Excellent fluoride decontamination and antibacterial efficacy of Fe–Ca–Zr hybrid metal oxide nanomaterial

Sustainable polymeric adsorbents for adsorption-based water remediation and pathogen deactivation: a review

Water is a fundamental resource, yet various contaminants increasingly threaten its quality, necessitating effective remediation strategies. Sustainable polymeric adsorbents have emerged as promising materials in adsorption-based water remediation technologies, particularly for the removal of contaminants and deactivation of water-borne pathogens. Pathogenetic water contamination, which involves the presence of harmful bacteria, viruses, and other microorganisms, poses a significant threat to public health. This review aims to analyze the unique properties of various polymeric materials, including porous aromatic frameworks, biopolymers, and molecularly imprinted polymers, and their effectiveness in water remediation applications. Key findings reveal that these adsorbents demonstrate high surface areas, tunable surface chemistries, and mechanical stability, which enhance their performance in removing contaminants such as heavy metals, organic pollutants, and emerging contaminants from water sources. Furthermore, the review identifies gaps in current research and suggests future directions, including developing multifunctional polymeric materials and integrating adsorption techniques with advanced remediation technologies. This comprehensive analysis aims to contribute to advancing next-generation water purification technologies, ensuring access to clean and safe water for future generations.

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.

One-pot solution combustion synthesis of porous spherical-shaped magnesium zinc binary oxide for efficient fluoride removal and photocatalytic degradation of methylene blue and Congo red dye

A novel porous spherical-shaped magnesium zinc binary oxide (MZO) was successfully prepared for the first time using a chemical process for fluoride removal and photocatalytic methylene blue (MB) and Congo red (CR) dye degradation. XRD, FESEM, and TEM were studied for phase formation, topographic, crystallographic, and detailed structural information. The surface charge and optical properties of the adsorbent were studied by zeta potential and photoluminescence spectra. The synthesized nano-adsorbents showed high fluoride removal capacity (43.10 mg/g) and photocatalytic activity with a degradation efficiency of 97.83% and 78.40% for MB and CR, respectively. The adsorption was strongly pH-dependent and worked well in the range 6-9. The kinetic studies were performed for both fluoride removal and dye degradation and were found to follow pseudo-second-order and first-order rate law, respectively. The samples were found to be extremely reusable and selective for fluoride removal in presence of co-ions such as NO3-, SO42-, and Cl-. The basic fluoride adsorption process of the samples can be related to ion exchange and electrostatic interactions, according to XPS and FTIR data. The detailed mechanistic study of photocatalytic dye degradation showed that the reaction occurred via OH radicals. Thus, MZO could be considered an effective and quick adsorbent for water purification in fluoride-containing groundwater and industrial dye wastewater.

Synthesis of Fe Doped Poly p-Phenylenediamine Composite: Co-Adsorption Application on Toxic Metal Ions (F- and As3+) and Microbial Disinfection in Aqueous Solution

Water is regarded as an important natural resource to sustain life, and its purification is an important criterion that determines its quality and usefulness. In this study, the incorporation of Fe³⁺ oxide onto a phenylenediamine (pPD) polymer matrix through chemical co-polymerization was prepared, and its arsenite and fluoride removal potentials at optimal conditions from aqueous solution were evaluated. The morphology and structural analysis of the synthesized Fe-doped pPD (Fe-pPD) were comparatively evaluated using the FT-IR, SEM, EDS, and XRD techniques. Fe was successfully incorporated onto pPD matrix as confirmed by different morphological characterizations. The rate of adsorption of F⁻ and As³⁺ onto the Fe-pPD composite best followed the pseudo-second-order kinetic model. The experimental data for both As³⁺ and F⁻ onto the Fe-pPD composite better fit the Freundlich isotherm model at different operating temperatures. Overall, the synthesized composite exhibited a strong affinity towards fluoride uptake (96.6%) than arsenite uptake (71.14%) with a maximum capacity of 6.79 (F⁻) and 1.86 (As³⁺) mg/g. Additionally, the synthesized adsorbent showed some level of antimicrobial activity against common water-borne bacterial. Therefore, the Fe-doped pPD composite has the potential ability for inorganic metal species pollutants remediation and bacterial disinfection in community-level water purification processes.

MOFs for the treatment of arsenic, fluoride and iron contaminated drinking water: A review

Over the last few decades, the global pollution of surface and groundwater poses a serious threat not only to human beings but also towards aquatic lives due to the presence of emerging contaminants. Among the others, the presence of arsenic, fluoride, and iron are considered as the most common toxic pollutants in water bodies. The emergence of metal organic frameworks (MOFs) with high porosity and surface area is represented as significant inclusion into the era of entrapping contaminants present in drinking water. In the present review article, an in-depth insight is provided on the recent developments in the removal of arsenic, fluoride, and iron from drinking water using MOFs. Various aspects related to the synthesis, latest technologies adopted for the modifications in the synthesis process and advanced applications of MOFs for the removal of such contaminants are explicitly discussed. A detailed insight was provided to understand the mechanism of various interactions of MOFs with arsenic and fluoride. With respect to arsenic, fluoride, and iron removal the ultrastructural morphology of MOFs is assessed based on different molecular arrangements. Further, commercial aspects of various MOFs are presented in order to highlight the process feasibility. Finally, various perspectives and challenges involved in process scale up are comprehensively narrated with an aspiration of futuristic developments. The paper will be beneficial to the readers for acquiring a piece of in-depth knowledge on MOFs and its various synthesis approaches along with remarkable achievements for the removal of arsenic, fluoride, and iron from contaminated drinking water.

One-pot synthesis of Cr(III)-incorporated Zr(IV) oxide for fluoride remediation: a lab to field performance evaluation study

A low-cost Cr(III)-incorporated Zr(IV) bimetallic oxide (CZ) was synthesized by simple chemical precipitation method for removal of fluoride from contaminated water. The physicochemical properties of CZ before and after fluoride removal were established with several instrumental techniques such as TEM with elemental mapping, SEM with EDX, XRD, IR, XPS, zeta potential measurement, etc. Batch adsorption technique were carried out to understand the factors affecting fluoride adsorption, such as effects of initial pH, adsorbent dose, co-occurring ions, contact time, and temperature. The maximum adsorption capacity observed at pH between 5 and 7. The fluoride adsorption processes on CZ obeyed the pseudo-second-order rate equations and both Freundlich and DR isotherm models. The maximum adsorption capacity of 90.67 mg g^-1 was obtained. The thermodynamic parameters ΔH⁰ (positive), ΔS⁰ (positive), and ΔG⁰ (negative) indicating the fluoride sorption system was endothermic, spontaneous, and feasible. The CZ also successfully used as fluoride adsorbent for real field contaminated water collected from the Machatora district, Bankura, West Bengal, India. Graphical abstract Schematic representation of CZ synthesis and its application for lab as well as field water purification purpose.

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

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

Fast Capture of Fluoride by Anion-Exchange Zirconium-Graphene Hybrid Adsorbent

Fluoride contamination is a severe problem affecting the safety of drinking water around the world. High-rate adsorbent materials are particularly desirable for potable water defluoridation. Current research on fluoride adsorbent materials is primarily focused on metal-based adsorbents with high capacities. However, they generally suffer from slow adsorption kinetics due to the adsorption mechanism of a sluggish exchange between coordinated hydroxyl groups and fluoride ions. Designing metal-based adsorbents to mimic the rapid ion-exchange behavior of anion-exchange resins is a promising approach to integrate fast adsorption and high capacity for fluoride removal. Herein, a ZrO(OH)_1.33Cl_0.66-reduced graphene oxide (rGO) hybrid adsorbent containing exchangeable chloride ions was synthesized with the assistance of cation-π interactions. Unlike most adsorbents requiring a high surface area, this composite has a negligible surface area (1.45 m² g^-1), but can deliver a fast fluoride capture performance (reaching equilibrium in 5 min) with high adsorption rate constants of 1.05 min^-1 and 0.171 mg g^-1 min^-1, around 10 times faster than the best result reported in the literature. Besides, ZrO(OH)_1.33Cl_0.66-rGO can also demonstrate a high fluoride uptake (44.14 mg g^-1) and high removal efficiency (94.4%) in 35 mg L^-1 fluoride solution, both among the highest performances for fluoride adsorption.

Coagulation removal of fluoride by zirconium tetrachloride: Performance evaluation and mechanism analysis

Fluoride (F^-) pollution is a worldwide issue. Coagulation with aluminum (Al) salts is an efficient and economical method for the removal of F^-. However, due to the strong complexation between Al³⁺ and F^-, the residual F^- and Al after coagulation usually exceed the limits. Zirconium (Zr) coagulants have drawn increasing attention due to their excellent flocculation ability for organic matter. In this work, the performance and mechanism of ZrCl₄ coagulation for F^- removal were investigated with the widely used Al₂(SO₄)₃ as a reference. The optimum pH range is 4.0-6.0 for ZrCl₄ and 8.0-10.0 for Al₂(SO₄)₃. ZrCl₄ was superior to Al₂(SO₄)₃ for F^- removal as the initial F^- concentration was less than 30.0 mg L^-1. Coexisting substances at environmental concentration levels showed negligible effects on F^- removal by ZrCl₄. Besides the better F^- removal, another advantage of ZrCl₄ over Al₂(SO₄)₃ was the much lower residual metal concentration in the pH range of 4.0-11.0. The hydrolysis of Al₂(SO₄)₃ was significantly inhibited due to the formation of Al-F complexes while the hydrolysis of ZrCl₄ was not influenced even under strongly acidic conditions. Therefore, F^- removal by Al₂(SO₄)₃ was mainly achieved by preliminary complexation between Al³⁺ and F^- and subsequent hydrolysis and polymerization of these complexes, while adsorption onto hydrolysates and ion exchange with surface hydroxyl groups were the main ways of F^- removal by ZrCl₄. The work here provides a new method for F^- removal and may shed light on the application of Zr coagulants for other pollutants.

Kinetics and Adsorption Studies of Mercury and Lead by Ceria Nanoparticles Entrapped in Tamarind Powder

In this study, novel adsorbent ceria nanoparticles (CeNPs) entrapped in tamarind powder (Tm@CeNPs) were efficiently utilized for the simultaneous adsorption of aqueous mercury [Hg(II)] and aqueous lead [Pb(II)]. Surface interactions between the adsorbent and heavy metal ions play an important role in the adsorption process, and the surface morphology can significantly improve the adsorption capacity of the adsorbent. The Langmuir adsorption capacity of Tm@CeNPs for Hg(II) and Pb(II) was found to be 200 and 142.85 mg/g, respectively. The surface area of utilized adsorbent was found to be very high, that is, 412 m2/g. The adsorption kinetics of Tm@CeNPs for both ions follow pseudo-second-order, and the adsorption process is also thermodynamically feasible. Column study favors multilayer adsorption of the heavy metal ion. The spectral analysis of the adsorbent revealed that hydroxyl, carboxylic, and ester groups, as well as CeNPs, are responsible for Hg(II) and Pb(II) adsorption. The cost-benefit analysis confirms the economic viability of the synthesized Tm@CeNPs composite for heavy metal removal. The adsorbent is best suited for Hg(II) adsorption as compared to Pb(II). This is a novel study on the utilization of tamarind leaf powder with CeNPs for heavy metal ion adsorption and its adsorption mechanism, which has not been reported to date.

Removal of fluoride from wastewater using HCl-treated activated alumina in a ribbed hydrocyclone separator

Excessive fluoride concentration in wastewater is a major health concern worldwide. The main objective of wastewater treatment is to allow industrial effluents to be disposed of without danger to the human health and the natural environment. In this current study, experiments have been conducted to remove fluoride from aqueous solution using alumina and HCl (Hydrochloric acid) treated activated alumina in a continuous mode. A spiral rib was introduced in the cylindrical part of the conventional hydrocyclone to increase the performance, and the new hydrocyclone is dubbed as ribbed hydrocyclone. Experiments were carried out to analyze the performance of the ribbed hydrocyclone and compared the results with the conventional hydrocyclone of the same dimension. The efficiency of conventional and ribbed hydrocyclone at a slurry flow rate of 50 LPM (liter per minute) for the solid concentration of 1.4 wt% were 80% and 93.5% respectively. The cut size d₅₀ of the conventional and ribbed hydrocyclone was 18 µm and 13 µm respectively at a slurry velocity of 50 LPM. Fluoride removal efficiency using alumina and HCl-treated alumina was also investigated in a continuous mode by the ribbed hydrocyclone. Maximum fluoride removal efficiency was 49.5%, and 80% for alumina and HCl-treated alumina for the initial concentration of 10 mg/L at a slurry flow rate of 50 LPM.

Iron oxide-mediated semiconductor photocatalysis vs. heterogeneous photo-Fenton treatment of viruses in wastewater. Impact of the oxide particle size

The photo-Fenton process is recognized as a promising technique towards microorganism disinfection in wastewater, but its efficiency is hampered at near-neutral pH operating values. In this work, we overcome these obstacles by using the heterogeneous photo-Fenton process as the default disinfecting technique, targeting MS2 coliphage in wastewater. The use of low concentrations of iron oxides in wastewater without H₂O₂ (wüstite, maghemite, magnetite) has demonstrated limited semiconductor-mediated MS2 inactivation. Changing the operational pH and the size of the oxide particles indicated that the isoelectric point of the iron oxides and the active surface area are crucial in the success of the process, and the possible underlying mechanisms are investigated. Furthermore, the addition of low amounts of Fe-oxides (1mgL^-1) and H₂O₂ in the system (1, 5 and 10mgL^-1) greatly enhanced the inactivation process, leading to heterogeneous photo-Fenton processes on the surface of the magnetically separable oxides used. Additionally, photo-dissolution of iron in the bulk, lead to homogeneous photo-Fenton, further aided by the complexation by the dissolved organic matter in the solution. Finally, we assess the impact of the presence of the bacterial host and the difference caused by the different iron sources (salts, oxides) and the Fe-oxide size (normal, nano-sized).

Preparation of a novel CeO2/SiO2 adsorbent and its adsorption behavior for fluoride ion

The silica-based CeO2 adsorbent (CeO2/SiO2) was prepared for removing fluoride from the aqueous solution. The synthesized adsorbent was characterized by scanning electron microscope, energy dispersive spectrum, X-ray diffractometer, Fourier transform infrared spectrometer, and zeta potential measurement analyses. The adsorption batch experiments in the various experimental conditions including solution pH, contact time, initial fluoride concentration, and adsorption temperature were performed and investigated. The maximum adsorption capacity of fluoride into CeO2/SiO2 was 2.441 mmol/g at pH 3 and 298 K. The adsorption kinetics and isotherms were well described by the pseudo-second-order model and the Langmuir model, respectively. The fluoride adsorption reached the equilibrium in 15 min from the aqueous solution with the initial fluoride concentration of 400 mg/l at 298 K. In the temperature range of 298–338 K, the maximum adsorption capacity of fluoride decreased from 2.441 mmol/g to 2.109 mmol/l at pH 3. The adsorption thermodynamics study revealed that this process was a spontaneous, exothermic, and entropy-driving adsorption. Furthermore, the mechanism of adsorption was identified as the anion exchange and the electrostatic interaction. The desorption efficiency of fluoride-loaded CeO2/SiO2 adsorbent could reach about 95% by 0.1 mol/l NaOH.

Development of Mg–Al–La tri-metal mixed oxide entrapped in alginate for removal of fluoride from wastewater

New biopolymer beads, composite of Mg–AL–La tri-metal oxides and alginate, were synthesized, characterized and tested for their fluoride removal efficiency from wastewater. The maximum adsorption capacity of the adsorbent was 30.9 mg g⁻¹.

Hydrous TiO2@polypyrrole hybrid nanocomposite as an efficient selective scavenger for the defluoridation of drinking water

An adsorptive process for the defluoridation of drinking water was performed using a hybrid nanocomposite of hydrous titanium oxide@polypyrrole (HTiO₂@PPy), as a scavenger.

Aluminum substituted nickel ferrite (Ni–Al–Fe): a ternary metal oxide adsorbent for arsenic adsorption in aqueous medium

In this article synthesis and characterization of ternary metal oxide of aluminum substituted nickel ferrite and its adsorption capability for arsenic [(As(iii)) and (As(v))] species have been reported.

Fluoride adsorption on a cubical ceria nanoadsorbent: function of surface properties

Development of ceria with high fluoride loading capacity at pH 7.0 within 2 h at 1 g L⁻¹ adsorbent dose.