iping Hu

Synthesis of a novel silica-supported dithiocarbamate adsorbent and its properties for the removal of heavy metal ions.

Silica-supported dithiocarbamate adsorbent (Si-DTC) was synthesized by anchoring the chelating agent of macromolecular dithiocarbamate (MDTC) to the chloro-functionalized silica matrix (SiCl), as a new adsorbent for adsorption of Pb(II), Cd(II), Cu(II) and Hg(II) from aqueous solution. The surface characterization was performed by FT-IR, XPS, SEM and elemental analysis indicating that the modification of the silica surface was successfully performed. The effects of media pH, adsorption time, initial metal ion concentration and adsorption temperature on adsorption capacity of the adsorbent had been investigated. Experimental data were exploited for kinetic and thermodynamic evaluations related to the adsorption processes. The characteristics of the adsorption process were evaluated by using the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption isotherms and adsorption capacities were found to be 0.34 mmol g(-1), 0.36 mmol g(-1), 0.32 mmol g(-1) and 0.40 mmol g(-1) for Pb(II), Cd(II), Cu(II) and Hg(II), respectively. The adsorption mechanism of Hg(II) onto Si-DTC is quite different from that of Pb(II), Cd(II) or Cu(II) onto Si-DTC, which is demonstrated by the XPS and FT-IR results.

Effect of grinding atmosphere on the leaching of mechanically activated pyrite and sphalerite

Abstract The effects of grinding atmosphere, such as highly pure nitrogen (99.999 vol.%) (abbreviated as nitrogen), less air, and air on the leaching of pyrite and sphalerite mechanically activated for 20 and 120 min, respectively, were investigated. The results indicate that the leaching recovery of mechanically activated pyrite varies with the grinding atmosphere, and increases in the sequence of nitrogen, air, and less air. In contrast, the leaching recovery of mechanically activated sphalerite is insensitive to the different grinding atmospheres. The structural changes of the sulfide minerals mechanically activated under different grinding atmospheres were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD) and X-ray diffraction laser particle size analysis. The results show that the XRD spectra and the specific granulometric surface area ( S G ) do not vary with the grinding atmosphere, neither do the S2p and Zn2p XPS spectra of mechanically activated sphalerite and Fe2p XPS spectra of mechanically activated pyrite. However, a change was observed in the S2p XPS spectra of pyrite mechanically activated under different grinding atmospheres. The lattice distortion, S G and the elemental sulfur contents of pyrite and sphalerite mechanically activated under nitrogen were also investigated using XRD, X-ray diffraction laser particle size analysis and a gravimetric method, respectively. The results indicate that the elemental sulfur content of mechanically activated pyrite rises significantly and the lattice distortion ratio ( e ) rises only slightly with increasing grinding time. In contrast, the elemental sulfur content of mechanically activated sphalerite remains constant at 0.5 mg/g while the lattice distortion ratio ( e ) increases rapidly with increasing grinding time. Therefore, the formation of lattice defects on the surface of mechanically activated pyrite, and the lattice distortion on the surface of mechanically activated sphalerite may be mainly responsible for the enhancement of the leaching process for the corresponding sulfide minerals.

The recovery of Zn and Pb and the manufacture of lightweight bricks from zinc smelting slag and clay.

Novel lightweight bricks have been produced by sintering mixes of zinc smelting slag and clay. A two-stage sintered process has been proposed to recovery of Zn and Pb and reutilization of the zinc smelting slag. In the first stage of the process, called reduction and volatilization procedure, zinc and lead were reduced by the carbon contained in the zinc smelting slag and volatilized into the dust, and the dust can be used as a secondary zinc resource. In the second stage of the process, called oxidation sintering procedure, a lightweight brick was produced. Samples containing up to 60 wt.% zinc smelting slag and 40 wt.% kaolin clay were reduced at 1050°C for 6h, and then sintered at 1050°C for 4h. The recoveries of Zn and Pb from the brick are 94.5 ± 0.6% and 97.6 ± 0.2%, respectively. Low bulk density (1.42 g cm(-3)) and relatively high compressive strength (2 2MPa) sintered bricks were produced, and the leaching toxicity of the sintered bricks was below the regulatory thresholds of Chinese National Standards.

Amine/acid catalyzed synthesis of a new silica-aminomethyl pyridine material as a selective adsorbent of copper

A novel silica-supported 2-aminomethyl pyridine adsorbent was synthesized using a post-grafting route. This synthetic route involved the reaction of 2-aminomethyl pyridine (AMP) with γ-chloropropyltrimethoxysilane (CPTS) prior to immobilization on the silica support. Based on the extensive evidences that amines and acids can play an important role in silanization as an activator, meglumine and a mixture of hydrochloric acid and ethanol were utilized as a gentle but effective catalyst. Accordingly, three different synthetic pathways were investigated and the catalysis mechanisms of the amine and/or acid were discussed in detail. The synthesized silica-supported 2-aminomethyl pyridine adsorbent under both amine and acid catalyzed conditions was abbreviated as Si-AMP-M-H and characterized, its adsorption properties of Cu2+, Ni2+ and Co2+ were also studied. The adsorption capacity of Si-AMP-M-H for Cu2+ is comparable to commercial silica-supported AMP adsorbent. And the possible adsorption mechanism of Cu2+ onto Si-AMP-M-H is discussed. Moreover, Si-AMP-M-H shows a favorable selectivity for Cu2+ in simulated cobalt electrolyte solution in the presence of nickel. Adsorbed Si-AMP-M-H can be readily regenerated by acid-ammonia treatment. The results suggest that the Si-AMP-M-H prepared here could be promising for cobalt hydrometallurgical purification processes.

Microscopic Insights into Extraction Mechanism of Copper(II) in Ammoniacal Solutions Studied by X-ray Absorption Spectroscopy and Density Functional Theory Calculation

A microscopic investigation on the extraction process of copper(II) in ammoniacal solutions has been performed by X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculation. The structural change of copper(II) species in ammoniacal solution has been derived from X-ray absorption near-edge spectroscopy (XANES) by principal component analysis and linear combination fitting. It was found that the coordination structure of the extracted copper complex in the organic phases is planar square and independent of the aqueous pH, whereas the geometries of copper(II) species in ammoniacal solutions changed from axially elongated octahedron to distorted planar square with increase of pH. The coordination geometry and structural parameters of copper(II) species were further obtained by extended X-ray absorption fine structure (EXAFS) fitting and DFT calculation with the B3LYP functional. These results reveal that the formation of tetracoordinated copper(II) ammine species can evidently inhibit the copper extraction reaction. Thus, the extraction mechanism of copper(II) in ammoniacal solutions has been elucidated in view of the microscopic structural aspects of copper species in both organic phase and ammoniacal solutions.

Phase separation in solvent extraction of copper or nickel from acidic solution using a sulfonic acid (HDNNS) and a carboxylate ester (4PC)

Abstract Phase separation behavior is a critical character in determining the usefulness of a solvent extraction system in hydrometallurgy. A survey of the synergistic mixture containing dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexly 4-pyridinecarboxylate ester (4PC) for the extraction of copper or nickel from acidic single metal sulfate solution has been carried out to suggest how the physicochemical properties (density, viscosity and interfacial tension) and the morphology of the reverse micelles in the loaded organic phase affect the phase separation behavior in this paper. The specific settling rates (SSR), physicochemical properties, metal concentration and the excess water uptake (the content of water solubilized into the water pool of the reverse micelles) in the loaded organic phase during the extraction of Cu(II)/Ni(II) have been measured. The results show that the most effective parameters affecting the phase separation behavior are the viscosity and the excess water uptake of the loaded organic phase. We assume that the deceleration of the SSR is mainly due to the apparent increase of these two parameters or in a microscopic view, the apparent change of the morphology of the reverse micelles in the loaded organic phase. The small angle X-ray scattering (SAXS) results provide a direct evidence of such microstructural changes and well supports our assumption. Graphical Abstract

Structural insights into the extraction mechanism of cobalt(II) with dinonylnaphthalene sulfonic acid and 2-ethylhexyl 4-pyridinecarboxylate ester

Abstract In this work, to elucidate the synergistic extraction mechanism of cobalt(II) with dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexyl 4-pyridinecarboxylate ester (L), hexaaquacobalt(II) naphthalene-2-sulfonate (compound 1) was prepared using naphthalene-2-sulfonic acid (HNS, the short chain analog of HDNNS) and di-methyl isonicotinate tetraaquacobalt(II) naphthalene-2-sulfonate (compound 2) was prepared using methyl isonicotinate (LI, a short chain analog of 2-ethylhexyl 4-pyridinecarboxylate ester) and HNS; the compounds were studied by single crystal X-ray diffraction. Moreover, 2 and the actual extracted cobalt(II) complex were further investigated by Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The results indicated that the actual extracted cobalt(II) complex possesses a similar coordination structure as 2. Combined with the results obtained by single crystal X-ray diffraction of 1 and 2, FT-IR and ESI-MS of 2 and the actual extracted cobalt(II) complex, it is reasonable to conclude that the extracted cobalt(II) complex with the actual synergistic mixture is much more stable than the cobalt(II) complex with HDNNS alone. Therefore, the extraction selectivity cobalt(II) is effectively enhanced with the addition of 2-ethylhexyl 4-pyridinecarboxylate ester to HDNNS.

Insights into the extraction mechanism from the coordination chemistry of copper(II) with a synergistic mixture which mimics Versatic10 and 2-ethylhexyl 4-pyridinecarboxylate ester

Abstract In the present work, a copper(II) synergist complex with methyl isonicotinate (LI, a short chain analog of 2-ethylhexyl 4-pyridinecarboxylate ester) and isobutyric acid (HBI, a short chain analog of Versatic10) was synthesized and studied by X-ray single-crystal diffraction. The results indicated that the copper(II) synergist complex obtained with isobutyric acid and methyl isonicotinate crystallizes in the monoclinic C2/c space group and confirmed the composition [Cu(BI)2(LI)]2. The crystal structure consisted of centrosymmetric dimeric units, in which the two Cu ions are bridged in pairs by four carboxylate groups of the deprotonated isobutyric acid. In order to bridge the gap between the solid-state structure of the copper(II) synergist complex obtained with isobutyric acid and methyl isonicotinate and the solution structure of the extracted copper(II) complex in the non-polar organic phase, the two copper(II) complexes were further investigated by Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The results indicated that the extracted copper(II) complex in the non-polar organic phase has a similar coordination structure as the copper(II) synergist complex obtained with isobutyric acid and methyl isonicotinate.

FT-IR, XPS and Density Functional Theory Study of Adsorption Mechanism of Sodium Formate onto Goethite or Hematite

The adsorption of sodium formate on goethite or hematite surface was investigated by FT-IR and XPS, respectively. Periodic plane-wave density functional theory (DFT) calculations were performed on models of carboxylate surface complexes on the goethite (101), (100) surfaces or hematite (001) surface. The photoemission core-level shifts (CLS) of the adsorbed surface iron sites calculated with periodic interfacial structures were compared with the experimental XPS. FT-IR results reveal that the interfacial structures may be assigned to bidentate mononuclear (BM) complexes formed via bonding of one surface iron atom of goethite or hematite to both oxygen atoms of carboxylate group. In agreement with the adsorption energies determined by DFT calculations, the calculated results show that only the calculated Fe2p CLS of the adsorbed surface iron sites on goethite (100) and hematite (001) surfaces are correspondingly in accordance with the experimental observed Fe2p CLS, which confirms that the BM structure occurs upon adsorption.