A new approach to heavy metal ion adsorbents based on the covalent grafting of 3-mercaptopropylsilyl groups to the framework pore walls of mesoporous silica molecular sieves has been investigated with regard to hydroxyl group densities, channel dimensions, and morphologies. Two types of silicas were examined, namely, MCM-41 with an initially anionic silicate framework and HMS with an electrically neutral framework. The MCM-41 derivative was obtained through electrostatic S+X-I+ assembly, where S+ was a quaternary ammonium ion surfactant, X- was a halide, and I+ was the silica precursor derived from tetraethyl orthosilicate (TEOS) in acidic solution. HMS silicas were assembled by a S°I° pathway using alkylamines as surfactants (S°) and TEOS as the neutral silica source (I°). Prior to thiol functionalization of the mesostructures by a one-step grafting procedure, S+ was removed from MCM-41 by calcination, whereas for HMS, S° was removed by solvent extraction. The grafting process was much more effective for...

Heavy Metal Ion Adsorbents Formed by the Grafting of a Thiol Functionality to Mesoporous Silica Molecular Sieves: Factors Affecting Hg(II) Uptake

Chelating polymers and related supports for separation and preconcentration of trace metals.

Chelating Resins and Their Applications in the Analysis of Trace Metal Ions

The removal of mercury(II) from wastewaters (coal-fired utility plant scrubber solutions) using a thiol functional organoceramic composite (SOL-AD-IV) is investigated. A simulant is employed as a surrogate to demonstrate the removal of mercury from real waste solutions. Equilibrium studies show a mercury uptake capacity of 500 mg/g at a low mercury concentration of 0.5 mg/L and 726 mg/g at saturation. Adsorption is observed to be independent in the pH range 3−5. The kinetic performance assessed on a recycle batch reactor shows a rapid rate of adsorption. Selectivity is found to be in the order Hg(II) > Pb(II) ∼ Cd(II) > As(V) > Cr(III). Regeneration of SOL-AD-IV is accomplished using 12 M HCl. Effluent mercury concentrations of <0.001 mg/L are achieved using a fixed-bed adsorption column. A stability test operated for 25 cycles indicates a capacity loss of <10%. A high potential is demonstrated for application for mercury cleanup of wastewaters.

Mercury(II) adsorption from wastewaters using a thiol functional adsorbent

The sorption of copper, cadmium, nickel and zinc ions on thiol (-SH) based chelating polymeric resins (thiomethyl resin and Duolite GT-73) has been investigated. The physical and chemical characterisation of these polymers in the form of scanning electron micrographs (SEM), BET and Langmuir surface area measurements, Fourier transform infra red spectroscopy (FTIR) analysis, X-ray photoelectron spectroscopy (XPS) analysis, atomic composition measurement, sodium capacity determination and zeta potential measurements have been conducted to assess their performance as sorbents for trace toxic metal removal. Density functional theory (DFT) has been used to analyse the pore size distribution data. The adsorption of metal ions from aqueous solution on these sorbents has been studied in batch equilibrium experiments. The influence of pH on metal adsorption capacity has also been examined. The kinetic performance of these polymers has been assessed and the results have been analysed by a pore diffusion mo...

Hiroaki Hashizume

Papers

Preparation and properties of macroreticular resins containing thiazole and thiazoline groups.

Synthesis and properties of a new chelating resin containing the oxime group