Selective Separation of Molybdenum as Volatile Halides from Deep-Sea Ferromanganese Nodules

Abstract

A simple and rapid method for a selective separation of Mo from deep-sea ferromanganese nodules is described. Sulfation of the ground nodule material with a gas mixture of SO₂ and O₂ at elevated temperatures results in the sublimation of the Mo therein. The sublimates are mainly composed of pure MoCl₄ and MoO₂Cl₂ which are readily soluble in water. Addition of alkali metal halides to the nodules prior to sulfation increases the Mo recovery to over 95% in 30-min sulfation at 400 to 500 [ddot]C. The sulfation process, developed primarily for the selective separation of Mn, Cu, Ni, and Co, can be effectively used for Mo separation without complication.     

Recovery of Metals from Process Streams of Deep-Sea Ferromanganese Nodules by Adsorptive Bubble Techniques

Abstract

A method for the separation of Cu, Co, Ni, and Zn with varying degrees of selectivity from chemically treated deep-sea ferromanganese nodules is described. Quantitative removal of these species is achieved primarily by precipitate flotation of insoluble sulfides. Recovery of residual metal values of Cu, Co, Ni, and Zn in process rejects of the nodules is also possible. The quantitative removal of Pb and V, which are the most abundant toxic elements in nodules and tailings, is achieved simultaneously. Cationic and anionic surfactants are employed for collection depending on zeta potentials of the flocs generated upon addition of Na₂S to sample solutions. Separations are more selective and efficient at lower pH than previously reported for flotation of metals from nodules as insoluble hydroxides. Modifications resulting in slight improvements over previously employed high temperature sulfation processes are also described.     

Separation of Metals from Sulfated Deep-Sea Ferromanganese Nodules by Adsorbing Colloid Flotation

Abstract

Adsorbing colloid flotation (ACF) is applied to aqueous leach solutions of sulfated deep-sea ferromanganese nodules and their process tailings. Metal cations of Cu, Co, Ni, Mn, Al, and Zn are separated simultaneously by flotation with hydroxide collectors and cationic surfactants from the leach liquors of sulfated ferromanganese nodules. Applications of ACF to the nodule tailings also makes possible the recovery of residual Cu, Co, Ni, Ti, Zn, Al, Fe, Mn, and the separation of Pb and V, the most abundant toxic species in the nodules and tailings.     

Effects of O2 on aqueous SO2 leaching of Co,Cu and Ni from discard smelter slag

In the leaching of non‐ferrous smelter slag with a dissolved gas mixture of SO₂ and O₂, the behaviour of Co, Cu, Ni, Zn and Fe was studied in a 1‐L batch reactor. The parameters investigated include P_SO2, P_O2, temperature, particle size and pH. Co, Zn and Fe behaved similarly while Ni and Cu displayed distinguishable characters. The addition of O₂ prevented the precipitation of Cu after dissolution, and increased acidity of the leaching solution. The increase in acid strength resulted in an increase in the extraction of Co, Zn and Fe. The effect of acidity on Cu and Ni extraction was however much weaker. The combination of SO₂ and O₂ was found to be a more effective oxidant of Fe(II) to Fe(III) than O₂ alone. Simultaneous extraction of valuable metals and removal of Fe could be achieved by leaching at pH of 3 to 4. Maximum selectivities obtained for Co, Ni and Cu over Fe were 300, 2000 and 4000, respectively.     

Cobalt and Copper Composite Oxides as Efficient Catalysts for Preferential Oxidation of CO in H2-Rich Stream

A series of Co–Cu composite oxides with different Co/Cu atomic ratios were prepared by a co-precipitation method. XRD, N₂ sorption, TEM, XPS, H₂-TPR, CO-TPR, CO-TPD and O₂-TPD were used to characterize the structure and redox properties of the composite oxides. Only spinel structure of Co₃O₄ phase was confirmed for the Co–Cu composite oxides with Co/Cu ratios of 4/1 and 2/1, but the particle sizes of these composite oxides decreased evidently compared with Co₃O₄. These composite oxides could be reduced at lower temperatures than Co₃O₄ by either H₂ or CO. CO and O₂ adsorption amounts over the composite oxides were significantly higher than those over Co₃O₄. These results indicated a strong interaction between cobalt and copper species in the composite samples, possibly suggesting the formation of Cu _x Co_3?x O₄ solid solution. For the preferential oxidation of CO in a H₂-rich stream, the Co–Cu composite oxides (Co/Cu = 4/1–1/1) showed distinctly higher catalytic activities than both Co₃O₄ and CuO, and the formation of Cu _x Co_3?x O₄ solid solution was proposed to contribute to the high catalytic activity of the composite catalysts. The Co–Cu composite oxide was found to exhibit higher catalytic activity than several other Co₃O₄-based binary oxides including Co–Ce, Co–Ni, Co–Fe and Co–Zn oxides.     

Effects of sulfation on the activity of Ce0.67Zr0.33O2 supported Pt catalyst for propane oxidation

The sulfated Ce_0.67Zr_0.33O₂ support was prepared by impregnated with sulfuric acid solution, and the influence of sulfation on propane oxidation activity of the corresponding Pt supported catalysts was evaluated. Sulfation of the ceria–zirconia mixed oxides inhibits its intrinsic activity severely but promoted the Pt supported catalysts significantly. It is evidenced by CO adsorption that the interaction between sulfates and platinum makes the latter in more deficient states (Pt^δ+). These metastable Pt^δ+ species are liable to the atmosphere and act as active sites for propane oxidation.     

Effect of sulfur dioxide on nitric oxide adsorption and decomposition on Cu-containing micro- and mesoporous molecular sieves

NO decomposition was studied at different temperatures on copper-exchanged ZSM-5, AlMCM-41 and NbMCM-41 molecular sieves. Cu-ZSM-5 zeolites presented the highest activity. SO₂ poisoning was also performed and Cu–NbMCM-41 was found to be more resistant. IR results of NO and SO₂ coadsorption either at room temperature or at 573 K show evidence that sulfate formation occurred at 573 K and partially prevented NO adsorption on Cu²⁺ in square planar structure in Cu-ZSM-5. Sulfation of Cu–NbMCM-41 was quite low due to niobium incorporated into the lattice. By contrast, niobium present in the extra-lattice position in CuNb-ZSM-5 and CuNb–AlMCM-41 did not protect the catalyst from sulfation. H₂-TPR results suggested that sulfates were formed on copper sites. IR spectra after treatment under SO₂ + O₂ at 673 K indicated that sulfated species were covalently bonded, their structure varying according to the nature of the support. This revised version was published online in August 2006 with corrections to the Cover Date.     

Acid dissolution of manganese nodules after electric discharge

Valuable metals in manganese nodules can be rendered highly soluble in sulphuric acid by forming an electric cell with manganese nodules as a cathode active material and by discharging the cell, eliminating the need for treatment under severe conditions such as elevated temperatures and/or high pressures which is often the method for conventionally treating manganese nodules. A partial electric discharge has yielded higher metal extractions, eg nearly 95% of the Ni, Co and Cu metals contained, rather than a complete drainage of the electric current from the deep-sea nodules. Even in the latter case, however, the discharged nodules have shown a much better extractability of the metals by subsequent H₂SO₄ treatment, in comparison with the direct H₂SO₄ leaching.     

DRIFTS study of the catalytic N2O reduction by SO2 on FeZSM-5

SO₂ has been recognized as an effective reducing agent for N₂O over iron-containing zeolite catalysts, lowering the operation temperature up to 100 K with respect to the direct N₂O decomposition. This unique behavior contrasts with the common poisoning effect of SO₂ over other active de-N₂O metals (e.g. Co, Cu, Rh, and Ru). The formation of surface sulfates has been generally posed as the main cause for catalyst deactivation by SO₂. Through the use of in situ infrared spectroscopy (DRIFTS), we show that steam-activated FeZSM-5 indeed builds up stable sulfate species during the N₂O + SO₂ reaction. Significant amounts of sulfur were detected in the used catalyst by elemental analysis and X-ray photoelectron spectroscopy. However, the enhanced N₂O conversion is remarkably stable, indicating that the reducing action by SO₂ and the sulfation of the surface are decoupled. The resulting sulfate species are thus spectators in the catalytic process and do not block or alter the structure of the active sites for N₂O reduction and decomposition.     

Recovery of Al,Co, Cu,Fe, Mn,and Ni from Spent LIBs after Li Selective Separation by the COOL-Process. Part 1: Leaching of Solid Residue from COOL-Process

Lithium recycling from spent LIBs along the COOL-process produces a Li-free metal rich black mass, which still contains the entire fraction of valuable metal such as Co, Ni, and Mn. A recycling process was developed, which allows for mobilizing these metals. The first process stage is the selective leaching of Li via COOL-process. Subsequently, two inorganic (H₂SO₄ and HCl) and two organics acids (citric and gluconic acid) were tested for mobilizing the metals from the solid residue. To optimize this process stage, acid concentration as well as addition of H₂O₂ as a reduction reagent were investigated. The optimal conditions to dissolve valuable metals such as Co, Cu, Fe, Mn, and Ni was identified as 2 N H₂SO₄ and 2 vol % H₂O₂.     

Binary spinel cobaltites of nickel,copper and zinc as precursors of catalysts for carbon oxides methanation

The hydrogenation of carbon oxides (CO and CO₂) on bimetallic Cu/Co and Ni/Co as well as Co/ZnO catalysts obtained by reduction of the corresponding spinel cobaltites Me_xCo_3-xO₄ is investigated. The predominant hydrogenation process is methanation and in the case of nickel cobaltite high and stable activity and selectivity are reached, no carbon deposition and carbide formation being observed.     

Mechanism for the reduction of NOx on Rh/sulfated titanias

Titanias of different surface areas have been sulfated and used as supports of Rh oxide for the selective catalytic reduction of nitrogen oxides. Only the sulfation of TiO₂ of large surface areas gives strong Br?nsted acid sites, retaining pyridine up to 773 K. Low surface area anatase is unable to retain sulfates. The catalytic activities measured at 523 K, increase with the number of acid sites, and then reach a plateau, showing the intervention of acidity in the SCR. This is true only for Rh but not for Pt. The investigation of the elemental steps on Rh/sulfated TiO₂ by in situ diffuse reflectance spectroscopy permits to clarify a few points: the oxidation of propene, presumably to acetaldehyde, occurs by the reaction with nitrates adsorbed on the support. The further oxidation of this intermediate by NO₂ yields an isocyanate, which can be hydrolysed to ammonia.     

Characterization and Catalytic Activities of Al2O3-Promoted Sulfated Tin Oxides

A series of Al₂O₃-doped (0.5–3 mol%) sulfated tin oxides have been prepared by a co-precipitation method, followed by sulfation and calcination. Textural and structural characterizations of these samples were performed by means of XRD, N₂ adsorption, XPS, DTG, Raman spectroscopy, diffuse reflectance UV-vis spectroscopy and ²⁷Al MAS NMR. FT-IR spectra of adsorbed pyridine were used to determine the acid properties. The addition of small amounts of Al₂O₃ (0.2–1.5 mol%) to sulfated tin oxide brings about a dramatic improvement of catalytic activity from 36.1 to 52.4–58.0% for acylation of 2-methoxynaphthalene with acetic anhydride.     

Heterogeneous Catalyzed Ozonation using Cu-Ni-Co Oxides for Degradation of Dichlorophenol

The ozone initiated oxidation of dichlorophenol (DCP) in aqueous medium, catalyzed by various loadings of Cu, Ni and Co oxides supported on γ-Al₂O₃ was studied, as function of ozonation time and pH. Ternary catalyst materials synthesized by a wet-impregnation were fully characterized. The XRD results showed metal oxides were well incorporated within the alumina phase. Microscope images illustrated that metal oxide particles are dispersed on the surface of the support. Dihydroxyfumaric acid and oxalic acid were, respectively, found to be major and minor oxidation products. The oxidation products were characterized by FT-IR, ¹H NMR, and mass spectral data.     

Simutaneous Removal of Heavy Metal Ions from Wastewater by Foam Separation Techniques

Abstract

The objective of the present work is to extend the application of adsorbing colloid flotation techniques to remove mixtures of metal ions. The systems studied are: 1) Co(II) and Cr(VI); 2) Co(II), Ni(II), and Cr(VI); 3) Cr(VI), Cu(II), and Zn(II); 4) Cr(VI), Cu(II), Zn(II), and Ni(II); 5) Cd(II), Pd(II), and Cu(II). Ferric hydroxide and aluminum hydroxide were used as the coprecipitant, and sodium lauryl sulfate was used as the collector and frother. The ionic strength of the solution was adjusted with NaNO₃ or Na₂SO₄. It was found that all the heavy metals can be removed effectively by a single step foam flotation treatment.     

New thermochemical cycles for hydrogen production

The ease of decomposing some metal sulfates to oxides and sulfur trioxide is employed in the search for efficient closed cycle thermochemical methods for water splitting. The main features of the new processes are the production of O₂ through the decomposition of SO₂ and/or SO₃, the production of hydrogen by the decomposition of H₂S, reaction of H₂S with a metal, reaction of water with a metal, and/or reaction of water with sulfides.     

Characteristics of Cobalt Adsorption on Prepared TiO2 and Fe-Ti-O Adsorbents in High Temperature Water

Abstract

TiO₂ and Fe-Ti-O adsorbents were prepared by hydrolysis of Ti(OC₃H₇)4 and by alkalizing an equimolar mixed solution of TiCl₄ and FeCl₂, followed by heat treatment of their hydroxides. Their structures were studied by x-ray diffractometry and TG-DTA. The Co²⁺ adsorption characteristics of the adsorbent in high temperature water were investigated in a stirred autoclave. The prepared Fe-Ti-O adsorbent was found to be a stable nonstoichiometric ferrous/ferric titanium oxide with pseudobrookite and rutile structures. The Co²⁺ adsorption capacity of the Fe-Ti-O adsorbent was determined to be larger (0.38 meq Co²⁺/g adsorbent at 280[ddot]C) than that of TiO₂ at high temperature. The enthalpy changes (ΔH[ddot]) of about 34 and 49 kJ·mol^?1 due to the adsorption of Co²⁺ on the TiO₂ and Fe-Ti-O adsorbents, respectively, indicates that the adsorption is endothermic in the experimental temperature range (150–280[ddot]C). It is shown that the specific surface areas of these adsorbents are not dominant factors for Co²⁺ adsorption on oxides at high temperature.     

Trace metal distribution in fractions of solvent-refined coal by ICP-OES and implications regarding metal speciation

Separations of Amax solvent-refined coal according to its acid/base/neutral components and by selective elution from a silica column (SESC) to yield nine fractions have been carried-out. After ashing with H₂O₂-H₂SO₄, twenty metals (Mg, Al, P, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Mo, Cd, Sr, Zr, W, Hg and Ba) were analysed by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). A majority of elements (Zn, Cd, Hg, Cr, Mo, W, and Fe) were found concentrated in the acid fraction while Co, Ni and Cu preferred the neutral and base fraction. In the step gradient SESC fractions, the greatest concentration of metal was found in fractions that had been characterized as enriched with phenols.     

A thermogravimetric and FT-IR study of the reduction by H2 of sulfated Pt/CexZr1−xO2 solids

The nature, concentration and reducibility by H₂ of sulfate species formed from SO₂ oxidation were studied over a range of Pt/Ce_xZr_1−xO₂ catalysts using infrared spectroscopy and thermogravimetry. Ionic sulfates were formed over ceria and Ce-containing catalysts, even at high Zr content. The sample-specific surface area, the presence of platinum and the zirconium proportion affected the rate and extent of formation of sulfate in the bulk of the materials. Sulfate reduction by H₂ first occurred at the Ce_xZr_1−xO₂ surface. Bulk-like S-containing species subsequently migrated towards the surface to continuously replace surface sulfates removed by the reduction. The temperature required for sulfate migration as well as that necessary for sulfate reduction increased with the Zr content. The amount of stored sulfur is closely linked to the specific surface area of the sample. Finally, we have clearly shown that thermogravimetry was an appropriate technique for evaluating the oxygen storage capacity (OSC) of sulfated ceria–zirconia mixed oxides, despite the additional complexity due to the presence of sulfate compounds and various reduced S-species that can be formed during sample reduction.     

A comparative study of different leaching processes for the extraction of Cu,Ni and Co from a complex matte

The extraction behaviors of Cu, Ni and Co from a complex matte under different leaching conditions have been discussed. The synthetic Cu-Ni-Co-Fe-S matte was prepared by melting the pure metals. The matte contained 24.95% Cu, 35.05% Ni, 4.05% Co, 11.45% Fe, 24.5% S, similar composition as is expected to be obtained by reduction smelting of the Pacific Ocean nodules followed by sulphidisation of the alloy. The different phases identified are CuFeS₂, CuS₂, (FeNi)₉S₈, (FeNi)S₂, Ni₉S₈, Ni₃S₂, (CoFeNi)₉S₈ and Co metal. The merits and demerits of each process of dissolution i.e., H₂SO₄/oxygen pressure leaching, atmospheric FeCl₃ leaching, NH₄OH/(NH₄)₂SO₄ pressure leaching are discussed in detail. Out of the three, the H₂SO₄/oxygen pressure leaching process is found to be the most suitable with more than 99% metal extraction efficiency within 1 h of leaching time. From the X-ray diffraction analysis, the different undissolved phases corresponding to different leaching processes have been identified. The metal extraction efficiency decreased in case of atmospheric FeCl₃ leaching and NH₄OH/(NH₄)₂SO₄ pressure leaching processes due to the formation of product layer such as elemental sulfur and goethite, respectively.