Functionalized Nanoporous Silica for the Removal of Heavy Metals from Biological Systems: Adsorption and Application

Department of Biomedical Engineering, OHSU School of Medicine, Portland, Oregon 97239, USA.
ACS Applied Materials & Interfaces (Impact Factor: 6.72). 10/2010; 2(10):2749-58. DOI: 10.1021/am100616b
Source: PubMed

ABSTRACT Surface-functionalized nanoporous silica, often referred to as self-assembled monolayers on mesoporous supports (SAMMS), has previously demonstrated the ability to serve as very effective heavy metal sorbents in a range of aquatic and environmental systems, suggesting that they may be advantageously utilized for biomedical applications such as chelation therapy. Herein we evaluate surface chemistries for heavy metal capture from biological fluids, various facets of the materials' biocompatibility, and the suitability of these materials as potential therapeutics. Of the materials tested, thiol-functionalized SAMMS proved most capable of removing selected heavy metals from biological solutions (i.e., blood, urine, etc.) Consequentially, thiol-functionalized SAMMS was further analyzed to assess the material's performance under a number of different biologically relevant conditions (i.e., variable pH and ionic strength) to gauge any potentially negative effects resulting from interaction with the sorbent, such as cellular toxicity or the removal of essential minerals. Additionally, cellular uptake studies demonstrated no cell membrane permeation by the silica-based materials generally highlighting their ability to remain cellularly inert and thus nontoxic. The results show that organic ligand functionalized nanoporous silica could be a valuable material for a range of detoxification therapies and potentially other biomedical applications.

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    • "In order to facilitate the manipulation and recovery of nanoadsorbent, one promising approach is to incorporate the magnetism into the nanoparticles. Compared to other nanoadsorbents, such as carbon nanotubes (Kosa et al., 2012) or nanoporous silica (Yantasee et al., 2010), magnetic nanoparticles offer some significant advantages as adsorbent, such as easy control and fast recovery under the application of magnetic field. "
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    ABSTRACT: Divalent cations, especially calcium (Ca 2ϩ), are known to significantly affect the performance of anionic surfactants and polymers used in enhanced oil recovery (EOR) processes. An efficient technique to remove Ca 2ϩ from brine is reported, which is based on selective adsorption of Ca 2ϩ onto functionalized iron oxide magnetic nanoparticles (IOMNPs). Upon adsorption, the IOMNPs can be separated by applying a magnetic field, leaving behind softened water. IOMNP was synthesized by coprecipitation, and the amine-functionalization of its surface was obtained according to an aqueous APTES coating process. Chelating agent, polyacrylic acid (PAA), was successfully coated on amine-functionalized IOMNPs via amidation of carboxylic acid using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). PAA modification significantly enhanced the adsorption capacity of IOMNPs due to their great ability to chelate Ca 2ϩ . The effect of pH on adsorption capacity was also investigated. The adsorption capacity of Ca 2ϩ onto PAA-IOMNPs was found to be as high as 57.2 mg/g at pH 7 from the 400 mg/L Ca 2ϩ solution. However, in American Petroleum Institute (API) standard brine (8ϫ10 4 mg/L NaCl and 2ϫ10 4 mg/L CaCl 2), the adsorption capacity of IOMNPs decreased to 9.8 mg/g since the high salinity screens the charges on the surface of PAA-IOMNPs and results in the formation of nanoparticle aggregates. PAA-IOMNPs can be reused after treated by acetic acid solution. A geochemical model was developed to describe the competitive adsorption of Ca 2ϩ and H ϩ onto amine-functionalized IOMNPs as a function of solution pH and Ca 2ϩ concentration. Comparison between the model and the experiments shows that the adsorption isotherms predict the behavior of the system very well. Below pH 4, adsorption of Ca 2ϩ is negligible and becomes important above pH 7. This opens the possibility of recovering the nanoparticles after the divalent cation removal, and reusing them for the repeated water softening.
    2014 International Petroleum Technology Conference; 12/2014
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    • "The development of improved heavy metal absorbent materials that enhance the metal specificity has been a continued objective for environmental remediation purposes [1,2]. Porous materials, with large surface area and specificity, can be used as metal concentrator for detection purposes in possible metal pollution sites to make the transport and handling of the samples easier and relatively safe. "
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    ABSTRACT: Thiol-functionalized porous silicon (PS) monolayer was evaluated for its possible application in As (III) adsorption. Dimercaptosuccinic acid (DMSA) attached to mesoporous silicon via amide bond linkages was used as a chelate for As (III). Two different aminosilanes namely 3-(aminopropyl) triethoxysilane (APTES) and 3-aminopropyl (diethoxy)-methylsilane (APDEMS) were tested as linkers to evaluate the relative response for DMSA attachment. The aminosilane-modified PS samples were attached to DMSA by wet impregnation followed by the adsorption of As (III). Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) have been used to identify the functional groups and to estimate the As (III) content, respectively. FTIR spectroscopy confirmed the covalent bonding of DMSA with amide and R-COOH groups on the nanostructured porous surface. XPS confirms the preferred arsenic adsorption on the surface of PS/DMSA samples as compared to the aminosilane-modified and bare PS substrates.
    Nanoscale Research Letters 09/2014; 9(1):508. DOI:10.1186/1556-276X-9-508 · 2.78 Impact Factor
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    • "activated carbons, coal compounds, metal phosphonates , clays, zeolites, biopolymers or ion-exchange resin beads), silica sol–gel hybrids appear quite attractive solids for low-cost, effective removal of heavy metal ions from water [1] [2]. In this case, modification of the silica surface using functional organosilanes is necessary in order to enhance metal uptake through ion-exchange or chelation [1] [2] [3]. Typically, the organosilane co-condenses with (RO) 4 Si in order to obtain robust, yet water-stable hybrids that, however, display relatively low functional group (R) loadings due to dilution of the matrix [1]. "
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    ABSTRACT: A phosphonate-rich organosilica layered hybrid material (PSLM) made of 3-(trihydroxysilyl)propyl methylphosphonate, monosodium salt, as the single silica source, has been obtained from its aqueous solution through a xerogel process and mild thermal aging. The method is simple, affording bulk quantities of powdered PSLM in a single-step. The hybrid is stable in water and possesses a high content of phosphonate groups fixed on the solid matrix. In addition, PSLM shows good thermal stability, which exceeds 300°C in air. The material was characterized using SEM, TEM, XRD, FT-IR and TGA techniques. Potentiometric titrations show that PSLM bears high-surface density of phosphonate groups (3mmolg(-1)). As a result, the material displays high metal uptake capacity for heavy metal ions such as Cu(2+) (2.72mmolg(-1)), Pb(2+) (1.67mmolg(-1)) and Cd(2+) (1.00mmolg(-1)) at neutral pH values e.g. the pH of natural waters. Detailed theoretical modeling using a Surface Complexation Model combined with Electron Paramagnetic Resonance (EPR) spectroscopy shows that the surface distribution of surface bound Cu(2+) ions is rather homogeneous e.g. copper-binding phosphonate sites are arranged in average distances 5-8Å.
    Journal of hazardous materials 02/2014; 270C:118-126. DOI:10.1016/j.jhazmat.2014.01.045 · 4.53 Impact Factor
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