Article

Adsorption of heavy metal cations by organic ligands grafted on porous materials Aleksey N. Vasiliev, Leonid V. Golovko, Vladimir V. Trachevsky, Gene S. Hall, Johannes G. Khinast Microporous and Mesoporous Materials 118 (2009) 251–257

Department of Chemistry and Biochemistry, Rutgers University, Piscataway, NJ, USA
Microporous and Mesoporous Materials (Impact Factor: 3.21). 01/2009; 118:251–257. DOI: 10.1016/j.micromeso.2008.08.026

ABSTRACT The purpose of this work is the development of new sorbents containing different ligands grafted on the surface of a porous support. These materials are capable of immobilizing heavy metals in order to prevent leaching into the ground water. In this study, we grafted the ligands on silica gel, and two types of zeolites: ZSM-5 and Y. Due to the highest achievable loading, silica gel was selected for further studies. Immobilized complexes with Cd, Cu, Ni, Pb and Zn were prepared and studied by physical and chemical methods in order to determine their composition and structural characteristics. The stability of the complexes with heavy metals and the metal leaching from the sorbents were studied for different pH values. Studies of the immobilized metals by NMR and ESR showed that the metals form several complexes of different structures. The resulting silica-grafted materials can be used for the treatment of contaminated soils containing heavy metals, thus allowing a safe disposal of sludge, without the risk of contaminant leaching, in order to increase the environmental security in contaminated areas.
Keywords: Silica gel; Zeolites; Immobilization; Heavy metals; Adsorption

0 Followers
 · 
401 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Centimeter-long surface gradients in bi- and tridentate chelating agents have been formed via controlled rate infusion, and the coordination of Cu(2+) and Zn(2+) to these surfaces has been examined as a function of distance by X-ray photoelectron spectroscopy (XPS). 3-(Trimethoxysilylpropyl)ethylenediamine and 3-(trimethoxysilylpropyl)diethylenetriamine were used as precursor silanes to form the chelation gradients. When the gradients were exposed to a metal ion solution, a series of coordination complexes formed along the length of the substrate. For both chelating agents at the three different concentrations studied, the amine content gradually increased from top to bottom as expected for a surface chemical gradient. While the Cu 2p peak area had nearly the same profile as nitrogen, the Zn 2p peak area did not and exhibited a plateau along much of the gradient. The normalized nitrogen-to-metal peak area ratio (N/M) was found to be highly dependent on the type of ligand, its surface concentration, and the type of metal ion. For Cu(2+), the N/M ratio ranged from 8 to 11 on the diamine gradient and was ∼4 on the triamine gradient, while for Zn(2+), the N/M ratio was 4-8 on diamine and 5-7 on triamine gradients. The extent of protonation of amine groups was higher for the diamine gradients, which could lead to an increased N/M ratio. Both 1:1 and 1:2 ligand/metal complexes along with dinuclear complexes are proposed to form, with their relative amounts dependent on the ligand, ligand density, and metal ion. Collectively, the methods and results described herein represent a new approach to study metal ion binding and coordination on surfaces, which is especially important to the extraction, preconcentration, and separation of metal ions.
    Langmuir 08/2014; 30(33):10019. DOI:10.1021/la502088k · 4.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Lead (Pb(II)) is a very toxic heavy metal that even at low concentration can affect living organisms. Therefore, designing effective materials with high selectivity and cost-effeciency is essential for the control capturing of toxic Pb(II) ions. This study developed a ligand based conjugate adsorbent for simultaneous Pb(II) detection and removal from water samples. The organic ligand of 4-dodecyl-6-((4-(hexyloxy)phenyl)diazenyl) benzene-1,3-diol (DPDB) was synthesized and DPDB was successfully immobilized onto mesoporous silica by a direct immobilization approach. The Pb(II) ion was detected by the charge transfer (π–π transition) transduction mechanism with sensitivity and selectivity. The experiment conditions were optimized based on contact time, solution acidity, initial Pb(II) concentration and pH value and diverse metal salt concentrations. The adsorbent was highly sensitive, and the limit of detection was 0.18 μg/L for Pb(II) ions. The Pb(II) sorption synthetic aqueous solution also underwent batch tests. However, the sorption capacity depended on the solutions pH, initial concentration and to some extent on the competing ions. The experimental data revealed that the maximum Pb(II) sorption was possible at pH 5.0. The presence of other cations and anions did not adversely affect the Pb(II) capturing by the adsorbent. The maximum sorption capacity was determined to be as high as 195.31 mg/g. The extraction of Pb(II) ions from the saturated adsorbent was possible with 0.20 M HCl. The regenerated adsorbent that remained maintained the high selectivity to Pb(II) ions and exhibited almost the same sorption capacity as that of the original adsorbent. However, the sorption efficiency slightly decreased after ten cycles. Therefore, the proposed adsorbent offered a cost-effective material and may be considered a viable alternative for effectively monitoring and removing toxic Pb(II) ions from water samples without the need for sophisticated instrument.
    Microporous and Mesoporous Materials 09/2014; 196:261–269. DOI:10.1016/j.micromeso.2014.05.021 · 3.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel magnetic functionalized MCM-48 mesoporous silica with amine (NH2) and melamine-based dendrimer amines (MDA) were synthesized that can be easily separated from aqueous solutions by applying a magnetic field. The synthesis adsorbent (MDA-magMCM-48) was characterized by low angle XRD, TEM, FT-IR, TGA and N2 adsorption-desorption isotherm techniques. Batch adsorption experiments were carried out to study the sorption behavior of MDA-magMCM-48 toward Pb(II), Cu(II), Cr(VI) and Cd(II) metal ions. The adsorption of metal ions was well modeled by pseudo-second-order model and Langmuir sorption isotherm with maximum adsorption capacities of 127.24, 125.80, 115.60 and 114.08 mg g−1 Pb(II), Cu(II), Cr(VI) and Cd(II) metal ions, respectively. MDA-magMCM-48 was regenerated and found to be suitable for reuse in successive adsorption-desorption cycles for three times without significant loss in adsorption capacity.
    Chemical Engineering Research and Design 01/2015; 93:779-788. DOI:10.1016/j.cherd.2014.07.018 · 2.28 Impact Factor

Full-text (2 Sources)

Download
244 Downloads
Available from
Jun 1, 2014