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Nanostructured cobalt is one of the key elements in catalysis and therapeutic drug delivery. To design and prepare nanosize-controllable cobalt, a better understanding of its growth mechanism is essential. Growth of Co nanoparticles encapsulated in carbon-shell (Co@C) during temperature-programmed carbonization of the Co2+-β-cyclodextrin (CD) complex at 363–573 K was, therefore, studied by in situ synchrotron small-angel X-ray scattering and X-ray absorption near edge structure spectroscopy. The carbon-shell having a thickness of about 2 nm can prevent the core Co from being aggregated and oxidized. A relatively slow reduction of Co(II) to Co is observed at 393–423 K (stage I) prior to a particle growth transition-state possessing Co of 2.2 nm in diameter at 423–483 K. At 483–513 K (stage II), an increasing Co(II) reduction rate coupled with a rapid fusion and coalescence of Co nanoparticles is found. The average growth rates of Co at stages I and II are about 27 and 98 atoms/min, respectively. The most-probable particle diameter of the ripened Co is 5.9 nm. The carbon-shell can be removed by steam reforming to yield the Co nanoparticles. This work also exemplifies the possible temperature-controllable growth of Co@C, especially in the Co size range of 2–6 nm in diameter.

Because global natural metal resources are depleting, this study aim to examine the chemical feasibility of recovering chromium as Cr(VI) from a Cr(OH) 3 -containing plating sludge through a co-heating procedure of the plating sludge with a incinerator fly ash that is rich in calcium hydroxide. The critical step in the process of recovering Cr from plating sludge would be to convert the water-insoluble Cr(OH) 3 into water-soluble Cr(VI). Results from Cr K-edge X-ray absorption near edge spectrum (XANES) suggest that majority of the Cr is in the form of CaCrO 4 after the co-heating procedure of plating sludge and the incinerator fly ash at different temperatures. Heating the mixture of the plating sludge and the incinerator fly ash results in an oxidation of Cr(OH) 3 that is basically water insoluble to Cr(VI) which is water soluble, consequently more Cr(VI) can be extracted with water and recovered from the heated mixture than from the non-heated plating sludge.

High-temperature plasma is used to stabilize the Ni in two wastes: a Ni-plating sludge cake and a spent Ni-containing solid catalyst. Only the latter sample had been thermally treated to recover precious metal by industrial practitioners before we received the wastes. The reaction temperature in the plasma chamber is >1500 °C, the chamber pressure is 0–6000 Pa less than the atmospheric pressure, and the reaction time for stabilizing the wastes is 60 min. The molecular environments of Ni in the stabilized and pre-stabilized sludge cake and spent catalyst samples are investigated with X-ray absorption spectroscopy (XAS) technique. All main peaks in the X-ray absorption near-edge structure (XANES) spectra from both plasma-treated wastes and the as-received spent catalyst are characterized with a shoulder towards the edge jump, suggesting a highly distorted Ni(II) environment in all samples except in the as-received plating sludge cake. Results from one-shell fitting of the Fourier transforms of X-ray absorption fine structure (EXAFS) spectra indicate that treating the spent catalyst with plasma barely increases the first-shell coordination number (from 5.59 to 5.81). For the plating sludge cake treated with plasma, however, Ni first-shell coordination number slightly increases from 5.74 to 6.60, suggesting that treatment at >1500 °C with plasma enhances the crystallite size of nickel compounds due to a greater sintering and/or melting reaction. In addition, the Ni second coordination shell in the sludge cake case before plasma treatment is well resolved; while it mixes with the outer (third and greater) shells after plasma treatment. Because the plating sludge cake (i.e., as-received) has never experienced any high-temperature environment like which the spent catalyst did prior to the plasma treatment, it is concluded that plasma treatment incurs considerable change in Ni molecular environment in the plating sludge cake.

Speciation and distribution of copper and zinc in the channels of the surface modified MCM-41 (MCM-41-SH) (pore opening = 2.6 nm) has been studied by X-ray absorption near edge structural (XANES) and X-ray absorption fine structural (EXAFS) spectroscopies in the present work. By least-square fitted XANES spectroscopy, mainly CuO and ZnO are observed in the channels of MCM-41-SH after calcination at 298–1173 K. Interestingly, a small amount of Cu–Zn alloys is also found in the MCM-41-SH at the calcination temperature of 573 K. At T > 573 K, nanosize CuO and Zn 2 SiO 4 are the copper and zinc compounds in the MCM-41-SH. Due to aggregation of nanosize CuO at 1173 K, the bond distance of Cu–O is increased to 1.97 A with the coordination number (CN) of 3.3. A decrease of the Zn–O bond distance (1.94 A) at 1173 K is also observed. This work is also an example of the usefulness of the XANES and EXAFS spectroscopies for revealing the chemical structure of copper and zinc and possible reaction paths in the channels of MCM-41-SH during calcination at elevated temperatures.

Soil sample from a site heavily contaminated with >10 wt.% zinc is sampled and extracted with aqueous solutions of ethylene diamine tetra-acetic acid (EDTA) that is a reagent frequently used to extract heavy metals in soil remediation. Three liquid/soil ratios (5/1, 20/1, and 100/1) were used in the extracting experiment. The molecular environment of the residual Zn in the EDTA-extract residues of zinc-contaminated soil is investigated with XANES technique. The results indicate that EDTA does not show considerable preference of chelating for any particular Zn species during the extraction. Zn species distribution in the sampled soil is found to resemble that in all EDTA-extract residues; Zn(OH)2 is determined as the major zinc species (60–70%), seconded by organic zinc (21–26%) and zinc oxide (9–14%).

Rice husk ash is a good sorbent to remove copper ions from industrial wastewater. To recover the sorbed copper, two reagents (nitric acid and sodium thiosulfate) were used to desorb copper from the rice husk ash. XAS was used to investigate speciation of the residual copper in the rice husk ash after desorption. XANES simulation indicates that the copper species distributions in all pre-desorbed and post-desorbed solid samples are 40–45% CuSO4 + 41–52% CuO + 7–16% Cu(OH)2. On the other hand, in the liquid phase collected from desorption by Na2S2O3, Cu2O accounts for 48% of the total copper. Formation of Cu2O is attributed to the chemical reduction of Cu(II) with Na2S2O3 that is a reductant.

Speciation of copper in a contaminated soil during electrokinetic remediation (EKR) assisted by H 3PO4 was studied by in situ X-ray absorption near edge structural (XANES) spectroscopy. The least-square fit of the XANES spectrum showed that CuCO 3 (68%) and CuCl2 (32%) were the major copper species in the contaminated soil. In the presence of H3PO4 (40%), most of CuCl2 and about 24% of CuCO3 were dissolved into the aqueous phase. After 90 min of EKR, at least 30% of Cu(II) ions were transported towards the cathode by electric field. A similar dissolution behavior of copper from the soil with 40% H 3PO4 and 2% H2O2 was also observed. Nevertheless, migration of Cu(II) ions to the cathode was highly enhanced in the presence of H3PO4 and H2O2 by EKR for the first 90 min. © 2005 Elsevier B.V. All rights reserved.

Speciation of copper on ZrO2 during the catalytic hydrogenation of CO2 has been studied by in situ extended X-ray absorption fine structural (EXAFS) spectroscopy in the present work. The EXAFS data indicated that about 3.1 nearest oxygen atoms surrounded the Cu atoms with a Cu O bond distance of 1.95 A in the calcined Cu/ZrO2 catalyst. Reduction of the catalyst in hydrogen at 573 K led to a formation of Cu Cu (2.56 A) bonds with a coordination number (CN) of 5.6. Mainly CO and CH3OH were generated in the hydrogenation of CO2 catalyzed by the reduced Cu/ZrO2 catalyst at 673 K. About 76% of the Cu(0) species was oxidized to Cu(I) (27%) and Cu(II) (49%) on ZrO2 during the catalytic hydrogenation process.

Mineralization of CCl4 with CuO has been studied by in situ X-ray absorption spectroscopy (XAS) in the present work. The least-square fitted X-ray absorption near-edge structural (XANES) spectra showed that 18.9–20.1% of CuCl2 was yielded in the mineralization of CCl4 with CuO at 513–603 K for 20 min. By in situ extended X-ray absorption fine structural (EXAFS) spectroscopy, the structural perturbation of CuO during mineralization was observed. The perturbation may be due to an insertion of Cl species into the matrix of CuO and formation of CuCl2. Bond distances of Cu O (first shell) and Cu (O) Cu (2nd shell) were increased by 0.01–0.04 A with slight decreases of their coordination numbers (CNs) in the mineralization process. CuCl2 in the CCl4-mineralized product solids possessed Cu Cl bond distances of 2.10–2.12 A, which were greater than that of the CuCl2 model compound (2.05 A). The in situ XAS technique exemplifies a direct observation of perturbation of CuO by Cl species during the mineralization at elevated temperatures.

By small angle X-ray scattering (SAXS) spectroscopy, changes of electronic density of selected element can be determined. A size growth of Cu–ZnO nanoparticles encapsulated in the carbon shell during temperature-programmed carbonization of Cu 2+ - and Zn 2+ -starch (Cu-to-Zn ratio = 1) at 343–523 K was observed by in situ SAXS. The Cu–ZnO@C behaves like a nanoreactor for catalytic partial oxidation of methanol (POM) to yield H 2 -rich product gas. It seems that the enhanced POM may be associated with the high collision frequency of methanol, oxygen (as O atoms) and copper catalytic species in the confined nanoreactor.

Dissolution of nanosize CuO in the chemical mechanical planarization (CMP) waste water in the presence of micropores (0.74 nm) of Y and mesopores (4 nm) of MCM-41 has been studied by X-ray absorption near edge structure (XANES) spectroscopy in the present work. Since pore openings of Y and MCM-41 are much less than the size of nano-CuO (about 13 nm) in the CMP waste water, CuO is not able to be incorporated directly into the pore systems. At least two reaction paths might be involved in the incorporation process: (1) dissolution of CuO and (2) incorporation of Cu 2+ into Y and MCM-41. Experimentally, during the incorporation process, Y might possess equivalent electric fields of 20–50 V/cm for dissolution of nanosize CuO. Interestingly we found that dissolution of nanosize CuO in the CMP waste water was enhanced, for instance, about 65% and 87% of nanosize CuO were incorporated (as Cu 2+ ) and incorporated into Y and MCM-41, respectively.

Speciation of zinc in phosphor wastes during electrokinetic treatments has been studied by in situ X-ray absorption near edge structure (XANES) spectroscopy in the present work. The least-square fits of the in situ XANES spectra show that the major zinc species in the phosphor waste are ZnS (77%), ZnO (10%), and Zn(OH)2 (13%). During the electrokinetic treatment for 90 min, 25% of ZnS and 4% of ZnO are dissolved. About 42% of zinc is enriched on the cathode under the electric field (5 V/cm). Prolonging the electrokinetic treatment time to 4 h under the electric field of 5 V/cm, at least 80% of zinc in the phosphor waste can be recovered. © 2007 Elsevier B.V. All rights reserved.

In order to enhance the sensitivity (ethanol) of the ZnO films, Fe3+ was incorporated onto the ZnO (Fe/ZnO) thin films. The least square fitted the X-ray absorption near edge structure (XANES) spectra show that the main species in the ZnO–Fe thin film are ZnO, Fe2O3 and Fe3O4. When sensing of 300 ppm ethanol, the in situ extended X-ray absorption fine structure (EXAFS) spectra indicate that the bond distances of Zn O and Fe O are 1.90 and 1.98 A, respectively and restored to 1.91 and 1.97 A in the absence of ethanol.

Tracking of copper in the soils contaminated by a nearby printed circuit board (PCB) waste recycling plant and the wire-burnt residue has been studied by X-ray absorption near edge structure (XANES) spectroscopy. The contaminated soils have a very high total and leaching concentrations of copper which are in excess of limit (15 mg/L). By XANES, we found that Cu(OH)2 (44%), CuCl2 (34%), and CuSO4 (16%) were the main copper compounds in the soil contaminated by the copper slag that was discharged from the PCB recycling plant. The additional contaminated site caused by the illegally wire-burnt residue also has high total and leaching copper concentrations. The main copper compounds in the contaminated soil were CuSO4 (41%), CuCl2 (39%), and Cu2O (19%). In the downstream soil (nearby a river (2 m)), the main copper compounds such as Cu(OH)2 (46%), Cu(NO3)2 (35%), and Cu2O (9%) were found. The speciation of copper in the contaminated soils can be very helpful in the development of effective remediation methods. © 2007 Elsevier B.V. All rights reserved.

Speciation of copper in the laboratory waste incineration ashes and plasma-melted slag has been studied by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXFAS) spectroscopies. The component-fitted XANES spectra show that main copper species in the bottom and fly ashes are CuO (9–45%), Cu(OH) 2 (25–40%) and nanosize CuO (30–35%). During the plasma melting process at 1773 K, about 97% of Cu 2 S in the slag is observed possibly due to sulfurization and self-reduction of CuO at high temperatures. By EXAFS, we also found that copper in the bottom and fly ashes possessed Cu O bond distances of 1.97 and 1.99 A with coordination numbers (CNs) of 2.1 and 2.3, respectively. In the slag, the bond distance of Cu–S is 2.3 A with a CN of 3.8.

Experimentally, 70–80% of copper in the chemical–mechanical planarization (CMP) wastewater was abstracted in the molecular sieve MCM-41 and zeolites Y at 298 K (for 4 h). The least-square fitted X-ray absorption near edge structural (XANES) spectra showed that mainly CuO clusters (47%) and adsorbed copper (CuO) (22%) were abstracted in MCM-41. In zeolite Y, CuO clusters (42%), Cu 2+ (41%) and CuO (14%) were found. Moreover, about 20% of nano-CuO in the CMP wastewater were abstracted and formed as CuO clusters in the channels of MCM-41. The Fourier transformed extended X-ray absorption fine structural (EXAFS) data also indicated that the abstracted copper in MCM-41 or zeolite Y possessed Cu O bond distances of 1.96–1.97 A with a coordination number (CN) of 3.4.