Adsorption Of Sr Research Articles

Recovery of strontium (Sr2+) from seawater using a hierarchically structured MnO2/C/Fe3O4 magnetic nanocomposite

The recovery of strontium ions (Sr2+) from seawater has attracted much attention as an approach to securing Sr resources to meet increasing industrial demand. In this study, we synthesized a magnetic MnO2 nanocomposite (MnO2/C/Fe3O4) using a simple redox reaction under ambient conditions and applied this nanocomposite to the extraction of Sr2+ from natural seawater. The synthesized nanocomposite exhibited a hierarchical structure of MnO2, carbon, and Fe3O4 with a saturation magnetization of 25 emu/g that enabled effective separation under an external magnetic force. Regardless of the initial Sr2+ concentration, the adsorption of Sr2+ onto MnO2/C/Fe3O4 proceeded rapidly (within <10 min) following a pseudo-second-order kinetic model and agreed well with the Langmuir isotherm model, indicating a maximum adsorption capacity of 42 mg/g. Among the competitive ions, Mg2+ and Ca2+ significantly hindered Sr2+ adsorption onto MnO2/C/Fe3O4, whereas Na+ and K+ had little effect on Sr2+ adsorption. A detailed study of the distribution coefficient (Kd) revealed 11.2-fold and 1.8-fold higher selectivities toward Sr2+ than toward Mg2+ and Ca2+, respectively. The Sr2+ ions adsorbed onto MnO2/C/Fe3O4 were completely recovered through desorption in 0.1 M HCl eluent. Finally, a Sr2+-enriched solution with a concentration of 501 mg/L could be obtained via seawater adsorption and subsequent acid desorption over 8 iterative cycles, demonstrating its effectiveness for practical applications of Sr2+ recovery from seawater.

Strontium Adsorption on Manganese Oxide (δ-MnO2) at Elevated Temperatures: Experiment and Modeling

Strontium adsorption was studied by acid–base potentiometric titration at various pH, ionic strength, the sorbate/sorbent ratio, and temperatures (at 25, 50, and 75°C). The experimental data were interpreted using two models of surface complexation with two different electrostatic models of the interface: the constant capacitance (CCM) and triple-layer (TLM) models. Although both models are able to take into account acid–base reactions and surface complexation of Sr on birnessite, we believe that TLM is more suitable for the description of the H+–>MnOH–Sr2+ heterogeneous system. At a low ionic strength and negatively charged surface, Sr2+ ions compete with electrolyte ions and form both inner- and outer-sphere complexes. Although the application of CCM in describing Sr adsorption may be mathematically satisfactory, it has little physical sense. We suggest a model that involves both inner-sphere (>MnOHSr2+, >MnOSr+, >MnOSrOH0) and outer-sphere ([>MnO–Sr2+]+) surface complexes. The corresponding constants of formation of these surface complexes were calculated at 25, 50, and 75°C.

Adsorption of Sr(II) cations onto phosphated mesoporous titanium dioxide: Mechanism, isotherm and kinetics studies

In this work, phosphate-modified titanium dioxide nanoparticles with mesoporous structure were synthesized and utilised as an efficient nanoadsorbent for Sr(II) removal from aqueous environment. The globular titania particles with a 3–4 nm diameter with chemosorbed on their surfaces phosphate groups = Ti(O2POOH) have been obtained by liquid-phase synthesis. The characterization of titania nanoparticles were performed using XRD, TEM, IR-spectroscopy and Brunauer-Emmett-Teller analyses. The synthesized modified adsorbents exhibited SBET = 396–410 m2 g−1 and mesopore volume of 0.262 – 0.275сm3 g−1. The isotherm and kinetic models were used for the description of Sr(II) adsorption. The sample 4P-TiO2 showed the best adsorption ability for strontium ions removal. The adsorption capacity of Sr(II) onto modified 2P-TiO2, 4P-TiO2 and 8P-TiO2 samples was found to be 94.1, 172.5, 128.9 mg/g, respectively. An adsorption mechanism for Sr(II) removal was proposed. The adsorption/desorption studies were conducted to find the reusability of phosphated adsorbents. A titanium dioxide-based mesoporous material possesses a significant adsorption activity due to high content of surface acid sites. All the outcomes revealed that the phosphate modified titania showed great potential in Sr(II) removal from aqueous environment and nuclear effluents.

Adsorptive removal of strontium ions from aqueous solution by graphene oxide.

Graphene oxide (GO) was prepared, characterized, and applied for adsorption of Sr(II) in aqueous solution. The adsorption capacity was calculated to be 137.80 mg/g according to the Langmuir model. The observation by scanning electron microscope with energy dispersive X-ray detector (SEM-EDX), high-resolution transmission electron microscope (HRTEM), and X-ray diffraction (XRD) revealed the crystal structure of Sr compound on the surface of graphene sheets. The analyses by the Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated the involvement of O-C=O, C-O, and C-O-C groups during the adsorption. The X-ray absorption fine structure (XAFS) analysis provided the detail information of GO-Sr composites, and the fitting results were given by Sr(HCOO)2 and SrCO3 model, and the coordination numbers (CN) and interatomic distances (R) of Sr-O shell and Sr-C shell were calculated. The adsorption mechanism of Sr(II) was attributed to complexation between Sr and the acidic oxygen-containing groups, which lead to the agglomeration of graphene oxide. Two types of crystals were proposed. Type 1 was formed by coordination between Sr(II) and O-C=O groups, and type 2 was formed by coordination between Sr(II) and C-O/C-O-C groups.

Preparation of potassium niobium sulfide and its selective adsorption properties for Sr2+ and Co2+

A novel metal sulfide: potassium niobium sulfide (KNbS) was prepared by hydrothermal method. The morphology and composition of KNbS were characterized by scanning electron microscopy and X-ray diffraction. It was confirmed that the adsorption process of KNbS was carried out by exchange reaction of K+ with Co2+ and Sr2+. The effects of pH, contact time, coexisting ions and initial concentration of strontium and cobalt on the adsorption of Sr2+ and Co2+ by KNbS were studied by static adsorption experiments. Thus, the optimal adsorption conditions of KNbS for Co2+ and Sr2+ were determined. The results show that KNbS has a greater affinity for Sr2+ and Co2+ than other coexisting ions. In addition, the adsorption mechanism was analyzed by kinetic, Weber–Morris, Boyd and isothermal models. It was revealed that the adsorption of Co2+ and Sr2+ by KNbS was chemical adsorption of monolayer and the intraparticle diffusion was the main rate-control step.

Development the sorption behavior of nanocomposite Mg/Al LDH by chelating with different monomers

Methacrylic acid, acetonitrile, dimethylsulfoxide and 1,4 dioxane intercalated Mg–Al layered double hydroxide (LDH) was made by the use of coprecipitation and the chelation techniques. The elimination of strontium, nitrate, and borate in polluted solution was scrutinized. The adsorption of Sr2+, NO3−, and B4O72− on methacrylate intercalated Mg–Al LDH (methacrylic acid (MAA)-Mg-Al LDH) proved that the adsorption process was spontaneous and increased randomness in the system. The equipped LDHs were performed by HNMR, scanning electron microscopy (SEM), thermogravemitric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy and dynamic light scattering (DLS). It was established that different monomer types could intercalate inside an interlayer of the Mg–Al LDH. Methacrylic acid-intercalated Mg–Al LDH can effectively adsorb strontium, nitrate, and borate in aqueous solutions more effectively than other prepared LDHs. The dependability of the (MAA)-Mg-Al LDH was premeditated by iterating consecutive adsorption/desorption cycle.

Adsorption and Desorption Characteristics of Sr, Cs, and Na Ions with Na-A Zeolite Synthesized from Coal Fly Ash in Low-Alkali Condition

Adsorption and Desorption Characteristics of Sr, Cs, and Na Ions with Na-A Zeolite Synthesized from Coal Fly Ash in Low-Alkali Condition

Removal and recovery of strontium (Sr(II)) from seawater by Fe3O4/MnO2/fulvic acid nanocomposite

In this study, Fe3O4/MnO2/FA nanocomposite was synthesized as a low cost adsorbent with high adsorption capacity, desorption efficiency and reusability for Sr(II) extraction from seawater. FT-IR, FESEM-EDS, XRD, VSM and BET experiments were used to characterize the composite. Sr(II) adsorption onto Fe3O4/MnO2/FA followed a pseudo-first-order kinetic model and was well fitted with the Langmuir isotherm model. Fe3O4/MnO2/FA has demonstrated an excellent adsorption capacity of 227.3 mg/g for Sr(II) ions at 25 °C and pH 8. The composite showed high selective uptake of Sr(II) in the presence of cations Na, Mg and Ca. However, Ca ions reduced the Sr(II) uptake from 49.1 to 41.0 mg/g at 600 mg/L Ca. Sr(II) desorption was performed using 0.1 M HCl which showed an excellent desorption efficiency. In natural seawater containing 9.4 mg/L Sr(II), without changing the physicochemical conditions, Fe3O4/MnO2/FA composite showed 6.4 mg/g of Sr(II) adsorption, which leads to save time and energy consumption.

Efficient removal of Sr(II) from aqueous solution by melamine-trimesic acid modified attapulgite composite

Melamine (MA)-trimesic acid (TMA) modified attapulgite (ATP–TMA–MA) with high adsorption capability for Sr(II) was successfully synthesized using attapulgite (ATP) as a matrix via a facile two-step approach. Batch adsorption experiments indicated that the adsorption kinetics followed the pseudo-second-order equation and isothermal adsorption data fitted well with the Freundlich isotherm model. The adsorption thermodynamic analysis indicated that Sr(II) adsorption onto ATP–TMA–MA was a spontaneous and endothermic process. Sr(II) adsorption mechanism of ATP–TMA–MA was mainly decided by chemisorption. TMA–MA molecules grafted on ATP surface markedly improve the removal efficiency of ATP–TMA–MA for Sr(II).

Highly efficient adsorption of strontium ions by carbonated mesoporous TiO2

In this study, mesoporous carbonated TiO2 nanoparticles were synthesized by sol-gel route using a complex [Ti(OH2)6]3+·3Cl− and a modifying agent Na2CO3 and used as an adsorbents for Sr(II) removal from aqueous medium. The characterization of nanoadsorbents was accomplished using XRD, SEM, EDS, TEM, TG-DTG-DTA, IR, BET, pHPZC analyses. It was found that the sizes of carbonated TiO2 nanoparticles was ~4 nm. The presence of mononuclear bidentate carbonate groups on the titania surface was approved by IR spectroscopy. The kinetic data was analyzed by pseudo-first-order, pseudo-second-order, Elovich, and an intraparticle diffusion models. The adsorption isotherms were fitted by using Langmuir, Freundlich, and Dubinin–Radushkevich models. The fittings show that the pseudo-second-order kinetics and Langmuir isotherm are suitable models for the adsorption process. The sample with 4% (wt.) of carbonate groups showed the best adsorption performance towards Sr(II) cations. The mesoporous carbonated samples demonstrated a higher adsorption capacity for strontium ions than the basic TiO2. The adsorption capacities of modified 2C-TiO2, 4C-TiO2 and 8C-TiO2 samples were 170.4, 204.4, 190.8 mg/g respectively, while it was 70.9 mg/g for the unmodified TiO2 towards Sr(II). Higher removal of Sr(II) was observed in the alkaline medium due to the formation of SrОН+ cations. A mechanism for Sr(II) adsorption was described and the number of chemosorbed ≡Ті(О2СО) groups and active adsorption centers onto unmodified and modified TiO2 surface were calculated. The titania adsorbents have high reusability and retain their adsorption capacity during five adsorption-desorption cycles. The presented results indicated that the mesoporous carbonated adsorbents were appropriate materials for the removal of Sr(II) from aqueous medium.

Effects of ferrihydrite nanoparticle incorporation in cementitious materials on radioactive waste immobilization.

To enhance the long-term immobilization of radioactive wastes, ferrihydrite nanoparticles were incorporated into cementitious materials. The effects of ferrihydrite nanoparticles on the physicochemical and mechanical properties of cementitious materials and the immobilization of uranium (U), strontium (Sr) and cesium (Cs) were investigated. Adding ferrihydrite nanoparticles at 0.65%, 1.30%, 3.90% and 6.50% of cement weight slightly improved compressive strength by 5-11%, but dramatically reduced U leaching by 50-57%. The enhanced U immobilization was attributed to the strong adsorption of U by ferrihydrite nanoparticles, and the structural incorporation of U into hematite formed during ferrihydrite recrystallization. Although ferrihydrite nanoparticles had weaker effect than hematite nanoparticles on improving cement hydration and reducing permeability, they exhibit stronger U immobilization capacity. In contrast, incorporating ferrihydrite nanoparticles into cementitious materials had no significant effects on Cs and Sr leaching and no detectable adsorption of Sr and Cs. This study elucidated the fundamental differences in the interactions between ferrihydrite nanoparticles and U, Sr or Cs within cementitious systems that led to the distinctive immobilization mechanisms for these radionuclides. It generated new mechanistic understandings of U, Sr and Cs leaching from cementitious barriers modified by Fe-based nanoparticles, and proposed a new approach for enhancing long-term immobilization of U.

Effects of chemosorbed arsenate groups on the mesoporous titania morphology and enhanced adsorption properties towards Sr(II) cations

Mesoporous titania samples modified by sodium arsenate to form arsenate functionalities were synthesized using titanium aqua complex [Ті(ОН2)6]3+·3Cl− and salt Na3AsO4 as precursors. The structure, morphology, and texture of the samples were characterized using XRD, IR spectroscopy, TG-DTA, TEM, and nitrogen adsorption methods. The adsorption properties of the samples located in the aqueous media were analyzed with respect to Sr(II) removal. The modified titania samples have a large specific surface area (up to 405 m2/g) and appropriate pore volume (up to 0.26 сm3/g) with a major contribution of mesopores. The maximum adsorption capacity of modified titania (with 4% of arsenate groups) towards Sr(II) is 262.9 mg/g. It is much smaller for unmodified titania (92.1 mg/g). The equilibrium adsorption isotherms were fitted using the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The results revealed that the adsorption equilibrium data match with the Langmuir isotherm model (R2 > 0.993) that corresponds to the localized adsorption onto uniform surface. The adsorption kinetics fitted well by the pseudo-second-order kinetic model. A possible adsorption mechanism was analyzed. Sr(II) removal can be attributed to = Ti(О2AsОOН) groups located at a mesopore surface of the adsorbents. The materials demonstrate the stability of the degree of the Sr(II) adsorption during ten cycles. Thus, arsenate-modified mesoporous titania could be considered as an effective adsorbent for Sr(II) removal from wastewater.

Sulfone-modified chitosan as selective adsorbent for the extraction of toxic Hg(II) metal ions

In this study, a new category of sulfone-modified chitosan derivatives as surface-selective adsorbents for the extraction of toxic Hg(II) metal has been synthesized in good yield. Sulfone-modified chitosan/5–20 based on variable loading of the corresponding phenacyl bromide (5, 10, 15, and 20% with respect to the original weight of the pure chitosan) was synthesized. The β-ketosulfone derivative, namely 1–(4-bromophenyl)-2-(phenylsulfonyl)ethanone, was first prepared by treatment of the corresponding phenacyl bromide with a sufficient amount of sodium benzene sulfinate; its chemical structure was confirmed by spectral analyses, including Fourier transform infrared spectroscopy, 1H-NMR, 13C-NMR, and mass spectrometry. Then, sulfone-modified chitosan/5–20 derivatives were synthesized by the interaction of chitosan with a freshly prepared p-bromo-β-ketosulfone derivative in a mildly acidic aqueous solution using the solution-blending technique. Sulfone-modified chitosan/5–20 derivatives were identified and characterized using common characterization techniques, including Fourier transform infrared spectroscopy, field-emission scanning electron microscope, powder X-ray diffraction, and thermal behaviour. A strong interaction was displayed between chitosan and its corresponding β-ketosulfones in powder X-ray diffraction, which was confirmed by significant 2θ shifts. Sulfone-modified chitosan/5–20 derivatives were detected as catalysts, which efficiently increased the thermal decomposition of pure chitosan. More particularly, the efficiency of sulfone-modified chitosan/5–20 derivatives for Hg(II), Pb(II), Ni(II), Al(III), Sr(II), Cr(III), Fe(III), Zn(II), and Mn(II) detection and adsorption was also investigated using inductively coupled plasma optical emission spectrometry. The sulfone-modified chitosan/5 derivative exhibited the highest adsorption efficiency. The most effective quantitative adsorption onto the sulfone-modified chitosan/5 surface was detected at pH = 2. In addition to that, the adsorption isotherm showed that the adsorption capacity of sulfone-modified chitosan/5 for Hg(II) was 122.47 mg g−1 and that its adsorption isotherm was in agreement with the Langmuir adsorption isotherm.

Simultaneous Adsorption and Incorporation of Sr2+ at the Barite (001)–Water Interface

Ionically bonded minerals are ubiquitous and play a determinative role in controlling the mobility of toxic metals in natural environments. However, little is known about the mechanism of ion uptake by these mineral surfaces. Here, the sorption of strontium ions (Sr2+) to the barite (001)–water interface was studied using a combination of synchrotron X-ray scattering and three types of computational simulations (density functional theory, classical molecular dynamics (CMD), and CMD-metadynamics). In situ resonant anomalous X-ray reflectivity (RAXR) revealed that Sr2+ adsorbed on the barite surface as inner-sphere surface complexes and was incorporated within the outermost barite atomic layers. Density functional theory combined with CMD simulations confirmed the thermodynamic stability of these species, demonstrating almost equal magnitudes in the free energy of sorption between these species. Metadynamics simulations showed a more detailed feature in the free energy landscape for metal adsorption where a...

Sorption/desorption study of strontium on Ain Oussera soils around the Es-Salam reactor facility

Four types of undisturbed soils around the Es-Salam reactor (Algeria) were used to evaluate the sorption behavior of strontium. The batch study was carried out under different experimental conditions. The kinetics were well fited by pseudosecond order model. Soils’s activation energies were 12.37, 14.76, 15.5 and 16.17 kJ mol−1, corresponding to ion-exchange-type sorption. Sorption was exothermic (ΔH° < 0), spontaneous (ΔG° < 0) and favorable at low temperature. Competing cations, particularly Ca2+ reduce the Sr adsorption. Desorption reaction showed a higher value of Sr in the easily extractible phase indicating a relative availability of the element.

Adsorption of Sr(II) from water by mercerized bacterial cellulose membrane modified with EDTA

The treatment of low-level radioactive wastewater is a critical and considerable challenge. Bacterial cellulose membrane (BCM) modified with ethylenediaminetetraacetic acid (EDTA) using (3-aminopropyl) triethoxysilane (APTES) as a crosslinker were used to remove Sr2+ in this work. SEM, XPS, and FTIR were used to characterize the morphology, structure, chemical shift, and functional groups of the as-prepared adsorbent. The synthesized BCM@APTES-EDTA presented a three-layer structure of membrane-net-membrane with nano-sized fibers (<100 nm). The adsorption of Sr2+ onto BCM@APTES-EDTA was investigated as a function of contact time and initial concentration of Sr2+. Results showed that the adsorption of Sr2+ followed the pseudo second-order kinetic model (R2 = 0.999), and fitted well with the Langmuir isotherm model (R2 = 0.996). The maximum adsorption capacity was calculated to be 44.86 mg g-1, which was comparable to other adsorbents. Additionally, the mechanism of Sr2+ adsorbed by the as-prepared adsorbent was studied through FTIR and XPS analysis, which indicated that the tertiary amines and carboxylate from grafted EDTA participated in the adsorption of Sr2+.

Effects of enhanced clusterization of water at a surface of partially silylated nanosilica on adsorption of cations and anions from aqueous media

Adsorption of metal species Ba(II), Sr(II), Zn(II), Ca(II), and Mg(II) and anions Cl−, Br−, and I− at a surface of unmodified and partially silylated nanosilica A-300 was studied in aqueous media upon changes in the degree of substitution of silanols to trimethylsilyl groups (ΘTMS) at ΘTMS = 0.272–0.483. The cation adsorption increases in series Sr(II) < Mg(II) < Zn(II) < Ca(II) < Ba(II) with increasing value of ΘTMS. Nanosilica at ΘTMS = 0.483 adsorbs 1.8 mmol/g of Ba(II) from 0.01 M BaCl2 solution that is three times higher than that for the unmodified silica. Among anions, the adsorption of Cl− is maximal (1.34 mmol/g of Cl− from 0.01 M CaCl2 solution) onto silylated nanosilica at ΘTMS = 0.272 that is eight times greater than that for the unmodified nanosilica. An increased adsorption ability of partially silylated nanosilica in comparison to unmodified silica can be explained by nonuniformity of a modified silica surface resulting in enhanced clusterization of adsorbed water that leads to reduction of its activity as a solvent. Therefore, the desolvation energy decreases for adsorbed cations and anions having smaller solvated shells near the modified silica surface.

Adsorption and Separation of Sr(II) and Y(III) by Extraction Chromatography Using HDEHP-impregnated Adsorbent

Adsorption and Separation of Sr(II) and Y(III) by Extraction Chromatography Using HDEHP-impregnated Adsorbent

Strontium in fin whale baleen: A potential tracer of mysticete movements across the oceans?

Strontium is a metal broadly distributed in oceanic waters, where its concentrations follow gradients mainly driven by oceanographic and biological factors. Studies on terrestrial vertebrates show that Sr can accumulate in mammalian hair in amounts mainly related to the external environment, a property that has been scarcely investigated in aquatic mammals. Cetaceans are marine mammals whose skin is generally hairless, but the species belonging to the mysticete group feed through a filtering apparatus made of keratinous baleen plates that, like hair, grow continuously. During their annual latitudinal migrations, mysticetes cross water masses with variable chemo-physical characteristics that may be reflected in these tissues. In the present study, baleen plates were sampled from 10 fin whales obtained from NW Spain (N = 5) and SW Iceland (N = 5) to investigate Sr concentrations along the plates growth axis. Samples were taken longitudinally at regular 1 cm-intervals on each plate. Sr concentrations, determined through mass spectrometry, ranged from 5 to 40 mg kg−1 and increased from proximal to distal positions along plates. These results suggest a progressive adsorption of Sr on the plate surface, a process that also occurs in mammalian hair. Increasing trends were similar in the two regions but overall concentrations were significantly higher in NW Spain, reflecting different Sr baseline concentrations in the two areas and indicating isolation between the two whale populations. Some oscillations in Sr longitudinal trends were also detected, likely indicating that whales migrate across water masses with different Sr baselines. These results suggest that Sr concentrations in keratinous tissues of marine mammals can be used as ecological tracers of their migrations and habitat use.

Demonstration of Seawater Strontium (Sr(II)) Extraction and Enrichment by a Biosorption Technique through Continuous Column Operation

Alginate beads are promising strontium (Sr(II)) adsorbents because of their high Sr(II) adsorption capacity and cost-effectiveness. This study analyzed the selective adsorption by alginate beads in the column operation mode to recover and enrich Sr(II) from seawater. Alginate beads of 2–8 wt % were prepared and bead size was varied to optimize the column module. All beads expanded 10–20% in seawater because of its high ion content, but decreased slightly in 0.1 M HCl, which was used in the eluent but did not cause bead destruction after reaction for 14 days. In the batch adsorption experiment, 8 wt % alginate beads showed a maximum Sr(II) uptake from seawater of 147.3 mg/dm3, a concentration 25-fold higher than the Sr(II) concentration (≈ 6.1 mg/L) in seawater. Using a continuous Sr(II) adsorption column system, Sr(II) adsorption equilibrium was achieved at 12 h with a 50–100 mL/min flow rate. Elution from this column yielded an eluent containing 24.3 mg/L of Sr(II). Three consecutive elutions with pH con...