducted in batch at room temperature under controlled conditions of pH 4-8) and ionic strength (1-10mM KNO₃). Experimental data indicated that adsorption processes followed a PSO kinetic where initial rates have showed to be influenced by pH solution. The necessary time to reach an equilibrium state had resulted approximately 30min. Equilibrium adsorption studies were performed at pH 8 which is similar to the natural groundwater. For that, fluoride adsorption data were successfully adjusted to Dubinin-Ataskhov model determining that the fluoride adsorption onto soil particles mainly followed a physical mechanism with a removal capacity of 0.48mgg^-1. Finally, a natural groundwater was tested with laterite obtaining a reduction close to 30% from initial concentration and without changing significantly the physicochemical properties of the natural water. Therefore, it was concluded that the use of lateritic soils for fluoride removal is very promising on a domestic scale.

Development of nanohybrid adsorbent for defluoridation from aqueous systems

The objective of present study is advancement of an efficient nanomaterial which was investigated to substantiate its efficiency, using kinetic studies to ensnare fluoride in order to make water potable. A new crystalline ZrAlCa nanohybrid adsorbent for fluoride removal was successfully synthesized by a co-precipitation method in this study. The prepared adsorbents were characterized by XRD, FT-IR, TGA, BET and FESEM and EDX. The adsorption properties of the developed adsorbent were studied using batch adsorption method which shown the noticeable fluoride removal efficiency up to 99% at near neutral pH as well as in acidic pH range. The reaction kinetics for adsorption of fluoride was established using reaction based kinetic models which fitted well with Avarami kinetic model as compared to pseudo-first-order, pseudo second-order and power function rate expression. The equilibrium isotherm modelling described adsorption process and Langmuir, Jovanovic, Temkin and Freundlich isotherms provides best fit to experimental data. The fluoride loaded adsorbent was efficiently regenerated by using an alkali solution and has no significant counter ion effect on fluoride adsorption efficiency. Interestingly, the developed nanomaterial has fluoride removal efficacy over varied concentration ranges. It has capability of reanimate and reuse the nanohybrid adsorbent makes it an attractive sustainable material.

Adsorption process of fluoride from drinking water with magnetic core-shell Ce-Ti@Fe3O4 and Ce-Ti oxide nanoparticles

Synthesized magnetic core-shell Ce-Ti@Fe₃O₄ nanoparticles were tested, as an adsorbent, for fluoride removal and the adsorption studies were optimized. Adsorption capacity was compared with the synthesized Ce-Ti oxide nanoparticles. The adsorption equilibrium for the Ce-Ti@Fe₃O₄ adsorbent was found to occur in <15min and it was demonstrated to be stable and efficient in a wide pH range of 5-11 with high fluoride removal efficiency over 80% of all cases. Furthermore, isotherm data were fitted using Langmuir and Freundlich models, and the adsorption capacities resulted in 44.37 and 91.04mg/g, at pH7, for Ce-Ti oxides and Ce-Ti@Fe₃O₄ nanoparticles, respectively. The physical sorption mechanism was estimated using the Dubinin-Radushkevich model. An anionic exchange process between the OH^- group on the surface of the Ce-Ti@Fe₃O₄ nanomaterial and the F^- was involved in the adsorption. Moreover, thermodynamic parameters proved the spontaneous process for the adsorption of fluoride on Ce-Ti@Fe₃O₄ nanoparticles. The reusability of the material through magnetic recovery was demonstrated for five cycles of adsorption-desorption. Although the nanoparticles suffer slight structure modifications after their reusability, they keep their adsorption capacity. Likewise, the efficiency of the Ce-Ti@Fe₃O₄ was demonstrated when applied to real water to obtain a residual concentration of F^- below the maximum contaminated level, 1.5mg/L (WHO, 2006).

Synthesis and characterisation of cerium(iv)-incorporated hydrous iron(iii) oxide as an adsorbent for fluoride removal from water

Surface-altered hydrous iron(iii) oxide incorporating cerium(iv) (CIHFO) was prepared and characterised via modern analytical tools for applications in fluoride removal from groundwater.

Synthesis of [H22·Zr5·WO4·10 P2O7]n·26n H2O by response surface methodology to adsorb Ca(II) in manganiferous wastewater

The presence of calcium challenges the manganese recovery from manganiferous wastewater. In this paper, a kind of mesoporous material named [H₂₂·Zr₅·WO₄·10 P₂O₇]n·6n H₂O is investigated as an ion exchanger to remove calcium ion from manganese slag percolate. The synthesis of zirconium tungstopyrophosphate (ZWPP) was optimized by response surface methodology , and its adsorption capacity and equilibrium were tested. The adsorption data have been confirmed by the use of various techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy and Brunauer, Emmett and Teller. An empirical formula of ZWPP was obtained by X-ray diffraction and thermal analysis. The adsorption process conformed to pseudo-second-order kinetics and the Langmuir isotherm, which described the equilibrium powerfully. Furthermore, different thermodynamic parameters were evaluated. And it was found that Gibbs free energy change is negative, indicating the adsorption process was spontaneous, whereas the enthalpy change and entropy change are positive indicating endothermy and increased randomness nature of the adsorption process. As a result, ZWPP could be a possible ion exchanger material in the area of removing Ca²⁺ from processing water or wastewater.

Removal of Fluoride from Aqueous Solutions Using Chitosan Cryogels

In this study, crosslinked chitosan cryogels (QE) and chitosan’s cryogels modified with iron (QEFe) were synthesized. They were characterized by BET, PZC, FTIR, and XPS spectroscopies. Results show a specific surface area of 36.67 and 29.17 m2g−1 and 7.0 and 6.1 of PZC for the cryogels QE and QEFe, respectively. FTIR results show the characteristic bands of amino and hydroxyl groups, while in the XPS analysis, interactions between iron and oxygen with fluorine were observed. The removal of fluoride at temperatures of 303, 313, and 323 K in cryogels was tested. The Ho model is the best fit for the experimental data, suggesting that there is a chemisorption process involved in the removal of fluoride. The Langmuir-Freundlich model is the best to represent the behavior of the cryogels, and it is used to sorbents with heterogeneous surfaces. A maximum fluoride adsorption capacity of 280 and 295 mg F−/g for QE and QEFe, respectively, at 303 K was obtained, showing that the removal of fluoride is favored by the iron incorporated in the polymer matrix of the cryogels. The thermodynamic parameters were obtained for both cryogels, where the values of ΔH° and ΔG° indicate that both systems are endothermic and nonspontaneous.

Facile synthesis of magnetic La–Zr composite as high effective adsorbent for fluoride removal

A novel magnetic composite of La–Zr was prepared by co-precipitation method, and its fluoride removal ability was investigated in batch studies.

Novel magnetic core–shell Ce–Ti@Fe3O4 nanoparticles as an adsorbent for water contaminants removal

Magnetic core–shell Ce–Ti@Fe₃O₄ nanoparticles were synthesized by coating cerium titanate on magnetite under mild experimental conditions.

Cyclic tetra[(indolyl)-tetra methyl]-diethane-1,2-diamine (CTet) impregnated hydrous zirconium oxide as a novel hybrid material for enhanced removal of fluoride from water samples

A hybrid material was prepared by incorporating cyclic tetra[(indolyl)-tetra methyl]-diethane-1,2-diamine (CTet) into hydrous zirconium oxide (HZO) via thorough mixing of previously prepared CTet in methanol and stirred for 7 h at 27 °C.

Rapid scavenging of methylene blue dye from a liquid phase by adsorption on alumina nanoparticles

The adsorption behavior of methylene blue on as-synthesized alumina nanoparticles has been investigated.