Study Of Selective Adsorption Research Articles

Microporous organic nanotube networks from hyper cross-linking core-shell bottlebrush copolymers for selective adsorption study

We report a synthesis of microporous organic nanotube networks (MONNs) by a combination of hyper cross-linking and molecular templating of core-shell bottlebrush copolymers. The intrabrush and interbrush cross-linking of polystyrene (PS) shell layer in the core-shell bottlebrush copolymers led to the formation of micropores and large-sized nanopores (meso/macrospores) in MONNs, respectively, while selective removal of polylactide (PLA) core layer generated mesoporous tubular structure. The size of PLA-templated mesoporous cores and porous structure both at micro- and meso-scale could be controlled by simple tuning of the ratio of core/shell or the PLA core fraction in the bottlebrush precursors. Moreover, the resultant MONNs showed a highly selective adsorption capacity for the positively charged dyes on the basis of multi-porosity and carboxylate group-rich structure. In addition, MONNs also exhibited effective performance in size-selective adsorption of biomacromolecules. This work represents a new avenue for the preparation of MONNs and also provides a new application for molecular bottlebrushes in nanotechnology.

Syntheses, crystallization and selective dye adsorption of three Co(II) coordination polymers via one-pot reaction

Three novel Co(II) coordination polymers, namely [Co(HL)(4,4′-bibp)]n (1), [Co(HL)(4,4′-bibp)]n (2) and {[Co2(L)(4,4′-bibp)2(H2O)3(HCOO)]·2H2O·HCOOH}n (3) (H3L=5-(2′′-carboxylphenoxy)isophthalic, 4,4′-bibp=4,4′-bis(imidazol-1-yl)biphenyl) were synthesized through one-pot reaction under co-crystallization conditions. These complexes were characterized by elemental analysis, IR spectra, powder X-ray diffraction (PXRD), thermogravimetric (TG) analysis and single-crystal X-ray diffraction. Complexes 1 and 2 were supramolecular isomers with different 2D configurations. Complex 1 shows a sql 2D-network with a [Co(HL2−)]n single-strand helix chain and another [Co(4,4′-bibp)]n single-strand helix chain, which are further assembled into 3D supramolecular architectures through H-bonds and C–H⋯N bonds. While complex 2 exhibits another 2D-network with two different [Co(HL2−)]n helix chains (left and right) and one [Co(4,4′-bibp)]n zigzag chain, which further constructing a 3D supramolecular structure through H-bonds. Compared with 1 and 2, 3 also shows a sql 2D-network with a bigger channel which influenced by the coordination environment of metal ions. Furthermore, the selective dye adsorption studies indicate that complex 1 can highly and selectively adsorb Methyl Orange (MO) in a short time, and complex 2 shows a highly adsorption activity for Alizarin Red S (ARS) than Methyl Orange, and complex 3 can selectively adsorb Methyl Orange.

A novel surface imprinted polymer/magnetic hydroxyapatite nanocomposite for selective dibenzothiophene scavenging

Highly selective adsorbent for dibenzothiophene (DBT) was successfully designed and prepared. Molecularly imprinted polymer (MIP) and magnetic hydroxyapatite (MHAP) were used as building blocks for the novel nanocomposite adsorbent. MIP/MHAP was synthesized by grafting polymerization and surface molecular imprinting using DBT as a template molecule. The microstructure and morphology of the designed nanoadsorbent were examined via FTIR, SEM and VSM. Specific surface area and pore size distribution were determined by Quantachrome Nova 3200S automated gas sorption apparatus. Additionally, static adsorption experiments, isotherms and selective recognition adsorption studies were carried out. Reversed-phase high performance liquid chromatography (RP-HPLC) was used to determine DBT. The experimental data exhibits excellent adsorption capacity for DBT reaches 247mg/g within 60min. Competitive adsorption results proved that MIP/MHAP have a greater affinity towards DBT molecules than benzothiophene analogues. Pseudo-second-order model and the Langmuir isotherm were used to describe the adsorption process.

Reusability and selective adsorption of Pb2+ on chitosan/P(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylic acid) hydrogel

Reusability and selective adsorption toward Pb2+ with the coexistence of Cd2+, Co2+, Cu2+ and Ni2+ ions on chitosan/P(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylic acid) [CS/P(AMPS-co-AA)] hydrogel, a multi-functionalized adsorbent containing –NH2, –OH, –COOH and –SO3H groups was studied. The CS/P(AMPS-co-AA) was prepared in aqueous solution by a simple one-step procedure using glow discharge electrolysis plasma technique. The reusability of adsorbent in HNO3, EDTA-2Na and EDTA-4Na was investigated in detail. The competitive adsorption of the metal ions at the initial stage was compared between their equal mass concentration and equal molar concentration. In addition, the adsorption mechanism of the adsorbent for adsorption of Pb2+ was also analyzed by XPS. The results showed that the optimum pH of adsorption was 4.8, and time of adsorption equilibrium was about 180 min. Adsorption kinetics fitted well in the pseudo second-order model. The equilibrium adsorption capacities of Pb2+, Cd2+, Co2+, Cu2+, and Ni2+ at pH 4.8 were obtained as 673.3, 358.3, 176.7, 235.0 and 171.7 mg g−1, in their given order. The adsorbent displayed an excellent reusability using 0.015 mol L−1 EDTA-4Na solution as the eluent, and the desorption ratio could not correctly reflect the true characteristics of adsorption/desorption process. Moreover, the adsorbent showed good adsorption selectivity for Pb2+. The molar adsorption capacity at the initial stage with equal molar concentration was more reliable than the mass adsorption capacity during the study of selective adsorption. According to the XPS results, the adsorption of Pb2+ ions by the CS/P(AMPS-co-AA) absorbent could be attributed to the coordination between N atom and Pb2+ and ion-exchange between Na+ and Pb2+.

Synthesis of Fe Ionic-Imprinted Polyeugenol Using Polyethylene Glycol Diglycidilether as Cross-Linking Agent for Sorption of Fe(III)

Fe-Ionic Imprinted Polymer (IIP) from polyeugenol as base polymer and polyethylene glycol diglycidyl ether (PEGDE) as cross-linking agent had been synthesized to adsorb Fe(III) from aqueous media. The non-imprinting material (NIP) and polyeugenol were used in the adsorption study as control. Synthesis work included polymerization, template uploading, crosslinking and template removal, optimized for different template ion upload pH and concentrations. The polymers were characterized by FTIR spectroscopy, XRD and SEM-EDX, followed by adsorption test to study the adsorption kinetics and isotherms for all adsorbents. Selective adsorption study of IIP was carried out using binary mixtures of Fe(III) and Cr(III), Pb(II), Cd(II). Experimental results showed that the optimum conditions for the synthesis was template upload pH of 3, Fe/polyeugenol ratio of 1 mg/g, while the optimum adsorption pH was 3. The adsorption mechanism of Fe(III) on all adsorbents was dominated by hydrogen bond formation. The adsorption kinetics followed the pseudo-second-order model while the equilibrium data was best explained by the Langmuir isotherm model. The adsorption capacity of Fe(III) on the IIP was 12.73 mg/g, higher than that of the other adsorbents. Results also show that IIP-Fe was more selective toward Fe than NIP by 2.69 (Cd), 1.66 (Cr) and 1.6 (Pb) fold, respectively.

Theoretical and experimental studies on the performances of barbital-imprinted systems.

By using density functional theory, we studied the interaction process between barbital and 2-vinyl-4,6-diamino-1,3,5-triazine in acetonitrile at 333 K. Barbital and 2-vinyl-4,6-diamino-1,3,5-triazine were used as the template and functional monomer, respectively. The molecularly imprinted polymer microspheres containing barbital and 2-vinyl-4,6-diamino-1,3,5-triazine were synthesized through precipitation polymerization. After removing the template molecule barbital, the average diameter of the obtained molecularly imprinted polymers was 1.45 μm. By optimizing the molar ratio of barbital and the 2-vinyl-4,6-diamino-1,3,5-triazine, the resulting molecularly imprinted polymers showed the highest adsorption for the barbital. The analysis of the Scatchard plot revealed that the dissociation constant (Kd ) and apparent maximum adsorption quantity (Qmax ) of the molecularly imprinted polymers were 30.69 mg/L and 8.68 mg/g, respectively. The study of selective adsorption showed that molecularly imprinted polymers exhibited higher selectivity for barbtital than that for 1,3-dimethyl barbituric acid and pentobarbital. Herein, the studies can provide theoretical and experimental references for the barbital-imprinted system.

Hollow poly(cyclotriphosphazene-co-phloroglucinol) microspheres: An effective and selective adsorbent for the removal of cationic dyes from aqueous solution

Hollow poly(cyclotriphosphazene-co-phloroglucinol) (PCPP) microspheres, synthesized by a facile precipitation polymerization method and then a simple solvent-treatment procedure, were evaluated as a potential adsorbent for the removal of cationic dyes from aqueous solution. The adsorbent was characterized by SEM, TEM, FTIR, N2 adsorption/desorption isotherms, zeta potential and particle size analysis. The adsorption process with respect to operating parameters was investigated to evaluate the adsorption characteristics of the hollow PCCP microspheres for methylene blue (MB). Systematic research including equilibrium, kinetics and thermodynamic studies were performed. The results showed the hollow PCCP microsphere was a potential adsorbent with an adsorption capacity of 50.7mg/g at 298K. The adsorption behavior followed the pseudo-second-order kinetic model and the adsorption equilibrium data obeyed the Langmuir isotherm well. Thermodynamic analyses confirmed that the adsorption was a physisorption process with endothermic, spontaneous and random characteristics. In addition, the possible adsorption mechanism was also proposed based on the experimental results. The study of selective adsorption further indicated the hollow PCCP microspheres could also remove other cationic dyes efficiently and be used a selective adsorbent.

Theoretical study of conformational disorder and selective adsorption of small organic molecules in the flexible metal-organic framework material MIL-53-Fe

Many of the potential applications for metal-organic framework (MOF) materials require molecular level understanding of their adsorption of small organic molecules, which are not readily accessible from experiment. Through high-level van der Waals corrected, hybrid density functional theory calculations, we elucidate the adsorption configurations of several, representative small organic guest molecules in an archetypal flexible MOF material, MIL-53-Fe. The predicted relative energies between low-energy adsorption configurations of 1,4-benzoquinone in MIL-53-Fe are in very good agreement with the thermal transition temperatures observed experimentally and suggest that thermodynamic factors govern the precise arrangements and loading of guests in the MOF host. Experimentally observed conformational disorder of small organic molecules in MIL-53-Fe is explained by predicted multiple low-energy adsorption configurations that are comparable with the thermal energy of the guests, kT. Finally, we show that the previously observed selective adsorption of pyridine and 2,6-lutidine molecules in water by MIL-53-Fe, can be rationalised through a careful analysis of the host–guest and guest–guest interactions and is controlled by thermodynamic factors.

Study of selective adsorption of aromatic compounds from solutions by the flexible MIL-53(Al) metal-organic framework

The dynamic method under conditions close to equilibrium was applied to study the liquid-phase adsorption in the Henry region for a series of aromatic compounds on the MIL-53(Al) metal-organic framework at different temperatures. The interpretation of the obtained experimental adsorption data was based on the TOPOS analysis of the structure of the cavities in the MIL-53(Al) framework using the Voronoi—Dirichlet polyhedra concept. It is shown that the adsorption activity of the investigated material under the liquid-phase conditions is governed by a possible expansion of the channels and cavities in the structure and by a breathing effect of the structure caused by the temperature variation. The selectivity of adsorption shown by MIL-53(Al) for a series of the studied compounds is due to the adsorbate—adsorbent π—π-interaction and hydrogen bonding of adsorbate molecules with Bronsted acid sites of the metal-organic framework. High adsorption selectivity of the MIL-53(Al) framework were found for compounds differed in the number of aromatic rings in the molecule and the presence of the methyl substituent, as well as for aromatic hydrocarbons and their sulfur-containing heterocyclic analogs.

Biosorption of palladium(II) from aqueous solution by grafting chitosan on persimmon tannin extract

A low-cost and environmentally green biosorbent (PTCS) was prepared by grafting chitosan onto persimmon tannin extract and its potentiality for efficient adsorption of palladium ion (Pd(II)) from aqueous solution was evaluated. Various adsorption parameters such as pH, the initial Pd(II) concentration and temperature were investigated. The maximum adsorption capacity reached 330mg/g at 323K and pH 5.0 when the initial Pd(II) concentration was 100mg/L. The equilibrium adsorption data were satisfactorily fitted with Freundlich isotherm model and biosorption kinetics was found to be in good agreement with pseudo-second-order kinetics model. Thermodynamic calculations indicated that the adsorption process was endothermic and spontaneous in nature because of the negative value of free energy change (ΔG) and positive value of enthalpy change (ΔH). The positive value of entropy change (ΔS) revealed the increased randomness at the solid–liquid interface. FT-IR and XRD analysis verified that Pd(II) adsorption on PTCS was electrostatic interaction and redox reaction. Moreover, selective adsorption study revealed that the adsorbent exhibited good adsorption ability to Pd(II) in the mixture metal ions solutions. All these results indicated that the PTCS biosorbent could be used as a low-cost alternative for the adsorption of Pd(II) in waste-water treatment.

A Pilot Study of Selective Lipopolysaccharide Adsorption and Coupled Plasma Filtration and Adsorption in Adult Patients with Severe Sepsis

Aim: To evaluate the safety and effectiveness of combined extracorporeal therapy in patients with severe sepsis after cardiac surgery. Materials and Methods: Twenty patients received combined extracorporeal therapy (LPS-adsorption with Toraymyxin columns + CPFA). The inclusion criteria were clinical signs of severe sepsis, EAA = 0.6, and PCT >2 ng/ml. 20 comparable patients in the control group received only standard therapy. Results: Each patient in the study group received 2 daily treatments of combined extracorporeal therapy. In contrast to controls, we noted an increase in the values of MAP from 73 to 82 mm Hg, (p < 0.001) and the mean oxygenation index (from 180 to 246, p < 0.001), decrease of EAA from 0.77 to 0.55, p < 0.001, and PCT (from 6.23 to 2.83 ng/ml, p < 0.001). The 28-day survival rate was 65 and 35% in the study and control groups respectively, p = 0.11. Conclusion: The combined use of LPS-adsorption and CPFA in a single circuit with standard therapy is a safe and possibly effective adjunctive method for treating severe sepsis.

Theoretical Design and Experimental Performance Research on Barbital Imprinting Polymer

On the basis of the density functional theory of M062 X,we performed the interaction processes between the barbital(BAR) and different functional monomers by Gaussian 09 software. The functional monomers are methacrylic acid( MAA),acrylamide( AM),4-vinylpyridine(4-Vpy),and N,N'-methylenebisacrylamide(MBAD),respectively. The excellent functional monomer was optimized according to the hydrogen bond and binding energies(ΔE). The calculation results indicated that the number of hydrogen bonds was the largest,the bond length was the shortest,the ΔE was the lowest,and the interaction was the strongest between the MAA and the template molecule when the molar ratio of reaction for BAR-MAA was 1∶ 6. The molecular imprinted polymer microspheres(MIPs) composed of the BAR and MAA was synthesized by precipitation polymerization. The results showed that the stability and selective adsorption for MAA and BAR were the highest compared with the AM,4-Vpy and MBAD. The average diameters of BAR-MIPs synthesized in acetonitrile was 190 nm. Analysis of the Scatchard plot revealed that the binding sites of BAR-MIPs to BAR were equal class under the studied concentration range,the dissociation constant(Kd) and apparent maximum adsorption quantity(Qmax) of BAR-MIPs were 63.3 mg/L and 17.5 mg/g,respectively. The thermodynamic study indicated that the adsorption of BAR-MIPs to BAR was an exothermic process,and the adsorption effect was better under the 293 K. The study of selective adsorption showed that BAR-MIPs had higher selectivity for BAR than that for 1,3-dimethyl barbituric acid( DMBA),2-thiobarbituric acid( TMB),and pelltobarbitalum natricum(PBS). The studies can provide theoretical and experimental bases for the BAR molecular imprinted system,such as the selection of functional monomers,the optimization of reaction ratios,and the prediction of adsorption performance.

Adsorption of U(VI) from aqueous solution by sulfonated ordered mesoporous carbon

The sulfonated mesoporous carbon (CMK-3-SO3H) prepared by functionalizing mesoporous carbon (CMK-3) via vapor transfer method has been explored for the removal and recovery of uranium from aqueous solutions. The influences of different experimental parameters such as solution pH, initial concentration, contact time and temperature on adsorption were investigated. The results showed that CMK-3-SO3H has the highest uranium sorption capacity at initial pH of 5.0 and contact time of 120 min, and the adsorption process could be better described by the pseudo-second-order model and Langmuir isotherm. Selective adsorption studies showed that the CMK-3-SO3H could selectively remove of U(VI), and the selectivity coefficients of mesoporous carbon in the presence of co-existing ions, Mg(II), Zn(II), Mn(II), Cu(II), Ni(II), Sr(II) and Hg(II) improved after functionalization.

Removal of thorium(IV) from aqueous solutions by carboxyl-rich hydrothermal carbon spheres through low-temperature heat treatment in air

The number of carboxyl groups on the surface of hydrothermal carbon spheres (HCSs) has been largely increased by simply heating at lower temperature in air. The textural properties of the carboxyl-rich hydrothermal carbon spheres were characterized using Boehm titrations, scanning electron microscopy, Fourier transform infrared spectrometer (FT-IR), and elemental analysis (EA). The result of Boehm titrations indicated that the content of carboxyl groups on HCSs increased significantly from 0.53 to 3.81 mmol/g after heat treatment at 300°C, which was also confirmed by FT-IR and EA qualitatively. The ability of heat-treated HCSs has been explored for the removal and recovery of thorium from aqueous solutions, and the influences of different experimental parameters, such as solution pH, heat treatment temperature, contact time, initial thorium concentration, temperature, and ionic strength on adsorption, were investigated. The Th(IV) sorption capacity of HCSs increased from 17.76 to 69.93 mg/g after heat treatment at 300°C for 5 h. Adsorption kinetics was better described by the pseudo-second-order model and the adsorption process was well defined by the Langmuir isotherm. Thermodynamic parameters indicated that the adsorption process was feasible, endothermic, and spontaneous in nature. Selective adsorption studies showed that the heat-treated HCSs could selectively remove Th(IV), and the selectivity coefficients were improved after heat treatment in the presence of coexisting ions, Na(I), Ni(II), Sr(II), Mn(II), Mg(II), Zn(II), and Hg(II). The adsorbed heat-treated HCSs could be effectively regenerated by 1.0 mol/L HCl solution for the removal and recovery of Th(IV). Complete removal (≈100%) of Th(IV) from 1.0 L artificial sea water containing 25.0 mg Th(IV) ions was possible with 1.5g heat-treated HCSs.

Adsorptive removal of U(VI) from aqueous solution by hydrothermal carbon spheres with phosphate group

The phosphorylated hydrothermal carbon spheres (HCS-PO4) were developed by functionalizing hydrothermal carbon spheres (HCS) with o-phosphoethanolamine, and the structure and textural property were characterized by SEM and FT-IR. The parameters that affect the uranium(VI) sorption, such as solution pH, initial U(VI) concentration, contact time, and temperature, had been investigated. The HCS-PO4 showed the highest uranium sorption capacity at initial pH 6.0 and contact time of 120 min. The adsorption kinetics was better described by the pseudo-second-order model, and the adsorption process could be well defined by the Langmuir isotherm and the maximum monolayer adsorption capacity increased from 80.00 to 434.78 mg/g after phosphorylation. The thermodynamic parameters, ∆G° (298 K), ∆H° and ∆S°, demonstrated shown that the sorption process of U(VI) onto HCS-PO4 was feasible, spontaneous and endothermic in nature. The spent HCS-PO4 could be effectively regenerated by 0.1 mol/L EDTA solution for the removal and recovery of U(VI) and reused for ten cycles at least. Selective adsorption studies showed that the HCS-PO4 could selectively remove U(VI), and the selectivity coefficients of HCS in the presence of co-existing ions, Mg(II), Na(I), Zn(II), Mn(II),Co(II), Ni(II), Sr(II), Cs(I) and Hg(II) improved after functionalization.

Fabrication of nano- to micron-sized patterns using zeolites: Its application in BSA adsorption

Nano to micron-sized zeolite A (Z-A) and silicalite (Z-SIL) patterns were generated using the combinations of electron beam lithography (EBL) or photolithography (PL) with direct attachment method to be able to generate differentiated areas on a single surface in a cheap and facile way. The possibility to generate minimum sized zeolite patterns on top of zeolite monolayers was investigated by using EBL to understand the capability of the system for the first time. Also generation of large scale zeolite patterns on top of a different zeolite monolayer was investigated by using PL allowing the generation of differentiated surfaces for various potential applications such as selective adsorption studies. With this combination, it was shown that creating 3D zeolite architectures of different types with a perfect control in all dimensions was possible without the using any chemical linker. In order to test the potential different behaviors that zeolites of different properties are offering in the adsorption of biomolecules, zeolite patterned surfaces developed by PL were subjected to adsorption studies with bovine serum albumin (BSA). Irrespective of zeolite type, BSA always preferred the patterned regions rather than the underlying zeolite monolayers. It can be speculated that the obtained difference in roughness values facilitates the protein to be selectively adsorbed onto surfaces with increased roughness, i.e., the patterned regions. Moreover, we observed ∼2-fold fluorescence intensity difference between Z-SIL and Z-A patterns, which were subjected to FITC-BSA solution. Hydrophobic interactions and charge repulsion are considered as two critical forces responsible for the observed adsorption differences.

Removal of uranium(VI) from aqueous solutions by new phosphorus-containing carbon spheres synthesized via one-step hydrothermal carbonization of glucose in the presence of phosphoric acid

The novel phosphorus-rich hydrothermal carbon spheres (HCSs–PO4) have been synthesized via one-step hydrothermal carbonization of glucose in the presence of phosphoric acid. The textural and surface chemistry properties were characterized using Boehm titrations, scanning electron microscopy and Fourier transform infrared spectrometer. The content of oxygen-containing functional groups on the surface of HCSs increased from 0.053 to 1.009 mmol g−1 by phosphate group modification. The adsorption ability of HCSs–PO4 has been explored for the removal of uranium from aqueous solutions. The adsorption kinetic data were best described by the pseudo-second-order equation. Adsorption process could be well defined by the Langmuir isotherm, the adsorption capacity of HCSs increased from 80.00 to 285.70 mg g−1 after phosphate group modification. And thermodynamic parameters indicated the adsorption process was feasible,endothermic and spontaneous. Selective adsorption studies showed that the HCSs–PO4 could selectively remove U(VI), and the selectivity coefficients had been improved in the presence of co-existing ions, Na(I), Ni(II), Sr(II), Mn(II), Mg(II) and Zn(II). Complete removal (99.9 %) of U(VI) from 1.0 L industry wastewater containing 15.0 mg U(VI) ions was possible with 12.0 g HCSs–PO4.

Enhanced and selective adsorption of heavy metal ions on ion-imprinted simultaneous interpenetrating network hydrogels

Ion recognition-based separation techniques have received much attention because of the high selectivity for target ions. In this study, a novel Cu(II) ion-imprinted hydrogel [Cu(II)–IIH] with interpenetrating network structure has been prepared to remove Cu(II) ions with high selectivity. The Cu(II)–IIH was prepared by free radical/cationic hybrid photopolymerization of acrylamide (AAm) and triethylene glycol divinyl ether (DVE-3) using Cu(II) ions as template. The ability of the Cu(II)–IIH to adsorb and remove Cu(II) ions from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed at pH 5.0, and the adsorption process could be well described by the Freundlich isotherm. The adsorption equilibrium was achieved within 16 min, and the kinetics of adsorption followed a pseudo-second-order rate equation. Selective adsorption study indicated that ion imprinting resulted in stronger affinity of the Cu(II)–IIH toward Cu(II) ions than other competitor metal ions compared with the non-imprinted hydrogel. The prepared Cu(II)–IIH was repeatedly used and regenerated for five times without a significant decrease in metal binding affinity.

Removal of uranium(VI) from aqueous solutions by carboxyl-rich hydrothermal carbon spheres through low-temperature heat treatment in air

Carboxyl-rich hydrothermal carbon spheres were prepared by simply heating pristine hydrothermal carbon spheres (HCSs) at lower temperature in air, and the textural properties were characterized using Boehm titrations, scanning electron microscopy, Fourier transform infrared spectrometer (FT-IR) and elemental-analysis. The result of Boehm titrations indicated that the content of carboxyl groups on HCSs increased significantly from 0.53 to 3.81 mmol/g after heat-treatment at 300 °C, which was also confirmed by FT-IR and EA qualitatively. The ability of heat-treated HCSs has been explored for the removal and recovery of uranium from aqueous solutions, and the influences of different experimental parameters, such as heat-treatment temperature, contact time and ionic strength, on adsorption were investigated. The U(VI) sorption capacity of HCSs increased from 55.0 to 179.95 mg/g after heat-treatment at 300 °C for 5 h. Selective adsorption studies showed that the heat-treated HCSs could selectively remove U(VI), and the selectivity coefficients were improved after heat-treatment in the presence of co-existing ions, Na(I), Ni(II), Sr(II), Mn(II), Mg(II) and Zn(II). The adsorbent HCSs could be effectively regenerated by 0.05 mol/L HCl solution for the removal and recovery of U(VI). Complete removal (99.0 %) of U(VI) from 1.0 L industry wastewater containing 15.0 mg U(VI) ions was possible with 5.0 g heat-treated HCSs. In addition, a reaction mechanism for newly generating carboxyl groups on pristine HCSs surface during heat-treatment process and uranyl ion interaction with carboxyl-rich hydrothermal carbon spheres were also supposed.

Thermoresponsive Ion-Imprinted Hydrogels with Interpenetrating Network Structure for Removal of Heavy Metal Ions

A novel thermoresponsive Cu(II) ion-imprinted hydrogel [Cu(II)-IIH] with interpenetrating network structure has been prepared to remove Cu(II) ions with high selectivity. The Cu(II)-IIH was prepared by free radical/cationic hybrid photopolymerization of N-isopropylacrylamide (NIPAM) and triethylene glycol divinyl ether (DVE-3) using Cu(II) ion as template. The Cu(II)-IIH was used to remove heavy metal ions from aqueous solution at 20 and 40oC. The Cu(II)-IIH selectively bound the template ion above a lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAM). The memory was fixed by shrinking above the LCST, and was deleted by swelling below the LCST. Selective adsorption study indicated that ion imprinting resulted in stronger affinity of the Cu(II)-IIH toward Cu(II) ions than other competitor metal ions compared with the non-imprinted hydrogel (NIH).