A novel flake-ball-like magnetic Fe3O4/γ-MnO2 meso-porous nano-composite: Adsorption of fluorinion and effect of water chemistry

Biomimetic ZrO2-modified seaweed residue with excellent fluorine/ bacteria removal and uranium extraction properties for wastewater purification

Exploring and developing promising biomass composite membranes for the water purification and waste resource utilization is of great significance. The modification of biomass has always been a focus of research in its resource utilization. In this study, we successfully prepare a functional composite membrane, activated graphene oxide/seaweed residue-zirconium dioxide (GOSRZ), with fluoride removal, uranium extraction, and antibacterial activity by biomimetic mineralization of zirconium dioxide nanoparticles (ZrO2 NPs) on seaweed residue (SR) grafted with oxidized graphene (GO). The GOSRZ membrane exhibits highly efficient and specific adsorption of fluoride. For the fluoride concentrations in the range of 100-400 mg/L in water, the removal efficiency can reach over 99 %, even in the presence of interfering ions. Satisfactory extraction rates are also achieved for uranium by the GOSRZ membrane. Additionally, the antibacterial performance studies show that this composite membrane efficiently removes Escherichia coli (E. coli) and Methicillin-resistant Staphylococcus aureus (MRSA). The high adsorption of F- and U(VI) to the composite membrane is ascribed to the ionic exchange and coordination interactions, and its antibacterial activity is caused by the destruction of bacterial cell structure. The sustainability of the biomass composite membranes is further evaluated using the Sustainability Footprint method. This study provides a simple preparation method of biomass composite membrane, expands the water purification treatment technology, and offers valuable guidance for the resource utilization of seaweed waste and the removal of pollutants in wastewater.

Remediation of water tainted with noxious aspirin and fluoride ion using UiO-66-NH2 loaded peanut shell

One green adsorbent, UiO-66-NH2 modified peanut shell (c-PS-MOF), was prepared in a green synthetic route for improving the capture level of aspirin (ASP) and fluoride ion (F-). The adsorption properties of c-PS-MOF were evaluated by batch experiments and its physicochemical properties were explored by various characterization methods. The results showed that c-PS-MOF exhibited a wide range of pH applications (ASP: 2-10; F-: 3-12) and high salt resistance in the capturing processes of ASP and F-. The unit adsorption capacity of c-PS-MOF was as high as 84.7 mg·g-1 for ASP as pH = 3 and 11.2 mg·g-1 for F- under pH = 6 at 303 K from Langmuir model, respectively. When the solid-liquid ratio was 2 g·L-1, the content of ASP (C0 = 100 mg·L-1) and F- (C0 = 20 mg·L-1) in solution can be reduced to 0.48 mg·L-1 and 1.05 mg·L-1 separately. The recycling of c-PS-MOF can be realized with 5 mmol·L-1 NaOH as eluent. Analysis of simulated water samples showed that c-PS-MOF could be used to remove ASP and F- from actual water. The c-PS-MOF is promising to bind ASP and F- from rivers, lakes, etc.

Synthesis of Composites for the Removal of F- Anions

This work presents the synthesis of amine and ferrihydrite functionalized graphene oxide for the removal of fluoride from water. The synthesis of the graphene oxide and the modified with amine groups is developed by following the modified Hummer's method. Fourier transform infrared spectrometry, X-ray, Raman spectroscopy, thermogravimetric analysis, surface charge distribution, specific surface area and porosity, adsorption isotherms, and the van't Hoff equation are used for the characterization of the synthesized materials. Results show that the addition of amines with ferrihydrite generates wrinkles on the surface layers, suggesting a successful incorporation of nitrogen onto the graphene oxide; and as a consequence, the adsorption capacity per unit area of the materials is increased.

Nano Biomass Material functionalized by β-CD@Ce(NO)3 as a high performance adsorbent to removal of fluorine from wastewater

Fluorine pollution has become one of the key issues of water pollution, and the adsorption materials for efficient removal of fluorine ions have attracted much attention. It is rarely reported that the self-synthesized biomass materials were functionalized by the β-CD@Ce(NO)₃. This paper mainly proposed a new synthetic method of the self-synthesized biomass materials were modified by the β-CD@Ce(NO)₃ and removal of fluorine ions. The effects of this materials on the adsorption efficiency of fluorine ions under different conditions were explored, and the kinetic and thermodynamic simulations were carried out. The results show that the self-synthesized biomass materials were modified by the β-CD@Ce(NO)₃ has significant pore structure, large specific surface area and multi-functional group. Adsorption experiment showed that the reaction reached adsorption equilibrium at 30 min. The removal rate of fluorine ions reached 93.13%, and the fluorine ions adsorption capacity was 37.25 mg/g under neutral conditions. The material can be recycled for more than 5 times, and the adsorption efficiency remains above 94%. The adsorption kinetics accorded with the pseudo second-order model and the adsorption isotherm equation is in line with the Langmuir isotherm adsorption model. PO₄^3- and CO₃^2- have the most impact on fluorine ions adsorption. This method reduces the synthesis cost of high-performance adsorption materials and improves the adsorption performance, which is conducive to the popularization and application in the future.

Species transformation and removal mechanism of various iodine species at the Bi2O3@MnO2 interface

Long-term exposure to excessive iodine via drinking water significantly increases the risk of thyroid diseases. Further, the mechanisms and feasible technologies for iodine removal are far from being well elucidated. In this study, we constructed a heterogeneous Bi₂O₃@MnO₂ interface with oxidation and adsorption efficiency toward iodide (I^-), and investigated the performance and mechanisms involved in iodine removal. Bi₂O₃@MnO₂ at the optimized Bi/Mn ratio of 0.05:1 had a maximum adsorption capacity of 1.19, 1.21, and 1.06 mg/g toward I^-, iodine elemental (I₂), and iodate (IO₃^-), respectively. According to the density functional theory (DFT) calculation, Bi₂O₃@MnO₂ had an adsorption energy of -2.34, -2.11, and -3.89 eV for I^-, I₂, and IO₃^-, and exhibited a better band structure and state density character for iodine removal. Based on the results of XPS, HPLC, and LC-ICP-MS characterization, Bi₂O₃ plays an important role in adsorbing and capturing I^- whereas MnO₂ dominates the moderate oxidation of I^- and the adsorption of I^- and I₂. The adsorbed I^- and I₂ concentrations on the Bi₂O₃@MnO₂ surfaces were 146.3 μg/L and 18.3 μg/L. Notably, IO₃^- was not detected owing to its moderate oxidation effect. The coexisting ions of chloride (Cl^-) and bromide (Br^-) tended to occupy the Bi₂O₃ lattice and form insoluble BiOCl and BiOBr. Further, reductive species, such as sulphite (SO₃^2-), may reduce MnO₂ to Mn(III) and Mn(II). The synergistic effect between moderate oxidation and adsorption led to Bi₂O₃@MnO₂ with high iodine removal capability. Overall, this study proposes a strategy for designing suitable interfaces and adsorbents for iodine removal; however, further studies are necessary to advance its application in practice.

Synchronous Moderate Oxidation and Adsorption on the Surface of γ-MnO2 for Efficient Iodide Removal from Water

Long-term exposure to excessive iodine via drinking water presents health risks. Moderate oxidation of iodide (I^-) to iodine (I₂) has a better iodine removal effect than excessive oxidation to iodate (IO₃^-). This study combines computational and experimental methods to construct a heterogeneous interface with synchronous I^- moderate oxidation and I₂ adsorption to increase the total iodine removal. Compared to other forms of crystal manganese dioxide (MnO₂), theoretical calculations predict that MnO₂ with a γ-crystal structure has the lowest adsorption energy, that is, -1.20 eV, and a slight overlap between the conduction and valence bands, which favors electron transfer between I^- and Mn(IV) and I₂ adsorption. Thus, γ-type MnO₂ was designed by adjusting the precursor Mn sources and hydrothermal reaction conditions. The liquid chromatography-inductively coupled plasma-mass spectrometry and high-performance liquid chromatography confirmed that the total iodine concentration in water decreased from 173.7 to 36.3 μg/L after 2 h, with 200 mg/L γ-MnO₂ dosage lower than the national standard of 0.1 mg/L. A minute proportion of I^- in water was converted to IO₃^- (approximately 1.1 μg/L). The current I^- adsorbent performed better than previously reported ones. During iodine removal, most of the I^- migrated from water to the surface of γ-MnO₂, and the ratio of I^- to I₂ was determined to be 1:0.6 by X-ray photoelectron spectroscopy. This study evaluates iodine species transformation and an optimum strategy for heterogeneous interface design; it is promising for treating high-iodine groundwater.

High-performance lanthanum-based metal-organic framework with ligand tuning of the microstructures for removal of fluoride from water

Excess fluoride in water poses a threat to ecology and human health, which has attracted global attention. In this study, a series of lanthanum-based metal-organic frameworks (La-MOFs) were synthesized by varying the organic ligands (i.e., terephthalic acid (BDC), trimesic acid (BTC), biphenyl-4,4-dicarboxylic acid (BPDC), 2,5-dihydroxyterephthalic acid (BHTA), and 1,2,4,5-benzenetetracarboxylic acid (PMA)) to control the microscopic structure of the MOFs and subsequently apply them for the removal of fluoride in water. The maximum capture capacities of La-BTC, La-BPDC, La-BHTA, La-PMA, and La-BDC at 298 K are 105.2, 125.9, 145.5, 158.9, and 171.7 mg g^-1, respectively. The adsorption capacity is greater than most reported adsorbents. The adsorption isotherms of La-MOFs for fluoride are well fit to the Langmuir isotherm model. In addition, the adsorption kinetics of La-BTC, La-BPDC, La-BHTA, La-PMA, and La-BDC follows the pseudo-second-order kinetic model, and the kinetic rate-limiting step of adsorption is chemical adsorption. Thermodynamics revealed that temperature is favorable for the adsorption of fluoride. Meanwhile, La-BTC, La-BPDC, La-BHTA, La-PMA, and La-BDC are suitable for the removal of fluoride in a relatively wide pH range (4.0-9.0). Simultaneously, from X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis, electrostatic attraction and ligand exchange are identified as the main action mechanisms for the adsorption of fluoride of La-MOFs. The prepared La-MOFs are used as efficient adsorbents for removal of fluoride in actual water, indicating that they have great potential in removing fluoride in real and complex environmental water. This work provides a new strategy for designing adsorbents with adjustable microstructure and expected function to effectively recover fluorosis in water.

Nanomaterials in Water Applications: Adsorbing Materials for Fluoride Removal

Fluoride is an important pollutant in many countries, such as China, India, Australia, the United States, Ethiopia, etc [...].

Defluorination by ion exchange of SO42- on alumina surface: Adsorption mechanism and kinetics

Electrostatic and complexation effects have been considered as the primary adsorption mechanisms for defluorination using aluminum based materials, while the effect of ion exchange between anions and fluorine ion has been mostly ignored, although synthesized alumina materials usually contain a large amount of anions, such as SO₄^2-, NO₃^-, and Cl^-. In this study, the effect of anions exchanges and its key role on defluorination were systematically investigated for adsorption by aluminas loaded with various typical anions (SO₄^2-, NO₃^- and Cl^-). Experimental results showed that SO₄^2-- loading alumina had the best defluorination performance (94.5 mg/g), much higher than NO₃^- (45.0 mg/g) and Cl^- (19.1 mg/g). The contribution ratio of ion exchange between SO₄^2- and F^- was as high as 20-60% in all potential defluorination mechanisms. By using Density Functional Theory calculation, the detailed mechanism revealed that the ion exchange process was mainly driven by the tridentate chelation of SO₄^2- which reduced the exchange energy ( [Formula: see text] 4.8 eV). Our study clearly demonstrated that ion exchange between SO₄^2- and F^- is a critical mechanism in defluorination using aluminum-based materials and provides a potential alternative method to enhance the adsorption performance of modified alumina.

Lignin-based nanoparticles for recovery and separation of phosphate and reused as renewable magnetic fertilizers

In this work, magnetic lignin-based nanoparticles (M/ALFe) were developed and used to adsorb phosphorus to obtain phosphorus-saturated nanoparticles (M/ALFeP). The nanoparticles were then used as renewable slow-release compound fertilizers. First, aminated lignin was synthesized via Mannich reaction, and then Fe₃O₄ nanoparticles were loaded and Fe³⁺ was chelated on the aminated lignin to prepare M/ALFe. Finally, M/ALFeP were obtained after adsorption of phosphorus. The effects of nanoparticle dosage, solution pH and adsorption time on adsorption efficiency were determined. Adsorption isotherm and adsorption kinetics results suggested that the adsorption was coincided with the pseudo-second-order and Temkin model, respectively. The cumulative release of Fe and phosphorus from M/ALFeP increased gradually and reached to 67.2% and 69.1% in soil after 30 days, respectively. After the release of nutrients, M/ALFeP can be separated by a magnet with a high recovery ratio from water or soil and regenerated for phosphate recovery again. Therefore, the magnetic lignin-based nanoparticles have a promising application potential as an efficiently separated and renewable nanomaterial for removal of low concentration phosphate in wastewater treatment and as a slow-release fertilizer in sustainable agriculture.

Controlled preparation of cerium oxide loaded slag-based geopolymer microspheres (CeO2@SGMs) for the adsorptive removal and solidification of F- from acidic waste-water

A new cerium oxide loaded slag-based geopolymer microspheres (CeO₂@SGMs) was prepared by a two-step i.e. dispersion-suspension-solidification and in-situ co-precipitation method. The optimal parameters for the preparation of 0.02CeO₂@SGMs were slag (30 g), 1.7 M water glass (12.86 g), water (8 g) and 0.02 mol/L of Ce⁴⁺. 0.02CeO₂@SGMs was characterized by SEM, XRD, BET, EDX, FTIR, XPS and PSD techniques. The leaching concentration of Ca²⁺ (95.65 mg/L) was only 1/5 of the SGMs at pH 2 after the modification of CeO₂. Adsorption data fitted well with Freundlich isotherm model suggesting multilayer adsorption mechanism with a maximum adsorption capacity for F^- by 0.02CeO₂@SGMs of 121.77 mg/g at 298 K. The negative values of thermodynamic parameters (ΔH⁰ and ΔS⁰) indicated the exothermic nature of the adsorption process with reduced chaos of the whole system. 0.02CeO₂@SGMs exhibited excellent dynamic adsorption performance at 4 mL/min F^- solution flow rate. The influence of various co-existing anions on adsorption of F^- over 0.02CeO₂@SGMs followed an order of: Cl^- ≈ NO₃^- < SO₄^2- << PO₄^3-. Attributed to the facile preparation process, cost-effectiveness and environmental friendliness, the newly designed 0.02CeO₂@SGMs can be deemed of promising industrial applications for the abatement of F^- from wastewater.

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.

Synthesis of an optical catalyst for cracking contaminating dyes in the wastewater of factories using indium oxide in nanometer and usage in agriculture

Herein, the photocatalytic degradation of the Congo Red (CR) and Crystal Violet (CV) dyes in an aqueous solution were discussed in the presence of an indium(III) oxide (In2O3) as optical catalyst efficiency. The caproate bidentate indium(III) precursor complex has been synthesized and well interpreted by elemental analysis, molar conductivity, Fourier transform infrared (FT-IR), UV-Vis, and thermogravimetric (TGA) with its differential thermogravimetric (DTG) studies. The microanalytical and spectroscopic assignments suggested that the associated of mononuclear complex with 1:3 molar ratio (M3+:ligand). Octahedral structure is speculated for this parent complex of the caproate anion, CH3(CH2)4COO− ligand. The In2O3 NPs with nanoscale range within 10–20 nm was synthesized by a simple, low cost and eco-friendly method using indium(III) caproate complex. Indium oxide nanoparticles were formed after calcination of precursor in static air at 600°C for 3 hrs. The structural, grain size, morphological and decolorization efficiency of the synthesized NPs were characterized using the FT-IR, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM) analyses. It was worthy mentioned that the prepared In2O3 NPs showed a good photodegradation properties against CR and CV organic dyes during 90 min.

Enhanced degradation of sulfadiazine by novel β-alaninediacetic acid-modified Fe3O4 nanocomposite coupled with peroxymonosulfate

Magnetic nanocomposite β-alaninediacetic acid-modified Fe₃O₄ (β-ADA@Fe₃O₄) was prepared, characterized and evaluated to activate peroxymonosulfate (PMS) for improved degradation of sulfadiazine (SD). The results reveal that β-ADA@Fe₃O₄ express more efficient catalytic activity in PMS inducement compared with Fe₃O₄, and the observed pseudo first rate constant (k_obs) of SD degradation is enhanced from 1.05 × 10^-2 to 7.02 × 10^-2 min^-1 when Fe₃O₄ is replaced by β-ADA@Fe₃O₄. The highest removal rate 54.0% occurs when [PMS]₀ and m(β-ADA@Fe₃O₄)₀ was 0.3 mM and 0.8 g/L at neutral pH. High intensity of hydroxyl radicals (OH) and relatively low intensity of sulfate radicals (SO₄^-) are distinguished in system by scavenging experiments and electron paramagnetic resonance (EPR) tests. Results point that β-ADA would significantly promote the circulation of Fe²⁺-Fe³⁺ on the surface of β-ADA@Fe₃O₄, producing more radicals (OH, SO₄^-). The findings herein imply that β-ADA@Fe₃O₄ is an efficient and green catalyst in activation of peroxymonosulfate under neutral environment.