RESUMO
Uranium extraction from radioactive nuclear waste is vital for sustainable energy supply and ecological security. Herein, a polyethyleneimine-chitosan composite microspheres n-PEI/ECH-CTS (n = 0.1, 0.2, 0.3, 0.4, 0.5) were synthetized for efficient and selective uranium adsorption. The prepared chitosan microspheres with uniform size, uniform dispersion and good mechanical strength combine cost-effectiveness and environmental benefits. The 0.4-PEI/ECH-CTS exhibits the highest adsorption capacity of 380.65 mg g-1 within only 4 h due to high nitrogen content of 6.57 mol kg-1. The DFT calculations confirms that the optimal coordination mode of UO22+ and 0.4-PEI/ECH-CTS is one UO22+ chelated with two -NH2 from two adsorption units, respectively. Adsorption efficiency of U(VI) from simulated nuclear wastewater achieves to 100%, and the Kd value is up to 1.1 × 104 mL g-1, which is 1.7 × 104-6.1 × 104 times that of coexisting ions. The CU(VI) reduces in simulated wastewater from 10.98 mg L-1 to 1 µg L-1, which is well below the US Environmental Protection Agency uranium limits for drinking water (30 µg L-1). Besides, 0.4-PEI/ECH-CTS still maintains above 95% adsorption efficiency after seven cycles. In short, the 0.4-PEI/ECH-CTS microspheres integrate high performance, practicality and cost-effectiveness, which has great advantages in practical industrial applications.
Assuntos
Quitosana , Resíduos Radioativos , Urânio , Polietilenoimina , Águas Residuárias , Microesferas , Cinética , Adsorção , Concentração de Íons de HidrogênioRESUMO
Evaporation-induced self-assembly method (EISA) was a facile and reliable method to synthesize porous materials. Herein, we report a kind of hierarchical porous ionic liquid covalent organic polymers (HPnDNH2) under cetyltrimethylammonium bromide (CTAB) assisted by EISA for ReO4-/TcO4- removal. Unlike covalent organic frameworks (COFs), which usually needed to be prepared in a closed environment or with a long reaction time, HPnDNH2 in this study was prepared within 1 h in an open environment. It was worth noting that CTAB not only served as a soft template for forming pore, but also induced ordered structure, which was verified by SEM, TEM, and Gas sorption. Benefit from its hierarchical pore structure, HPnDNH2 exhibited higher adsorption capacity (690.0 mg g-1 for HP1DNH2 and 808.7 mg g-1 for HP1.5DNH2) and faster kinetics for ReO4-/TcO4- than 1DNH2 (without employing CTAB). Additionally, the material used to remove TcO4- from alkaline nuclear waste was seldom reported, because combining features of alkali resistance and high uptake selectivity was not easy to achieve. In this study, in the case of HP1DNH2, it displayed outstanding adsorption efficiency toward aqueous ReO4-/TcO4- in 1 mol L-1 NaOH solution (92%) and simulated Savannah River Site High-level waste (SRS HLW) melter recycle stream (98%), which could be a potentially excellent nuclear waste adsorbing material.
RESUMO
Reasonable design of the structure and complementary compounding of electrode materials is helpful to enhance capacitive deionization (CDI) performance. Herein, a novel 0D-3D hierarchical electrode material containing Na2Ti3O7 nanoparticles anchored at hollow red blood cell (HRBC)-like nitrogen-rich carbon (HRBC-NTO/N-C-60) was prepared via selective protection, pyrolysis, and alkalization. Specifically, a HRBC-like NH2-MIL-125-based material (HRBC-MOF-60) was first constructed by a selective protection approach of tannic acid (TN), which addresses the shortcomings of using sacrificial templates or corrosive agents. Afterwards, HRBC-NTO/N-C-60 was obtained in situ by annealing and alkalization of HRBC-MOF-60. The nitrogen-rich carbon with a HRBC-like structure has the ability to rapidly transport electrons, and its porous structure enables remarkable charge transfer. Benefiting from the grafted 3D N-doped porous carbon with a HRBC-like structure, well-dispersed 0D Na2Ti3O7 nanoparticles, and satisfactory bonding effects, HRBC-NTO/N-C-60 exhibited high specific capacitance and fast ionic and electronic diffusion kinetics. Moreover, HRBC-NTO/N-C-60 was well-suited for desalination by functioning as a cathode material for capacitive deionization (CDI), and delivering a high desalination capacity of 66.8 mg g-1 in 200 mg L-1 NaCl solution at 1.4 V. This work introduces an excellent high-performance candidate for electrochemical deionization as well as affording afflatus for accurately inventing OD-3D hierarchical materials with hollow structures.
RESUMO
Imidazolium-based ionic liquids (ILs) are a promising candidate for efficient separation of radioactive pertechnetate (TcO4-) from nuclear waste. However, their effective fixation, availability of active sites and slow adsorption kinetics remain challenges. Here, we incorporated the bisimidazolium-based ILs into porous metal-organic frameworks (MOFs) via a combination of immersion grinding and in-situ polymerization. 3,3'-divinyl-1,1'(1,4-butanediyl) diimidazolium dichloride is tightly bound inside and outside the porous MOFs matrix by uniform immersion grinding, which facilitates the exposure of more adsorption sites and provides channels for the anions to travel through quickly. Solvent-free polymerization reduces environmental pollution and energy consumption. Notably, the composite P[C4(VIM)2]Cl2@MIL-101 possesses an admirable removal efficiency (673 mg g-1) compared with the pristine poly(ionic liquid)s (215 mg g-1). Meanwhile, it exhibits fast sorption kinetics (92% in 2 min), good ß and γ radiation-resistance, excellent regeneration and eminent removal efficiency in high alkaline conditions (83%). These superior traits endow that P[C4(VIM)2]Cl2@MIL-101 effectively separated TcO4- from simulated Hanford Low-activity Waste (LAW) Melter off-gas scrubber solution tested in this work. DFT density functional theory confirms that the strong electrostatic attraction and minimum Gibbs free energy (-6.2 kcal mol-1) achieve high selective adsorption for TcO4-. P[C4(VIM)2]Cl2@MIL-101 demonstrates the considerable potential to remove TcO4- from radioactive contaminants.
RESUMO
In order to enhance the catalytic performance of the Gd-modified Co3O4 catalyst (Gd0.06Co) for the N2O decomposition, alkali metal K was introduced as the promoter by impregnating the Gd0.06Co powder with an aqueous solution of KNO3 (with K/Co ratios 0.01-0.05). With the doping of K, the catalytic activity over Gd0.06Co was significantly improved and the temperature of N2O complete decomposition was decreased from 350 °C to 300 °C. Combining the results of XPS and O2-TPD, the superior catalytic performance of the optimum catalyst K0.025Gd0.06Co was mainly owing to the synergistic effect of Gd and K, which weakened the Co-O bond and endowed the catalyst surface with much more amount of oxygen vacancies. Even under the coexist of the impurity gases, such as 5 vol% O2, 100 ppmv NO and 2 vol% H2O, the K0.025Gd0.06Co catalyst exhibited prominently better catalytic activity than Gd0.06Co and K0.025Co catalysts.
RESUMO
Graphene oxide (GO) has great potential in metal recovery and water purification owing to their high surface area, abundant hydroxyl (OH) and carboxyl (COOH) groups. To fully understand the influence of the dispersity of GO on the adsorption capacity of metal ions, a series of polyacrylic acid (PAA) functionalized GO (PAA/GO) composites with different dispersity were prepared. The charge density of the PAA/GO composites were much higher than that of the untreated GO in acidic conditions, demonstrating a significant improvement of dispersibility by introducing PAA on the surfaces. Moreover, recovery of gallium by employing the PAA/GO composites as adsorbent were studied. The maximum adsorption capacity towards gallium ions of the adsorbent can reach 196.84â¯mg·g-1, much higher than that of other commercially available resins (CL-P204, P507). This superiority could be attributed to the abundant COOH groups on the surfaces and the good dispersity of the PAA/GO composites. These results revealed that the PAA/GO composites could be promising adsorbents for selective adsorption and efficient recovery of Ga(III).
RESUMO
Diethanolamine functionalized cellulose based on rice husk (DEA-EPI-RH) was prepared to separate gallium ions from As(III) or/and Ge(IV) mixtures. The contents of hydroxyl functional group in the DEA-EPI-RH were up to 1.48â¯mmolâ¯g-1, and the maximum adsorption capacity for Ga(III) achieved to 130.44â¯mgâ¯g-1. The adsorption mechanism depended on the ion exchange of Ga(OH)2+, Ga(OH)2+, or Ga3+ with trihydroxy hydrogen on the surface of the DEA-EPI-RH. The DEA-EPI-RH showed superior selectivity with high adsorption capacity towards gallium as compared to As(III) or/and Ge(IV) with several times higher than concentration of Ga(III). Furthermore, the excellent reusability of the DEA-EPI-RH were confirmed by the desorption and regeneration experiments. The studied adsorbent was deemed to be promising, environment-friendly and low-cost materials to recovery of gallium from aqueous solution containing As(III) or/and Ge(IV).
Assuntos
Etanolaminas/química , Gálio/isolamento & purificação , Oryza/anatomia & histologia , Oryza/química , Adsorção , Epicloroidrina/química , Concentração de Íons de Hidrogênio , Íons , Oryza/ultraestrutura , Soluções , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , beta-Ciclodextrinas/químicaRESUMO
The increasing demand for rare-earth elements (REEs) due to their extensive high-tech applications has encouraged the development of new sustainable approaches for REE recovery and separation. In this work, a series of acrylic acid-functionalized metal-organic framework materials (named as y-AA- x@MIL-101s) were prepared and used for selective adsorption of Sc(III). The adsorbent was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, nitrogen adsorption, X-ray photoelectron spectroscopy, and zeta potential and surface functional-group titration. The adsorption isotherm and kinetics data were accurately described by the Langmuir and pseudo-second-order models. The adsorption capacity of the material for Sc(III), Nd(III), Gd(III), and Er(III) was 90.21, 104.59, 58.29, and 74.94 mg g-1, respectively. Importantly, the adsorbent was better for selective recovery of Sc(III) not only from the 16 REE mixed system but also the Cu(II), Zn(II), Mn(II), Co(II), and Al(III) coexistence solution. Except for Sc(III), the material displayed high affinity for Nd(III) in the light rare-earth mixture and for Gd(III) in the middle rare-earth mixture. All in all, this study provides a new method for separation and recovery of REEs, which makes this work highly significant in separation and enrichment.
RESUMO
In nickel electrolyte, Ag(I) was present at trace level concentration (10-20 mg L(-1)) and existed in the form of AgCli(1-i) coordination anion, instead of Ag(+) positive ion usually in several sources. In the present study, TSC-NH3-OCS adsorbent based on natural corn stalk modified by ammonia (NH3)-thiosemicarbazide (TSC) was synthesized and characterized using some instrumental techniques. The TSC-NH3-OCS adsorbent could selectively adsorb Ag(I) as AgCl(i)(1-i) coordination anion from the Ag(I)-Cu(II)-Ni(II) simulate nickel electrolyte, especially in the case of the very high levels of Cu(II) and Ni(II), which significantly outperforms the commercial available resins. The adsorption mechanism was believed to be electrostatic interaction of the protonated bands of AgCl4(3-) with protonated thiol form of the thioamide units by FTIR and XPS analysis. The maximum adsorption capacity in the Ag(I) single and Ag(I)-Cu(II)-Ni(II) ternary system were obtained and calculated as 153.54 and 46.69 mg g(-1), respectively. The reasons that the maximum adsorption capacity of AgCl(i)(1-i) from the single and ternary system varied widely could be explained by adsorption kinetic and thermodynamic results. In addition, three successive sorption/desorption cycle runs from ternary system were performed which indicated that the TSC-NH3-OCS adsorbent has a good performance for recovery Ag(I) from simulate nickel electrolyte.
Assuntos
Amônia/química , Complexos de Coordenação/química , Níquel/química , Caules de Planta/química , Semicarbazidas/química , Prata/química , Adsorção , Cobre/química , Eletrólitos , Glutaral/química , Reciclagem , Zea maysRESUMO
Brown algae Laminaria japonica was chemically modified with sulfuric acid to obtain a crosslinked brown algae gel (CAS). The CAS gel showed a high affinity for Re(VII) comparing with other biomass gels, and the maximum adsorption capacity was evaluated as 37.20 mg g(-1) in case of pH 6, which could be explained by their different adsorption mechanisms. The adsorption equilibrium, kinetics and thermodynamic study for Re(VII) on the CAS gel was discussed in detail by the several models, such as Langmuir, Freundlich, Temkin and Dubinin-Radushkevich model for kinetics analysis, the pseudo first, the second-order, the Elovich and intraparticle diffusion equation for equilibrium analysis. Reutilization of the CAS gel was confirmed up to three adsorption-elution cycles in column-mode operation with no damage of gel, packed in the column. The result also provides a new approach for the recovery of Re(VII) from Re-containing wastewater by using the modified brown algae gel.
Assuntos
Laminaria/metabolismo , Rênio/isolamento & purificação , Águas Residuárias/análise , Purificação da Água/métodos , Adsorção , Géis , Concentração de Íons de Hidrogênio , Cinética , Modelos Químicos , Estrutura Molecular , Rênio/química , Rênio/metabolismo , Espectroscopia de Infravermelho com Transformada de Fourier , TermodinâmicaRESUMO
The effects of basic strength and steric hindrance of gels modified by dimethylamine, diethylamine, di-n-octylamine and di-2-ethylhexylamine, respectively, on rhenium (Re(VII)) adsorption capacity and selectivity were discussed. By comparing with the adsorption of other coexisting metals, such as Mo(VI), Cu(II), Pb(II), Fe(III), Zn(II), Mn(VII) and Ni(II), the gel modified by di-n-octylamine (DNOA-OCS) showed a high affinity for Re(VII) at higher hydrochloric acid concentration (C(H)(+)≥1.0 mol L(-1)), and the maximum adsorption capacity was 98.69 mg g(-1). This article not only described the adsorption behavior but also suggested isotherms, kinetics and thermodynamics of Re(VII) onto the DNOA-OCS gel in an aqueous medium using several models. Further study on adsorption of rhenium in a fixed-bed column packed with the DNOA-OCS gel under continuous and recirculating modes could confirm that the corn stalk gel modified by di-n-octylamine could be used as the adsorbent of Re(VII) from Mo-containing wastewater.
Assuntos
Aminas/química , Rênio/isolamento & purificação , Zea mays/química , Adsorção , Biodegradação Ambiental , Géis/química , Resíduos Industriais/análise , Íons , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , TitulometriaRESUMO
Astringent persimmon was chemically cross-linked by formaldehyde to obtain a novel kind of adsorption gel, which was named as APF gel. The adsorption behaviors of Mo(VI) and Re(VII) along with other coexisting metals onto the APF gel were studied in the present paper. The APF gel was found to be effective for the adsorption of Mo(VI) while the gel is almost completely inert toward rhenium and calcium over the whole hydrochloric acid concentration region. The APF gel has a low affinity for iron, copper, lead, nickel, manganese and zinc ions when the concentration of HCl is higher than 1 mol/L. The gel exhibited selectivity only for Mo(VI) with a remarkably high adsorption capacity 1.05 mol/kg, and the adsorption behavior obeys the Langmuir model. According to the thermodynamic and kinetic studies, the endothermic adsorption process followed pseudo-second order kinetics. Also, its excellent adsorption characteristics for Mo(VI) were confirmed by the adsorption and elution tests using a column packed with the APF gel. The result provides a new approach for the recovery of Mo(VI) from a industrial waste effluent.
Assuntos
Diospyros/química , Molibdênio/química , Molibdênio/isolamento & purificação , Rênio/química , Rênio/isolamento & purificação , Eliminação de Resíduos Líquidos/métodos , Adsorção , Algoritmos , Flavonoides/análise , Formaldeído/análise , Ácido Clorídrico/química , Concentração de Íons de Hidrogênio , Resíduos Industriais/análise , Metais/análise , Fenóis/análise , Polifenóis , Taninos/análise , TermodinâmicaRESUMO
Persimmon waste was chemically modified by crosslinking with concentrated sulfuric acid to obtain a novel kind of adsorption gel, which was termed as crosslinked persimmon tannin (CPT), hereinafter. The adsorption behaviors of Mo(VI) with other coexisting metal ions onto the CPT gel were investigated. The gel exhibited selectivity only for Mo(VI) ions evidenced by the high value of separation factor of molybdenum and rhenium (ß(Mo/Re)=164.37), and the adsorption mechanism of Mo(VI) as a multispecies was studied. The molybdenum adsorption behavior conforms to the Langmuir model with a remarkably high adsorption capacity of 0.56 mol/kg. A kinetic study for the adsorption of molybdenum at various temperatures confirmed that the endothermic adsorption process followed pseudo-second order kinetics. Moreover, its excellent adsorption properties and applicability for Mo(VI) were demonstrated by the removal and separation of Mo(VI) from different Mo-Re containing industrial wastewaters.