Adsorption behavior of zirconium and molybdenum from nitric acid medium using low-cost adsorbent

Targeted elimination of molybdenum ions from a leaching solution with the ability of radiated grafting GMA-PAN nanofibers

In this study, electrospun polyacrylonitrile nanofibers were effectively functionalized for enhanced molybdenum ion adsorption through a multi-step approach. Initially, glycidyl methacrylate was grafted onto the nanofibers via irradiation-induced grafting polymerization, followed by chemical modification with various amino groups, with triethylamine identified as the optimal modifier. The impacts of key synthesis parameters and reaction conditions on grafting level and adsorption capacity were thoroughly investigated, with a focus on achieving maximum efficiency. The resulting nanofibers were characterized using FTIR, SEM, and BET techniques, confirming the successful modification and structural features conducive to adsorption. Furthermore, a comprehensive experimental design, incorporating a central composite design, yielded optimal conditions for molybdenum adsorption, with key parameters including monomer concentration, irradiation dose, adsorbent mass, initial concentration, time, pH, temperature, and amine concentration. The adsorption kinetics were effectively described by the pseudo-second-order model, while the Langmuir isotherm model provided valuable insight into the adsorption behavior. Impressively, the adsorbent exhibited exceptional adsorption efficiency, surpassing 98% even after six adsorption-desorption cycles using 0.5 M HCl. Thermodynamic analysis revealed the exothermic nature of the adsorption process, along with decreased entropy and overall spontaneity, underlining the favorable conditions for molybdenum adsorption. Notably, the synthesized adsorbent demonstrated notable selectivity for molybdenum and achieved an impressive adsorption capacity of 109.79 mg/g, highlighting its potential for practical applications in molybdenum removal from aqueous solutions.

How Well Do Our Adsorbents Actually Perform?-The Case of Dimethoate Removal Using Viscose Fiber-Derived Carbons

Growing pollution is making it necessary to find new strategies and materials for the removal of undesired compounds from the environment. Adsorption is still one of the simplest and most efficient routes for the remediation of air, soil, and water. However, the choice of adsorbent for a given application ultimately depends on its performance assessment results. Here, we show that the uptake of and capacity for dimethoate adsorption by different viscose-derived (activated) carbons strongly depend on the adsorbent dose applied in the adsorption measurements. The specific surface areas of the investigated materials varied across a wide range from 264 m² g^-1 to 2833 m² g^-1. For a dimethoate concentration of 5 × 10^-4 mol L^-1 and a high adsorbent dose of 10 mg mL^-1, the adsorption capacities were all below 15 mg g^-1. In the case of high-surface-area activated carbons, the uptakes were almost 100% under identical conditions. However, when the adsorbent dose was reduced to 0.01 mg mL^-1, uptake was significantly reduced, but adsorption capacities as high as 1280 mg g^-1 were obtained. Further, adsorption capacities were linked to adsorbents' physical and chemical properties (specific surface area, pore size distribution, chemical composition), and thermodynamic parameters for the adsorption process were evaluated. Based on the Gibbs free energy of the adsorption process, it can be suggested that physisorption was operative for all studied adsorbents. Finally, we suggest that a proper comparison of different adsorbents requires standardization of the protocols used to evaluate pollutant uptakes and adsorption capacities.

Decontamination of 137Cs,95Zr, 154Eu and 144Ce from aqueous solutions using polyacrylamide titanium tungstosilicate

Polyacrylamide titanium tungstosilicate (PAM/TiWSi) composite was synthesised using a sol–gel process and characterized via FT-IR, SEM, XRD, and TGA methods. The effects of several factors on the adsorption of Cs+, Eu3+, Ce3+and Zr4+ have been studied, including contact duration, pH, temperature, and starting concentration. PAM/TiWSi sorption of Cs+, Eu3+, Ce3+and Zr4+ was studied in terms of isotherms and kinetics. The Freundlich model was better linked with isotherm data than the Langmuir model. Cs+, Eu3+, Ce3+and Zr4+ have maximum sorption capacities (Qmax) of 30.7, 26.6, 25,3 and 29.7 mg.g−1, respectively. Furthermore, the sorption process was found based on pseudo-second-order.

Sorbent extraction behavior of cesium and strontium from nitric acid solutions using a new high thermal stability material

In this study a new low-cost carbonaceous material was prepared from husks of opuntia-ficus-indica as a starting material (precursor) which was accomplished by chemical activation route using H₃PO₄ impregnation. The material has been identified by different analytical tools. The sorption performance of Cs(I) and Sr(II) from HNO₃ solutions was examined through batch system. Variations of the distribution coefficients (K_d) as a function of HNO₃ concentration in the range 0.001-5.0 M were presented. Some of separation probabilities were suggested. The results attained signals that the Sr(II) selectivity is higher than that of Cs(I) at high molarities. The retention capacity (q_e) of Cs(I) and Sr(II) ions increased with growing temperature. The capacities at 0.001 M HNO₃ are 34 and 108 mg/g for Cs(I) and Sr(II), respectively. Whereas, at 2.0 M HNO₃ capacities were about 4 and 37 mg/g for each of Cs(I) and Sr (II), respectively. This studies demonstrates that the prepared carbonaceous sorbent is an economically effective sorbent for retention of Cs(I) and Sr(II) species from HNO₃ solutions. Cs(I) and Sr(II) removal potential was tested from simulated low- and intermediate-level radioactive waste samples.

Fusion-Based Neutron Generator Production of Tc-99m and Tc-101: A Prospective Avenue to Technetium Theranostics

Presented are the results of ^99mTc and ¹⁰¹Tc production via neutron irradiation of natural isotopic molybdenum (Mo) with epithermal/resonance neutrons. Neutrons were produced using a deuterium-deuterium (D-D) neutron generator with an output of 2 × 10¹⁰ n/s. The separation of Tc from an irradiated source of bulk, low-specific activity (LSA) Mo on activated carbon (AC) was demonstrated. The yields of ^99mTc and ¹⁰¹Tc, together with their potential use in medical single-photon emission computed tomography (SPECT) procedures, have been evaluated from the perspective of commercial production, with a patient dose consisting of 740 MBq (20 mCi) of ^99mTc. The number of neutron generators to meet the annual 40,000,000 world-wide procedures is estimated for each imaging modality: ^99mTc versus ¹⁰¹Tc, D-D versus deuterium-tritium (D-T) neutron generator system outputs, and whether or not natural molybdenum or enriched targets are used for production. The financial implications for neutron generator production of these isotopes is also presented. The use of ¹⁰¹Tc as a diagnostic, therapeutic, and/or theranostic isotope for use in medical applications is proposed and compared to known commercial nuclear diagnostic and therapeutic isotopes.

Synergistic adsorption behavior of a silica-based adsorbent toward palladium, molybdenum, and zirconium from simulated high-level liquid waste

In this study, the synergistic adsorption behavior of palladium [Pd(II)], molybdenum [Mo(VI)], and zirconium [Zr(IV)] in simulated high-level liquid waste was systematically investigated based on various factors, such as the contact time, concentration of nitric acid, adsorption amount, and temperature using a silica-based adsorbent impregnated with N,N'-dimethyl-N,N'-di-n-hexyl-thiodiglycolamide (Crea) and 2, 2', 2' -nitrilotris[N,N-bis(2-ethylhexyl)acetamide] (TAMIA-EH). The adsorption rates of Pd(II), Mo(VI), and Zr(IV) in this synergistic adsorption system were high; thus, equilibrium states could be obtained in only 1 h with high uptake percentages of more than 90%. The adsorption abilities of Pd(II), Mo(VI), and Zr(IV) were only slightly affected by variation in the concentration of nitric acid in the range of 0.1-5 M and solution temperature in the range of 288-313 K. Selective stripping of the adsorbed Re(VII), Pd(II), Zr(IV), and Mo(VI) was successfully achieved under elution with 5 M HNO₃, 0.2 M Tu (pH 1), 50 mM DTPA (pH 2), and 50 mM DTPA dissolved in 0.5 M Na₂CO₃ (pH 11) solutions using the chromatography method. In addition, the adsorption performance in solid-state was studied using the particle-induced X-ray emission (PIXE) method; the obtained results were in good agreement with the results obtained via column separation.

Kinetics and adsorption equilibrium of some radionuclides on polyaniline/SiO2 composite

The sorption kinetics and equilibrium isotherms of zirconium, uranium, and molybdenum ions onto synthetic polyaniline/SiO2 composite (PAn/SiO2) have been studied using batch-sorption techniques. This study was carried out to examine the sorption behavior of the PAn/SiO2 for the removal of Zr(IV), U(VI), and Mo(VI) ions from an aqueous solution. The influence of some parameters on the sorption process was also studied. The maximum sorption for Zr(IV), U(VI), and Mo(VI) ions was achieved at 60 min shaking time. Langmuir isotherm model is the most representative for discussing the sorption process with a maximum sorption capacity of 24.26, 21.82, and 13.01 mg/g for Zr(IV), U(VI), and Mo(VI) ions, respectively. Kinetic modeling revealed that the sorption of all ions follows the pseudo-second-order kinetic model. The results demonstrated that both the external and intra-particular diffusion are taken into account in determining the sorption rate. Thermodynamic parameters like ΔG°, ΔH°, and ΔS° for the sorption process were evaluated. The synthetic composite has been successfully applied for the removal and recovery of U(VI) ions from real solution (monazite leachate) using a chromatographic column packed with PAn/SiO2 composite with a breakthrough capacity equal to 239.70 mg/g.

Adsorptive removal of PAR and Arsenazo-III from radioactive waste solutions by modified sugarcane bagasse as eco-friendly sorbent

In this paper, sugarcane bagasse (SCB) was modified using phosphoric acid. The modified sugarcane bagasse (MSCB) has been used to remove 4-(2-pyridylazo)resorcinol (PAR) and Arsenazo-III (Ar-III) from liquid radioactive waste. The surface morphology and functional groups of the MSCB were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Adsorption ability of MSCB has been tested by batch mode through some relevant factors like initial pH, reaction time, initial coloring reagents (PAR and Ar-III) concentrations, and adsorbent weight. At adsorption equilibrium time 180 min and pH values of 3 and 1 for PAR and Ar-III; the maximum removal (%) for both PAR and Ar-III were 93 and 57%, respectively. The adsorption isotherm data are representative well to Freundlich isotherm model. The mean free energy of adsorption, E (kJ/mol), has been estimated as 5.75 and 2.28 kJ/mol for PAR and Ar-III, respectively, which suggests that the adsorption occurred physically. The maximum adsorption capacity of MSCB for PAR and Ar-III is 96.62 and 15.18 mg/g, respectively. The adsorption kinetics are better fitted by the pseudo-second-order model. The partial film along with intra-particle diffusion controlled the diffusion of coloring reagents from the solution bulk to the particle interior pores. Application of MSCB for removing PAR and Ar-III from simulated liquid radioactive waste containing U(VI) and Th(VI) ions has been achieved successfully.

Removal of strontium radionuclides from liquid scintillation waste and environmental water samples

Strontium-90 (t_1/2 = 29 y) is one of the most concerned isotopes in both nuclear accidents and reprocessing of nuclear fuel. In this study, the removal of strontium using low cost and valuable Dowex-HCR-S/S (DHS) resin was achieved. The kinetic and equilibrium sorption studies have been investigated using batch technique. The results of kinetic studies showed that the pseudo-second-order kinetic model was found to correlate well with the experimental data. Equilibrium data were also analyzed by sorption isotherm models indicating that the monolayer capacity of Sr(II) at equilibrium is 400.0 mg/g. It was concluded that resin has an efficient sorption capacity compared to many sorbents. The thermodynamic parameters of the removal (ΔH^o, ΔS^o, and ΔG^o) were also determined. The removal process was endothermic and spontaneous. The resin has been successfully applied for the removal of ⁸⁵Sr from organic liquid scintillator waste and some environmental waters such as tap water, river water, sea water and ground water samples. The present work concludes that the low-cost and commercial DHS resin used under these conditions has a major possibility as an efficacious material for the removal of ⁹⁰Sr from environmental and real radioactive wastewaters. It can therefore have a site in the treatment of radioactive liquid waste because it is of an affordable and commercially available retention material.

Influence of sorption parameters on cesium-137 removal using modified activated carbon obtained from corchorus olitorius stalks

Removal of 137Cs radionuclides from the environment has engrossed the concern of researchers after Fukushima accident. The leakage of radioactive cesium ions can lead up to surface and groundwater contamination, and this leads to pollution of drinking water sources. In this work, corchorus olitorius stalks has been used as a novel precursor for production of low-cost meso porous a ctivated c arbon ( Meso-AC ) and HNO3/H2O2- m odified Meso-AC ( m-Meso-AC ). The physicochemical properties of all adsorbents were evaluated. The influences of sorption parameters and presence of some ligands (humic acid, fulvic acid, and EDTA) on the sorption of 137Cs were studied. The maximum 137Cs capacity of m-Meso-AC was found to be 58.74 mg/g. Efficiency of the new adsorbent to remove 137Cs radionuclides from natural waters (tap, river, and groundwater) was investigated. The studies showed that new adsorbent could be used as promising material for the retention of 137Cs from real radioactive waste and natural water samples.

Sorption of some radionuclides from nuclear waste effluents by polyaniline/SiO2 composite: Characterization, thermal stability, and gamma irradiation studies

Polyaniline/SiO₂ composite was successfully prepared via in situ polymerization using polyvinyl alcohol as a surfactant. The prepared PAn/SiO₂ composite was used for the removal of Zr(IV), U(VI), and Mo(VI) ions from their liquid solutions. PAn/SiO₂ composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The synthesized composite was irradiated with γ-radiation from a Co-60 radioactive source with absorbed dose 50, 100, and 150 kGy and the corresponding changes in structural properties of the composites were studied. The thermal and radiation stabilities of PAn/SiO₂ composite in terms of saturation capacities were studied. PAn/SiO₂ composite has a good thermal stability as it retained about 78.83% of its saturation capacity upon heating at 400±1 °C, while the saturation capacity of PAn/SiO₂ composite was increased from 191.28 to 319.16 mg/g for Zr(IV) with varying the irradiated doses from 0 to 150 kGy. The sorption studies for several metal ions revealed marked selectivity of PAn/SiO₂ composite towards Zr(IV), U(VI), and Mo(VI) ions with selectivity order; Zr(IV) > U(VI) > Mo(VI). The results indicated that PAn/SiO₂ composite removed 95.33, 75.97, and 52.87% from Zr(IV), U(VI), and Mo(VI) ions, respectively at pH 3.26. Hence, analytical utility of PAn/SiO₂ composite was accomplished by performing some quantitative separation such as separation of U(VI) ions from monazite leachate and separation of Zr(IV), U(VI), and Mo(VI) ions from simulated liquid waste. Thermodynamic parameter studies concluded that the adsorption of Zr(IV), U(VI), and Mo(VI) ions was spontaneous and endothermic in nature.

Synthesis and characterizations of a novel CoFe2O4@CuS magnetic nanocomposite and investigation of its efficiency for photocatalytic degradation of penicillin G antibiotic in simulated wastewater

In the present study, efficiency of a new magnetic nanocomposite (CoFe₂O₄@CuS) for photocatalytic degradation of PG in aqueous solutions was investigated. Structural characteristics of synthesized magnetic nanoparticles were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating-sample magnetometer (VSM), Thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), Energy-dispersive X-ray spectroscopy (EDX) and Raman spectroscopy. Also, the effect of important parameters such as pH (3-11), nanoparticle dosage (0.1-0.8 g/L), PG concentration (10-100 mg/L) and contact time (10-120 min) were investigated. Results of FT-IR, XRD, EDX and Raman analyses showed successful synthesis of CoFe₂O₄@CuS magnetic nanocomposite. SEM and TEM images showed that the size of CoFe₂O₄@CuS magnetic nanocomposite was below 100 nm. Also, results of VSM analyses showed that CoFe₂O₄@CuS magnetic nanocomposite still has magnetic properties (Ms = 7.76 emu/g). According to the results of study, in photocatalytic degradation process of PG by CoFe₂O₄@CuS magnetic nanocomposite by UV light and in optimum condition (pH = 5, nanocomposite dose: 0.2 g/L, PG concentration: 10 mg/L and contact time: 120 min), maximum degradation of PG was 70.7%. Also the photocatalytic reaction almost followed the pseudo-first order kinetics. In addition, after five consecutive runs, the catalyst efficiency wasn't reduced significantly.