Ion-imprinted Mesoporous Silica Research Articles

Dual Ion-Imprinted Mesoporous Silica for Selective Adsorption of U(VI) and Cs(I) through Multiple Interactions.

Separation of uranium and cesium from low-level radioactive effluents (LLRE) is of great significance for sustainable development of the nuclear industry and for the environment. However, high salinity and massive coexisting ions of LLRE are giant challenges for the separation. To address the challenges, we report a strategy for efficient and simultaneous separation of uranium and cesium from a high-salt environment by dual ion-imprinted mesoporous silica based on multiple interactions. The as-prepared adsorbents can reach equilibrium for uranium and cesium within 1 h with a maximum capacity of 221.7 mg U g-1 and 34.5 mg Cs g-1. The sorption mechanism demonstrates that the highly active phenolic hydroxyl groups of imprinted cavities can extract uranium and cesium effectively through multiple interactions, including coulomb attraction, redox, ion exchange, and complexation. The synergism of multiple interactions and imprinted cavity endows the sorbent with good selectivity for uranium and cesium over other cations and with excellent salt tolerance. This work demonstrates a new strategy of selective extraction of nuclides by multifunction adsorbent through multiple interactions.

Fabrication and investigation of gold (III) ion-imprinted functionalized silica particles.

Au (III) ion-imprinted mesoporous silica particles (Au-Si-Py) was manufactured by the condensation reaction of (3-Aminopropyl)triethoxysilane (AT)and 2-pyridinecarboxaldehyde (Py). The obtained AT-Py Schiff base ligand was then coordinate with the template gold ions and the polymerizable gold-complex was allowed to gel in presence of tetraethoxysilane (TEOS) and then the coordinated gold ions were leached out of the obtained silica matrix using acidified thiourea solution. During the synthetic steps, the obtained materials were investigated utilizing advanced instrumental and spectral methods. Moreover, the morphological structure of both Au (III) ions imprinted Au-Si-Py and non-imprinted NI-Si-Py silica particles were visualized using scanning electron microscope (SEM). Various adsorption experiments had been carried out using both Au-Si-Py and NI-Si-Py to examine their potential for selective extraction of gold ions under different conditions.

Preparation and Adsorption Studies of Tridentate Monomer-functionalized Lead Ion Imprinted Mesoporous Silica

Two novel lead ion imprinted adsorbents were prepared based on tridentate functionalized mesoporous silica material. Adsorption sites and behaviors were investigated. The adsorbent BPMA-Pb-IIMS pos...

Ion-Imprinted Mesoporous Silica for Selective Removal of Uranium from Highly Acidic and Radioactive Effluent.

It is strategically important to recycle uranium from radioactive liquid wastes for future uranium supply of nuclear energy. However, it is still a challenge to adsorb uranium selectively from highly acidic and radioactive waste. In this paper, we report a novel strategy for effective uranium removal from highly acidic and radioactive media by surface ion-imprinted mesoporous silica sorbent. The sorbent was successfully synthesized by a co-condensation method with uranyl as the template ion and diethylphosphatoethyltriethoxysilane as the functional ligands. The pseudo-second-order model and Langmuir model showed better correlation with the sorption kinetic and isotherm data, and the sorption equilibrium could be reached within 40 min, the maximum adsorption capacity from Langmuir model was 80 mg/g in 1 mol/L nitric acid (HNO3) solution at 298.15 K. The sorbent showed faster kinetics and higher selectivity toward uranium over other ions compared with nonimprinted mesoporous and other previous sorbents. Furthermore, the ion-imprinted materials exhibited remarkable radioresistance stability and could be regenerated efficiently after five cycles. This work may provide a new approach for highly efficient sorption of uranium from strong HNO3 and radioactive media.

Novel Pb(II) ion-imprinted materials based on bis-pyrazolyl functionalized mesoporous silica for the selective removal of Pb(II) in water samples

Three highly efficient adsorbents Pb-IIMS-SBA-15, Pb-IIMS-MCM-41 and Pb-IIMS-FDU-12 for Pb(II) were prepared by grafting the functional monomer 4-(di (1H-pyrazol-1-yl) methyl) phenol (DPP) on corresponding mesoporous silicas with Pb(II) as temple. All these three Pb(II) ion-imprinted mesoporous silica (Pb-IIMS) were characterized by Fourier transform-infrared spectroscopy (FT-IR), solid-state 29Si and 13C NMR spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), N2 adsorption–desorption analysis and small angel X-ray diffraction (XRD). The adsorption experiments revealed three Pb-IIMS all possessed considerable adsorption performance for Pb(II), their adsorption profiles obeyed pseudo-second-order kinetics and Langmuir isotherm model. Compared with their corresponding non-imprinted materials, three Pb-IIMS displayed satisfactory selectivity to Pb(II) over seven competing metal ions. Among them, Pb-IIMS-MCM-41 particularly owned outstanding adsorption performance and selectivity, the maximum adsorption capacity as high as 344.8 mg g−1, as well as excellent reusability through twelve adsorption-desorption cycles. Additionally, Pb-IIMS-MCM-41 was employed as packing material to construct a solid-phase extraction column for detection of Pb(II), which exhibited detection limit of 0.015 μg L−1, then method was successfully applied to the removal and determination of trace Pb(II) in practical water samples.

A Facile Synthesis of Ion Imprinted Mesoporous Silica Adsorbents by a Co-Condensation Pathway and Application in a Fixed-Bed Column Study for Lead Removal

Highly selective lead ion imprinted mesoporous silica adsorbents (PbII-IMS) were prepared through a co-condensation pathway with 3-(γ-aminoethylamino)propyltrimethoxysilane (AAPTS) (PbII-IMS-NN) and 3-aminepropyltriethoxysilyl (APTES) (PbII-IMS-N) as monomers. The prepared adsorbents were characterised by FT-IR spectroscopy, X-ray photoelectron spectroscopy, power X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, and nitrogen adsorption–desorption techniques. The results showed that the synthesised adsorbents presented a highly ordered mesoporous structure. In comparison with PbII-IMS-N, PbII-IMS-NN demonstrated a higher adsorption capacity in a series of static and dynamic adsorption experiments, and was further applied to a continuous fixed-bed column study under different conditions. It was found that the breakthrough time of the fixed-bed increased with an increase in bed depth, but decreased with increased flow rate and initial PbII concentration, and the dynamic adsorption data was more consistent with the Thomas model than the Adams–Bohart model. Furthermore, the PbII-IMS-NN showed a greater recognition and binding affinity towards the target lead ions than PbII-IMS-N.

Preparation of ion-imprinted mesoporous silica SBA-15 functionalized with triglycine for selective adsorption of Co(II)

A novel Co(II)-imprinted polymer (Co(II)-IIP) aimed at the selective adsorption and separation of Co(II) was prepared by modifying the surface of ordered mesoporous silica SBA-15 with triglycine (Gly–Gly–Gly) in the presence of Co(II). The prepared polymer was characterized by FT-IR, SEM, TEM and N2 adsorption–desorption techniques. The results showed that the synthesized polymer maintained high ordered mesoporous structure. The factors affecting the separation and preconcentration of the target Co(II), including solution pH, temperature, time for adsorption equilibrium, and conditions of elution were investigated in detail. The kinetics adsorption and adsorption capacity of Co(II)-IIP were estimated using batch mode experiments. The mechanism for static adsorption of Co(II) onto Co(II)-IIP was found to follow pseudo-second-order and Freundlich isotherm model. Compared with the non-imprinted polymer (NIP), the Co(II)-IIP exhibited faster adsorption rate and higher adsorption capacity. The adsorption equilibrium for Co(II)-IIP could be reached in 50min, and the maximum static adsorption capacity obtained at 25°C was 181.67mgg−1. Furthermore, the Co(II)-IIP showed excellent recognition and binding affinity toward the target cobalt ions, and the relative selectivity coefficient (k′) values of Co(II)/Fe(II), Co(II)/Cu(II), Co(II)/Zn(II) and Co(II)/Ni(II) were 19.64, 18.29, 22.03 and 27.43, respectively. Desorption and regeneration studies suggested that the prepared Co(II)-IIP could be reused five times without an obvious decrease in adsorption capacity. The results showed that this novel adsorbent could be employed as an effective material for the selective removal of Co(II) from aqueous solutions.

Ion-imprinted mesoporous silica hybrids for selective recognition of target metal ions

A novel ion-imprinted functional ligand derivative bearing periodic mesoporous organosilica (IIPMO) was obtained using a sol–gel process from a chemically synthesized organopolysilane precursor with a metal template (Co2+ ion) imprinted ligand centre with tetraethylorthosilicate (TEOS) and cetyltrimethylammoniumbromide (CTAB) as a structural directing surfactant under basic conditions. The imprinted metal template was easily leached out from the hybrid materials during an acid treatment, which resulted in a template-free ion-imprinted network in the PMO pore wall framework with an unaltered particle size and morphology. The ion-imprinted hybrid PMO materials were characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, solid-state 29Si and 13C cross polarization magic angle spinning nuclear magnetic resonance spectroscopy, N2 adsorption–desorption analysis and elemental analysis. Furthermore, the removal of the imprinted metal template was confirmed by inductively coupled plasma-atomic emission spectroscopy. The selective rebinding ability of the template ions on the ion-imprinted PMO hybrid adsorbents was examined using a cobalt nitrate solution. The rebinding results showed that the selective efficiency of Co2+ ions on the IIPMOs were 10.1, 7.4 and 9.3 for Cu2+, Cd2+ and Zn2+, respectively.

Highly ordered metal ion imprinted mesoporous silica particles exhibiting specific recognition and fast adsorption kinetics

We prepared highly ordered metal ion imprinted mesoporous silica (IIMS) through co-condensation using a combination of molecular imprinting technology and traditional mesoporous materials. Copper ion is used as the template. Besides the periodic hexagonal structure, nano-sized wall thickness, and large surface area, it is found that the IIMS has highly specific recognition ability for the template. The imprinting factor of IIMS exhibits a maximum value of 3.7 at pH 2.5. The material shows fast binding kinetics for Cu2+ (complete equilibrium reach only within 5 min) and the saturation adsorption capacity reaches up to 0.39 mmol g−1. Homogeneous binding sites are confirmed by the Langmuir isothermal model and the Langmuir–Freundlich isothermal model. The heterogeneity index is 0.992 with a value similar to those found for molecularly imprinted polymers prepared using covalent imprinting. The recovery of the silica stays above 90% after six extraction–stripping cycles. Furthermore, the silica has significant potential for water treatment applications.

Synthesis of ion-imprinted mesoporous silica gel sorbent for selective adsorption of copper ions in aqueous media

A new Cu(II) ion-imprinted sorbent was synthesized by a surface imprinting technique and characterized by FT-IR and SEM. Compared to the non-imprinted sorbent, the Cu(II) ion-imprinted sorbent had a higher adsorption capacity and selectivity for Cu(II). The static adsorption capacity of the Cu(II) ion-imprinted sorbent and non-imprinted sorbent for Cu(II) were 84.5 and 46.5 μmol g−1, respectively. The best selectivity coefficient over Zn(II) or Cd(II) ion was over 12. The relative selectivity coefficients of the sorbent for Cu(II) in the presence of Zn(II) and Cd(II) were 13 and 35, respectively. Furthermore, the new sorbent possessed a fast kinetics for Cu(II) sorption from aqueous solution with saturation time of <30 min, and could be used repeatedly. The standard deviation for 11 replicate determinations of 0.5 mg L−1 Cu(II) was 0.8%. This new Cu(II) ion-imprinted sorbent can be used as an effective solid-phase extraction material for the selective preconcentration and separation of Cu(II).