Facile preparation of oxine functionalized magnetic Fe3O4 particles for enhanced uranium (VI) adsorption

Reversible Hydrophobic Deep Eutectic Solvent-Based Uranyl-Sensing Optode Film in Aqueous Streams: Color Transformation and Reusability

A hydrophobic deep eutectic solvent (HDES)-based optode was designed for the preconcentration and determination of the UO22+ ion in aqueous media using spectroscopic techniques [energy-dispersive X-ray fluorescence (EDXRF) and solid-state absorption]. The optode was developed by incorporation of HDES (tri-n-octyl phosphine oxide and decanoic acid in an equimolar ratio), tri-(2-ethylhexyl) phosphate, and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol into a cellulose triacetate matrix. Characterization studies were carried out using different techniques to understand the roles of HDES as a plasticizer, UO22+ extractant, and Br-PADAP immobilizer. Uptake studies revealed that the optimal pH was 3 and sorption followed the type II adsorption isotherm. Uranium in the U-sorbed optode can be directly analyzed over a large concentration range of 0.021 × 10-3-2.1 × 10-3 Mol L-1 using EDXRF. The optode film exhibited a linear dynamic range of 0.84 × 10-6-84 × 10-6 Mol L-1 for uranium, with a lowest limit of detection of 0.084 × 10-6 Mol L-1 by colorimetric analysis. This optode-based method was employed for seawater analysis for its UO22+ concentration without any matrix separation, and the concentration was found to be 1.30 ± 0.06 × 10-8 Mol L-1. The optode exhibited better selectivity for UO22+ in the presence of various cations including Sr2+ and Cs+ in an aqueous medium. Compared to other prevailing optical sensors, this optode performed better in terms of key factors like pH, equilibration time, reusability, and detection limit.

Emerging Nanomaterials toward Uranium Extraction from Seawater: Recent Advances and Perspectives

Nuclear energy holds great potential to facilitate the global energy transition and alleviate the increasing environmental issues due to its high energy density, stable energy output, and carbon-free emission merits. Despite being limited by the insufficient terrestrial uranium reserves, uranium extraction from seawater (UES) can offset the gap. However, the low uranium concentration, the complicated uranium speciation, the competitive metal ions, and the inevitable marine interference remarkably affect the kinetics, capacity, selectivity, and sustainability of UES materials. To date, massive efforts have been made with varying degrees of success to pursue a desirable UES performance on various nanomaterials. Nevertheless, comprehensive and systematic coverage and discussion on the emerging UES materials presenting the fast-growing progress of this field is still lacking. This review thus challenges this position and emphatically focuses on this topic covering the current mainstream UES technologies with the emerging UES materials. Specifically, this review elucidates the causality between the physiochemical properties of UES materials induced by the intellectual design strategies and the UES performances and further dissects the relationships of materials-properties-activities and the corresponding mechanisms in depth. This review is envisaged to inspire innovative ideas and bring technical solutions for developing technically and economically viable UES materials.

Adsorbents for the Uranium Capture from Seawater for a Clean Energy Source and Environmental Safety: A Review

On the global level, uranium is considered the main nuclear energy source, and its removal from terrestrial ores is enough to last until the end of the current century. Therefore, a major focus is attracted toward the capture of uranium from a sustainable source (seawater). Uranium recovery from seawater has been reported over the last few decades, and recently many efforts have been devoted to the preparation of such adsorbents with higher selectivity and adsorption capacity. The purpose of this review is to report the advancement in adsorbent preparation and modification of porous materials. It also discusses challenges such as adsorbent selectivity, low uranium concentration in seawater, contact time, biofouling, and the solution to the problems necessary to ensure a better adsorption performance of the adsorbent.

Synergetic and advanced isotherm investigation for the enhancement influence of zeolitization and β-cyclodextrin hybridization on the retention efficiency of U(vi) ions by diatomite

In synergetic investigations, the adsorption effectiveness of diatomite-based zeolitic structure (ZD) as well as its β-cyclodextrin (CD) hybrids (CD/ZD) towards uranium ions (U(vi)) was evaluated to examine the influence of the transformation procedures. The retention behaviors and mechanistic processes have been demonstrated through analyzing the steric and energetic factors employing the modern equilibrium approach (a monolayer model with a single energy level). After the saturation phase, the uptake characteristics of U(vi) were dramatically improved to 297.5 mg g-1 after the CD blending procedure versus ZD (262.3 mg g-1) or 127.8 mg g-1. The steric analysis indicated a notable increase in binding site levels after the zeolitization steps (Nm = 85.7 mg g-1) as well as CD implementation (Nm = 91.2 mg g-1). This finding clarifies the reported improvement in the ability of CD/ZD to effectively retain the U(vi) ions. Furthermore, every single active site of the CD/ZD material has the capacity to adsorb around four ions, which are aligned according to a vertical pattern. The energetic aspects, specifically Gaussian energy (<8 kJ mol-1) along with retention energy (<40 kJ mol-1), validate the regulated influences of the physical mechanistic processes. The physical adsorption of U(vi) seems to depend on various intermolecular forces, such as van der Waals forces, in conjunction with zeolitic ion exchanging pathways (0.6-25 kJ mol-1). The thermodynamic assets have been evaluated to confirm the exothermic together with spontaneous adsorption U(vi) by ZD and its blend with CD (CD/ZD).

Magnetic nanocomposites based on Zn,Al-LDH intercalated with citric and EDTA groups for the removal of U(vi) from environmental and wastewater: synergistic effect and adsorption mechanism study

The efficient removal of U(vi) ions from contaminated natural waters and wastewaters of industrial processing plants by novel magnetic nanocomposites based on magnetite and Zn,Al-layered double hydroxides intercalated with citric and EDTA groups (Fe3O4/Zn,Al-LDH/Cit and Fe3O4/Zn,Al-LDH/EDTA) was shown. These adsorbents were obtained using co-precipitation and ion-exchange techniques. The infrared spectroscopy confirmed the existence of O-containing groups on the surfaces of Fe3O4/Zn,Al-LDH/Cit and Fe3O4/Zn,Al-LDH/EDTA, which could provide active sites in the interlayer of the adsorbents for the pollutants removal. The intercalation of Zn,Al-LDH with chelating EDTA-groups significantly increased the adsorption capacity toward U(vi) ions (131.22 mg g-1) compared to citric moieties in a wide range of pH (3.5-9.0). The maximum adsorption capacities of U(vi) at pH 7.5 were 81.12 mg g-1 for Fe3O4/Zn,Al-LDH/EDTA and 21.6 mg g-1 for Fe3O4/Zn,Al-LDH/Cit. The higher adsorption capacity of Fe3O4/Zn,Al-LDH/EDTA vs. the citric sample might be explained by high affinity of LDH-supports and high-activity of the chelating groups in formation of the complexes in the interlayer space of the magnetic nanocomposite. The removal of U(vi) by the magnetic nanocomposites occurred due to interlayer complexation and electrostatic interactions. The cations (Na+, K+, Ca2+), HCO3 - and fulvic acid anions being typical for natural waters were practically not affected upon the removal of U(vi) from aqueous media. The adsorption performance of Fe3O4/Zn,Al-LDH/EDTA nanocomposites was evaluated in the analysis of environmental and wastewater samples with recoveries in the range of 95.8-99.9%. This superior intercalation performance of LDH-supports provides simple and low-cost adsorbents, providing a strategy for decontamination of radionuclides from wastewater.

Appreciatively Efficient Sorption Achievement to U(VI) from the El Sela Area by ZrO2/Chitosan

The need to get uranium out of leaching liquid is pushing scientists to come up with new sorbents. This study uses the wet technique to improve the U(VI) sorption properties of ZrO2/chitosan composite sorbent. To validate the synthesis of ZrO2/CS composite with Zirconyl-OH, -NH, and -NH2 for U(VI) binding, XRD, FTIR, SEM, EDX, and BET are used to describe the ZrO2/chitosan wholly formed. To get El Sela leaching liquid, it used 150 g/L H2SO4, 1:4 S:L ratio, 200 rpm agitation speed, four hours of leaching period, and particle size 149–100 µm. In a batch study, the sorption parameters are evaluated at pH 3.5, 50 min of sorbing time, 50 mL of leaching liquid (200 mg/L U(VI)), and 25 °C. The sorption capability is 175 mg/g. Reusing ZrO2/CS for seven cycles with a slight drop in performance is highly efficient, with U(VI) desorption using 0.8 M acid and 75 min of desorption time. The selective U(VI) recovery from El Sela leachate was made possible using ZrO2/CS. Sodium diuranate was precipitated and yielded a yellow cake with a purity level of 94.88%.

Biosorption of Uranium from aqueous solution by green microalga Chlorella sorokiniana

Uranium and its compounds are radioactive and toxic, as well as highly polluting and damaging the environment. Novel uranium adsorbents with high biosorption capacity that are both eco-friendly and cost-effective are continuously being researched. The non-living biomass of the fresh water green microalga Chlorella sorokiniana was used to study the biosorption of uranium from aqueous solution. The biosorption of uranium from aqueous solutions onto the biomass of microalga C. sorokiniana was investigated in batch studies. The results showed that the optimal pH for uranium biosorption onto C. sorokiniana was 2.5. Uranium biosorption occurred quickly, with an equilibrium time of 90 min. The kinetics followed a pseudo-second-order rate equation, and the biosorption process fit the Langmuir isotherm model well, with a maximum monolayer adsorption capacity of 188.7 mg/g. The linear plot of the DKR model revealed that the mean free energy E = 14.8 kJ/mol, confirming chemisorption adsorption with ion exchange mode. The morphology of the algal biomass was investigated using a scanning electron microscope and energy dispersive X-ray spectroscopy. The FTIR spectroscopy analysis demonstrated that functional groups (carboxyl, amino, and hydroxyl) on the algal surface could contribute to the uranium biosorption process, which involves ion exchange and uranium absorption, and coordination mechanisms. Thermodynamic simulations indicated that the uranium biosorption process was exothermic (ΔH = -19.5562 kJ/mol) and spontaneous at lower temperatures. The current study revealed that C. sorokiniana non-living biomass could be an efficient, rapid, low-cost, and convenient method of removing uranium from aqueous solution.

Sorption of uranium(VI) from aqueous solution using nanomagnetite particles; with and without humic acid coating

In this study, iron oxide nanoparticles (Fe3O4) and iron oxide nanoparticles with humic acid coatings (Fe3O4/HA) were investigated for the removal of U(VI). The effect of contact time, adsorbent mass, U(VI) concentration, and pH was studied by batch technique. The sorption kinetic data follows pseudo-second order, while the isotherms obey Langmuir with Qmax values of 238.0, 195.6 mg/g for Fe3O4 and Fe3O4/HA, respectively. According to the study, humic acid decreases the sorption capacity of magnetite due to the formation of a polyanionic organic coating, altering the surface properties of the particles, reducing magnetite aggregation, and stabilizing magnetite suspension.

Fabrication of a novel magnetic rubidium ion-imprinted polymer for selective separation

A novel magnetic ion-imprinted polymer (MIIP) for Rb+ was synthesized by combining the surface imprinting technology with the magnetic separation technology.

Theoretical and experimental studies on uranium(vi) adsorption using phosphine oxide-coated magnetic nanoadsorbent

In this study, novel Cyanex-923-coated magnetite nanoparticles (Fe3O4@Cyanex-923) were prepared, comprehensively characterized, and employed for uranium(vi) ion adsorption from aqueous solutions. FTIR and TGA data confirmed that Fe3O4 has successfully gained Cyanex-923 surface functionality. Particle size and morphological studies via DLS, HR-TEM, and SEM showed uniform-dispersed quasi-spherical nanoparticles with a mean diameter of ca. 44 nm. Magnetism measurement data revealed the superparamagnetic properties of the Fe3O4@Cyanex-923 nanoadsorbent. The effect of different experimental settings on the adsorption efficiency was studied to determine the best operational conditions. The experimental results were analyzed using Langmuir, Freundlich, and Temkin isotherms; where the adsorption data obeyed the Langmuir model showing a theoretical adsorption capacity of 429.185 mg g-1 at 298 K. Kinetics data analysis revealed a fast adsorption process that could reach equilibrium within 60 min and is well-fitted to the pseudo-2nd-order model. Temperature affected the adsorption process and the thermodynamic data indicated that uranium(vi) adsorption was spontaneous and exothermic. Fe3O4@Cyanex-923 nanoparticles displayed a good regeneration behavior over three sequential adsorption-desorption cycles. The Fe3O4@Cyanex-923 nanoadsorbent showed a high uranium adsorption capacity, fast equilibration time, economic nature, good reusability, and easy separation; making it a promising candidate for uranium(vi) removal from nuclear waste streams.

Synthesis of phosphorylated hyper-cross-linked polymers and their efficient uranium adsorption in water

Uranium (U) is hazardous and radioactive, wastewater containing U(VI) should be treated before being discharged. Here, two novel uranium adsorbents, phosphorylated hyper-cross-linked bisphenol A (PHCP-1) and fluorene-9-bisphenol (PHCP-2) were separately synthesized via Friedel-Crafts reaction followed by phosphorylation using phosphorus oxychloride. PHCPs had a BET surface area (up to 564 m²/g) with pore sizes of 2.2-2.8 nm. These adsorbents were used for the first time for uranium adsorption from water and demonstrated outstanding adsorption performance. PHCP-2 had a great uranium adsorption capacity (297.14 mg/g) and a very fast sorption rate (85% removal rate within 5 min). The adsorption data were well fitted with Freundlich isotherm and the pseudo-second-order kinetic model. PHCPs displayed selective adsorption capacity for U(VI) from solution that including a variety of competing metal ions. The reusability was confirmed through three regeneration cycles. Based on a series of spectroscopic analyses, the mechanism of action between PHCPs and U(VI) is primarily derived from the complex between phosphate functional groups and U (VI). The sorption performance of PHCPs is attributed to their huge specific surface area and the strong complex between phosphate groups and U(VI). These findings suggest that PHCPs could be useful in the effective adsorption of uranium from water.

Diamidoximated cellulosic bioadsorbents from hemp stalks for elimination of uranium (VI) and textile waste in aqueous systems

Selective abolition of hazardous U(VI) ions from nuclear power plants and removal of toxic colorants from textile industries pose great challenge. The work aims to develop cellulosic bioadsorbents from waste stalks of local weed, Cannabis sativa, commonly known as hemp. Cellulose nanofibers (PCFs) were chosen as substrates owing to their unique characteristics like surface hydroxyl groups, large surface to volume ratio and excellent mechanical properties. PCFs were isolated from hemp stalks and their structural characterization using FTIR, TGA and XRD ensured retrieval of pure crystalline cellulose. PCFs were modified via copolymerization to obtain diaminomaleonitrile adorned cellulose grafts (DAMNC) and further converted to get diamidoxime functionalized cellulose (DAOC). DAOC exhibited exceptional affinity with uranium (VI) ions, safranin-o and methylene blue dyes due to presence of two amidoxime groups. Sorption capability was ascertained for optimization of parameters like contact time, pH selectivity, adsorbent dosage and concentration. Sorption followed Pseudo second-order kinetic model with maximum sorption of 220 mg/g, 19.01 mg/g and 46.4 mg/g for U(VI) ions, SO and MB, respectively. EDX mapping revealed uniform adsorption of all the three pollutants on DAOC while XPS ascertained that the sorption originated from multiple interactions between the adsorbent and the pollutants.

Efficiently immobilizing uranium (VI) by oxidized carbon foam

Oxidized carbon foam (oxidized CF) was prepared by using a facile chemical oxidation treatment at relatively low temperature of 450 °C and applied to capture uranyl cation [U(VI)] from aqueous solutions. The effects of pH, contact time, initial U(VI) concentration, and temperature on the U(VI) absorption performance of oxidized CF were investigated by batch experiments. The oxidized CF was illustrated to exhibit fast sorption kinetics (92% removal within 15 min and 98% removal in 2 h) and high sorption capacity (305.77 mg g^-1 at pH 5) toward U(VI). Integrated analyses combining energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy were applied on the U(VI)-loaded oxidized CF, showing the introduction of carboxyl groups as U(VI) sorption sites on the surface of CF after oxidation treatment. Furthermore, extended X-ray absorption fine structure spectroscopy was employed to identify the binding modes of U(VI) indicating that each UO₂²⁺ cation is coordinated with one or two carboxyl groups on the equatorial plane. Notably, the low content of U(VI) in wastewater can be efficiently immobilized by the oxidized CF, and the immobilized U(VI) can be further concentrated and converted into Na₂U₂O₇ or U₃O₈ by a simple sintering step. These findings presented in this work suggest the potential of using oxidized CF for further treatment of low concentration wastewater containing U(VI).

Rapid and selective magnetic separation of uranium in seawater and groundwater using novel phosphoramidate functionalized citrate-Fe3O4@Ag nanoparticles

One-pot magnetic separation of uranium (U) in seawater and groundwater samples has been made possible by synthesizing phosphoramidate functionalized Ag coated citrate-Fe₃O₄ nanoparticles (NPs). The magnetic saturation value of these functionalized NPs is 27.1 emu g^-1. The synergistic extraction mechanism of U(VI) ion by the surface-modified phosphoramidate and citrate molecules make these NPs highly selective towards U(VI). The adsorption kinetics follows a pseudo-second-order model and the adsorption isotherm fits successfully to the Langmuir adsorption model. The functionalized NPs show quantitative extraction efficiency in the pH range of 6.5-8 with a maximum loading capacity (Q_m) of 108.7 mg g^-1. The equilibration time required by these functionalized NPs to attain the Q_m value is 120 s. The recycling of these NPs can be done up to 5-6 times with 1.0 mol L^-1 of Na₂CO₃ or NH₄OH for quantitative extraction of U(VI). These functionalized NPs show high resilience towards large number of naturally abundant metal ions.

Effective decontamination of As(V), Hg(II), and U(VI) toxic ions from water using novel muscovite/zeolite aluminosilicate composite: adsorption behavior and mechanism

Muscovite/phillipsitic zeolite was introduced as a novel inorganic composite of stunning adsorption properties. The composite was investigated in the uptake reactions of Hg(II), As(V), and U(VI) as highly toxic water contaminants considering different adsorption factors. The adsorption properties of muscovite/phillipsitic zeolite are highly dependent on the pH values and the best decontamination percentages can be obtained at pH 4, pH 5, and pH 5 for Hg(II), As(V), and U(VI), respectively. The kinetic studies demonstrated adsorption equilibrium for Hg(II), As(V), and U(VI) after 360 min, 300 min, and 360 min, respectively. The equilibrium modeling suggested monolayer uptake for all the metals and represented mainly by the Langmuir model considering both the values of determination coefficient and chi-squared (χ²). The estimated maximum capacities are 117 mg/g (Hg(II)), 122.5 mg/g (As(V)), and 138.5 mg/g (U(VI)) which are higher values than several studied adsorbents. The Dubinin-Radushkevich adsorption energies of Hg(II) (19.4 kJ/mol), As(V) (25.6 kJ/mol), and U(VI) (26.47 kJ/mol) signify chemical adsorption mechanisms and close to the obtained values for the ion-exchange process. Additionally, the composite is of high reusability properties and was applied effectively for five decontamination cycles. Graphical abstract.

Efficient extraction of uranium from environmental samples using phosphoramide functionalized magnetic nanoparticles: Understanding adsorption and binding mechanisms

Phosphoramide functionalized Fe₃O₄ nanoparticles (NPs) were synthesized by a three step procedure and its application for uranium extraction from different enviornmental matrices has been demonstrated. A maximum adsorption capacity of 95.2 mg of U/g of the sorbent has been achieved which is higher as compared to many reported magnetic NPs. pH dependent adsorption studies were performed at 1 ppm uranium concentrations which suggests more than 80% adsorption in pH range of 4-8 with maximum adsorption at pH 6. Interestingly this is the pH range of most naturally occurring water bodies suggesting the potential of this material to extract uranium from real environmental samples. Adsorption studies were carried out with tap water, drinking water and sea water and more than 90% uranium extraction was observed. Desorption studies were performed with different reagents suggesting that the material can be reused again. EXAFS studies have been carried out which suggests that the uranium binds with oxygens of three PO group at the surface of phosphoramide functionalized NPs and based on this, binding mode of uranium with the synthesized sorbent is proposed.

Ultra-High Performance of Hyper-Crosslinked Phosphate-Based Polymer for Uranium and Rare Earth Element Adsorption in Aqueous Solution

In this work, a new type of hyper-crosslinked phosphate-based polymer (HCPP) polymerized by bis(2-methacryloxyethyl)phosphate has been developed for uranium and rare earth element (REE) extraction in an aqueous solution. The influence of the pH value, contact time, initial concentration, temperature, and competing ions on uranium adsorption of HCPP is investigated in detail. HCPP exhibits a maximum uranium adsorption capacity of up to 800 mg g^-1 at pH = 6.0 and excellent selectivity toward uranium adsorption over coexisting ions, because of the high affinity between HCPP and uranium ions and dense phosphate groups on the backbone. It also demonstrates high adsorption performance in both simulated seawater with a high salt concentration and a real nuclear industrial effluent. Besides, the crosslinked network structure of HCPP endows this polymer with high chemical stability and reusability. Furthermore, the adsorption mechanism is probed by energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared measurements. It is confirmed that the adsorption of uranium on the adsorbent originates from the interaction between phosphate groups and uranium ions. Meanwhile, HCPP also displays high REE adsorption capacities. This work indicates that the phosphate-based HCPP could be utilized as a promising adsorbent for the effective removal of uranium and REEs from aqueous solution.

Preparation of Micro-Nano Material Composed of Oyster Shell/Fe3O4 Nanoparticles/Humic Acid and Its Application in Selective Removal of Hg(II)

Micro-nano composite material was prepared to adsorb Hg(II) ions via the co-precipitation method. Oyster shell (OS), Fe3O4 nanoparticles, and humic acid (HA) were used as the raw materials. The adhesion of nanoparticles to OS displayed by scanning electron microscopy (SEM), the appearance of the (311) plane of standard Fe3O4 derived from X-ray diffraction (XRD), and the transformation of pore sizes to 50 nm and 20 μm by mercury intrusion porosimetry (MIP) jointly revealed the successful grafting of HA-functionalized Fe3O4 onto the oyster shell surface. The vibrating sample magnetometer (VSM) results showed superparamagnetic properties of the novel adsorbent. The adsorption mechanism was investigated based on X-ray photoelectron spectroscopy (XPS) techniques, which showed the process of physicochemical adsorption while mercury was adsorbed as Hg(II). The effects of pH (3-7), initial solution concentration (2.5-30 mg·L-1), and contact time (0-5 h) on the adsorption of Hg(II) ions were studied in detail. The experimental data were well fitted to the Langmuir isotherm equation (R2 = 0.991) and were shown to follow a pseudo-second-order reaction model (R2 = 0.998). The maximum adsorption capacity of Hg(II) was shown to be 141.57 mg·g-1. In addition, this new adsorbent exhibited excellent selectivity.

Facile preparation and adsorption performance of graphene oxide-manganese oxide composite for uranium

To overcome the limits of low adsorption capacity and the separation difficulty of solid from liquid phase for graphene oxide (GO), a novel nanocomposite graphene oxide-manganese oxide (GOMO) was facilely fabricated under ultrasonic radiation. The structures and micro-morphology of the products were characterized by fourier transform infrared (FT-IR) spectroscopy, raman shift spectroscopy, X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM). The effect of solution pH, adsorbent dose, contact time, initial uranium concentration, ionic strength and temperature on uranium removal efficiency was studied by batch adsorption experiments. The product GOMO was used to examine the feasibility of the removal of high salt content in uranium-containing wastewater. The adsorption results were fitted using the Langmuir and Freundlich isotherm models. The kinetic parameters in the adsorption process were measured and fitted. Five adsorption/desorption cycles were performed using 3 M HNO₃ as the regenerant in order to evaluate the reuse of GOMO.

Magnetite-based adsorbents for sequestration of radionuclides: a review

As a result of extensive research efforts by several research groups, magnetite-based materials have gained enormous attention in diverse fields including biomedicine, catalysis, energy and data storage devices, magnetic resonance imaging, and environmental remediation. Owing to their low production cost, ease of modification, biocompatibility, and superparamagnetism, the use of these materials for the abatement of environmental toxicants has been increasing continuously. Here we focus on the recent advances in the use of magnetite-based adsorbents for removal of radionuclides (such as 137Cs(i), 155Eu(iii), 90Sr(ii), 238U(vi), etc.) from diverse aqueous phases. This review summarizes the preparation and surface modification of magnetite-based adsorbents, their physicochemical properties, adsorption behavior and mechanism, and diverse conventional and recent environmental technological options for the treatment of water contaminated with radionuclides. In addition, case studies for the removal of radionuclides from actual contaminated sites are discussed, and finally the optimization of magnetite-based remedial solutions is presented for practical application.

Rapid extraction of uranium from sea water using Fe3O4 and humic acid coated Fe3O4 nanoparticles

Uranium is one of the most toxic elements present in the environment and a number of methods have been developed for its extraction. Herein we have demonstrated a new method using magnetic nanoparticles (NPs) that can be used for uranium extraction from water and sea water matrix. Fe₃O₄ and humic acid (HA) coated Fe₃O₄ NPs with different amount of HA coating were synthesized and uranium sorption from water and sea water matrix was demonstrated. It was observed that sorption increases with increase in amount of HA coating. NPs settlement in presence of magnetic field was monitored where only bare Fe₃O₄ and Fe₃O₄/HA 1 NPs settles while no settlement was observed for Fe₃O₄/HA 2 and Fe₃O₄/HA 3 NPs. Considering both sorption and particle separation from the matrix Fe₃O₄/HA 1 NPs are the best among synthesized ones with maximum sorption capacity of 10.5mg of U/g of NPs. The results presented here reveal the exceptional potential of magnetic NPs and functionalized magnetic NPs for environmental remediation of uranium and to extract uranium from sea water on which to the best of our knowledge no report is available till now.

Environmental implications and applications of engineered nanoscale magnetite and its hybrid nanocomposites: A review of recent literature

This review focuses on environmental implications and applications of engineered magnetite (Fe3O4) nanoparticles (MNPs) as a single phase or a component of a hybrid nanocomposite that exhibits superparamagnetism and high surface area. MNPs are synthesized via co-precipitation, thermal decomposition and combustion, hydrothermal process, emulsion, microbial process, and green approaches. Aggregation/sedimentation and transport of MNPs depend on surface charge of MNPs and geochemical parameters such as pH, ionic strength, and organic matter. MNPs generally have low toxicity to humans and ecosystem. MNPs are used for constructing chemical/biosensors and for catalyzing a variety of chemical reactions. MNPs are used for air cleanup and carbon sequestration. MNP nanocomposites are designed as antimicrobial agents for water disinfection and flocculants for water treatment. Conjugated MNPs are widely used for adsorptive/separative removal of organics, dyes, oil, arsenic, phosphate, molybdate, fluoride, selenium, Cr(VI), heavy metal cations, radionuclides, and rare earth elements. MNPs can degrade organic/inorganic contaminants via chemical reduction or catalyze chemical oxidation in water, sediment, and soil. Future studies should further explore mechanisms of MNP interactions with other nanomaterials and contaminants, economic and green approaches of MNP synthesis, and field scale demonstration of MNP utilization.

Recovery of uranium(vi) from aqueous solutions using a modified honeycomb-like porous carbon material

A novel composite adsorbent, consisting of three-dimensional honeycomb-like porous carbon and MnO₂ nanowires (HLPC/MnO₂), has been successfully synthesized and is an excellent adsorbent for removing uranium(vi) ions from aqueous solutions.

Enhancing the sorption efficiency of polystyrene by immobilizing MgO and its application for uranium (VI) removal from aqueous solutions

Magnesium oxide immobilized polystyrene (PS/MgO) was prepared by the thermal attachment method for the removal of U(VI) from aqueous solutions. PS/MgO was characterized by different techniques [scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD)]. The effects of pH, adsorbent amount, contact time, initial U(VI) concentration, temperature and co-existing cations on the removal process were investigated by using batch technique. The results showed that the maximum adsorption capacity was 163 (mg g−1) at pH 6 and 293 K. The adsorption kinetics of U(VI) onto PS/MgO followed pseudo-second order and intra-particle kinetic models. The adsorption isotherms obeyed the Freundlich isotherm model. The thermodynamic parameters show that the process is endothermic and spontaneous. PS/MgO is an attractive adsorbent for U(VI) removal from aqueous solutions due to its accessibility, low preparation cost and high removal capacity