AXAD-16-3,4-dihydroxy benzoyl methyl phosphonic acid: a selective preconcentrator for U and Th from acidic waste streams and environmental samples

New insights into the radiolytic stability of metal(iv) phosphonate hybrid adsorbent materials

Stable metal(iv) phosphonate hybrids are a promising class of materials for the critical issue of nuclear waste cleanup. However, to be of practical use, adsorbent materials must demonstrate radiolytic stability and this property remains poorly understood. Therefore, the radiolytic stabilities of post-functionalised mesoporous zirconium titanate and zirconium phosphonate coordination polymers were compared. For the first time, solid-state ³¹P MAS-NMR was used to probe the radiolytic degradation of metal(iv) phosphonates and provide mechanistic insight. Polyphosphonate-functionalized hybrids were more stable than monophosphonate hybrids, as the monophosphonate readily detached from the oxide surface. The zirconium phosphonate coordination polymer (Zr-ATMP) demonstrated the greatest radiolytic stability, attributed to its high ligand loading and intimately mixed structure. Zr-ATMP maintained highly efficient sorption from strongly acidic solutions even after receiving doses of gamma radiation up to 2.9 MGy.

Preparation of chitosan functionalized polyamidoamine for the separation of trivalent lanthanides from acidic waste solution

The manuscript deals with the sorption of Am(III) and Eu(III) from pH medium using chitosan functionalized with dendrimer like polyamidoamine (PAMAM) polymers up to third generation. The PAMAM polymers were introduced into chitosan by two step processes and were characterized by various instrumental techniques like FTIR, XRD, TG-DTA. The sorption process was highly pH dependent for both Am(III) and Eu(III) with increasing trend for higher pH of the solution. Kinetics of equilibration was found to be fast with equilibrium attained in 10 min for both the metal ions. Pseudo 2nd order kinetics mechanism was found to be followed for both Am(III) and Eu(III). The sorption process of Eu(III) was found to fit the Langmuir isotherm model with maximum sorption capacity of 6.01 mg/g. There was no effect on the generation of PAMAM Dendron on the efficiency, kinetics or sorption capacity for Am(III) as well as Eu(III). The synthesized different generation of PAMAM functionalized chitosan is a promising material for removal of actinides and lanthanides from waste water solution.

Ship-in-a-bottle CMPO in MIL-101(Cr) for selective uranium recovery from aqueous streams through adsorption

Mesoporous MIL-101(Cr) is used as host for a ship-in-a-bottle type adsorbent for selective U(VI) recovery from aqueous environments. The acid-resistant cage-type MOF is built in-situ around N,N-Diisobutyl-2-(octylphenylphosphoryl)acetamide (CMPO), a sterically demanding ligand with high U(VI) affinity. This one-step procedure yields an adsorbent which is an ideal compromise between homogeneous and heterogeneous systems, where the ligand can act freely within the pores of MIL-101, without leaching, while the adsorbent is easy separable and reusable. The adsorbent was characterized by XRD, FTIR spectroscopy, nitrogen adsorption, XRF, ADF-STEM and EDX, to confirm and quantify the successful encapsulation of the CMPO in MIL-101, and the preservation of the host. Adsorption experiments with a central focus on U(VI) recovery were performed. Very high selectivity for U(VI) was observed, while competitive metal adsorption (rare earths, transition metals...) was almost negligible. The adsorption capacity was calculated at 5.32mg U/g (pH 3) and 27.99mg U/g (pH 4), by fitting equilibrium data to the Langmuir model. Adsorption kinetics correlated to the pseudo-second-order model, where more than 95% of maximum uptake is achieved within 375min. The adsorbed U(VI) is easily recovered by desorption in 0.1M HNO₃. Three adsorption/desorption cycles were performed.

Surface functionalized nanostructured ceramic sorbents for the effective collection and recovery of uranium from seawater

The ability to collect uranium from seawater offers the potential for a nearly limitless fuel supply for nuclear energy.

New generation Amberlite XAD resin for the removal of metal ions: A review

The direct determination of toxic metal ions, in environmental samples, is difficult because of the latter's presence in trace concentration in association with complex matrices, thereby leading to insufficient sensitivity and selectivity of the methods used. The simultaneous removal of the matrix and preconcentration of the metal ions, through solid phase extraction, serves as the promising solution. The mechanism involved in solid phase extraction (SPE) depends on the nature of the sorbent and analyte. Thus, SPE is carried out by means of adsorption, ion exchange, chelation, ion pair formation, and so forth. As polymeric supports, the commercially available Amberlite resins have been found very promising for designing chelating matrices due to its good physical and chemical properties such as porosity, high surface area, durability and purity. This review presents an overview of the various works done on the modification of Amberlite XAD resins with the objective of making it an efficient sorbent. The methods of modifications which are generally based on simple impregnation, sorption as chelates and chemical bonding have been discussed. The reported results, including the preconcentration limit, the detection limit, sorption capacity, preconcentration factors etc., have been reproduced.

Adsorption of uranium from aqueous solution by PAMAM dendron functionalized styrene divinylbenzene

A new polymeric chelating resin was prepared by growing third generation poly(amido)amine (PAMAMG3) dendron on the surface of styrene divinylbenzene (SDB) and characterized by FTIR, TGA and SEM. The ideal branching of dendron in the chelating resin was determined from potentiometric titration. Adsorption of uranium (VI) from aqueous solution using PAMAMG3-SDB chelating resin was studied in a series of batch experiments. Effect of contact time, pH, ionic strength, adsorbent dose, initial U(VI) concentration, dendron generation and temperature on adsorption of U(VI) were investigated. Kinetic experiments showed that U(VI) adsorption on PAMAMG3-SDB followed pseudo-second-order kinetics model appropriately and equilibrium data agreed well with the Langmuir isotherm model. Thermodynamic parameters (ΔH°, ΔS°, ΔG°) were evaluated from temperature dependent adsorption data and the uranium adsorption on PAMAMG3-SDB was found to be endothermic and spontaneous in nature. The sticking probability value (5.303 × 10(-9)), kinetic and isotherm data reveal the chemisorption of uranium on PAMAMG3-SDB and adsorption capacity of the chelating resin was estimated to be 130.25 mg g(-1) at 298 K. About 99% of adsorbed U(VI) can be desorbed from PAMAMG3-SDB by a simple acid treatment suggesting that the chelating resin is reusable.

BEHSA grafted polymer for selective extraction of U(VI), Th(IV) and La(III) from acidic matrices and environmental samples – a green process

A new class of polymeric resin called MCM-BEHSA, for extraction of U(VI), Th(IV) and La(III) was synthesized by grafting Merrifield chloromethylated polymer withN,N-bis-(2-ethyl-hexyl)-succinamic acid. The chemical modifications at each step of the grafting was confirmed by FT-IR spectroscopy, CPMAS solid state NMR spectroscopy, CHN elemental analysis and also by Thermo Gravimetric analysis. All the parameters influencing the quantitative metal ion extraction were optimized by both static and dynamic methods. The resin showed good extractability over a wide range of acidity (0.01-10 M) with fast exchange rate (saturation possible within 20 minutes) and high sorption capacities for U(VI), Th(IV) and La(III). Quantitative metal desorption was achieved by using 0.5 M (NH4)2CO3for all the analytes. A significant feature of this grafted polymer was its ability to extract Th(IV) from very high nitric acid concentrations. Interference studies with commonly encountered metal ions, rare earth ions and electrolytes showed very high tolerance limit for those ions. Enrichment factor values of 400, 550 and 350 with limit of quantification (LOQ) as 10 ng ml-1, 10 ng ml-1and 20 ng ml-1were observed for U(VI), Th(IV) and La(III), respectively. All the analytical data were within 3.2% rsd, reflecting the reproducibility and reliability of the developed method.