Ag Adsorbates Research Articles

Graphite oxide impregnated with LTA zeolite as a new adsorbent to uptake Ag (I) from aqueous solution and its subsequent reuse as an antimicrobial

This study presents, for the first time in the literature, a comprehensive investigation detailing the methodology and characterization of a novel material synthesized via the impregnation of graphite oxide with LTA zeolite for the purpose of Ag (I) adsorption. The new adsorbent was successfully characterized and compared with its precursor materials for Ag (I) adsorption, demonstrating superior performance. Furthermore, the Ag (I)-loaded adsorbent was explored for antimicrobial activity. Additionally, the material was evaluated for its adsorption capacity considering the pH effect. The adsorption followed the Pseudo-second-order kinetic model and the Freundlich isothermal model with an endothermic nature. The new material presented a remarkable Ag (I) uptake, reaching 142.06 mg g−1 at 55 °C. The material after adsorption also showed inhibition zones in the growth of Staphylococcus aureus and Escherichia coli of 8 mm and 9 mm, respectively. These results highlight the considerable potential of graphite oxide impregnated with LTA zeolite as an effective adsorbent for Ag (I) removal from aqueous streams. Additionally, the Ag (I)-loaded adsorbent demonstrates a notable capability for antimicrobial activity.

3D magnetic MXene as promising adsorbent materials for Ag(I) removal

An efficient route is proposed to synthesize a novel three-dimensional (3D) magnetic MXene aerogel (3D MXene/Fe3O4). 3D MXene were synthesized by self-assembly of 2D MXene Ti3C2Tx using ethylenediamine (EDA) as crosslinking inducer, then Fe3O4 was in situ coprecipitation onto 3D MXene. 3D MXene/Fe3O4 was applied as an adsorbent for Ag(I) removal from aqueous solutions. 3D MXene/Fe3O4 exhibits a cross-linked 3D porous network with magnetic Fe3O4 nanoparticles uniformly dispersed on its surface and edges. The maximum adsorption capacity of 3D MXene/Fe3O4 for Ag(I) was 2385 mg g−1. The kinetics and isothermal process during adsorption were described accurately by the pseudo-second-order model and the Freundlich isotherm model, and the adsorption process was driven by chemisorption and multilayer adsorption, where the diffusion mechanism involved surface diffusion and intraparticle diffusion. Furthermore, the 3D MXene/Fe3O4 are recyclable, retaining 71% of the initial removal rate after 5 adsorption/desorption cycles.

An ultrastable cationic covalent organic framework for selective capture of silver from aqueous solution

Recovery of silver from wastewater is a promising alternative from the economic and environmental perspective. Herein, we present an ultrastable ionic covalent organic framework (COF) as a recyclable adsorbent for Ag(I) recovery. The COF exhibits a large surface area, regular pores, and extremely high chemical stability combined with the confined ionic interface, which makes it an excellent material for silver adsorption with fast adsorption kinetics, excellent selectivity, and high saturated adsorption capacity (up to 349.6 mg/g). The superb uptake performance of the cationic COF is attributed to the in-situ precipitation of AgBr and adsorption as well as the coordination of O atoms on the framework to silver.

One-pot synthesis of magnetic N-doped mesoporous carbons as an efficient adsorbent for Ag(I) removal

An efficient strategy was proposed to fabricate magnetic N-doped mesoporous carbons (Fe0/NMC) via one-pot process. This one-pot strategy involved the synthesis of N-containing porous polymers using amphiphilic triblock copolymer (F127) through self-assembly of melamine formaldehyde resin, and the formation and entrapment of Fe0 nanoparticles by an in-situ carbothermal reduction approach. The surface morphology and the main chemical groups of the developed Fe0/NMC were characterized by various analytical methods such as XRD, FTIR, TGA-DTA, BET, TEM and VSM. Fe0/NMC exhibited a mesoporous structure and Fe0 nanoparticles were dispersed homogeneously on Fe0/NMC, with a saturation magnetization of 134.6 emu/g. As an adsorbent, Fe0/NMC showed an excellent adsorption capacity for Ag (I), reaching 335 mg/g. The adsorption process was consistent with the quasi-secondary kinetic model and Freundlich isothermal adsorption model, which indicated that the adsorption process was multilayer adsorption and the adsorbed element Ag was present on Fe0/NMC in the form of Ag(I) as well as chelates and Ag monomers. It could be believed that Fe0/NMC was a viable adsorption material for Ag(I) and had full-scale applications.

Synthesis of novel sulfydryl-functionalized chelating adsorbent and its application for selective adsorption of Ag(I) under high acid

• A novel sulfydryl-functionalized chelating adsorbent is synthesized by radiation grafting using stable polypropylene non-woven fabrics. • The adsorbent contains two functional groups, amine and sulfhydryl. • The adsorbent has two adsorption mechanisms for silver(Ⅰ) under high acid: ion exchange and chelate adsorption. The sulfhydryl has an excellent chelating affinity towards silver(Ⅰ) and the protonated amine adsorbs [Ag(NO 3 ) 2 ] −1 by ion exchange. • Silver(Ⅰ) is effectively and selectively adsorbed in high acid environment. A novel sulfydryl-functionalized adsorbent PP-g-GMA@MEA for recovery of Ag(I) was synthesized by γ-ray induced simultaneous grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) non-woven fabric, followed by ring-opening processes with mercaptoethylamine (MEA). The obtained adsorbents before and after adsorption of Ag(I) were fully characterized by SEM, EDS, FT-IR spectra, XRD and XPS. Batch adsorption experiments were carried out to evaluate adsorption abilities of the adsorbents under high acidity. The adsorption kinetics of Ag(I) were well fitted with pseudo-second-order kinetics model. The maximum adsorption capacity calculated by the Langmuir isotherm model was 262.51 mg/g at 25 °C. EDS, XRD and XPS analyses confirmed the mechanism of adsorption under high acidity was chelating reaction between -SH and Ag(I) and ion exchange adsorption towards [Ag(NO 3 ) 2 ] −1 . Through competitive adsorption tests, the PP-g-GMA@MEA was found remarkably selective towards Ag(I) when it coexisted with Cu(II), Co(II), Ni(II) and Cr(III) in high acidity medium. Therefore, the developed PP-g-GMA@MEA composite would be a promising adsorbent for Ag(I) recovery from industrial effluents.

Facile one-pot synthesis of ultrathin carbon layer encapsulated magnetite nanoparticle and graphene oxide nanocomposite for efficient removal of metal ions

In the past decades, graphene oxide (GO) exhibited great potential for enhancing the performance of magnetic nanocomposite in the removal of metal ions from aqueous environment. Fabricating GO adsorbents with high stability, excellent adsorption capacity and magnetic responsiveness is a pursuing issue. In this paper, the ultrathin carbon layer encapsulated magnetite nanoparticles and GO nanocomposite (Fe3O4@C-GO) was synthesized by a feasible one-pot hydrothermal method. Scanning electron microscope, transmission electron microscope, Fourier transform infrared, X-ray diffraction, x-ray photoelectron spectrometer, and Raman were conducted to inspect the structure and micromorphology of Fe3O4@C-GO nanocomposite. The results affirmed that the well dispersed Fe3O4 nanoparticles coated by ultrathin carbon layer were successfully combined onto the homogenous flake-like surface of the GO nanosheets containing abundant oxygen functional groups. The surface area and pore volume of the Fe3O4@C-GO nanocomposite were 160 m2/g and 0.283 cm3/g, respectively. The Fe3O4@C-GO nanocomposite was superparamagnetic indicated by VSM. The optimum conditions of the Fe3O4@C-GO nanocomposite as adsorbent for Ag(I), Pb(II), Cr(VI) and Al(III) in aqueous solutions were determined by batch adsorption experiments. The Fe3O4@C-GO nanocomposite exhibited excellent adsorption ability. The maximum adsorption capacities were respectively 162.9 mg/g, 125.8 mg/g, 158.2 mg/g and 173.9 mg/g for Ag(I), Pb(II), Cr(VI) and Al(III), at pH = 6 for Ag(I), Pb(II), and Al(III) as well as pH = 2 for Cr(VI). Adsorption kinetics and isotherms were furtherly investigated. Meanwhile, the adsorption mechanisms of Ag(I), Pb(II), Cr(VI) and Al(III) by Fe3O4@C-GO nanocomposite were detailedly conducted by XPS analysis. Thus, the Fe3O4@C-GO nanocomposite is a promising material for efficient removal of metal ions from aqueous environment.

Nitrogen-Doped Mesoporous Carbons Bearing Fe3O4 as Adsorbent for Effective Ag(I) Removal

An efficient route is proposed to synthesize magnetic nitrogen-doped mesoporous carbon (Fe3O4/NMC) composites. The nitrogen-doped mesoporous carbon (NMC) material was prepared using a melamine–formaldehyde resin as nitrogen and carbon source and fumed silica as a template via a template method, and Fe3O4nanoparticles were introduced via an in situ formation method. The effects of the loading amount of Fe3O4on the morphology, structure, magnetic properties and adsorption performance of the Fe3O4/NMC composites were investigated. Fe3O4nanoparticles dispersed well on the surface and inside the NMC, and the Fe3O4/NMC remained a mesoporous structure. Fe3O4/NMC exhibited superparamagnetic behavior, and the maximum saturation magnetization was 30.1[Formula: see text]emu/g. Fe3O4/NMC had a decreased specific surface area and pore volume compared to NMC, but the Fe3O4/NMC composites still showed excellent adsorption capacity for Ag(I), reaching 71.9[Formula: see text]mg/g. The adsorption efficiency of Fe3O4/NMC remained at 90.3% of the initial removal capability after five cycles, which demonstrated the potential large-scale industrial applications of these composites.

Adsorption behaviors and mechanism of graphene oxide for silver complex anion removal

Graphene oxide (GO) is an outstanding material for water treatment, their film structure and functional groups may play crucial roles in anion removal. Herein, the removal of silver complex anion Ag(CN)2− by GO was conducted to study the behavior and mechanism of GO in silver exceeded system. The work was carried out by the adsorption of Ag(CN)2− on GO as functions of pH, adsorption time and adsorbate concentration. The results, based on XRD, SEM, TEM, AFM, XPS, FT-IR, presented that the prepared GO has a film structure and amount of oxygenous functional groups. Further studies found that GO exhibits big adsorption capacity (100.7 mg/g) and high adsorption rate (0.0084 min−1) in accordance with the adsorption kinetics and isotherm, implying the GO might be a good potential adsorbent for Ag(CN)2− removal. The adsorption progress was found fits well with second-order adsorption model meanwhile follows Langmuir adsorption model well. The silver was confirmed adsorbed in form of Ag(CN)2− and distributed uniformly on GO. The adsorption performance and mechanism was ascribed to the film structure and the interactions between Ag(CN)2− and oxygenous functional groups, and the DFT calculation implied the groups contribute for adsorption in order of epoxy > hydroxyl > carboxyl.

Adsorption behavior of Ag(I) onto elemental sulfur-encapsulated silica nanocapsules for industrial applications

Pure silica nanocapsules (SiNC-P) and elemental sulfur-encapsulated silica nanocapsules (SiNC-ES) as Ag(I) adsorbents were successfully synthesized by a one-step water-in-oil microemulsion polymerization process. The characterization of the synthesized materials, such as surface morphology, surface area, porosity, functional groups and thermal characteristics, was carried out using various analytical techniques. The SiNC-P and SiNC-ES have nearly similar morphology, but the surface area and pore size of the SiNC-ES are higher than SiNC-P. The Ag(I) adsorption study showed that it increased with increasing elemental sulfur (ES) amount in the SiNC-ES. The SiNC-ES shows high adsorption capacity, independent of pH, and higher adsorption rate as compared to SiNC-P. The maximum Ag(I) adsorption capacity of SiNC-P and SiNC-ES was 50.49 mg g−1 and 98.51 mg g−1, respectively. The adsorption isotherm data were best described by the Langmuir model. The diffusion modeling analysis of the kinetic data indicated that film diffusion is the controlling step, while chemical reaction modeling obeys the pseudo-second-order kinetic model. The SiNC-ES was reusable and good adsorption performance up to four adsorption cycles was observed. The practical capability of the SiNC-ES to adsorb Ag(I) was successfully demonstrated using an industrial waste solution in which a high removal efficiency was observed (η>90%). This demonstrates that the SiNC-ES can be a potential adsorbent for Ag(I) recovery from industrial wastes.

Polyethylenimine modified potassium tungsten oxide adsorbent for highly efficient Ag+ removal and valuable Ag0 recovery.

Elemental Ag0 is well known for its remarkable catalytic and antibacterial properties, thus the regeneration of valuable Ag0 metal from Ag+ wastewater is of great significance. In this study, a novel polyethylenimine (PEI) modified potassium tungsten oxide (N-K2W4O13) adsorbent was prepared for Ag+ removal and reduction to Ag0 using glutaraldehyde as crosslinking agent. XPS and FT-IR spectra verified PEI successfully anchored on the surface O and W atoms of K2W4O13 through aldehyde bridges. The content of PEI in N-K2W4O13 was calculated as 8.74wt% by TG curve. A heterogeneous PEI coating was observed in the SEM and TEM images. The N-K2W4O13 exhibited larger Ag+ uptake (48.25mg/g) than the raw K2W4O13 (42.50mg/g) though required a longer equilibrium time. This was due to the combined results of strong chelation and weak electrostatic repulsion that meanwhile occurring on the positive-charged surface of N-K2W4O13. The maximum Ag+ uptake on N-K2W4O13 was 72.5mg/g, which was larger than many of the reported adsorbents. Furthermore, the prepared N-K2W4O13 displayed good anti-interference toward background ions (Na+, K+) and hold a stable Ag+ removal (>95%) after five runs of recycling tests. The mechanism studies elucidated that NH/N groups from the PEI modified N-K2W4O13 mainly accounted for the Ag+ adsorption and Ag0 recovery in the adsorption-reduction process. Ion-exchange between Ag+ and K+ from the N-K2W4O13 lattice also occurred. This work provided a facile method to synthesize a promising adsorbent for Ag+ wastewater remediation and valuable Ag0 recovery.

Adsorptive Applications of Montmorillonite Clay for the Removal of Ag(I) and Cu(II) from Aqueous Medium

The present work aims to investigate the ability of Saudi clay containing montmorillonite to remove Ag(I) and Cu(II) ions from aqueous solutions for waste water purification. The effect of pH, adsorbent mass, metal concentration, and contact time on the removal process has been investigated. The batch method was applied, using solution metal concentrations ranging from 40 to 2000 mg/L. Adsorption percentage and distribution coefficients (Kd) were determined as a function of metal concentration. pH 6 was found to be optimal for the adsorption. Adsorption reached equilibrium in 5 min for both Ag(I) and Cu(II) ions. The study on adsorption’s kinetic characteristics showed the adsorption process of these metal ions was of pseudo-second-order. Furthermore, the adsorption rate of Ag(I) was higher than that of Cu(II), and their adsorption appeared to follow the Langmuir isotherm. From the equilibrium studies, it was observed that the selectivity of Ag(I) was higher than that of Cu(II). The results showed that Saudi clay has the potential to be a suitable adsorbent for Ag(I) and Cu(II) removal from aqueous solutions compared with other adsorbents.

Anomalous Shape Evolution of Ag2O2 Nanocrystals Modulated by Surface Adsorbates during Electron Beam Etching.

An understanding of nanocrystal shape evolution is significant for the design, synthesis, and applications of nanocrystals with surface-enhanced properties such as catalysis or plasmonics. Surface adsorbates that are selectively attached to certain facets may strongly affect the atomic pathways of nanocrystal shape development. However, it is a great challenge to directly observe such dynamic processes in situ with a high spatial resolution. Here, we report the anomalous shape evolution of Ag2O2 nanocrystals modulated by the surface adsorbates of Ag clusters during electron beam etching, which is revealed through in situ transmission electron microscopy (TEM). In contrast to the Ag2O2 nanocrystals without adsorbates, which display the near-equilibrium shape throughout the etching process, Ag2O2 nanocrystals with Ag surface adsorbates show distinct facet development during etching by electron beam irradiation. Three stages of shape changes are observed: a sphere-to-a cube transformation, side etching of a cuboid, and bottom etching underneath the surface adsorbates. We find that the Ag adsorbates modify the Ag2O2 nanocrystal surface configuration by selectively capping the junction between two neighboring facets. They prevent the edge atoms from being etched away and block the diffusion path of surface atoms. Our findings provide critical insights into the modulatory function of surface adsorbates on the shape control of nanocrystals.

Model studies of the structure and optical properties of the TiO2(110) surface with an adsorbed Ag atom

ABSTRACTThe present studies of the atomic Ag adsorbate on the substrate TiO2(110) explore the importance of dispersion (or van der Waals) energies for determining the structure of the adsorbed Ag atom, using density functional theory (DFT) supplemented by a dispersion energy treatment, within the PBE-D3 treatment. It is also of interest to explore electronic excitation by light absorption. Electronic density of states (EDOS) are obtained without and with Ag adsorbed on the TiO2(110), to find the extent of change on the density of valence, conduction and intraband states. This is done using the hybrid HSE06 functional, which is known to provide good values for the energy band gap of the substrate. A computationally efficient PBE + BG procedure for these structures, which corrects the PBE band gap, is implemented to generate accurate EDOSs and light absorption intensities versus photon energies. This is followed by a reduced density matrix treatment of the dissipative dynamics of light absorption, generating state-to-state oscillator strengths and photoabsorbances for the pure and nanostructured TiO2(110) surfaces. Adsorption of Ag leads to a noticeable increase in light absorption at visible wavelengths, and very large increases in the UV region of the spectrum.

Thermodynamics of Hg2+ and Ag+ adsorption by 3-mercaptopropionic acid-functionalized superparamagnetic iron oxide nanoparticles

Superparamagnetic iron nanoparticles (SPION) have been functionalized with 3-mercaptopropionic acid (3-MPA), characterized and applied for the removal of Ag+, Hg2+ and Pb2+ metal ions from aqueous solutions by iron oxide (Fe3O4). The heavy metal adsorption has been investigated by means of ICP-OES and isothermal titration calorimetry. Experimental data ware better fitted by Langmuir rather than Freundlich isotherms, and the thermodynamic parameters for the adsorption process of the metal ions on the functionalized SPION nanoparticles (SPION@3-MPA) were obtained. Isothermal titration calorimetry (ITC) is applied to monitor heavy metal adsorption on SPION@3-MPA: the process results to be exothermic for Hg2+ and Ag+, while it is weakly endothermic in the case of Pb2+, and the adsorption enthalpies and entropies have been obtained. The values of the thermodynamic parameters suggest that the Ag+ and Hg2+ ions interact strongly with the thiol groups, while the Pb2+ ions seem to be adsorbed by the material mostly via electrostatic interaction. When compared to other thiol-functionalized materials, the obtained SPION@3-MPA NP can be considered a competitive adsorbent for Ag+ and Hg2+ ions. The comparison between the ICP-OES adsorption rate and the enthalpy trend obtained by ITC supports shows that the latter technique can be a good tool for a fast testing of materials to be applied for heavy metal separation from solutions.

Synthesis and application of a novel core-shell-shell magnetic ion imprinted polymer as a selective adsorbent of trace amounts of silver ions

AbstractIon-imprinted polymer (IIP) technology has received considerable attention for its greatest potential application. In this work, a novel magnetic nano ion-imprinted polymer (MIIP) for the selective and sensitive pre-concentration of silver (I) ions were used. It was obtained using Fe3O4@SiO2@TiO2 nanoparticles as a magnetic support of adsorbent, Ag(I)-2,4-diamino-6-phenyl-1,3,5-triazine (DPT) complex as the template molecule and methacrylic acid (MAA), 2,2′-azobisisobutyronitrile (AIBN), ethylene glycol dimethacrylate (EGDMA), as the functional monomer, the radical initiator and crosslinker, respectively. The synthesized polymer nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and Brunauer-Emmett-Teller (BET). Silver ions were separate from the polymer and measured by flame atomic absorption spectrometry (FAAS). The maximum adsorption capacity of the novel imprinted adsorbent for Ag(I) was calculated to be 62.5 mg g−1. The developed method was applied to the preconcentration of the analyte in the water, radiology film and food samples, and satisfactory results were obtained.

Metal Adsorbate-Induced Plasmon Damping in Gold Nanorods: The Difference Between Metals

We presented a single particle study on the metal adsorbate-induced plasmon damping in Au nanorods (AuNRs) through adsorbing clusters of different metals including Pt, Au and Ag. AuNRs with different longitudinal surface plasmon resonance (LSPR) wavelength were measured and investigated individually. Linewidth broadening, plasmon shift and reduction of plasmonic resonance of single AuNRs were studied and compared between Pt, Au and Ag adsorbates. The measured linewidths perfectly match the theoretical predictions of the billiard model with increased scattering coefficients resulted from the metal adsorbates. The results indicate that the plasmon damping in case of Ag is significantly weaker than Pt and Au, which can be attributed to longer relaxation time of free electrons in Ag and therefore less loss of the oscillating plasmon electrons. In contrast to the red shift observed from Au and Pt, blue shift of the LSPR is observed in case of Ag. It suggests that plasmonic properties brought by the metal adsorbates can exert dramatic influence on the nanoparticle that is adsorbed with. We believe that our study not only provides important understanding on plasmon damping but pave the road for the fabrication of complex nanostructures with two or more metal elements.

Application of magnetic nanocomposite modified with a thiourea based ligand for the preconcentration and trace detection of silver(I) ions by electrothermal atomic absorption spectrometry

In this study, a novel and simple modified magnetic nanocomposite was investigated for the analysis of trace amount of silver(I). For this purpose, the magnetically activated carbon/γ-Fe2O3 (AC/γ-Fe2O3) nanocomposite was successfully synthesized and modified with a symmetrical thiourea derivative, 4,4′-bis-(3-phenylthiourea)diphenyl methane (BPDM). The different experimental factors affecting the preconcentration and detection of the analyte ions were studied in detail. The effects of foreign ions on the extraction of Ag(I) ions were also investigated. Under the optimum conditions, a sensitive response to Ag(I) within a wide concentration range (0.01–28μgL−1) was achieved. The limit of detection (LOD, 3Sb/m) was 2.3ngL−1. The maximum adsorption capacity of the novel magnetic adsorbent for Ag(I) was found to be 32.6mgg−1. An enrichment factor (EF) of 125 was obtained by the ratio of the highest sample volume for analyte (125mL) and the lowest final eluent volume (1mL). The developed method was successfully applied to monitoring silver in water samples and the certified reference material. The procedure exhibited some advantages, such as simplicity, rapidity, high sensitivity, and low cost. In addition, the mechanism of silver extraction by modified nanocomposite was proposed.

Chemically functionalized γ-alumina with Alizarin red-s for separation and determination of trace amounts of Pb(II) and Ag(I) ions by solid phase extraction–Flame Atomic Absorption Spectrometry in environmental and biological samples

A novel column solid phase extraction was developed for the determination of traces of lead and silver in various samples. An alumina–sodium dodecyl sulfate (SDS) coated on with Alizarin red-s was used for preconcentration of lead and silver ions prior to determination by flame atomic absorption spectrometry. Lead and silver were adsorbed quantitatively on a modified column due to its complexation with Alizarin red-s and then eluted using 5.0mL 4.0molL−1 phosphoric acid. The influences of the analytical parameters such as pH, solid phase amount, ligand amount, types and concentration of eluting agent were investigated. The loading capacity of adsorbent for Pb and Ag were found to be 2.3 and 2.1mgg−1. The detection limits were 18.0 and 55.0μgL−1 for lead and silver respectively, applying a preconcentration factor of 100.0. The relative standard deviation under optimum conditions is lower than 2.0%. The presented procedure was successfully applied for the determination of analytes content in real samples. The results were obtained and are in good agreement with the reported method.

Functionalized hectorite clay mineral for Ag(I) ions extraction from wastewater and preparation of silver nanoparticles supported clay

A novel clay mineral-based adsorbent for Ag(I) ions extraction was obtained by modifying hectorite with 2-(3-(2-aminoethylthio)propylthio)ethanamine (AEPE-hectorite). The modified hectorite was used to recover Ag(I) ions from wastewater for further preparation of silver nanoparticles supported hectorite. The parameters affecting silver ions extraction by AEPE-hectorite were investigated. The adsorbent could extract Ag(I) ions from solution in a wide pH range (1–8) and high extraction efficiencies were achieved in the solution pH ranged from 4 to 9. AEPE-hectorite showed a good selectivity toward Ag(I) ions over Co(II), Ni(II) and Cd(II) ions and the solution ionic strength had no significant effect on extraction efficiency. The adsorption of Ag(I) ions onto AEPE-hectorite followed the Freundlich isotherm model with maximum adsorption capacity observed in the experiment of 49.5mgg−1. The adsorbent was successfully used to recover silver ions from a wastewater containing high concentration of silver and silver nanoparticles supported hectorite was obtained after reducing with NaBH4. These results show an alternative in the preparation of silver nanoparticles supported clay.

Light Absorption by Crystalline and Amorphous Silicon Quantum Dots with Silver Adsorbates and Dopants

Recent work on light absorption by model surfaces of Si has shown that Ag adsorbates increase the intensity of photoinduced electronic transitions at lower photon energies. Furthermore, another set of recent results for Si quantum dots (QDs) has shown that P and Al dopants shift the light absorbance toward lower photon energies. In this report, the optical absorbance of Si QDs with P and Al dopants and either one or three Ag adsorbed atoms has been calculated with TD-DFT using the PW91/PW91 density functionals to compare with our previous results. In general, the presence of Ag adsorbates shows both a decrease in the HOMO-LUMO gap and a drastic increase in the absorbance below 4 eV. The addition of dopants leads to a combined effect where the energy gap is further decreased to values below 2 eV. The molecular orbitals for the initial and final states involved in transitions with large oscillator strengths were also calculated, which qualitatively show the excited electrons moving toward the Ag during excitation. This study indicates that stronger absorption in the visible, near-UV, and near-IR parts of the spectrum can be achieved with a combination of Ag adsorbate clusters and doping.