Graphene oxide functionalized with nano hydroxyapatite for the efficient removal of U(VI) from aqueous solution

Amidoxime-grafted cotton fibers with anti-microbial sludge for efficient uranium recovery

Uranium as a nuclear fuel, its source and aftertreatment has been a hot topic of debate for developers. In this paper, amidoxime and guanidino-modified cotton fibers (DC-AO-PHMG) were synthesized by the two-step functionalization approach, which exhibited remarkable antimicrobial and high uranium recovery property. Adsorption tests revealed that DC-AO-PHMG had excellent selectivity and anti-interference properties, the maximum adsorption capacity of 609.75 mg/g. More than 85 % adsorption capacity could still be kept after 10 adsorption-desorption cycles, and it conformed to the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model as a spontaneous heat-absorbing chemical monolayer process. FT-IR, EDS and XPS analyses speculated that the amidoxime and amino synergistically increased the uranium uptake. The inhibitory activities of DC-AO-PHMG against three aquatic bacteria, BEY, BEL (from Yellow River water and lake bottom silt, respectively) and B. subtilis were significantly stronger, and the uranium adsorption was not impacted by the high bacteria content. Most importantly, DC-AO-PHMG removed up to 94 % of uranium in simulated seawater and extracted up to 4.65 mg/g of uranium from Salt Lake water, which demonstrated its great potential in the field of uranium resource recovery.

Advanced applications of hydroxyapatite nanocomposite materials for heavy metals and organic pollutants removal by adsorption and photocatalytic degradation: A review

This comprehensive review delves into the forefront of scientific exploration, focusing on hydroxyapatite-based nanocomposites (HANCs) and their transformative role in the adsorption of heavy metals (HMs) and organic pollutants (OPs). Nanoscale properties, including high surface area and porous structure, contribute to the enhanced adsorption capabilities of HANCs. The nanocomposites' reactive sites facilitate efficient contaminant interactions, resulting in improved kinetics and capacities. HANCs exhibit selective adsorption properties, showcasing the ability to discriminate between different contaminants. The eco-friendly synthesis methods and potential for recyclability position the HANCs as environmentally friendly solutions for adsorption processes. The review acknowledges the dynamic nature of the field, which is characterized by continuous innovation and a robust focus on ongoing research endeavors. The paper highlights the HANCs' selective adsorption capabilities of various HMs and OPs through various interactions, including hydrogen and electrostatic bonding. These materials are also used for aquatic pollutants' photocatalytic degradation, where reactive hydroxyl radicals are generated to oxidize organic pollutants quickly. Future perspectives explore novel compositions, fabrication methods, and applications, driving the evolution of HANCs for improved adsorption performance. This review provides a comprehensive synthesis of the state-of-the-art HANCs, offering insights into their diverse applications, sustainability aspects, and pivotal role in advancing adsorption technologies for HMs and OPs.

A review of remediation technologies for uranium-contaminated water

Uranium is a naturally existing radioactive element present in the Earth's crust. It exhibits lithophilic characteristics, indicating its tendency to be located near the surface of the Earth and tightly bound to oxygen. It is ecotoxic, hence the need for its removal from the aqueous environment. This paper focuses on the variety of water treatment processes for the removal of uranium from water and this includes physical (membrane separation, adsorption and electrocoagulation), chemical (ion exchange, photocatalysis and persulfate reduction), and biological (bio-reduction and biosorption) approaches. It was observed that membrane filtration and ion exchange are the most popular and promising processes for this application. Membrane processes have high throughput but with the challenge of high power requirements and fouling. Besides high pH sensitivity, ion exchange does not have any major challenges related to its application. Several other unique observations were derived from this review. Chitosan/Chlorella pyrenoidosa composite adsorbent bearing phosphate ligand, hydroxyapatite aerogel and MXene/graphene oxide composite has shown super-adsorbent performance (>1000 mg/g uptake capacity) for uranium. Ultrafiltration (UF) membranes, reverse osmosis (RO) membranes and electrocoagulation have been observed not to go below 97% uranium removal/conversion efficiency for most cases reported in the literature. Heat persulfate reduction has been explored quite recently and shown to achieve as high as 86% uranium reduction efficiency. We anticipate that future studies would explore hybrid processes (which are any combinations of multiple conventional techniques) to solve various aspects of the process design and performance challenges.

High efficiency adsorption of uranium by magnesia-silica-fluoride co-doped hydroxyapatite

Hydroxyapatite has a high affinity to uranium, and element doping can effectively improve its adsorption performance. In this study, magnesia-silica-fluoride co-doped hydroxyapatite composite was prepared by hydrothermal method, and the effect of single-phase and multiphase doping on the structure and properties of the composites was investigated. The results showed that the specific surface area of Mg-Si-F-nHA composites increased by 63.01% after doping. Comparing with nHA, U(VI) adsorption capacity of Si-nHA, Mg-Si-nHA and Mg-Si-F-nHA composites increased by 13.01%, 17.39% and 22.03%, respectively. The adsorption capacity of Mg-Si-F-nHA composite reached 1286.76 mg/g. Adsorbent dosage and pH obviously affected U(VI) adsorption, and the experimental data can be fitted well by PSO and Sips models. The physicochemical characterization before and after adsorption suggested that complexation, ion exchange and precipitation participated in uranium adsorption. In conclusion, different elements doping can effectively improve the uranium adsorption properties of hydroxyapatite composites.

Kinetic and equilibrium study of graphene and copper oxides modified nanocomposites for metal ions adsorption from binary metal aqueous solution

Presently, the main cause of pollution of natural water resources is heavy metal ions. The removal of metal ions such as nickel (Ni2+) and cadmium (Cd2+) has been given considerable attention due to their health and environmental risks. In this regard, for wastewater treatment containing heavy metal ions, graphene oxide (GO) nanocomposites with metal oxide nanoparticles (NPs) attained significant importance. In this study, graphene oxide stacked with copper oxide nanocomposites (GO/CuO-NCs) were synthesized and characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and atomic force microscopy (AFM) analytical procedures. The prepared GO/CuO-NCs were applied for the removal of Ni2+ and Cd2+ ions from a binary metal ion system in batch and continuous experiments. The obtained results revealed that GO/CuO-NCs exhibited the highest removal efficiencies of Ni2+ (89.60% ± 2.12%) and Cd2+ (97.10% ± 1.91%) at the optimum values of pH: 8, dose: 0.25 g, contact time: 60 min, and at 50 ppm initial metal ion concentration in a batch study. However, 4 mL/min flow rate, 50 ppm initial concentration, and 2 cm bed height were proved to be the suitable conditions for metal ion adsorption in the column study. The kinetic adsorption data exhibited the best fitting with the pseudo-second-order model. The adsorption isotherm provided the best-fitting data in the Langmuir isotherm model. This study suggested that the GO/CuO nanocomposites have proved to be efficient adsorbents for Ni2+ and Cd2+ ions from a binary metal system.

Biomimetic synthesis of polydopamine-graphene oxide/hydroxyapatite for efficient and fast uranium(VI) capture from aqueous solution

A novel and efficient mesoporous nano-absorbent for U(VI) removal was developed through an environment-friendly route by inducing the biomimetic mineralization of hydroxyapatite (HAP) on the bioinspired surface of polydopamine-graphene oxide (PDA-GO). PDA-GO/HAP exhibited the greatly rapid and efficient U(VI) removal within 2 min, and much higher U(VI) adsorption capacity of 433.07 mg·g-1 than that of GO and PDA-GO. The enhanced adsorption capacity was mainly attributed to the synergistic effect of O-H, -C=N-, and PO43- functional groups and the incorporation of uranyl ions by the formation of a new phase (chernikovite, H2(UO2)2(PO4)2·8H2O). The adsorption process of U(VI) fitted well with pseudo-second-order kinetic and Langmuir isotherm model. Moreover, PDA-GO/HAP showed a high U(VI) adsorption capacity in a broad range of pH values and owned good thermal stability. PDA-GO/HAP with various excellent properties made it a greatly promising adsorbent for extracting uranium. Our work developed a good strategy for constructing fast and efficient uranium-adsorptive biomimetic materials.

Simultaneous immobilization of lead and arsenic and improved phosphorus availability in contaminated soil using biochar composite modified with hydroxyapatite and oxidation: Findings from a pot experiment

Multi-metals/metalloids contaminated soil has received extensive attention because of their adverse health effects on the safety of the food chain and environmental health. In order to provide additional insight and aid in mitigating environmental risks, a pot experiment was directed to assess the impacts of biochars derived from rice straw (BC), and modified biochars i-e., hydroxyapatite modified (HAP-BC) and oxidized biochars (Ox-BC) on the redistribution, phytoavailability and bioavailability of phosphorus (P), lead (Pb), and Arsenic (As), as well as their effects on the growth of maize (Zea mays L.) in a Lead (Pb)/Arsenic (As) contaminated soil. The results showed that HAP-BC increased the soil total and available P, compared with raw biochar and control treatment. HAP-BC improved soil properties by elevating soil pH and electric conductivity (EC). The Hedley fractionation scheme revealed that HAP-BC enhanced the labile and moderately labile P species in soil. Both HAP-BC and Ox-BC assisted in the P build-up in plant roots and shoots. The BCR (European Community Bureau of Reference) sequential extraction data for Pb and As in soil showed the pronounced effects of HAP-BC towards the transformation of labile Pb and As forms into more stable species. Compared with control, HAP-BC significantly (P ≤ 0.05) decreased the DTPA-extractable Pb and As by 55% and 28%, respectively, subsequently, resulting in reduced Pb and As plant uptakes. HAP-BC application increased the plant fresh and dry root/shoot biomass by 239%, 72%, 222% and 190%, respectively. The Pb/As immobilization by HAP-BC was mainly driven by precipitation, ion exchange and surface complexation mechanisms in soil. In general, HAP-BC application indicated a great capability to be employed as an effective alternative soil amendment for improving P acquisition in soil, simultaneously immobilizing Pb and As in the soil-plant systems.

Efficient adsorption of low-concentration uranium from aqueous solutions

The development of nuclear energy has led to the depletion of uranium resources and now presents the challenge of treating radioactive wastewater. Extracting uranium from seawater and nuclear wastewater has been identified as an effective strategy for addressing these issues. However, extracting uranium from nuclear wastewater and seawater is still extremely challenging. In this study, an amidoxime-modified feather keratin aerogel (FK-AO aerogel) was prepared using feather keratin for efficient uranium adsorption. The FK-AO aerogel showed an impressive adsorption capacity of 585.88 mg·g^-1 in an 8 ppm uranium solution, with a calculated maximum adsorption capacity of 990.10 mg·g^-1. Notably, the FK-AO aerogel demonstrated excellent selectivity for U(VI) in simulated seawater that contained coexisting heavy metal ions. In a uranium solution having a salinity of 35 g·L^-1 and a concentration of 0.1-2 ppm, the FK-AO aerogel achieved a uranium removal rate of greater than 90 %, indicating its effectiveness in adsorbing uranium in environments having high salinity and low concentration. This suggests that FK-AO aerogel is an ideal adsorbent for extracting uranium from seawater and nuclear wastewater, and it is also expected that it could be used in industrial applications for extracting uranium from seawater.

In situ synthesis of magnesium-doped hydroxyapatite aerogel for highly efficient U(VI) separation with ultra high adsorption capacity and excellent recyclability

Mg-doped HAP aerogel (MHAPA) was firstly in situ prepared via freeze-drying-calcination technology to capture U(VI). The U(VI) removal capacity by MHAPA even arrived 2685.6 mg g^-1, which was about 2 times over purchased HAP, illustrating that the incorporation of Mg ions could greatly enhance the U(VI) removal capacity. Compared with HAP, MHAPA also showed better anti-ion interference ability and dynamic removal performances. In comparison with other HAP-based adsorbents, MHAPA possessed good recyclability and its desorption rate was up to 93.4% in the first cycle. The excellent U(VI) removal performances of MHAPA might be owing to its low crystallinity and grain size, fast ion exchange rate and partial ionization under acidic conditions, which would accelerate the process of electrostatic attraction, ion-exchange, and complexation to immobilize U(VI). To sum up, the prepared MHAPA was expected to be an environmentally friendly, recyclable and effective adsorbent to immobilize U(VI) in actual wastewater.

Nano-hydroxyapatite modified biochar: Insights into the dynamic adsorption and performance of lead (II) removal from aqueous solution

Adsorption of lead as Pb(II) using biochar is an environmentally sustainable approach to remediate this kind of pollution affecting wastewater. In this study, rice straw biochar (BC) was modified by combination with nano-hydroxy-apatite (HAP), resulting in a material designated as BC@nHAP, with enhanced adsorption performance. Based on Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses, it was evidenced that, after modification, HAP greatly enhanced surface functional groups (i.e., -COOH and/or -OH) of raw biochar's surface. Batch tests showed that the maximum sorption capacity of BC (63.03 mg g^-1) was improved due to the modification, reaching 335.88 mg g^-1 in BC@nHAP. Pseudo-second order (PSO) kinetics fitted well the adsorption data (R² = 0.99), as well as the Langmuir isotherm model (showing an adsorption value of 335.88 mg g^-1 for q_e). The results of thermodynamic calculations showed that the adsorption was primarily governed by chemisorption process. FTIR spectroscopy and XPS spectrum after adsorption further confirmed that the adsorption mechanisms were ion exchange with Pb²⁺ and surface complexation by -OH and -COOH. In addition, BC@nHAP revealed a brilliant regeneration capability. The maximum adsorption capacity by BC@nHAP was higher than that of raw biochar or other previously reported adsorbents. Therefore, BC@nHAP could be seen as a new sorbent material with high potential for real-scale heavy metal removal from wastewater, and specifically as a capable candidate new sorbent for Pb(II) removal from wastewater, which has clear implications as regard preservation of environmental quality and public health.

Highly efficient adsorptive extraction of uranium from wastewater by novel kaolin aerogel

An environment-friendly, low-cost and efficient kaolin aerogel adsorbent (named as KLA) was synthesized via a freeze-drying-calcination method to solve the defect of low uranium removal rate for kaolin (KL). The removal rate of uranium on KLA reached 90.6 %, which was much higher than that of KL (69.2 %) (C₀ = 10 mg L^-1, t = 24 h, pH = 5.0, T = 298 K and m/V = 1.0 g L^-1). The uranium removal behavior on KLA was satisfied with Pseudo-second-order and Langmuir model, which meant that the uranium ions were immobilized on the surface of KLA via chemical reaction. Meanwhile, high temperature was in favor of the removal of uranium on KLA, indicating that the removal process was a spontaneous endothermic reaction. Compared with KL, KLA also presented better cycle ability and its removal rate of uranium was up to 80.5 % after three cycles, which was still higher than that of KL at the first cycle (74.5 %). On basis of the results of SEM, XRD, FT-IR and XPS, it could be concluded that uranium ions were adsorbed by KLA via complexation. Hence, KLA could be regarded as a feasible candidate for the removal of uranium from aqueous solution.

Efficient extraction of U(VI) from uranium enrichment process wastewater by amine-aminophosphonate-modified polyacrylonitrile fibers

The enrichment and recovery of U(VI) from low-level radioactive wastewater in the process of uranium enrichment is important for the sustainable development of nuclear energy and environmental protection. Herein, a novel amine-aminophosphonate bifunctionalized polyacrylonitrile fiber (AAP-PAN), was prepared for the extraction of U(VI) from simulated and real uranium-containing process wastewater. The AAP-PAN fiber demonstrated a maximum adsorption capacity of 313.6 mg g^-1 at pH = 6.0 and 318 K in the batch experiments. During the dynamic column experiment, over 99.99% removal of U(VI) could be achieved by the fiber using multi-ion simulated solution and real wastewater with an excellent saturation adsorption capacity of 132.0 mg g^-1 and 72.5 mg g^-1, respectively. It also exhibited an outstanding reusability for at least 5 cycles of adsorption process. The mechanism for U(VI) removal was studied by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis in the assist of simulation calculation. It suggested that the amine and aminophosphonate groups can easily bind uranyl ions due to U(VI) is more likely to combine with oxygen atoms of CO and PO, respectively.

Facile synthesis of low-cost MnPO4 with hollow grape-like clusters for rapid removal uranium from wastewater

In order to deal with the environmental resource problems caused by nuclear pollution and uranium mine wastewater, it is particularly important to develop uranium removal adsorbent materials with low cost, high efficiency and controllable rapid preparation. In this work, the hollow grape-like manganese phosphate clusters (h-MnPO₄) were synthesized in 4 h by in-situ etching without template at room temperature, which can quickly and effectively remove uranium ions from wastewater. Due to the reasonable hollow structure, more effective adsorption sites are exposed. The obtained sample h-MnPO₄-200 reaches adsorption equilibrium in 1 h and can remove 97.20% uranyl ions (initial concentration is 100 mg L^-1). Under the condition of 25 ℃ and pH= 4, the maximum adsorption capacity of h-MnPO₄-200 for uranium was 751.88 mg g^-1. The FT-IR, XPS and XRD analysis showed that -OH and PO₄^3- groups played a key role in the adsorption process. Thanks to the synergistic adsorption mechanism of surface complexation and dissolution-precipitation, h-MnPO₄-200 maintained a high removal rate in the presence of competitive anions and cations. In a word, h-MnPO₄-200 can be rapidly synthesized through a facile and low-cost method and has a great application prospect in the practical emergency treatment of uranium-containing wastewater.

Enhanced immobilization of uranium(VI) during the conversion of microbially induced calcite to hydroxylapatite

Carbonate-bound uranium (U) is critical in controlling the migration of U in circumneutral to alkaline conditions. The potential release risk of carbonate-bound U should be concerned due to the contribution of mineral replacement. Herein, we explored the fate of U during the conversion process from microbial-induced calcite to hydroxylapatite (HAP) and investigated the phase and morphology evolution of minerals and the immobilization efficiency, distribution, and stability of U. The results showed that most calcite could convert to HAP during the conversion process. The aqueous residual U was below 1.0 mg/L after U-HAP formation, and the U removal efficiencies were enhanced by 20.0-74.4% compared to the calcite precipitation process. XRD and TEM results showed that the products were a mixture of HAP and uramphite. The elemental mapping results showed that most U concentrated on uramphite while a handful of U distributed homogeneously in calcite and HAP matrixes. The stability test verified that U-bearing HAP decreased the U solubility by 98-100% relative to calcite due to the uramphite formation and U incorporation into HAP. Our findings demonstrated that the combinations of microbial-induced calcite precipitation and calcite-HAP conversion could facilitate the U immobilization in treating radioactive wastewater and soil.

Ultra-high flexibility amidoximated ethylene acrylic acid copolymer film synthesized by the mixed melting method for uranium adsorption from simulated seawater

If U(VI) in seawater (unconventional uranium resource) can be extracted efficiently, it can provide important supplies and guarantees for the stable development of nuclear power. In this study, a mixing melting method without condensation agent was proposed to prepare ultra-high flexibility and different proportions DAMN modified EAA resin film (EAA-DAMN) through the condensation reaction between -COOH and -NH₂ and the uniform mixing of liquid EAA and DAMN. In addition, the dense film structure and -CN of EAA-DAMN were transformed into multiple pores structure and amidoxime groups of the amidoximated EAA (AO-EAA) by amidoxime reaction. The AO-EAA-3 showed the most excellent adsorption performance (q_e=146.40 mg g^-1) at pH = 5, which was 2.33 times that of EAA. Moreover, a hypothesis was proposed for the first time that -NH₂ in the material could combine with H⁺ ionized by water to form -NH₃⁺, and then adsorbed NO₃^- in the solution through electrostatic attraction, and O element from NO₃^- adsorbed on the surface and N-O from amidoxime groups of material as the adsorption active sites performed coordination with U(VI), thereby improving the adsorption performance of AO-EAA.

Heavy metal ions and particulate pollutants can be effectively removed by a gravity-driven ceramic foam filter optimized by carbon nanotube implantation

It is of great significance to develop a new gravity-driven filter to remove water pollutants, but it is still challenging. Here, a novel and simple strategy is demonstrated to manufacture fly ash (FA) ceramic foams showing a three-dimensional interconnected porous structure, with multiwalled carbon nanotubes (MWCNTs) implanted by combining carbamate grafting and polydimethylsiloxane coating. The polydimethylsiloxane formed a physical coating on the carbamate group, generating an effective thermal insulating layer on the outer side of the entire MWCNT. The FA foam, which shows a sufficient adsorption capacity for Pb(II) (51.67 ± 1.17 mg g^-1) and Cd(II) (30.12 ± 0.37 mg g^-1) at pH = 5, T = 25 °C, has a 96.33%, 95.12%, 89.50% removal efficiency for Cd(II), Pb(II), and particulate pollutants, and exhibits excellent recycling performance. This paper provides new opportunities to fabricate gravity-driven filters with low energy consumption for wastewater treatment.

Ion-imprinted guanidine-functionalized zeolite molecular sieves enhance the adsorption selectivity and antibacterial properties for uranium extraction

The important properties in the development of adsorbents for uranium extraction from seawater include specific selectivity to uranium ions and anti-biofouling ability in the ocean environment. In this paper, we report a novel strategy for efficient selective extraction of uranium from aqueous solutions and good anti-bacterial properties by surface ion-imprinted zeolite molecular sieves. Guanidine-modified zeolite molecular sieves 13X (ZMS-G) were synthesized and used as the support for the preparation of uranium(vi) ion-imprinted adsorbents (IIZMS-G) by ligands with phosphonic groups. The prepared IIZMS-G adsorbent was characterized via Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The results showed that guanidine groups have been successfully introduced onto the support while its morphology structure was maintained. The adsorption performance and selectivity to U(vi) ions, antibacterial property, and reusability of IIZMS-G were evaluated. The results showed that the maximum adsorption capacity reached 141.09 mg g⁻¹ when the initial concentration of metal ions was 50 mg L⁻¹ at pH 6 and 20 °C. The adsorption process followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm model. The IIZMS-G exhibits an efficient selective adsorption of U(vi) ions from aqueous solutions with competing ions. In addition, the IIZMS-G exhibited excellent inhibitory effects on Escherichia coli and Staphylococcus aureus, and the inhibitory rate was 99.99% and 98.96% respectively. These results suggest that the prepared IIZMS-G adsorbent may promote the development strategy of novel high selectivity and antifouling adsorbents for uranium recovery from seawater.

The important properties in the development of adsorbents for uranium extraction from seawater include specific selectivity to uranium ions and anti-biofouling ability in the ocean environment.

Graphene-based materials for the adsorptive removal of uranium in aqueous solutions

Ground water contamination by radioactive elements has become a critical issue that can pose significant threats to human health. Adsorption is the most promising approach for the removal of radioactive elements owing to its simplicity, effectiveness, and easy operation. Among the plethora of functional adsorbents, graphene oxide and its derivatives are recognized for their excellent potential as adsorbent with the unique 2D structure, high surface area, and intercalated functional groups. To learn more about their practical applicability, the procedures involved in their preparation and functionalization are described with the microscopic removal mechanism by GO functionalities across varying solution pH. The performance of these adsorbents is assessed further in terms of the basic performance metrics such as partition coefficient. Overall, this article is expected to provide valuable insights into the current status of graphene-based adsorbents developed for uranium removal with a guidance for the future directions in this research field.

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.

Uranium uptake from wastewater by the novel MnxTi1-xOy composite materials: Performance and mechanism

The novel Mn_xTi_1-xO_y composite materials with different mole ratios (Mn to Ti = 3:7, 5:5 and 7:3) were prepared to remove uranium species from wastewater. These composite materials were characterized by various techniques, such as thermogravimetric analysis (TG), X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) and scanning electron microscopy (SEM). It was found that the chitosan in Mn_xTi_1-x-Chi were completely removed after calcination at 650 °C and Mn_xTi_1-xO_y composites possessed uniform distribution of the porous structure as well as plentiful hydroxyl-containing groups. Moreover, the as-prepared Mn_xTi_1-xO_y composite materials were applied to remove uranium from solution to evaluate the adsorption performance. It was found that the Mn_0.5Ti_0.5O_y possessed relatively excellent uptake performance for uranium comparing with the Mn_0.3Ti_0.7O_y and Mn_0.7Ti_0.3O_y and its maximum uptake capacity and efficiency reach 695.2 mg/g and 98.6% (pH = 4, m/V = 0.1 g/L, T = 298 K), respectively, which were much superior than most of reported materials based on titanium oxide or manganese oxide. Besides, the uranium uptake on Mn_0.5Ti_0.5O_y was independent on ionic strength and it had considerable reusability, which might be the necessary condition for Mn_0.5Ti_0.5O_y to be applied in uranium uptake from uranium-containing wastewater. As a candidate adsorbent, Mn_0.5Ti_0.5O_y possessed a high potentiality to remove uranium from wastewater.

Construction of Core-Shell MOFs@COF Hybrids as a Platform for the Removal of UO22+ and Eu3+ Ions from Solution

The binary nanocomposites of metal/covalent-organic frameworks (NH₂-MIL-125(Ti)@TpPa-1) were constructed by solvothermal method, which was developed as a multifunctional platform with adsorption and photocatalysis for radionuclides removal. The batch experiments and physicochemical property (FT-IR, XRD, SEM, TEM, XPS, etc.) corroborated: (i) core-shell NH₂-MIL-125(Ti)@TpPa-1 had a more stable, multilayer pore structure and abundant active functional groups; (ii) NH₂-MIL-125(Ti)@TpPa-1 had fast a removal rate, as well as a high adsorption capacity of 536.73 mg (UO₂²⁺)/g and 593.97 mg (Eu³⁺)/g; (iii) the pseudo-second-order and Langmuir model provided a more reasonable description, indicating the immobilization process was endothermic, spontaneous chemisorption; (iv) the adsorption mechanism was chelation and electrostatic attraction, ascribed to the nitrogen/oxygen-containing functional groups. These results illustrated that NH₂-MIL-125(Ti)@TpPa-1 was a prospective adsorbent for the remediation polluted by radionuclides. In addition, the research provided the theoretical basis for further investigation on the UO₂²⁺(VI) photoreduction.

Design of 3D alumina-doped magnesium oxide aerogels with a high efficiency removal of uranium(vi) from wastewater

3D alumina-doped magnesium oxide (Al₂O₃/MgO) aerogels with remarkable adsorption properties for U(vi) were prepared via a simple lyophilization–calcination method.