Sorption studies of europium on cerium phosphate using Box-Behnken design

Amorphous cerium phosphate was prepared and characterized. Three-level Box-Behnken design (BBD) was employed to analyze the effect of process variables such as initial pH (2–6), contact time (60–180 min), and sorbent amount (0.05–0.15 g) on the sorption capacity of europium. Analysis of variance (ANOVA) revealed that the main effect of initial pH and sorbent amount has a substantial impact on the sorption of Eu(III). Probability F-value (F = 3 × 10^-3) and correlation coefficient (R2 = 0.97) point out that the model is in good accordance with experimental data. The maximum sorption capacity of Eu(III) was found to be 42.14 mg g^-1 at initial pH 6, contact time of 180 min, and a sorbent amount of 0.05 g. Sorption isotherm data was well explained by the Langmuir model and monolayer Eu(III) sorption capacity was obtained as 30.40 mg g^-1. Kinetic data were well described by the pseudo-second-order model. Thermodynamic data suggested that the process is endothermic and spontaneous.     

Sorption of americium from low-level liquid wastes by nanocrystalline MnO2

Nanocrystalline MnO₂, synthesized by alcoholic hydrolysis of KMnO₄, has been studied as a sorbent for removal of americium from low level liquid waste solutions. The synthesized MnO₂ was found to have BET surface area of 230 m² g^?1. Am(III) was found to be sorbed by MnO₂ quantitatively within 15 min at pH 5. The sorption was found to be more than 90 % at as low a pH as 1.2 and reached to near 100 % at all pH values above pH 3.0 There was no effect of ionic strength (0.01–1.0 M NaCl, CaCl₂) on the sorption suggesting the sorption following inner sphere complexation mechanism at all the pH values. Adsorption isotherm studies were carried out using Eu(III) as a chemical analogue of Am(III). These studies showed the isotherm data to follow Langmuir adsorption isotherm.     

Selective extraction of Th(IV) over U(VI) and other co-existing ions using eosin B-impregnated Amberlite IRA-410 resin beads

A new chelating polymeric sorbent as an extractant impregnated resin (EIR) has been developed using eosin B and Amberlite IRA-410 resin. The impregnation process was characterized by FT-IR spectroscopy. The eosin B-impregnated resin showed superior binding affinity for Th(IV) over U(VI) and many co-existing ions. The influence of various physicochemical parameters on the recovery of Th(IV) were optimized by both static and dynamic methods. The Langmuir adsorption isotherm gave a satisfactory fit of the equilibrium data. The kinetic studies performed for Th(IV) sorption revealed that <20 min was sufficient for reaching equilibrium metal ion sorption. A preconcentration factor of 100 was found for the column-mode extraction. The accuracy of the developed method in conjunction with Arsenazo III procedure was tested by analyzing geological reference materials and seawater sample, which are prepared, synthetically. Furthermore, the above procedure has been successfully employed for the analysis of natural water samples.     

Evaluation of Se(IV) removal from aqueous solution by GMZ Na-bentonite: batch experiment and modeling studies

Bentonite has been studied extensively because of its strong sorption and complexation ability. In this work, the sorption of Se(IV) on purified GMZ bentonite was investigated under ambient temperature as functions of contact time, pH, Se(IV) concentration and co-existing ion Eu(III) using batch techniques. Sorption kinetics of Se(IV) was successfully described by the pseudo-second-order rate equation. The sorption amount of Se(IV) was strongly dependent on the solution pH, and a positive effect was observed on Se(IV) and Eu(III) co-sorption when these two elements existed in the same system under high surface coverage of sorbent. Double layer model was set up and used to quantitatively interpret the sorption experimental data collected in binary and ternary sorption systems. From the experimental results, one can conclude that GMZ bentonite may have good potentialities for immobilizing selenium in nuclear wastes.     

Nanocomposites of polyaniline functionalized graphene oxide: synthesis and application as a novel platform for removal of Cd(II), Eu(III), Th(IV) and U(VI) in water

The characterization of the nanocomposites (PANI@GO) by SEM, TEM, Raman and FT-IR indicated that the GO has been functionalized via PANI successfully. PANI@GO as a novel platform for the removal of Cd(II), Eu(III), Th(IV) and U(VI) from aqueous solutions, the uptake process was a spontaneous endothermic process, and is strongly dependent of pH but independent of ionic strength. The adsorption kinetic and isotherm were fitted well the Pseudo-second-order equation and Langmuir model. PANI@GO were recycled and re-used without significant loss of adsorption capacity, and real samples were also treated which showed that had little interference with the performance of it.     

Quercetin immobilized on silica gel as a solid phase reagent for tin(IV) determination by using the sorption-spectroscopic method

New chelating sorbents are prepared by 3,3',4',5,7-pentahydroxyflavone adsorption from butanol and acetone-hexane (1:4) solutions, characterized by isotherm of sorption, IR-spectroscopy and studied for pre-concentrating and sorption-spectroscopic determination of Sn(IV). The solid-phase Quercetin with satisfactory analytical characteristics was formed by adsorption from acetone-hexane (1:4) mixture. The quantitative recovery of Sn(IV) from aqueous solution with modified sorbent was observed at pH 1.8-2.2. The tolerance limits of heavy metal ions in the sorption of Sn(IV) are reported. The limit of Sn detection is 0.06 mg l(-1). The linearity of calibration graph has been observed up to 1.2 mg l(-1). The method has been applied to determine Sn in high purity zinc materials.     

Magnetic chitosan grafted with polymerized thiourea for remazol brilliant blue R recovery: Effects of uptake conditions

Magnetic chitosan was prepared by co-precipitation with polymeric Schiff’s base resulting from the reaction of thiourea with glutaraldehyde. This material has great potential as high-effective sorbent for Remazol Brilliant Blue R (RBBR): maximum sorption capacity reached 0.441?mmol?g^?1 at pH 1.6 and at 25°C. Kinetic plots, pH dependence, isotherm data, and influences of ionic strength were reported. The data from equilibrium sorption experiments are well fitted to the Langmuir isotherm and the pseudo-second-order sorption kinetics indicates that chemisorption controls the process. The distribution coefficient was calculated at different temperatures and the thermodynamic parameters have been calculated: the sorption reaction is endothermic, spontaneous, and increases the entropy of the system. Alkaline solution (0.5?M NaOH) was used for desorbing RBBR from loaded sorbent. The sorbent exhibited good regenerability over several repeated adsorption/desorption cycles.     

Effect of phosphate on sorption of Eu(III) by montmorillonite

Eu(III) sorption by Na-montmorillonite, the principal component of bentonite, has been studied in absence and presence of phosphate under varying experimental conditions of pH, metal ion, phosphate and sorbent concentration. The sorption edge was found to shift to high pH with decreasing sorbent concentration indicating site heterogeneity on the clay. Eu(III) sorption by Na-montmorillonite was found to increase in presence of phosphate at lower sorbent concentration of 0.5 g/L while at higher sorbent loading no effect of phosphate was observed. ATR–FTIR spectroscopy has been used to understand transition from surface complexation to surface precipitation with decreasing sorbent concentration.     

Manganese ferrite (MnFe2O4) as potential nanosorbent for adsorption of uranium(VI) and thorium(IV)

Journal of Radioanalytical and Nuclear Chemistry - The adsorption behavior of U(VI) and Th(IV) metal ions by MnFe2O4 NPs was studied as a function of pH, mass of sorbent, contact time, and...     

Effect of pH,fulvic acid and temperature on sorption of Th(IV) on zirconium oxophosphate

Sorption of Th(IV) on Zr₂O(PO₄)₂ as a function of contact time, reaction temperature, pH, ionic strength and solid-to-liquid ratio (m/V) is studied under ambient condition by using batch technique. Effects of fulvic acid (FA), phosphate, sulfate and citrate on Th(IV) sorption are investigated in detail. A pseudo-second-order rate equation is used to simulate the kinetic sorption. The removal of Th(IV) increases with increasing pH and hardly depends on ionic strength. Sorption of Th(IV) increases with increasing m/V and reaction temperature. The presence of FA and phosphate enhances the sorption of Th(IV) on Zr₂O(PO₄)₂ while sulfate and citrate decrease the sorption. The Langmuir and Freundlich models are used to simulate the sorption isotherm of Th(IV) on Zr₂O(PO₄)₂ at different temperatures. The thermodynamic data (i.e., ∆H ⁰, ∆S ⁰, ∆G ⁰) are calculated from temperature dependent sorption isotherms. The results suggest that the sorption process of Th(IV) on Zr₂O(PO₄)₂ is spontaneous and endothermic.     

Adsorption of Pb(II) and Cu(II) from aqueous solution on magnetic porous ferrospinel MnFe2O4

The adsorption of Pb(II) and Cu(II) from aqueous solution on magnetic porous ferrospinel MnFe(2)O(4) prepared by a sol-gel process was investigated. Single batch experiment was employed to test pH effect, sorption kinetics, and isotherm. The interaction mechanism and the regeneration were also explored. The results showed that Pb(II) and Cu(II) removal was strongly pH-dependent with an optimum pH value of 6.0, and the equilibrium time was 3.0 h. The adsorption process could be described by a pseudo-second-order model, and the initial sorption rates were 526.3 and 2631.5 μmol g(-1)min(-1) for Pb(II) and Cu(II) ions, respectively. The equilibrium data were corresponded well with Langmuir isotherm, and the maximum adsorption capacities were 333.3 and 952.4 μmol g(-1) for Pb(II) and Cu(II) ions, respectively. The adsorbed Pb(II) and Cu(II) ions were in the form of the complex with oxygen in carboxyl and hydroxyl groups binding on the surface of magnetic porous MnFe(2)O(4). The sorbent could be reused for five times with high removal efficiency.     

Sorption of Eu(III) on GMZ bentonite in the absence/presence of humic acid studied by batch and XAFS techniques

Bentonite has been extensively studied because of its strong sorption ability and low permeability. In this work, the Na-bentonite from Gaomiaozi County (China) has been characterized by XRD, FTIR and acid-base titration. The sorption of Eu(III) on Na-bentonite in the absence/presence of humic acid (HA) was studied at T = 25 ± 2 °C and in 0.01 mol/L NaClO₄ solution. The effects of pH, HA, contact time and initial Eu(III) concentrations were also investigated. The results indicate that the sorption of Eu(III) on Na-bentonite was dependent on pH values. The presence of HA had little effect on Eu(III) sorption at low pH values, but decreased Eu(III) sorption at high pH values. X-ray absorption fine structure spectroscopy (XAFS) was applied to characterize the local structural environment of the adsorbed Eu(III) on bare Na-bentonite and HA-bentonite hybrids. The results indicate that Eu(III) was bound to O atoms at a distance of about 2.39 Å at pH 4.15. The results are crucial for the evaluation of the sorption and migration of other trivalent lanthanides and actinides in bentonite as backfill materials.     

Removal of Arsenic (III) from natural contaminated water using magnetic nanocomposite: kinetics and isotherm studies

The application of newly synthesized Fe₃O₄/TiO₂–SiO₂ that is modified with zinc (FTSZ) as a sorbent, for the removal of arsenic from contaminated water has been investigated in the present study. SEM, FTIR, XRD, BET, Zeta potential sizer (ξ) analyses are used to determine the sorbent characterization. The effect of the operational parameters such as initial pH, initial concentration, and the contact time were studied. In addition, the equilibrium behavior of FTSZ in As(III) removal was investigated in the temperature range of 20–40 °C. The results showed that the equilibrium data were fitted well with Langmuir than Freundlich isotherm model. The maximum monolayer adsorption capacity estimated by Langmuir isotherm was 24.010 mg g^?1. Thermodynamic parameters, ?H°, ?S° and ?G° were also calculated from graphical interpretation of the experimental data. Standard heats of sorption (?H°) were found to be endothermic and ?S° values were calculated to be positive for the sorption of As(III) onto the adsorbent.     

Sb(III)-Imprinted Organic-Inorganic Hybrid Sorbent Prepared by Hydrothermal-Assisted Surface Imprinting Technique for Selective Adsorption of Sb(III)

Sb(III)-imprinted organic-inorganic hybrid sorbent was prepared by hydrothermal-assisted surface imprinting technique and was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy coupled to an energy dispersive spectrometer and N₂ adsorption/desorption isotherms. Hydrothermal-assisted process can improve the selectivity of the Sb(III)-imprinted hybrid sorbent for Sb(III) due to stable control of temperature and pressure. The Sb(III)-imprinted hybrid sorbent IIS indicated higher selectivity for Sb(III), had high static adsorption capacity of 37.3 mg g^–1 for Sb(III), displayed stable adsorption capacity in pH range from 4 to 8, reached an rapid adsorption equilibrium within 30 min. According to the correlation coefficient (r² > 0.99), the experimental data fitted better the pseudo-second-order kinetic model and Langmuir equilibrium isotherm.

     

Preconcentration of uranium(VI) and thorium(IV) from aqueous solutions using low-cost abundantly available sorbent

Olive cake as low-cost abundantly available sorbent has been characterized by N₂ at 77 K adsorption, porosity analysis, elemental analysis and IR spectra and has been used for preconcentrating of uranium(VI) and thorium(IV) ions prior to their determination spectrophotometrically. The optimum pH values for quantitative sorption of U(VI) and Th(IV) are 4–7 and 3–7, respectively. The enrichment factor for the preconcentration of U(VI) and Th(IV) were found to be 125 and 75 in the given order. The sorption capacity of olive cake is in the range of 2,260–15,000 μg g⁻¹ for Th(IV) and in the range of 1,090–17,000 μg g⁻¹ for U(VI) at pH 3–7. The sorbent exhibits good reusability and the uptake and stripping of the studied ions were fairly rapid. The elution of U(VI) and Th(IV) was performed with 0.3–1 M HCl/1–2 M HNO₃ and 0.3–0.8 M HCl/1 M HNO₃, respectively. The precision of the method was 1.8 RSD% for U(VI) and 2.5 RSD% for Th(IV) in a concentration of 1.00 μg mL⁻¹ for 10 replicate analysis. The influence of some electrolytes and cations as interferents was discussed. Separation of U(VI) and Th(IV) from other metal ions in synthetic solution was achieved.     

纯相钙铝层状双氢氧化物对磷的吸附特性

采用乙醇辅助液相共沉淀法制备了纯相Ca-Al-LDH层状双金属氢氧化物,考察了Ca-Al-LDH的投加量、吸附时间、pH值、无机电解质(Na₂CO₃ ,KCl ,Na₂SO₄,KNO₃)和温度等因素对磷吸附的影响,结果表明,纯相Ca-Al-LDH对磷酸根离子具有很好的吸附性能,最大饱和吸附量可达160.78 mg/g,当pH值为5.1、温度为45 ℃、吸附时间为600 min、LDH投加量为0.6 g/L、磷初始浓度为80 mg/L时,磷的去除率高达95.88%;无机阴离子会抑制磷在吸附剂上的吸附,当Cl^-浓度从2.5 g/L升高到25 g/L时,Ca-Al-LDH对磷酸盐的最大饱和吸附量从69.96 mg/g降至53.18 mg/g,降低了23.99%;当SO₄^2-浓度从2.5 g/L升高到25 g/L时,Ca-Al-LDH对磷酸盐的最大饱和吸附量降低了24.79%,其它无机阴离子对磷在吸附剂上的吸附也有一定的影响。 Ca-Al-LDH对水中磷的吸附符合二级动力学方程和Langmuir等温模型。 采用扫描电子显微镜、傅里叶变换红外光谱仪和X射线衍射仪等技术手段对制备的纯相Ca-Al-LDH及其吸附磷酸根后的产物进行表征,揭示了Ca-Al-LDH对磷酸根的吸附可能是静电吸引、化学吸附和阴离子插层等过程协同作用的吸附机理。     

Sorption of palladium(II), rhodium(III), and platinum(IV) on Fe(3)O(4) nanoparticles

The adsorption of palladium(II), rhodium(III), and platinum(IV) from diluted hydrochloric acid solutions onto Fe(3)O(4) nanoparticles has been investigated. The parameters studied include the contact time and the concentrations of metals and other solutes such as H(+) and chloride. The equilibrium time was reached in less than 20 min for all metals. The maximum loading capacity of Fe(3)O(4) nanoparticles for Pd(II), Rh(III), and Pt(IV) was determined to be 0.103, 0.149, and 0.068 mmol g(-1), respectively. A sorption mechanism for Pd(II), Rh(III), and Pt(IV) has been proposed and their conditional adsorption equilibrium constants have been determined to be logK=1.72, 1.69, and 1.84, respectively. Different compositions of eluting solution were tested for the recovery of Pt(IV), Pd(II), and Rh(III) from Fe(3)O(4) nanoparticles. It was found that 0.5 mol L(-1) HNO(3) can elute all of the metal ions simultaneously, while 1 mol L(-1) NaHSO(3) was an effective eluting solution for Rh(III), and 0.5 mol L(-1) NaClO(4) for Pt(IV). In competitive adsorption, the nanoparticles showed stronger affinity for Rh(III) than for Pd(II) and Pt(IV).     

Modifying attapulgite clay by ammonium citrate tribasic for the removal of radionuclide Th(IV) from aqueous solution

The ammonium citrate tribasic was successfully modified to attapulgite clay and the effect of modifying was characterized by FTIR and XRD techniques. Experimental results showed that the ammonium citrate tribasic modified attapulgite clay had a strong sorption ability to remove Th(IV) from aqueous solutions. The sorption of Th(IV) from aqueous solutions has been systematically investigated as a function of several variables including contact time, solid content, pH, ionic strength, Fulvic acid (FA)/humic acid (HA) and temperature under ambient conditions. The results indicate that the sorption of Th(IV) onto ammonium citrate tribasic modified attapulgite clay is strongly dependent on pH, Th(IV) initial concentration, ionic strength, temperature and HA/FA. Surface complexation and ionic exchange are the main sorption mechanisms. Sorption of Th(IV) onto ammonium citrate tribasic modified attapulgite is quick and can be fitted by a pseudo-second-order rate model very well. Sorption of Th(IV) onto ammonium citrate tribasic modified attapulgite is promoted at higher temperature and the sorption reaction is an endothermic process. Langmuir isotherm model fits the experimental data better than Freundlich and D-R isotherm models. The results suggest that the ammonium citrate tribasic modified attapulgite sample is a suitable material in the preconcentration and solidification of radionuclide Th(IV) from large volumes of aqueous solutions.     

Adsorption of fluoride, chloride, bromide, and bromate ions on a novel ion exchanger

A novel ion exchanger based on double hydrous oxide (Fe2O3Al2O3xH2O) was obtained by the original sol-gel method from easily available and cheap raw materials and employed for adsorption of F-, Cl-, Br-, and BrO-3 from simultaneous solutions. Adsorbent was characterized by potentiometric titration, zeta-potential, and poremetrical characteristics. A technologically attractive pH effect of F-, Br-, and BrO-3 sorption on the investigated double hydroxide of Fe and Al, which is capable of working in the pH range 3 to 8.5, was observed. Kinetic data on fluoride and bromide sorption fit well the pseudo-second-order model. Isotherms of fluoride, bromide, chlorine, and bromate ion sorption on Fe2O3Al2O3xH2O were obtained at pH 4. The isotherm of F- sorption fit well the Langmuir model; sorption affinity (K=0.52 L/mg) and sorption capacity (90 mg F/g) were high. In the competitive adsorption of bromide and bromate, bromide dominated at equilibrium concentrations of the ions >40 mg/L. The mechanism of fluoride adsorption to the surface of the model cluster of the sorbent synthesized and the geometry of the cluster itself were modeled with the HyperChem7 program using the PM3 method.     

Adsorptive removal of U(VI) and Th(IV) from aqueous solutions using polymer-based electrospun PEO/PLLA fibrous membranes

Fibrous membranes based on poly(ethylene oxide) and poly(l-lactide) fabricated by electrospinning were evaluated for the first time as substrates for the adsorption of tetravalent thorium (Th(IV)) and hexavalent uranium (U(VI)) from aqueous media. The membranes consisted of microfibers with diameters of approximately 2 μm as revealed by scanning electron microscopy. The adsorption of Th(IV) and U(VI) on the membrane was investigated as a function of pH, ionic strength and initial metal concentration under normal atmospheric conditions. The experimental data indicated increased affinity of the membrane for Th(IV) and U(VI), which was pH depended and reaches maximum values (>90 %) for Th(IV) and U(VI) at pH 3 and pH 6.5, respectively. The maximum adsorption capacity (q _max) at optimum conditions was evaluated from the Langmuir isotherm and was found to amount 50.08 and 9.3 mmol kg^?1 for Th(IV) and U(VI), respectively. In addition, studies on the effect of ionic strength on the adsorption efficiency did not show any significant effect indicating that the adsorption of Th(IV) and U(VI) on the membrane was most probably based on specific interactions and the formation of inner-sphere surface complexes. The significantly higher adsorption efficiency of the membrane for Th(IV) in acidic media (pH ≤ 3) could be utilized for a pH-triggered, selective separation of Th(IV) from U(VI) from aqueous media.