Poly Amidoxime Research Articles

Hydroxyapatite synergistic polyamidoxime functionalized macroporous xerogels for fast removal of U (VI) in wastewater

Recovering uranium (VI) from wastewater is crucial for the sustainable development of nuclear energy industry and ecological environment health. Polyamidoxime (PAO) based 3D hydrophilic adsorbents are regarded as ideal materials for their high selectivity and adsorption capabilities. However, constructing efficient 3D hydrophilic adsorbents from inorganic and PAO composites remains a challenge. This study exploited high internal phase emulsions (HIPEs) as template to fabricate hydroxyapatite (HAP)-PAO hydrophilic xerogels for U(VI) extraction. The oil-in-water HIPEs were constructed using sodium dodecyl sulfonate (SDS) modified HAP particles as stabilizers and acrylamide (AAm) with dissolved PAO as continuous phase. After the polymerization of AAm, macroporous xerogels were prepared by removing the water and oil phases. Xerogels exhibited the removal efficiency of 99.9 % for U(VI) within 3 h with a maximum adsorption capacity of 223 mg∙g−1. The outstanding removal performance was ascribed to the specific structure of HAP and PAO which can effectively integrate with U(VI) ions in the presence of a hydrophilic network. This work provided a new approach to fabricate the complex adsorbents of inorganic particles with PAO for the rapid clean-up of U(VI) in wastewater.

Amidoxime‐based Star Polymer Adsorbent with Ultra‐High Uranyl Affinity for Extremely Fast Uranium Extraction from Natural Seawater

AbstractPolymer adsorbents functionalized with amidoxime groups are widely considered to have the most industrial potential for uranium extraction from seawater. However, the entanglement upon the collapse of polymer chain in seawater greatly reduces the utilization ratio of amidoxime ligands. Herein, a novel star‐shaped molecular brush adsorbent (β‐CD‐g‐PAO) is obtained by densely grafting polyamidoxime (PAO) chains from β‐cyclodextrin (β‐CD). Experimental and theoretical results reveal that, in contrast to conventional linear polymer adsorbents, the star polymer adsorbent with a high grafting density of PAO side chains enables strong steric repulsion between the polymer chains, leading to increased persistence length and disentanglement of side chains. As a result, the star polymer adsorbent shows higher accessibility of the adsorption ligands with lower adsorption energy, achieving an adsorption capacity of up to 944.75 mg g−1 in uranium‐spiked seawater, surpassing that of conventional linear PAO by 3.2 times. Remarkably, this star polymer adsorbent demonstrates an extraordinarily adsorption capacity of 10.9 mg−1 g−1 in only 1 day in natural seawater, coupled with excellent affinity for uranyl ions (K = 0.31 pM). The unique topological structure design provides a new approach to solving the problem of low utilization ratio of functional ligands in polymer adsorbents.

Hydrogel polyamidoxime shell layer constructed on cyclized polyacrylonitrile nanofibrous mats for efficient uranium extraction from seawater

Extracting uranium from seawater, which contains hundreds of times more than terrestrial ores, furnishes a sustainable energy resource while curbing carbon emissions. Nanofibrous-based amidoxime is the most reliable uranium adsorbent due to its abundant chelating sites and large surface area. However, the amidoximation (AO) of polyacrylonitrile nanofiber (PAN NFs) produces brittle and shrunk AO-PAN NFs, and the spinning of pre-amidoximed PAN produces sub-micro stiff poly amidoxime (PAO) NFs, restricting their applicability. Herein, pre-cyclization (210 °C) and optimized amidoximation are applied to construct a hydrogel shell layer from PAO on cyclized electrospun PAN NFs. Among different amidoximation ratios, AO10-CPAN mats (10 g/L) with a thin hydrogel PAO shell layer exhibit excellent mechanical strength, high uranium adsorption capacity reached 380 mg/g at pH 8, and maintained their structure and 89 % of their initial adsorption capacity after six adsorption-desorption cycles. Furthermore, a 20.6 mg/g uranium adsorption capacity is reached after 15 days of circulating spiked (300 ppb uranium) natural seawater through the AO10-CPAN mats, proving their excellent selectivity and the open-chain amidoxime is the main compound of PAO shell. The surface amidoximed cyclized PAN (AO10-CPAN) mats satisfy the mechanical and physiochemical requirements for effectively extracting uranium from seawater.

Revealing the role of interlayer spacing in radioactive-ion sieving of functionalized graphene membranes

Functionalization of graphene enables precise control over interlayer spacing during film formation, thereby enhancing the separation efficiency of radioactive ions in graphene membranes. However, the systematic impact of interlayer spacing of graphene membranes on radioactive-ion separation remains unexplored. This study aims to elucidate how interlayer spacing in functionalized graphene membranes affects the separation of radioactive ions. Utilizing polyamidoxime (PAO) to modify graphene oxide, we controlled the interlayer spacing of graphene membranes. Experimental results indicate that tuning interlayer spacing enables control of the permeation flux of radioactive ions (UO22+ 1.01 × 10−5–8.32 × 10−5 mol/m2·h, and K+ remains stable at 3.60 × 10−4 mol/m2·h), and the K+/UO22+ separation factors up to 36.2 at an interlayer spacing of 8.8 Å. Using density functional theory and molecular dynamics simulations, we discovered that the effective separation is mainly determined via interlayer spacing and the quantity of introduced functional groups, explaining the anomalous high permeation flux of target ions at low interlayer spacing (4.3 Å). This study deepens our comprehension of interlayer spacing within nanoconfined spaces for ion separation and recovery via graphene membranes, offering valuable insights for the design and synthesis of high-performance nanomembrane materials.

Yeast-Raised Polyamidoxime Hydrogel Prepared by Ice Crystal Dispersion for Efficient Uranium Extraction from Seawater.

Uranium extraction from seawater has attracted worldwide attention due to the massive reserves of uranium. Due to the straightforward synthesis and strong affinity toward uranyl ions (UO2 2+), the amidoxime group shows promise for use in highly efficient uranium capture. However, the low mass transfer efficiency within traditional amidoxime-based adsorbents severely limits the adsorption rate and the utilization of adsorption sites. In this work, a macroporous polyamidoxime (PAO) hydrogel is prepared by yeast-based biological foaming combined with ice crystal dispersion that effectively maintained the yeast activity. The yeast-raised PAO (Y-PAO) adsorbent has numerous bubble-like holes with an average pore diameter >100µm. These macropores connected with the intrinsic micropores of PAO to construct efficient diffusion channels for UO2 2+ provided fast mass transporting channels, leading to the sufficient exposure of hidden binding sites. The maximum adsorption capacity of Y-PAO membrane reached 10.07mg-U/g-ads, ≈1.54 times higher than that of the control sample. It took only eight days for Y-PAO to reach the saturation adsorption capacity of the control PAO (6.47mg-U/g-ads, 28 days). Meanwhile, Y-PAO possessed excellent ion selectivity, good reusability, and low cost. Overall, the Y-PAO membrane is a highly promising adsorbent for use in industrial-scale uranium extraction from seawater.

Polyamidoxime (PAO) granules for solar-enhanced uranium extraction from seawater

Extracting uranium (U(vi)) from seawater can effectively solve the shortage of uranium resources on land.

Electric-field strengthening uranium extraction from seawater assisted by nanofiltration membranes with sieving-adsorption properties

Electric-field driven uranium extraction from seawater has been proved to greatly enhance the performances of various adsorbents via gathering uranyl ions at the surfaces, but high-concentration interfering cations would also be enriched which generates shielding effects to reduce adsorption capacity. To address this issue, we have fabricated nanofiltration membranes with sieving-adsorption properties by choosing polyamidoxime (PAO) as substrates and polyamide as skin layers. On the one hand, the polyamide skin layers fabricated by interfacial polymerization could effectively separate uranyl ions from other metal ions according to the size-sieving effect since the size of uranyl ions is much larger than most interfering cations. The results demonstrated that the nanofiltration membranes could nearly 100 % reject uranyl ions while the rejections of other metal ions below 30 %. On the other hand, the rejected uranyl ions would be enriched at the surfaces of PAO substrates and followed by adsorption. The increased uranium concentrations are beneficial for both adsorption capacity as well as adsorption rate. Therefore, the adsorption capacity increased by 30 % compared with the pristine PAO adsorbents. This work not only provides a new strategy for the design of high-performance adsorbents, but also could promote the engineering process of uranium extraction from seawater which has an important scientific significance and application value.

Solar enhanced uranium extraction from seawater with the efficient strategy of MXene loaded nano-porous polyamidoxime membrane

Uranium extraction from seawater is a significant avenue for achieving sustainable energy development, but low uranium concentration and low water temperature in the ocean make it an eunormous challenge to extract uranium from seawater. To overcome these challenges, incorporating photothermal conversion components into the adsorbent holds great promise for enhancing solar-driven uranium extraction from seawater. Herein, a photothermal adsorbent PAO@MXene (PM) membrane was designed by combining 2D MXene with excellent photothermal conversion performance and polyamidoxime (PAO) with excellent uranium adsorption performance. We first fabricated a nano-porous PAO membrane via electrospinning and then prepared the PM membrane with high photothermal conversion and adsorption performance using a simple ultrasonication method. Under light condition, the adsorption capacity of PM membrane reached 452.42 mg g−1 while the adsorption capacity is 352.32 mg g−1 under dark. The adsorption capacity of light is 28.41 % higher than that of dark. Moreover, PM membrane exhibits a high uranium adsorption capacity of 2.19 mg g−1 after contact with natural seawater for a week. The results indicate that the suggested strategy can achieve solar enhanced uranium extraction from seawater through a simple method.

Janus photothermal adsorbent for solar-powered simultaneous uranium extraction and co-production of freshwater and sea salt from seawater

Ocean reserves massive water and mineral resources. The success in uranium extraction and desalination from seawater is expected to alleviate the severe situation of energy and freshwater scarcities around the world. Herein, a novel Janus photothermal adsorbent was fabricated via sequential electrospinning for simultaneous uranium extraction and co-production of freshwater and sea salt from seawater. It consisted of a hydrophilic polyamidoxime (PAO) nanofibrous mat as the bottom layer for uranyl ion adsorption and a hydrophobic polyvinylidene fluoride (PVDF)/MXene (Ti3C2Tx) composite nanofibrous mat as the upper layer to capture and convert solar energy to heat. With the assistance of 1-sun illumination, the Janus adsorbent exhibited 6.05 mg g−1 of uranium adsorption capacity within 28 days from natural seawater, resulting in a 30.1 % increase compared to that in dark and achieved 1.36 kg m–2h−1 of water evaporation rate in natural seawater. An outdoor solar-powered adsorption coupling with evaporation test of this Janus adsorbent demonstrates that 6.40 kg m−2 of freshwater, 2.02 mg m−2 of uranium and 0.22 kg m−2 of sea salt were co-produced within 9 h operation. This study on the Janus adsorbent paves a promising way to the comprehensive development of ocean resources in low-carbon and sustainable strategy.

Artemisia gum reinforced amidoxime gel membrane promotes rapid extraction of uranium from seawater

The development of high-efficiency adsorbents for rapid recovery of uranium from wastewater and seawater is considered an important condition for the sustainable development of nuclear energy. Herein, polyamidoxime (PAO) was introduced into a novel Artemisia sphaerocephala Krasch. gum -polyvinyl alcohol gel system, and ASKG-PVA/PAO gel membrane was prepared by crosslinking and membrane laying. Due to the high swelling capacity of ASKG, PAO chain is fully exposed, and ASKG-PVA/PAO membrane shows excellent uranium adsorption capacity of 681.20 mg·g−1 (pH = 6). The introduction of ASKG greatly improve the adsorption rate of the membrane, and the adsorption process reach equilibrium within 60 min (1/6 of original material). The static adsorption process conforms to the second-order kinetics and Langmuir model. X-ray photoelectron spectroscopy analysis shows that the strong coordination of N and O in amidoxime group is the main reason for uranium adsorption. ASKG-PVA/PAO membrane has great potential as uranium adsorbent due to its fast and efficient adsorption, easy separation and good recycling performance.

Polyamidoxime-loaded biochar sphere with high water permeability for fast and effective recovery of uranium from seawater

Given the plentiful uranium resources within the ocean, seawater uranium recovery holds significant importance for facilitating sustainable nuclear power development. There has been extensive research involving biochar materials for seawater uranium recovery. Existing biochar materials, on the other hand, exist primarily as powders, which are difficult to recover from use. Besides, traditional amidoxime-based adsorbents exhibited low uranium extraction rate, thus greatly hindering their practical application. In this study, a biochar sphere loaded with polyamidoxime (PAO) is prepared by using carbonized mycelium and PAO, designated as PAO-BS, in order to extract the uranium efficiently and quickly. Benefited from the ultrahigh porosity, hydrophilicity and water permeability, PAO-BS shows outstanding the adsorption efficiency of uranium. In comparison to other amidoxime-based adsorbents, the PAO-BS material demonstrates a remarkable extraction capacity of 211.35 mg g−1 in simulated seawater with an initial uranium concentration of 16 ppm, implying the high efficiency of functional group utilization in PAO-BS. Collectively, these results indicate that the rapid and highly effective recovery of uranium from natural seawater using PAO-BS has considerable potential.

Efficient extraction of uranium from seawater by reticular polyamidoxime-functionalized oriented holocellulose bundles

A novel multi-layered reticular polyamidoxime (PAO)-functionalized holocellulose bundles (ML-r-PAO@HB) with abundant oriented micro-channels and high mechanical strength was created via a facile solvent-exchange strategy and used for the first time to capture uranium from seawater. Due to the hydrophobic interaction of PAO chains induced by the solvent-exchange, multi-layered reticular PAO was successfully self-assembled onto the oriented micro-channels of the HB, which greatly improved the accessibility to the adsorption sites by increasing the exposed surface of PAO. The ML-r-PAO@HB exhibited high uptake capacity (851.42 mg g−1 PAO) and excellent adsorptive selectivity for U(VI) ions. After exposure to 500-L natural seawater for 28 days, an ultra-high uranium extraction capacity (9.74 mg g−1 PAO) was achieved by ML-r-PAO@HB. The N and O atoms in the –C(NH2)N-OH group were the main coordination sites for U(VI) uptake. These wonderful performances render the ML-r-PAO@HB highly desirable for the large-scale uranium extraction from seawater.

One-pot hydrolysis/amidoximation and self-assembly to polyamidoxime-based composite hydrogels for high-efficiency uranium capture

Nanostructuring or hydrophilic modification is critical to enhance uranium capture capability of polyamidoxime (PAO)-based adsorbents. Herein, PAO-based composite hydrogels, consisting of nanostructured PAO and interconnected sodium polyacrylate (PAA-Na), are produced via one-pot hydrolysis/amidoximation and self-assembly. The synergism of nanostructured PAO and hydrophilic PAA-Na network significantly promotes uranium capture from aqueous solutions, and a maximum adsorption capacity of 1849 mg-U/g is reached at pH= 7. Meanwhile, the composite hydrogels show a satisfied uranium uptake (21.8 mg-U/g) and a high selectivity in a simulated seawater containing profuse interfering metal ions. This study opens a facile and low-cost way for scalable production of PAO-based composite hydrogels towards high-efficiency uranium recovery in the wastewater and seawater.

Self-Emulsifying air-in-water HIPEs-Templated construction of amidoxime functionalized and chain entanglement enhanced macroporous hydrogel for fast and selective uranium extraction

A convenient design of amidoxime (AO)-functionalized hydrogel sorbent containing interconnected pores is critical for facilitating fast and selective uranium extraction. To address this, air-in-water high internal phase emulsions (HIPEs) templated construction of AO functionalized macroporous hydrogel sorbents (GMPAO) is reported for highly efficient extraction of uranium from aqueous solution. Curled gelatin methacryloyl (GelMA) chains, as amphiphilic Pickering emulsifier and molecular surfactant, endow self-emulsifying ability to stabilize the air/water interface. GMPAO exhibits an open-cell structure (diameter is about 80 % between 200 µm and 300 µm) with interconnecting pores (distribution is about 70 % between 55 µm and 75 µm), and the chain entanglement between polyamidoxime (PAO) and GelMA enhances mechanical strength. Benefitting from the macroporous structure and abundant affinity sites, GMPAO displays a spontaneous uranium adsorption capacity of 386.61 mg g−1 at 298 K and faster uptake within 60 min, which are superior to better than the previously reported hydrogel sorbent. In addition, GMPAO hydrogel still achieves the highest capacity and remarkable removal rate of almost 100 % towards uranium in the presence of competitive ions, as well as excellent recyclability toward uranium capture. Except for the coordination between uranium with amidoxime groups, the carboxylates from GelMA also cooperate as a synergistic effect for uranium uptake by charge interaction, which enhances the binding affinity of the adsorbent to uranium. Most importantly, this work demonstrates a new strategy for preparing macroporous hydrogel sorbents with enough stability and provides a new perspective for recovering uranium from an aqueous solution.

Application of poly(amidoxime)/scrap facemasks in extraction of uranium from seawater: from dangerous waste to nuclear power.

To effectively kill microorganisms on scrap facemasks (FMs) surface and provide new material for extracting uranium (U(VI)) from seawater, scrap FMs was treated by N2 capacitance coupled (CCP) plasma and modified with polyamidoxime (PAO). The obtained PAO/FMs was well characterized and applied as an adsorbent in the extraction of U(VI) from seawater. The effects of environmental conditions on the adsorption capability of PAO/FMs for U(VI) were briefly studied. Results showed that plasma technique can synchronously kill microorganisms and induce acrylonitrile (AN) polymerization on FMs surface. The prepared PAO/FMs presented excellent adsorption capability for U(VI). The experimental results highlighted the application of plasma technique in the management of scrap FMs, and PAO/FMs in the extraction of U(VI) from seawater.

Engineering biaxial stretching polyethylene membrane with poly(amidoxime)-nanoparticle and mesopores architecture for uranium extraction from seawater

Conventional polymeric adsorbents encapsulate most of their ligand groups (such as amidoxime, AO) in dense structures, leading to problems such as low adsorption capacity for Uranium extraction from seawater (UES). The uranium coordination environment of polymeric adsorbents has not been positively identified even after decades of research. Therefore, a new and functional Biaxially stretched polyethylene (BSPE) membrane with Poly-amidoxime (PAO) nanoparticles, mesoporous architecture, and nano-channels (PAO-BSPE) was fabricated in this study for UES, based on the interfacial self-assembly of axial grafting chains. The underlying mechanism involved in the formation of the PAO-BSPE membrane was elucidated using first-principles computations of the various reactions. The engineered PAO-BSPE membrane exhibited excellent hydrophilicity, good mechanical properties, high specific surface area, and contained mesoporous architecture and nano-channels, which facilitated advantages in terms of kinetics, capacity, and renewability in both laboratory experiments and marine field-testing. After 64 days of adsorption in natural seawater, the PAO-BSPE membrane with a low degree of grafting of 70.5% exhibited a high uranium-adsorption-capacity of 12.67 mg-U/g-ads, which was 1.77 times higher than that toward vanadium. The PAO-BSPE membrane efficiently extracted uranium in the presence of high concentrations of co-existing ions, with the distribution coefficient reaching 4.09 × 106 mL/g in natural seawater. The total amount of uranium recovered by the PAO-BSPE membrane was 15.0 g in terms of yellow cake during a total submersion time of 30 days in the ocean. The adsorbent exhibited a long service life of at least 12 cycles. Furthermore, near-edge and extended X-ray absorption fine structure spectroscopy analyses suggested that the mechanism of uranium adsorption involved the formation of a stable complex via the linkage of uranium with two amidoximes in a cooperative chelating fashion. This study presents a new adsorbent with improved efficiency for UES, which has significant implications for the development of polymer adsorbents with high selectivity.

Blow spinning of pre–acid-activated polyamidoxime nanofibers for efficient uranium adsorption from seawater

Polyamidoxime (PAO)-based adsorbents have been extensively studied for uranium (U) extraction from seawater for decades. ‘Hot alkali activation’ treatments are found to significantly improve the U adsorption capacity while inevitably decreasing the strength of PAO-based adsorbents, especially nanofiber (NF) adsorbents. Herein, for the first time, we report that, with proper modification, PAO can be dissolved in acid solution with high solubility, and the pre–acid-activated PAO (PA-PAO) exhibits high uranium capture ability (>1800 mg/g). For better use and collection in large-scale application, PA-PAO is mixed with chitosan (CS) and fabricated to PA-PAO/CS NFs via acidic aqueous solution blow spinning and glutaraldehyde vapor cross-linking. The covalently cross-linked PA-PAO/CS NFs are ready to use without postactivation treatment and achieve highly efficient U capturing performance in U-spiked seawater (913.13 mg/g) and natural seawater (4.91 mg/g, in 10 days), as well as enhanced mechanical stability and antibiofouling (antibacterial) activity. This strategy shows great potential for extraction of U from seawater and contaminated water in a cost-effective, industrial-scale manner.

Polymer brushes on graphene oxide for efficient adsorption of heavy metal ions from water

ABSTRACTThe pollution of heavy metal ions in water poses a serious threat to human being and ecosystems. Here, we report polyamidoxime (PAO) brush grafted graphene oxide (GO) as a highly efficient adsorbent for extraction of toxic metal cations from water. Surface‐initiated atom transfer radical polymerization was used to grow polyacrylonitrile (PAN) brushes on GO, followed by conversion of the nitrile groups in PAN into amidoxime groups, which had high binding affinity toward heavy metal cations. The PAO brush grafted GO demonstrated significantly fast adsorption kinetics and large adsorption capacity. At optimal pH 5, the PAO brush grafted GO can achieve maximum adsorption capacities of 116.7 mg g−1 for Pb(II), 258.6 mg g−1 for Ag(I), 192.2 mg g−1 for Cu(II), and 167.9 mg g−1 for Fe(III), which were significantly larger than those of small molecule functionalized GO. Mechanism analysis suggested that the enhanced adsorption performance was due to the myriads of functional groups in PAO brushes that were easily accessible to metal ions because of the swelling of the polymer brushes in water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48156.

Symbiotic Aerogel Fibers Made via In-Situ Gelation of Aramid Nanofibers with Polyamidoxime for Uranium Extraction.

The uranium reserve in seawater is enormous, but its concentration is extremely low and plenty of interfering ions exist; therefore, it is a great challenge to extract uranium from seawater with high efficiency and high selectivity. In this work, a symbiotic aerogel fiber (i.e., PAO@ANF) based on polyamidoxime (PAO) and aramid nanofiber (ANF) is designed and fabricated via in-situ gelation of ANF with PAO in dimethyl sulfoxide and subsequent freeze-drying of the corresponding fibrous gel precursor. The resulting flexible porous aerogel fiber possesses high specific surface area (up to 165 m2·g−1), excellent hydrophilicity and high tensile strength (up to 4.56 MPa) as determined by BET, contact angle, and stress-strain measurements. The batch adsorption experiments indicate that the PAO@ANF aerogel fibers possess a maximal adsorption capacity of uranium up to 262.5 mg·g−1, and the absorption process is better fitted by the pseudo-second-order kinetics model and Langmuir isotherm model, indicating an adsorption mechanism of the monolayer chemical adsorption. Moreover, the PAO@ANF aerogel fibers exhibit selective adsorption to uranium in the presence of coexisting ions, and they could well maintain good adsorption ability and integrated porous architecture after five cycles of adsorption–desorption process. It would be expected that the symbiotic aerogel fiber could be produced on a large scale and would find promising application in uranium ion extraction from seawater.

Green planting silver nanoparticles on Populus fibers and the catalytic application

Preparation and application of ecofriendly materials is becoming an urgent topic. In this work, a green approach for producing silver nanoparticles (AgNPs) embedded on natural Populus fibers (PF) was developed based on hydrothermal synthesis using polyamidoxime (PAO)-functionalized fibers (PF–g–PAO). Throughout the production process, PAO acts as a trapping, stabilizing, and reducing agent for AgNPs formation without involvement of any additional reagents. The effects of the hydrothermal synthesis temperature and PF–g–PAO immersion duration in silver ion solution on AgNPs formation were studied based on the morphology of the PF–g–PAO/AgNPs composites, and their application in catalytic reduction of 4-nitrophenol (4-NP) was investigated using scanning electron microscopy (SEM) and ultraviolet–visible (UV–vis) spectrophotometry. Under the optimal reaction condition, AgNPs with average size of 36 nm were embedded on the PF surface with high silver content (15.6 wt%), exhibiting high catalytic activity (2.40 s−1 g−1) and reusability (>5 cycles) in reduction of 4-NP to 4-aminophenol (4-AP). More importantly, the use of the renewable resource cellulose in this work represents a sustainable feature to reduce manufacturing cost and environmental impact.