Effective biosorption of U(VI) from aqueous solution using calcium alginate hydrogel beads grafted with amino-carbamate moieties

Journal of Radioanalytical and Nuclear Chemistry - The kinetics of Co ions sorption on CoTreat® was investigated in the 5–40 mg/L concentration range at a bulk temperature of...     

Synthesis of magnetic chitosan/graphene oxide nanocomposites and its application for U(VI) adsorption from aqueous solution

Journal of Radioanalytical and Nuclear Chemistry - The performance of a magnetic chitosan/graphene oxide composites (MCGO) have been investigated for the adsorption processes of U(VI) ions from...     

Competitive adsorption of uranium(VI) and thorium(IV) ions from aqueous solution using triphosphate-crosslinked magnetic chitosan resins

The triphosphate-crosslinked magnetic chitosan resins (TPP-MCR) with a diameter range of 200–350 nm were synthesized for the adsorption of U(VI) and Th(IV) ions from aqueous solutions. The adsorption experiments were conducted in both mono-component systems with pure actinide solution and bi-component systems with different U/Th mass ratios. The maximum adsorption capacities in mono-component systems determined by Langmuir model were 169.5 and 146.8 mg g^?1 for U(VI) and Th(IV), respectively. In bi-component systems, U(VI) and Th(IV) adsorption capacities were reduced significantly, and the combined sorption capacities were substantially lower (almost halved) compared to those obtained by the addition of sorption capacities using mono-component solutions, indicating that U(VI) and Th(IV) compete for the same sorption sites. Adsorption–desorption experiments for five cycles illustrated the feasibility of the repeated use of TPP-MCR for the adsorption of U(VI) and Th(IV) ions.     

Uranium(VI) recovery from its leach liquor using zirconium molybdophosphate composite: kinetic,equilibrium and thermodynamic studies

Journal of Radioanalytical and Nuclear Chemistry - A zirconium molybdophosphate composite was designed for the selective recovery of uranium ions. The synthesized composite was well-characterized...     

Adsorption of U(VI) onto the carboxymethylated chitosan/Na-bentonite membranes: kinetic,isothermic and thermodynamic studies

The carboxymethylated chitosan (CMC)/Na-bentonite (Na-Bt) composite membranes were prepared and throughly characterized. The Na-Bt/CMC mass ratio was optimized, and CB10 (membrane with Na-Bt/CMC mass ratio of 10%) was selected as the best membrane for U(VI) sorption. XPS analysis indicates that the main mechanism for UO₂²⁺ sorption onto CB10 is through inner-surface complexation. The sorption kinetics followed pseudo-second order model, indicating the chemisorption as the rate-controlling step. The U(VI) sorption on CB10 is endothermic and spontaneous, with the maximum mono-layer adsorption capacity of 115.6 mg/g at pH 5.0 and 298 K. Finally, the U(VI)-loaded CB10 can consecutively desorbed and reused for several cycles.     

Adsorption of uranium(VI) from aqueous solution by diethylenetriamine-functionalized magnetic chitosan

In this paper, the modified magnetic chitosan resin containing diethylenetriamine functional groups (DETA-MCS) was used for the adsorption of uranium ions from aqueous solutions. The influence of experimental conditions such as contact time, pH value and initial uranium(VI) concentration was studied. The Langmuir, Freundlich, Sips and Dubinin–Radushkevich equations were used to check the fitting of adsorption data to the equilibrium isotherm. The best fit for U(VI) was obtained with the Sips model. Adsorption kinetics data were tested using pseudo-first-order and pseudo-second-order models. Kinetic studies showed that the adsorption followed the pseudo-second-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. The present results suggest that DETA-MCS is an adsorbent for the efficient removal of uranium(VI) from aqueous solution.     

Effective adsorption of uranium(VI) from aqueous solution using ethylene-bridged mesoporous silica functionalized with ureido groups

Journal of Radioanalytical and Nuclear Chemistry - Ureido-functionalized ethylene-bridged mesoporous silica (UE-MS) was synthesized by co-condensation method for uranium(VI) uptake. The adsorbents...     

Removal of ammonium ion from aqueous solutions using natural zeolite: kinetic,equilibrium and thermodynamic studies

The aim of the present study is to investigate the removal of ammonium ions from aqueous solutions using the natural Western Azerbaijan zeolite by utilizing ion exchange process. Batch experimental studies were conducted to evaluate by changing relevant parameters such as pH, dosage of adsorbent, stirring time, initial ammonium concentration, and temperature. The results clearly confirmed that all mentioned parameters have vital affects on removing ammonium ions from wastewater and effluents, so got optimized. Adsorption kinetics and equilibrium data for the removal of ammonium ion were analyzed using Langmuir and Freundlich equations. The Langmuir model fits the equilibrium data better than the Freundlich model. According to the Langmuir equation, the maximum uptake for ammonium ion was 43.47 (mg g^?1). Pseudo-first-order and pseudo-second-order models were used to represent the kinetics of the process. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicate that the adsorption process is feasible, spontaneous, and endothermic at 20–50 °C. Based on the experimental results, it can be suggested that the natural Western Azerbaijan zeolite has the potential of application as an efficient adsorbent for the removal of ammonium ions from aqueous solutions, and is suggested for wastewater treatment purposes.     

Biosorption studies of uranium (VI) on cross-linked chitosan: isotherm,kinetic and thermodynamic aspects

The cross-linked chitosan (CS) gels synthesized by using glutaraldehyde (GLA), epichlorohydrin (EC), and ethylene glycol diglycidyl ether (EGDE) as cross-linkers respectively were used to investigate the adsorption of U(VI) ions in an aqueous solution. The pure chitosan (PCS) and the cross-linked chitosan gels were characterized by FTIR and SEM analysis. The kinetic, thermodynamic adsorption and adsorption isotherms of U(VI) ions onto unmodified and modified cross-linked chitosan were studied in a batch adsorption experiments. The effect of pH, contact time and temperature on the adsorption capacity were also carried out. At the optimum pH, the maximum adsorbed amount of PCS, GLACS, ECCS and EGDECS were 483.05, 147.05, 344.83 and 67.56 mg/g, respectively. The uranium (VI) adsorption process of PCS and ECCS followed better with pseudo-second-order kinetic model, while GLACS and EGDECS followed pseudo-first-order kinetic model well. The results obtained from the equilibrium isotherms adsorption studied of U(VI) ions were analyzed in two adsorption models, namely, Langmuir and Freundlich isothms models, the results showed that the Langmuir isotherm had better conformity to the equilibrium data. The thermodynamic parameters such as enthalpy (ΔHo), entropy (ΔSo), and Gibbs free energy (ΔGo) showed that the adsorption process was both spontaneous and endothermic.     

Characteristics of equilibrium and kinetic for U(VI) adsorption using novel diamine-functionalized hollow silica microspheres

Journal of Radioanalytical and Nuclear Chemistry - The diamine-functionalized hollow silica microspheres (DA-HSM) were successfully synthesized for highly efficient sorption of U(VI). The sorption...     

Biosorption of uranium(VI) by free and entrapped Chlamydomonas reinhardtii: kinetic,equilibrium and thermodynamic studies

Biosorption of uranium from aqueous solution onto the free and entrapped algae, “Chlamydomonas reinhardtii” in carboxymethyl cellulose (CMC) beads was investigated in a batch system using bare CMC beads as a control system. CMC can be a potential natural biosorbent for radionuclide removal as it contains carboxyl groups. However, limited information is available with the biosorption of uranium by CMC, when adsorption isotherm, kinetics and thermodynamics parameters are concerned. The biosorbent preparations were characterized by swelling tests, FTIR, and surface area studies. The effects of pH, temperature, ionic strength, biosorbent dosage, and initial uranium concentrations on uranium biosorption were investigated. Freely suspended algae exhibited the highest uranium uptake capacity with an initial uranium ion concentration of 1,000 mg/L at pH of 4.5 and at 25 °C. The removal of U(VI) ion from the aqueous solution with all the tested biosorbents increased as the initial concentration of U(VI) ion increased in the medium. Maximum biosorption capacities for free algal cells, entrapped algal cells, and bare CMC beads were found to be 337.2, 196.8, and 153.4 mg U(VI)/g, respectively. The kinetic studies indicated that the biosorption of U(VI) ion was well described by the pseudo-second order kinetic model. The variations in enthalpy and entropy for the tested biosorbent were calculated from the experimental data. The algal cells entrapped beads were regenerated using 10 mM HNO₃, with up to 94 % recovery. Algal cells entrapped CMC beads is a low cost and a potential composite biosorbent with high biosorption capacity for the removal of U(VI) from waters.     

Effective uranium biosorption by macrofungus (<Emphasis Type="Italic">Russula sanguinea</Emphasis>) from aqueous solution: equilibrium,thermodynamic and kinetic studies

Russula sanguinea (R. sanguninea) macrofungus was employed as a novel cost-effective biosorbent for efficient removal of U(VI) ions from aqueous solution. FT-IR spectroscopy and SEM/EDS technique were used for morphological and chemical characterizations. The maximum adsorption capacity of the macrofungus was found as 174.3 mg/g at pH 5 and 20 °C. The kinetic data best fit with the pseudo-second-order kinetic model (r²?>?0.99 for the studied temperatures). The exothermic and spontaneous nature of the biosorption process was confirmed by the thermodynamic findings. The reusability test demonstrated that the macrofungus had a good sorption/desorption performance.     

Removal of U(VI) from aqueous solutions by using MWCNTs and chitosan modified MWCNTs

In this paper, the multiwalled carbon nanotubes (MWCNTs) were modified with chitosan (CS) by using low temperature plasma grafting technique (denoted as MWCNT-CS). The prepared MWCNTs and MWCNT-CS were characterized by SEM, TEM, FTIR and Raman spectroscopy in detail and the results suggested that CS molecules were successfully grafted on the surfaces of MWCNTs. The materials were applied as adsorbents in the removal of U(VI) ions from large volumes of aqueous solutions as a function of environmental conditions. The removal of U(VI) from aqueous solution to MWCNTs and MWCNT-CS increased with increasing pH values at pH < 7, and then decreased with increasing pH values at pH > 7. The sorption of U(VI) on MWCNTs and MWCNT-CS was strongly dependent on pH and independent of ionic strength. The sorption of U(VI) on MWCNTs and MWCNT-CS was dominated by inner-sphere surface complexation rather than by ion exchange or outer-sphere surface complexation. The surface grafted chitosan molecules can enhances U(VI) sorption on MWCNTs obviously, which was also evidenced from the XPS spectroscopy analysis. The results of high sorption capacity of U(VI) on MWCNT-CS suggest that the MWCNT-CS nanomaterial is a suitable candidate in the preconcentration of U(VI) ions from large volumes of aqueous solutions.     

Adsorption of U (VI) ions from aqueous solution using silicon dioxide nanopowder

The adsorption kinetics for removal of uranium (V1) from aqueous solution using silicon dioxide nanopowder (nano-SiO₂) was investigated in batch and continuous techniques. Pseudo-first order and pseudo-second order were used to analyze the kinetics of batch experiments. In continuous technique the important parameters (initial concentration, flow rate and bed height) on the breakthrough curves were studied and the adsorption kinetics was analyzed using Thomas and Yoon and Nelson kinetic models. The comparison between the kinetic models was evaluated by the correlation coefficients (r²). The results indicated that the batch experiments fitted well with pseudo second-order kinetic model. The comparison of the experimental breakthrough curve to the breakthrough profile obtained from Thomas and Yoon and Nelson methods showed a satisfactory fit for silicon dioxide nanopowder.