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In this study, carboxylated graphene oxide (GO-COOH) was prepared via a simple and feasible method to enhance the adsorption of U(VI). GO-COOH were characterized by FT-IR, XRD and XPS technique, and then applied as the adsorbent for U(VI) ions removal from water. The effects of conditions for U(VI) adsorption, including initial pH of aqueous solution, adsorbent dose, contact time, and initial concentration of U(VI) solution were investigated. The result indicated that the maximum adsorption of U(VI) on GO-COOH was 315 mg/g at the optimum adsorption condition (C a = 0.2 g/L, pH = 6.0, t = 6 h, C 0 = 100 mg/L and T = 25 °C), which was significantly higher than that on GO (190 mg/g) in the same condition. Compared to GO, the maximum U(VI) adsorption capacity of GO-COOH increases by 65.8%. The adsorption process was described well with pseudo-second-order kinetics and the Langmuir isotherm model, indicating the chemisorption process and monolayer adsorption process. GO-COOH with increased carboxyl group content and expanded interface distance was successfully prepared from GO via a facile method. GO-COOH showed the enhanced adsorption of U(VI) compared to GO. Adsorption process was mainly dominated by chemisorption and monolayer adsorption. Image 1 • GO-COOH with increased carboxyl group content and expanded interface distance was prepared from GO via a facile method. • GO-COOH showed obviously higher adsorption capacity of U(VI) than GO. • The adsorption process for U(VI) was mainly dominated by chemisorption and monolayer adsorption. [ABSTRACT FROM AUTHOR]

• Synthesis of a novel U (VI) adsorbent HCP-Phenylalaninol (HCP-PAO), a porous hypercrosslinked aminol. • The hypercrosslinked product is simple to synthesize and shows porosity, large surface area and good thermodynamic stability properties. • HCP-PAO shows efficient U (VI) adsorption performance (Q e = 369.5 mg/g, pH = 7) and long service life. • HCP-PAO shows good selective toward uranium at simulated seawater. Uranium mining from seawater has sparked a lot of research curiosity. Here, we synthesized a porous hypercrosslinked phenylalaninol (HCP-PAO) for U (VI) adsorption from water, in which phenylalaninol bearing amino and hydroxyl groups was used as the monomer, and biphenyl dichlorobenzyl (BCMP) was used as the external crosslinker. The resulting porous adsorbent has a surface area of 562.6 m2/g and a pore volume of 0.41 cm3·g−1. The pore size distribution is focused around 3–4 nm, indicating that it is a typical mesoporous polymer. The adsorbent had the most promising adsorption performance at pH = 7, reaching adsorption saturation in a 100-ppm uranium-doped solution for 2 h (adsorption capacity of 369.5 mg/g). HCP-PAO was particularly sensitive to uranium in complicated settings (56.3 % removal rate), and the adsorption mechanism closely resembled the Langmuir model and the pseudo-second-order model well. The practically consistent adsorption capacity of the HCP-PAO after five adsorption/resolution studies indicated its high recyclability. The mechanism of uranium extraction by HCP-PAO is the synergistic coordination of –NH 2 and –OH with U (VI). HCP-PAO had an adsorption capacity higher than 100 mg/g at pH = 8 which is close to the pH of natural seawater, and showed good selectivity for U (VI) in simulated seawater experiments (removal rate over 55 %). Our research suggests that the novel hypercrosslinked product HCP-PAO can be applied as an adsorbent to efficiently capture U (VI) from water, and also it has great potential in seawater uranium extraction as well as expanding the research concept of porous uranium adsorbent. [ABSTRACT FROM AUTHOR]

In this study, a novel amidoxime functionalized graphene oxide adsorbent (GO-D-AO), based on the reaction of dopamine modified graphene oxide with acrylamide diacetonitrile and on the reaction of amidoximation, was successfully designed and prepared to effectively adsorb U(VI) ions. GO-D-AO was characterized by SEM, FT-IR, XRD and XPS techniques, and then applied as the adsorbent for the U(VI) adsorption. The GO-D-AO contained more amidoximation groups after the amidoximation modification due to the use of acrylamide diacetonitrile modifier. A series of adsorption experiments were carried out to investigate the influence factors in the adsorption process, including the pH values, contact time, temperature and initial concentration of U(VI) solution. The U(VI) maximum adsorption capacity of GO-D-AO was 1823.6 mg·g -1 , which was significantly higher than that of GO because of the excellent chelating ability of amidoxime group with U(VI) ions. And the U(VI) adsorption process of GO-D-AO fitted well with the Langmuir model and the pseudo-second-order kinetic model, indicating the adsorption process was monolayer and chemical adsorption. [Display omitted] • A highly efficient U(VI) adsorbent named GO-D-AO was designed and synthesized. • GO-D-AO contained abundant AO groups due to the use of acrylamide diacetonitrile. • GO-D-AO showed excellent adsorption capacity, Q max reached 1823.6 mg g−1 at pH = 7. • The adsorption process was dominated by chemisorption and monolayer adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amino acids were grafted onto MIL-101 to produce novel uranium adsorbents. • Histidine-modified MIL-101 shows the highest U(VI) adsorption capacity of 345 mg·g−1. • Imidazole and carboxyl group and large specific surface area play important role. Three novel uranium adsorbents were synthesized by modifying MIL-101 with three amino acids: glycine, histidine and cysteine. The BET (Brunauer-Emmett-Teller) specific surface areas of amino acid modified MIL-101 (MIL-101-Gly, MIL-101-His and MIL-101-Cys) are 429 m2∙g−1, 713 m2∙g−1 and 104 m2∙g−1, respectively, indicating that the modified MIL-101 retained high specific surface area. All the modified MIL-101 s showed good uranium adsorption performance, in which the uranium adsorption performance of MIL-101-His is the best that can reach 345 mg·g−1 at pH = 6. The adsorption process of three amino acid modified MIL-101 s all accord with Langmuir and pseudo-second-order model for monolayer chemical adsorption. In the existence of K, Ca, Na, Sr, Ba, Cd, Co and Pb, the uranium (VI) removal rate of MIL-101-His can reach 74% indicating its excellent selectivity. After five adsorption–desorption cycles, the adsorption capacity of MIL-101-His still remains good capacity of 300 mg·g−1. In short, we prepared three novel amino acid modified MIL-101 s, and the histidine modified MIL-101 showed the best uranium adsorption performance, including adsorption capacity, selectivity and recyclability. [ABSTRACT FROM AUTHOR]

Herein, a dual-function Zeolitic Imidazole Frameworks (ZIFs) ZIF-90 grafted with malononitrile by Knoevenagel reaction and following with an amidoximation reaction to form an efficient U (VI) adsorbent (ZIF-90-AO). The strong chelation power of amidoxime groups (AO) with uranium and ZIF-90 's mesoporous structure afforded ZIF-90-AO high maximum uranium adsorption capacity of 468.3 mg/g (pH = 5). In addition, the factors affecting uranium adsorption process were investigated by a batch of adsorption tests under different adsorption conditions. ZIF-90-AO displayed good selectivity to UO 2 2+ in the solution containing multiple co-existing ions and good regeneration property. More importantly, ZIF-90-AO showed excellent antimicrobial property against both E. coli and S. aureus. Therefore, ZIF-90-AO is a U-adsorbent with great application value for removing U (VI) from wastewater due to the high U (VI) adsorption capacity in weak acid condition and good anti-biofouling properties. [Display omitted] • A novel U (VI) adsorbent ZIF-90-AO with good anti-fouling performance is prepared. • The maximum U (VI) adsorption capacity of ZIF-90-AO (468.3 mg/g) is much higher than ZIF-90 at pH = 5. • The MICs of ZIF-90-AO against E. coli and S. aureus are 250 and 62.5 mg/L, respectively. • Perspectives about the adsorbent (ZIF-90-AO) for the removal of U (VI) from wastewater are presented. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Phosphorylation was performed on bisphenol type hyper-cross-linked polymer for the first time. • PHCPs have large BET surface area (PHCP-2 = 564 m2/g). • PHCP-2 showed a very fast sorption rate, the removal rate reached 85% within 5 min. • PHCPs showed selective adsorption ability for U(VI) from solution that contained multiple competing metal ions. [ABSTRACT FROM AUTHOR]

An efficient uranium adsorbent, amidoximated polyacrylonitrile foam (AOPAN) with a hierarchical pore structure, was prepared by freezing-extraction followed by amidoximation. AOPAN was analyzed by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), and showed an excellent uranium adsorption performance in aqueous solutions; the uranium adsorption capacity was 1058 mg/g. Even in the presence of competing ions, AOPAN showed a high selective removal ability for uranium (removal rate > 85%). After three cycles, the adsorption capacity and removal rate for uranium were still higher than 800 mg/g and 90%, respectively, which indicated the good recyclability of AOPAN. Furthermore, the adsorption process fitted the Freundlich model and the pseudo-second-order kinetic model. The calculated ΔH° and ΔG° indicated that the adsorption process was endothermic. The higher adsorption temperature could promote the adsorption on AOPAN. The XPS analysis indicated that the chelation between the amidoxime group and uranium plays a key role in the adsorption of uranium on AOPAN. Unlabelled Image • Porous amidoxime modified PAN with hierarchical pore (AOPAN) prepared by freeze-extraction. • AOPAN shows high U(VI) sorption capacity of 1058 mg/g. • High selectivity and good recyclability. • Hierarchical pore and strong chelation play important role. [ABSTRACT FROM AUTHOR]