Cesium removal from solution using PAN-based potassium nickel hexacyanoferrate (II) composite spheres

A polyacrylonitrile–potassium nickel hexacyanoferrates composite adsorbent was prepared to remove cesium ion in aqueous solution. The dual nozzle technique was applied to prepare a composite sphere. The physicochemical behavior of the ion exchanger was specified with different techniques including Fourier transform infrared spectroscopy, X-ray powder diffraction, specific surface analysis, scanning electron microscopy, and X-ray fluorescence spectroscopy analysis. The effects of contact time, solution initial pH, presence of various cations and initial cesium concentration on the adsorption was also investigated and the optimum conditions for separation of cesium were determined. In addition, adsorption kinetics and adsorption mechanism were studied by modeling the experimental data and related parameters were also evaluated, which showed that sorption data fitted to pseudo-second-order and film diffusion models. Adsorption isotherm in batch experiments showed that the sorption data were successfully fitted with Langmuir model. Finally the adsorption dynamic capacities of the synthesized composite in column experiments were evaluated at 139.925 and 119.539 mg/g for flow rate of 1 and 3 BV/min, respectively.     

Synthesis and characterization of a new surface modified Amberlite-7HP resin by nano-iron oxide (Fe3O4) and its application for uranyl ions separation

A new sorbent Amberlite-7HP modified by the nanoFe₃O₄ (7HPNFeO) formed by surface modification of Amberlite-7 HP using iron oxide magnetic nano-particles which was prepared by precipitation of iron(II) and iron(III) ions in an aqueous solution. The prepared particles have been characterized with transmission electron microscopy, energy dispersive X-ray/scanning electron microscope, X-ray diffraction, and infrared techniques. The sorption kinetics of U(VI) obeyed pseudo second-order and fitted to the intra-particle diffusion model. The sorption isotherms can be correlated to Langmuir isotherm with monolayer capacity of 47.169 mg/g. The breakthrough data obtained by column studies then utilized to model it with Thomas model and to estimate the loading capacity of U(VI) under the specified column conditions. The interfering effect of various anion and cations on the sorption process was examined. Oxalic acid was found suitable for U(VI) separation from the interfering ions Co(II), Cd(II), and Zr(IV) in aqueous solution. Results obtained showed that 7HPNFeO is a promising and effective sorbent and could be used in real samples for safeguard verification purposes.     

Uptake behavior of titanium molybdophosphate for cesium and strontium

This study investigates uptake of cesium and strontium from aqueous solution similar to nuclear waste on three samples of titanium molybdophosphate (TMP) synthesized under various conditions. Effects of concentration of sodium nitrate, pH and contact time on the uptake of cesium and strontium have been studied by bath method. The results showed that TMP has high affinity toward cesium and strontium at pH > 2 and relatively low concentration of sodium nitrate. Kinetic data indicated that cesium uptake process to achieve equilibrium was faster than strontium. Cesium and strontium breakthrough curves were examined at 25 °C using column packed with H₃O⁺ form of TMP and breakthrough curves showed symmetrical S-shaped profiles. At the same time, the calculated breakthrough capacity for cesium was higher than strontium. The results of desorption studies showed that over 99% of cesium and strontium was washed out of column by using 4 M NH₄Cl solution. This study suggests that TMP can have great potential applications for the removal of strontium and specially cesium from nuclear waste solution.     

Sorption of cesium on copper hexacyanoferrate/polymer/silica composites in batch and dynamic conditions

The sorption of cesium ions from aqueous solutions on composite sorbents was investigated in static (by the batch method) and dynamic (on column) conditions. The composite sorbents consisted of copper hexacyanoferrate retained by an anion-exchange polymeric layer bound to porous silica beads. The influence of cesium concentration and solution flow rates on cesium sorption were studied. The cesium sorption isotherm obtained is of the Langmuir type. The shape of the breakthrough curves and the sorption capacity for cesium depend on the preparation procedure of the composites.     

Investigation of cesium uptake from aqueous solutions using new titanium phosphates ion-exchangers

The uptake of cesium from aqueous solutions (pH 5) using titanium phosphates was investigated in the absence and presence of background electrolyte (0.1 M NaNO₃) using a batch technique. The determination of cesium was performed by gamma spectroscopy using ¹³⁷Cs as tracer. The obtained sorption isotherms could be satisfactorily reproduced by a Langmuir sorption equation. The maximum uptake capacity values (q _max) calculated fitting the experimental data by this equation were 167 and 118 mg/g for solutions of initial pH 5 in the absence and presence of background electrolyte. Kinetics data obtained at 293, 308 and 323 K could satisfactorily reproduced by the pseudo-second order equation. It was demonstrated that the new synthesized materials can remove considerable amounts of cesium from aqueous solutions and ion exchange is considered to be the principal mechanism for cesium removal. Toxicity characteristic leaching procedure and desorption tests provided data about the application of the sorbents in environmental remediation.     

Measuring the radon concentration and investigating the mechanism of decline prior an earthquake (Jooshan, SE of Iran)

Batch equilibrium studies were conducted at 20 ± 0.5 °C with indigenously synthesized spherical resorcinol–formaldehyde resin beads, using radioanalytical technique, to determine their capacity for sorption of cesium ions from alkaline medium. Equilibrium isotherm studies were carried out, by varying the initial concentrations of cesium from 0.1 to 50 mM. The liquid-to-solid phase ratio of ~100 ml:1 g was maintained for all the sorption experiments. The equilibrium data were fitted to Langmuir and Freundlich isotherm models. It was observed that Freundlich isotherm explains sorption process nicely. The effect of resin size on percentage cesium ion uptake was also investigated, and 20–40 mesh size was found to be the optimum particle size. The cesium sorption capacity of the beads was determined to be ~238 mg/g. The kinetics of the sorption was studied at different initial cesium ion concentrations, and the kinetics data were fitted into various kinetics models. The kinetics of the cesium ion sorption was found to be pseudo second-order. The mechanistic steps involved were found to be complex, consisting of both film diffusion and intraparticle diffusion with film diffusion as the rate limiting step.     

Removal of cesium and strontium from acid solution using a composite of zirconium molybdate and zirconium tungstate

A composite mixture of zirconium molybdate and zirconium tungstate was prepared and studied for the sorption of cesium and strontium as a function of nitric acid, metal ion concentration, time and temperature. The distribution coefficient (K_d) of 7000 ml/g (~90% sorption) and 70 ml/g (~20% sorption) was obtained for the sorption of cesium and strontium in 0.1M nitric acid, respectively. Experimental sorption capacity, b for cesium was found to be 50 mg/g from 0.1M HNO₃ and 30 mg/g for strontium from 0.001M nitric acid. The sorption of strontium on the sorbent was accompanied by the absorption of heat but the sorption of Cs⁺ results in the liberation of heat. Column studies were conducted by following a breakthrough (BT) curve of cesium and strontium up to C/C₀=1 and the results are reported.     

Sorption of cesium from aqueous waste solution on a SuperLigÒ644 resin

Summary The removal of cesium from aqueous waste solution was investigated in a column setup using a relatively coarse SuperLig^ò644 resin. The bed volume (BV=140) at the onset of breakthrough surpassed the design requirement of 100 BV at 50% breakthrough, and also corresponds to 99.96% cesium removal. Cesium elution with 0.5M HNO₃was satisfactory with a peak BV of 2.5. The elution BV for C/C₀=0.01 was 10, which is less than the target of 15 BV. The percent of sorbed cesium eluted was 99.88%. Further, the BV of the various solutions used for the supporting process steps was sufficient.     

Polyethylenimine and tris(2-aminoethyl)amine modified p(GA–EGMA) microbeads for sorption of uranium ions: equilibrium,kinetic and thermodynamic studies

Poly(glycidyl methacrylate-ethyleneglycol dimethacrylate), p(GA–EGMA), microbeads were prepared through suspension polymerization. It was decorated with polyethylene imine (PEIM) and tris(2-aminoethyl)amine (TAEA) ligands to decorate with polyamine groups. These microbeads were used for sorption of uranium ions from aqueous solution. The maximum sorption of uranium ions on the PEIM and TAEA modified microbeads was observed at pH 6.0. The maximum sorption capacity of acid hydrolyzed p(GA–EGMA)–OH, p(GA–EGMA)–PEIM and p(GA–EGMA)–TAEA microbeads was found to be 7.21, 87.8 and 64.3 mg g^?1. The sorption process conforms to the pseudo-second order kinetic model and the Langmuir and Temkin isotherm models well.     

Synthesis and characterization of ETS-10: supported hollow carbon nano-polyhedrons nanosorbent for adsorption of krypton at near ambient temperatures

Hollow carbon nano-polyhedrons (HCNPHs) supported on Engelhard Titanosilicate-10 (ETS-10) were synthesized by wet impregnation technique using tetrahydrofuran as a solvent. Synthesized HCNPHs/ETS-10 nanosorbent was characterized by X-ray diffraction, Raman spectra, N₂-adsorption–desorption isotherm, BET surface area, and scanning electron microscopy to confirm the morphology and uniformity of carbon particles ranging from 50 to 70 nm in diameter. Sorption characteristics of this nanosorbent for krypton at various carbon loadings were determined using a bench-scale column apparatus. The dynamic sorption capacity of HCNPHs/ETS-10 nanosorbent calculated from the breakthrough curve, 0.75 mmol/kg, which was ~15 % higher than for that of activated carbon. The effect of temperature on the adsorption capacity was studied between 263–293 K. Operational capacity of the nanosorbent was found to be 0.45 mmol/kg at 263 K. The experimental results indicate that 10 wt% HCNPHs/ETS-10 nanosorbent showed promising results for krypton adsorption, indicating its potential as an economical and active sorbent for krypton removal from the off-gas streams resulting from operations for recycle of used nuclear fuel.     

Kinetics and Equilibrium Models for Sorption of Cu(II) onto a Novel Manganese Nano-adsorbent

The studies of kinetics and equilibrium sorption of Cu(II) were undertaken using nanoscale zerovalent manganese (nZVMn) synthesized by chemical reduction in a single pot system. nZVMn was characterized using scanning electron microscopy, energy dispersive x-ray, and surface area determined by Brunauer–Emmett–Teller. The effect of pH, contact time, adsorbent dose, agitation speed, initial Cu(II) concentrations, temperature, and ionic strength on the sorption of Cu(II) onto nZVMn were investigated in a batch system. The kinetic data followed pseudo-second-order. The mechanism was governed by pore diffusion. The equilibrium sorption data were tested by Freundlich, Langmuir, Temkin, Dubinin–Kaganer–Raduskevich, and Halsey isotherm models. The Langmuir monolayer adsorption capacity (Q_max = 181.818 mg/g) is much greater compared to other nano-adsorbents used in sorption of Cu(II). The thermodynamic parameters (ΔH⁰, ΔS⁰, ΔG⁰) revealed a feasible, spontaneous, and endothermic adsorption process. nZVMn has a great potential for effective removal of copper (II) in aqueous solution.     

Sorption and desorption of radiocesium on calcareous soil: Results from batch and column investigations

The sorption and desorption of radiocesium on a calcareous soil from Jiuqian County of Gansu Province (China) were studied by using batch and column experiments. The sorption-desorption isotherms and the breakthrough curves, displacement curves on the whole soil and two treated soils were determined. Based on these results, it was found that the sorption and retention of cesium are mainly determined by the clay minerals, that the sorption-desorption hysteresis of cesium on the calcareous soil is obvious and that the organic matter has a little positive contribution and the calcium carbonate has a little negative contribution to the sorption of cesium on the whole soil. The results from batch experiments were consistent with the results from column experiments.     

Evaluation of perchlorate sorption behavior of calix[4]arene appended resin

In the present work, perchlorate sorption ability of calix[4]arene appended resin was investigated to develop a new efficient method for the removal of perchlorate from aqueous media. The column sorption process was performed at a wide range of pH (1–7) and perchlorate content in the effluent was determined through ion chromatography. From the results, it has been concluded that maximum sorption (97 %) of perchlorate is taking place at pH 3. The breakthrough curves were obtained as a function of time to get clear picture of sorption process and the data obtained was tested by applying two kinetic sorption models, i.e. Yoon-Nelson and BDST. The data obtained through experiments were compared with the theoretically calculated values and it has been found that both have close agreement with each other.     

Sorption of radiocesium on soils in the presence of electrolytes

The influence of background electrolytes (KCl, NH₄Cl, CTABr) in different concentrations on the sorption ability of radiocesium by measuring the distribution coefficient has been studied. Sorption isotherms of cesium for characterization of soil sorption ability were used. Sorption of cesium depends on its concentration and at least three different sorption sites are active in the sorption process. In the case of low cesium concentration, two very selective sites with high distribution coefficients are responsible for the sorption. With increasing cesium concentration in the aqueous phase, distribution coefficient is decreasing. Frayed edge sites of illite in soil and exchangeable potassium are probably responsible for nonlinear isotherms at low cesium concentrations. From sorption isotherms and determination of potassium by activation analysis, it was found that the capacity of very selective sites for different concentrations of background electrolyte was up to 7 mmol·kg^–1.     

Comparative Adsorption of Crystal Violet and Congo Red onto ZnCl2 Activated Carbon

In this study, the adsorption characteristics of crystal violet (CV) and Congo red (CR) dyes from the aqueous solution onto prepared activated carbon were examined. The activated carbon was prepared from wood apple shell by chemical activation with ZnCl₂. The parameters studied were the effect of contact time, initial dyes concentration, and pH of solution. The experimental equilibrium data were analyzed and fitted to Langmuir, Freundlich, and Temkin isotherms. The maximum monolayer adsorption capacities of CV and CR dyes were found to be 142.85 and 83.33 mg per gram of prepared activated carbon at 298 K. The kinetic data obtained at different concentrations were analyzed using pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. Batch adsorption kinetic studies showed that the adsorption of dyes followed pseudo-second-order kinetics and at four different concentrations of both dyes, indicating that chemisorption is the rate-limiting step. Thermodynamic studies reveal that the removal of dyes from aqueous solution onto activated carbon was a spontaneous, feasible, and endothermic process at a temperature greater than standard equilibrium temperature.     

Uranium recovery from UCF liquid waste by nanoporous MCM-41: breakthrough capacity and elution behavior studies

Adsorption and recovery of uranium by nanoporous MCM-41 from aqueous solutions (synthetic solution and uranium conversion facility liquid waste) were investigated by use of a fixed-bed column (1.2 cm diameter and 3.0 cm height). Adsorption was carried out at flow rates 0.2 and 0.5 mL min^?1, which correspond to retention times of 10 and 6 min. The maximum breakthrough capacity for uranium ions was achieved by use of nanoporous MCM-41 at the optimum pH of 3.6 and flow rate 0.2 mL min^?1 (61.95 μg g^?1). The Thomas and Yan models were applied to the experimental data, by use of linear regression, to determine the characteristics of the column for process design. The breakthrough curves calculated from the models were in good agreement with the experimental data. The elution behavior of uranium on nanoporous MCM-41 was studied with different eluents; the results showed that 0.1 M HCl is good eluent for uranium recovery. The regenerated column could be used in a multitude of adsorption–desorption cycles.     

Determination of sorption capacity of fucoidic sands for Cs+ and Sr2+ under dynamic column conditions

In this paper, the sorption behavior of Cs⁺ and Sr²⁺ on column of fucoidic sands under dynamic flow conditions was investigated, and their sorption capacities (SC) towards these two cations were studied. The determination of SC is based on the construction of respective breakthrough curves using ¹³⁷Cs and ⁸⁵Sr radionuclides as isotopic indicators in laboratory experiments. The samples were taken from several parts of the borehole in the area of interest. Undisturbed cores of 5 cm in diameter and 10 cm long were put in the glass columns and the cores were perfectly tightened using acrylate resin. In this time-dependence study, the so-called cenoman background groundwater was used. A concentration of 10^?6 mol/dm³ of Cs⁺ and Sr²⁺ in liquid phase individually was established using neutral salts of CsNO₃ and Sr(NO₃)₂, respectively. The groundwater was introduced at the bottom of the columns by a multi-head peristaltic pump, at a constant flow-rate of about 4 cm³/h. The results show that the sorption capacity of the investigated fucoidic sands for ¹³⁷Cs and ⁸⁵Sr is 0.1–1.5 and 0.05–0.5 μmol/100 g, respectively, in dependence on the evaluation of corresponding breakthrough curves. Some differences in the behavior of the cores during the experiments have also been observed and explained.     

A four-coordinate cadmium(II) polymer for efficient adsorption of Congo red,kinetic, isotherm,fluorescence and antibacterial activity

A 3-D cadmium-based coordination polymer, [CdCl₂L]_n (1) (where L = 1,1-(1,6-hexanediyl)bis(1,3-dihydro-3-methyl-1H-imidazole-2-thione), was synthesized and structurally characterized. The capability of the polymer as an efficient sorbent for Congo red (CR) removal from aqueous solution has been evaluated. Compound 1 has a tetrahedral arrangement with a CdS₂Cl₂ core. L in 1 is bidentate to two neighboring Cd^II centers via the methimidazole sulfurs to create 1D chains propagating along the c-axis. The remaining coordination sites are occupied by two terminal chlorides. The chains are further stabilized by intermolecular C–H?Cl hydrogen bonds between the chlorides and hydrogens of the imidazole rings. Parallel chains stack in the 3-D structure. The Cd^II polymer sorbent was characterized by infrared spectroscopy, elemental analysis, UV–vis, solid fluorescence and X-ray single-crystal diffraction. Sorption kinetics were studied by three kinetic models, second order, Elovich and intraparticle diffusion. The results indicate that the mechanism of the sorption process followed Elovich kinetic model. Sorption equilibrium was also studied with Langmuir, Temkin, and Freundlich isotherm models. The sorption process followed the Temkin isotherm. MIC, MBC, and DNA cleavage activities of 1 were also studied. Furthermore, the UV–vis and solid state fluorescence spectra of 1 were measured.     

Adsorption of Mercury(II) on Amidoxime Chelating Resins with Magnetic Properties

Two amidoxime chelating resins were prepared. The preparation process was carried out through copolymerization of acrylonitrile with N,N′-methylene-bis-acrylamide (MBA) as a crosslinker in the presence and absence of magnetite (Fe₃O₄) particles. The resins obtained were subsequently treated with hydroxylamine to give the corresponding amidoxime chelating resins. The uptake behavior of the resins toward Hg(II) in aqueous solutions using batch and column techniques was studied. The oxide containing resin gave higher uptake capacities relative to oxide free resin confirming the advantage of embedded particles on the uptake capacity. Thermodynamic and kinetic parameters of the uptake process were calculated. Regeneration of the resins was carried out using 0.5 M KI and the desorption ratio was found to be more than 97%.     

Simulation of a 2-site Langmuir model for characterizing the sorption capacity of Cs and Se in crushed mudrock under various ionic strength effects

The sorption capacity of cesium (Cs) and selenium (Se) in crushed mudrock was demonstrated in this study through a 2-site Langmuir model. To employ such a numerical analysis, batch tests were applied in this study in synthetic seawater and groundwater with sorption/desorption kinetic experiments (time-dependent) and different concentrations (10^?2–10^?7 M). The 2-site sorption models, which correspond to two rate constants (λ ₁ and λ ₂), might be more adequate than 1-site sorption models in characterizing Cs and Se sorption/desorption according to the least square errors between the numerical analysis and the results of the batch tests. The fitting results showed that a 2-site Langmuir model is capable of appropriately describing Cs and Se sorption in mudrock. Consequently, the sorption capacity was calculated at about 0.06 mol/kg for Cs and at 0.015 mol/kg for Se.