Precipitation Of Mn Research Articles

Holocene environmental changes reflected by pollen, diatoms, and geochemistry of annually laminated sediments of Lake Suminko in the Kashubian Lake District (N Poland)

Pollen, non-pollen palynomorphs (NPPs), diatoms, and geochemistry of lake sediments with partially preserved annual lamination were used to reconstruct post-glacial environmental changes of northern Poland in the Baltic region. The main stages in the lake's evolution indicate the following: (1) eutrophic conditions in the final stage of the Lateglacial, (2) very low trophy and strongly changeable water levels in the early Holocene, (3) slowly rising trophy through the mid- and late Holocene enabling persistence of the oligotrophic state of the lake up to c. AD 1450, (4) strong cultural eutrophication of the lake in the recent period (c. 150years), and (5) maximum Ca content in the early Holocene followed by a gradual decline to minimum values in recent time. Distinct, concurrent shifts in limnological proxies and tree pollen accumulation rates (PARs) enabled the identification of several potential Holocene cool climatic events of different magnitudes and durations. Strong reduction in Tetraëdron minimum and declines in tree PARs illustrate limitation of physiological processes in plants, which could result from shorter growing seasons and lower summer temperatures and insolation. Higher precipitation of Fe and Mn indicates more intensive weathering in the catchment, while peaks in Fe/Mn ratio and concurrent drops in Ca content suggest at least seasonal anoxia, which could result from a longer duration of ice cover and shorter periods of mixing. The data seem to display striking conformity of the main cooling events with the “Bond cycles” (Bond et al., 1997, 2001), but also indicate a more variable pattern that may reflect traces of a more complex cyclicity of climatic shifts.

Atom probe tomography characterization of nitrogen induced decomposition in low temperature plasma nitrided 304L austenitic stainless steel

A three-dimensional atomic characterization of AISI 304L plasma nitrided at 400°C has been carried out with atom probe tomography (APT). While only a single phase, usually called γN phase or expanded austenite, can be detected by the X-ray diffraction, APT reveals the formation of nanometric MN (M=Cr, Fe) precipitates. Preferential precipitation of MN at planar defects has been observed. These results suggest that even at moderate nitriding temperatures the diffusion of Cr takes place resulting in slow but nevertheless detectable precipitation kinetics.

Effect of composition and heat treatment on MnBi magnetic materials

The metallic compound MnBi is a promising rare-earth-free permanent magnet material, unique among all candidates for its high intrinsic coercivity (Hci) and its large positive temperature coefficient. The Hci of MnBi in thin-film or powder form can exceed 12 and 26kOe at 300 and 523K, respectively. Such a steep rise in Hci with increasing temperature is unique to MnBi. Consequently, MnBi is a highly sought-after hard phase for exchange coupling nanocomposite magnets. However, the reaction between Mn and Bi is peritectic, and hence Mn tends to precipitate out of the MnBi liquid during the solidification process. As result, when the alloy is prepared using conventional induction or arc-melting casting methods, additional Mn is required to compensate the precipitation of Mn. In addition to composition, post-casting annealing plays an important role in obtaining a high content of MnBi low-temperature phase (LTP) because the annealing encourages the Mn precipitates and the unreacted Bi to react, forming the desired LTP phase. Here we report a systematic study of the effect of composition and heat treatments on the phase content and magnetic properties of Mn–Bi alloys. In this study, 14 compositions were prepared using conventional metallurgical methods, and the compositions, crystal structures, phase content and magnetic properties of the resulting alloys were analyzed. The results show that the composition with 55at.% Mn exhibits both the highest LTP content (93wt.%) and magnetization (74emug−1 with 9T applied field at 300K).

Pollution control and metal resource recovery for acid mine drainage

Although the metals contained in acid mine drainage (AMD) are considered environmental pollutants, they may also be valuable resources. The traditional chemical precipitation processes for AMD not only produce large amounts of sludge, but also make it difficult to recycle the waste metals. This study comprehensively investigated the recycling of Fe, Cu, Zn and Mn from AMD. Ferrous ions were first oxidised by 0.15ml/L 30% H2O2, and then a four-step fractional precipitation was applied with the selective addition of Ca(OH)2 and Na2S solutions. The Fe, Cu, Zn and Mn contents of particular sludges were 45.91%, 11.58%, 31.06% and 7.95% respectively, and the recovery efficiencies of Fe, Cu, Zn and Mn from AMD reached 99.51%, 86.09%, 87.87% and 79.71%, respectively. The metals contained in the effluent were below the Code of Federal Regulations (CFR) limits after the Mn precipitation process. Technology for the complete reuse of the sludge was also tested. Fe oxide red was obtained by roasting the Fe sludge for 30min at a temperature of 500°C, resulting in a Fe2O3 content of 85.18%. Cu and Zn crude concentrates were generated by a flotation process; the Cu and Zn contents of these concentrates were 35.72% and 55.13% respectively, and the recovery efficiencies of the Cu and Zn were 72.66% and 76.18%, respectively. The Mn sludge obtained can be used in cement mixes to replace 45% of ordinary Portland cement (OPC). Based on the technology tested, a comprehensive metal recovery process is proposed here for the control of metal pollution and metal recovery from AMD.

Synthesis of Fe 3 O 4 @SiO 2 @Ce 0.5 Mn 0.5 O 2 core–shell–shell magnetic submicrospheres as photocatalyst for methyl orange degradation

Core-shell-shell composite (Fe 3 O 4 @SiO 2 @Ce 0.5 Mn 0.5 O 2 ) submicrospheres were successfully synthesised by homogeneous precipitation of Ce and Mn on Fe 3 O 4 @SiO 2 spheres, which were prepared by a modified sol-gel method with the presence of Fe 3 O 4 particles. The synthesised multilayer-structured nanocomposites were characterised by X-ray diffraction, Fourier transform infrared spectroscopy, a transmission electron microscope and a vibrating sample magnetometer. The results show that the magnetic Fe 3 O 4 cores were well wrapped by the coating layer of SiO 2 with a thickness of 20 nm in the amorphous phase, and the Ce 0.5 Mn 0.5 O 2 nanoparticles with a diameter of about 20 nm were attached on the SiO 2 shell. The magnetic measurements indicated that the Fe 3 O 4 @SiO 2 @Ce 0.5 Mn 0.5 O 2 submicrospheres had a superparamagnetism property with the saturation magnetisation of 32.5 eum g -1 . At the same time, the composites demonstrated a high photocatalytic activity for methyl orange (MO) degradation with efficiency up to 94.5% under UV irradiation within 1 h. Moreover, the submicrospheres were found to be stable under repeated applications of up to five successive cycles with a nearly constant photocatalytic activity. It is expected that the catalyst could be used for trace pollutants (MO) removal from water and recycled because of its superparamagnetism properties and high photocatalytic activity.

The cathodic behaviour of Al–Mn precipitates during atmospheric and saline aqueous corrosion of a sand-cast AM50 alloy

The behaviour of Al–Mn precipitates during atmospheric and aqueous corrosion of an AM50 Mg alloy was investigated using site-specific analytical electron microscopy. After air-exposure, localized attack was observed close to Al–Mn precipitates, with the top layer of the intermetallic enriched in Al and O. During immersed corrosion, these precipitates developed protruding domes of corrosion products, with crystalline Mg(OH)2 on top and an inner layer of crystalline MgO. After prolonged immersion, these precipitates showed evidence of preferential Al dissolution, ultimately developing a fragmented interlayer of Mn3O4. This phase transformation is linked to the enhanced hydrogen evolution rates adjacent to these precipitates.

Radionuclide X-ray fluorescence analysis of selected elements in drug samples with 8-hydroxyquinoline preconcentration

The preconcentration performance characteristics of precipitation of Mn, Fe, Co, Cu, Zn, Pb, Ni and Hg with 8-hydroxyquinoline (8HQ) and subsequent filtration through cellulose nitrate membrane were investigated for the X-ray fluorescence spectrometry identification and determination of trace metal ions in drug samples. Several parameters of the method were optimised, including pH and amount of 8HQ. The investigated ions were collected on cellulose nitrate membrane filter (Pragopor 4) as their complexes after the reaction with 8HQ. To conclude, optimal reaction conditions were found out (pH 10.5 for Fe, Co and pH 11.5 for Mn, Cu Zn, Pb and Hg, volume of 20 μl of the 2 % solution of hydroxyquinoline). Thereafter, the content of these elements was determined in the active substances of the infusion and injection solutions, i.e. NaCl, glucose and dextrane, and the results were compared with those ones obtained after the preconcentration with thioacetamid. The rapidity of this method, its multi-element character and low detection limits proved this method to be a very promising in rapid screening in quality control of drugs.

Fe/Al ratios of suspended particulate matter from intermediate water in the Okhotsk Sea: Implications for long-distance lateral transport of particulate Fe

We have found that the ratio of Fe to Al in suspended particulate matter (SPM) in the intermediate layer of the Okhotsk Sea increases to the open ocean from the dense shelf water on the northwestern continental shelf, which is the source of southward-flowing Okhotsk Sea Intermediate Water (OSIW). The SPM concentration and the Al content of the SPM decrease along the course of the OSIW, whereas the ratios of Ba and Mn to Al increase. The SPM samples on the continental shelf were collected in waters characterized by low N⁎ (the deviation from the stoichiometric relationship between nitrogenous nutrients and phosphate). These low N* values imply that sedimentary denitrification occurs on the continental shelf, and both Fe and Mn are concomitantly reduced in the sediments and diffuse from the sediments to the overlying waters, where they are subsequently oxidized and precipitate. We assume that the SPM in the intermediate layer is influenced mainly by horizontal transport from the continental shelf to the ocean interior and that Ba can be used as a proxy for organic matter. Based on these assumptions, the results could reflect the following processes: 1) a gradual loss of denser lithogenic matter, evidenced by the decreases of the SPM concentration and of the Al content of the SPM, and 2) a relative increase of the Fe and Mn fractions associated with the organic matter in the SPM, which is derived from the continental shelf. The organic matter-related Fe and Mn could also be affected by the precipitation of both Fe and Mn just above the reduced sediments of the continental shelf. Our results show that the particulate Fe associated with organic matter is preferentially transported from the northwestern continental shelf to the open ocean.

Combining sedimentological, trace metal (Mn, Mo) and molecular evidence for reconstructing past water-column redox conditions: The example of meromictic Lake Cadagno (Swiss Alps)

Here, we present sedimentological, trace metal, and molecular evidence for tracking bottom water redox-state conditions during the past 12,500years in nowadays sulfidic and meromictic Lake Cadagno (Switzerland). A 10.5m long sediment core from the lake covering the Holocene period was investigated for concentration variations of the trace metals Mn and Mo (XRF core scanning and ICP-MS measurements), and for the presence of anoxygenic phototrophic sulfur bacteria (carotenoid pigment analysis and 16S rDNA real time PCR). Our trace metal analysis documents an oxic-intermediate-sulfidic redox-transition period beginning shortly after the lake formation ∼12.5kyr ago. The oxic period is characterized by low sedimentary Mn and Mo concentrations, as well as by the absence of any remnants of anoxygenic phototrophic sulfur bacteria. Enhanced accumulation/preservation of Mn (up to 5.6wt%) in the sediments indicates an intermediate, Mn-enriched oxygenation state with fluctuating redox conditions during a ∼2300-year long transition interval between ∼12.1 and 9.8kyr BP. We propose that the high Mn concentrations are the result of enhanced Mn2+ leaching from the sediments during reducing conditions and subsequent rapid precipitation of Mn-(oxyhydr)oxide minerals during episodic and short-term water-column mixing events mainly due to flood-induced underflows. At 9800±130calyr BP, a rapid transition to fully sulfidic conditions is indicated by the marked enrichment of Mo in the sediments (up to 490ppm), accompanied by an abrupt drop in Mn concentrations and the increase of molecular biomarkers that indicate the presence of anoxygenic photosynthetic bacteria in the water column. Persistently high Mo concentrations >80ppm provide evidence that sulfidic conditions prevailed thereafter until modern times, without any lasting hypolimnetic ventilation and reoxygenation. Hence, Lake Cadagno with its persistently stable chemocline offers a framework to study in great temporal detail over ∼12kyr the development of phototrophic sulfur bacteria communities and redox processes in a sulfidic environment, possibly depicting analogous conditions in an ancient ocean. Our study underscores the value of combining sedimentological, geochemical, and microbiological approaches to characterize paleo-environmental and -redox conditions in lacustrine and marine settings.

Effect of Aluminum on the Nucleation of Intragranular Ferrite in Ti-Added Carbon Structural Steel

AbstractThe features of inclusion and microstructure for Ti-added carbon structural steel were studied through the scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). From the SEM-EDS mapping images, two kinds of titanium-contained oxides are observed. The type I is the Al-Ti-O phase, in which the elements of Al and Ti coexist. The type II is the titanium-contained oxides, which precipitate on the Al2O3. Through the statistical analysis, it can be seen that the former type is dominating in number and smaller in size. After etching, the microstructure of intragranular acicular ferrites (IAF) is observed, which is totally different from that in the comparison sample without Ti addition. Furthermore, it’s found that the type I inclusion can act as nucleation sites for the IAF. However, the similar nucleation phenomenon is complex for the type II inclusion. This complexity is attributed to the diversity of precipitation of Ti and Mn.

Enhanced ferromagnetic response in ZnO:Mn thin films by tailoring composition and defect concentration

The presence of structural defects degrade the crystalline quality of ZnO:Mn thin films and affects the magneto-optical properties of ZnO:Mn thin films. The donor defects in ZnO, which are known to be the source of n-type conductivity in ZnO host matrix, play an important role in limiting the ferromagnetism to lower temperatures. A systematic study of structural, optical and magnetic properties was carried out with the primary focus on understanding the relationship between the defect concentration, material composition and ferromagnetic properties. Single phase ZnO:Mn thin films with wurtzite structure were grown under ambient argon–oxygen admixture to investigate the effect of stoichiometry and interstitial oxygen on magnetic properties. A consistent increase in crystallinity of ZnO:Mn thin films (without precipitation of Mn) with increasing argon–oxygen admixture gas pressure was observed. Extended near band edge (NBE) emission spectra with marked decrease in photoluminescence (PL) ratio in optical characterization revealed improved optical quality of ZnO:Mn thin films. Magnetic measurements revealed enhanced room temperature ferromagnetism (RTFM) in sample grown at optimum argon–oxygen ambient pressure. The enhancement was directly related to maximal core level X-ray photoelectron spectroscopic peak of stoichiometric ZnO which, in turn, favors strong hybridization of Mn in the ZnO host matrix.

Carbide and nitride precipitation during laser cladding of Inconel 718 alloy coatings

The microstructure of the laser clad Inconel 718 alloy coating was observed by scanning electron microscope (SEM). The chemical composition of precipitation phases was investigated by energy dispersive spectrometer (EDS) and solid phase microextraction (SPME). The crystal structure and lattice constants of precipitation are determined by transmission electron microscope (TEM). Vickers hardness of the coatings and the nanohardness of the interstitial phases were measured. The insular carbide (MC) and the tetragonal nitride (MN) with face-centered cubic (FCC) structure are rich in Ti and Nb but depleted in Ni, Fe and Cr due to the interdiffusion and redistribution of alloying elements between MC and MN and supersaturated matrix. MC and MN were precipitated in the forms of (Nb0.12Ti0.88)C1.5 and (Nb0.88Ti0.12)N1.5, and the Gibbs free energies of formation can be expressed as ΔG[(Nb0.12Ti0.88)C1.5]0=−122.654–3.1332T(kJ/mol) and ΔG[(Nb0.88Ti0.12)N1.5]0=−157.814–3.0251T(kJ/mol). The nanohardness and Young's modulus of the MC and MN were much higher than the matrix, and the plastic deformation energy of interstitial phases was lower than the matrix. The precipitation of MC and MN is beneficial to the mechanical properties of coating.

Theoretical simulation and experimental study on nickel, cobalt, manganese separation in complexation–precipitation system

The theoretical simulations and experiments on metal separation in complexation–precipitation system of Me(Ni, Co, Mn)–OH−–NH3–CO32- were carried out. The Gibbs free energy change ΔG for metal precipitation reactions was calculated. The ΔG–pH curves showed that the precipitation difficulty order was Mn>Co>Ni at pH range of 8–11. Separation experiments indicated that Mn and Co were able to precipitate successively in solution of different compositions mainly in the forms of carbonates. pH, initial carbonate concentration [C] and initial ammonia concentration [N] had different influence on Ni, Co and Mn precipitation behaviors: the separation effect was best at about pH 10; [C] had little effect on the metal separation in the [C] range of 0.05–0.4mol/L; changing [N] could regulate precipitation step by step, as Ni in solution and Mn/Co in precipitate at [N] 1mol/L, and Ni/Co in solution and Mn in precipitate at [N] 2.5mol/L. The experimental results basically consisted with the theoretical predictions. The Ni solution after Mn/Co precipitation could be electrodeposited to obtain Ni metal. Finally a separation process in complexation–precipitation system of Me(Ni, Co, Mn)–OH−–NH3–CO32- characterized by the theoretical simulation was proposed, of which the Ni, Co and Mn precipitation could be predicted or controlled by flexibly importing parameters of [C], [N], pH, etc. The process can provide a reference to metal comprehensive recovery from similar nickel–cobalt secondary resources.

Manganese precipitation kinetics and cobalt adsorption on MnO2 from the ammoniacal ammonium sulfate leach liquor of Indian Ocean manganese nodule

Precipitation of manganese from the SO2-roast leach ammoniacal ammonium sulfate solution bearing both high and low concentrations of manganese in the presence of copper, cobalt and nickel ions was carried out in a stainless steel reactor fitted with a turbo grid. Air/O2 was used to precipitate Mn as MnO2 from the solution. There was adsorption loss of cobalt from the solution. Precipitation of manganese from the solution was 57.2–99.9%. The maximum adsorption loss of Co was 22.1%. The precipitation of Mn and adsorption loss of cobalt from the solution followed the first order kinetics. The rate constants for the precipitation of manganese and loss of cobalt were evaluated and the experimental data were fitted to Freundlich and Langmuir adsorption isotherms.

Production of Chemical Manganese Dioxide from Lithium Ion Battery Ternary Cathodic Material by Selective Oxidative Precipitation of Manganese

We have conducted studies to produce chemical manganese dioxides (CMDs) from ternary cathodic materials by oxidative precipitation. In this study, a cathodic material was concentrated by pretreatment and leached with sulfuric acid to recover 1L of a leachate containing 22.0g/dm 3 of Co, 21.6g/dm 3 of Mn, 24.2g/dm 3 of Ni, 9.5g/dm 3 of Li and 8mg/dm 3 of Al as valuable metals. For selective oxidative precipitation of Mn (II), the leachate was reacted with 1 equivalent of Na2S2O8 based on the Mn concentration with stirring at 500rpm at a temperature of 363K for 18000s. As a result of the reaction, it was confirmed that the majority of Mn was precipitated from the solution. XRD, PSA, TG­DTA, LECO and ICP analyses were performed to characterize the precipitate. The analytical results revealed the production of a chemical manganese dioxide (CMD) having a chemical composition of 84.60% MnO, 1.40% Co3O4, 0.11% Li2O, 0.25% NiO, 0.02% Al2O3, 0.06% S and 0.52% Na2O, an average particle diameter of 10.7µm, a crystal form of £-MnO2, and a purity of at least 98%. [doi:10.2320/matertrans.M2012379]

Constraints on superoxide mediated formation of manganese oxides

Manganese (Mn) oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide () both of biogenic and abiogenic origin as an effective oxidant of Mn(II) leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III) and Mn(III/IV) oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide (H2O2), a product of the reaction of with Mn(II), inhibits the oxidation process presumably through the reduction of Mn(III). Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III)-ligand complexes. While complexing ligands played a role in stabilizing Mn(III), they did not eliminate the inhibition of net Mn(III) formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II) by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II) by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation.

Study of Precipitating Methods for Elimination of Heavy Metals from Acid Mine Drainage

Abstract The submitted paper deals with the study of combination of chemical and biological-chemical methods for the heavy metals elimination from the acid mine drainage. The experiments were carried out at the laboratory scale using a synthetic solution with similar properties to the real sample of acid mine drainage, originating from the zinc mine located in Tùnel Kingsmill outflow of the Rio Yaulì (district of Yauli - Perù). The successive repetition of the metal precipitations as hydroxides (chemical method) and sulphides (biological-chemical method) at the various acid mine drainage pH was the basis of the examined processes. For the hydrogen sulphide production the sulphate-reducing bacteria of genus Desulfovibrio were used. Results confirmed the precipitation of Fe, As, Al and Mn in the hydroxide form; Cu and Zn in the form of sulphides. For the selective removal of Cu, Zn, Al and Mn the excellent results were received. Selective precipitation of Fe and As was not so successful since the co-precipitation of Fe and As was later determined as a main mechanism of the precipitate forming.

Climate-controlled variability of iron deposition in the Central Arctic Ocean (southern Mendeleev Ridge) over the last 130,000 years

Distinct brown-coloured Mn-rich layers are common features in Quaternary sediments of the central Arctic Ocean, but their paleoenvironmental significance is disputed. Glacial–interglacial changes in bottom water ventilation, variable riverine input, and diagenetic processes have all been suggested to cause the cyclicity in optical and geochemical parameters in these deposits. To better assess the nature and origin of these sediment intervals and their implications for nutrient cycles, we applied bulk geochemical analyses and a sequential Fe extraction scheme to a sediment record covering the last ~130ka on the southern Mendeleev Ridge. All brown layers in this core are enriched in Mn, but also in Fe (oxyhydr)oxides (e.g., ferrihydrite, lepidocrocite, goethite) that contribute to the characteristic sediment colour. Phosphorus and several trace metals (As, Co, Cu, Mo, Ni) are also enriched, indicating that both Mn and Fe (oxyhydr)oxides adsorbed P and trace metals from the water column. The metal enrichments are most probably caused by a combination of enhanced Mn and Fe input from Arctic rivers and/or the erosion of shelf deposits, coupled with early diagenetic processes leading to precipitation of authigenic Mn and Fe (oxyhydr)oxides close to the sediment–water interface. Both primary supply and diagenetic recycling of metals should have been enhanced by a more intense hydrological cycle under warmer climate conditions, combined with seasonal increases in productivity and reactive organic matter export during ice-free conditions in the Central Arctic Ocean. Consequently, the studied metal (oxyhydr)oxide-rich layers were formed under interglacial/interstadial climatic conditions. In contrast, sheet silicate-bound Fe (e.g., chlorite), a second major Fe pool in these sediments (15–35% of total Fe), is enriched between the oxide-rich layers. Thus, the delivery of Fe-rich sheet silicates from the East Siberian hinterland or the Bering Sea, and subsequent deposition on the Mendeleev Ridge, was enhanced by more intense physical weathering during glacial/stadial periods. These contrasts in Fe speciation between the brown layers and the adjacent sediments document the direct response of biogeochemical element cycles to glacial–interglacial variations in river input, weathering regime, and sea level in the Arctic Ocean.

Image-analytically derived conceptual model of Albeluvisol morphological degradation induced by artificial drainage in France

Soils are a non-renewable resource and evolve through time in response to changes in land-use and environmental conditions. To predict this soil evolution requires the development of mechanistic modelling. Only a few attempts of this kind exist in the literature, and these often use an extremely simplified representation of soil structure, with the soil being frequently considered as a succession of homogeneous “boxes”. In this paper we have quantified the evolution of the soil structure during pedogenesis using image analysis. This analysis was performed along a sequence of morphological degradation in an Albeluvisol perpendicular to a drain. These soils, which are commonplace in Europe, are characterised by horizons consisting in a juxtaposition of soil volumes differing in texture (silty to clayey) and colour (ochre, pale-brown, white-grey and black). The image analysis approach was based on these differences in colour and combined i) a supervised training method using ERDAS IMAGINE® to assign the different pixels to the different types of soil volumes and ii) ARCInfo™ for characterisation of the morphology of the different soil volumes. The organisation of the different volumes in space suggests that ochre volume is transformed to pale-brown one and then to grey-white one, whilst black volume is formed within the residual ochre one, due to precipitation of Mn. As the process progresses along the drainage sequence, progressive indentation and final disintegration of the ochre volume are responsible for the release of the black volume into the pale-brown matrix. Ochre volume alteration takes place mainly at the border of the volume which is indicated by the geometry of the pale-brown and ochre volumes. Finally, the formation of the white-grey volume from the pale-brown one occurs in the core of the latter, mainly by eluviation, and is centripetal. We conclude that soil structure needs to be considered when modelling pedogenetic soil evolution.

Chemical and electrochemical recycling of the nickel, cobalt, zinc and manganese from the positives electrodes of spent Ni–MH batteries from mobile phones

Chemical and electrochemical recycling methods for the Ni, Co, Zn and Mn from the positives electrodes of spent Ni–MH batteries were developed. The materials recycled by chemical precipitation have the composition β-Ni(OH)2, Co(OH)2, Zn(OH)2 and Mn3O4. The powder retains sulphate, nitrate and carbonate anions from the mother solution as well as adsorbed water. Studies using cyclic voltammetry show that the current density decreases for scan rates greater than 10 mV s−1 because of the formation of hydroxide films. The amounts of Ni2+, Co2+, Zn2+ and Mn2+ were obtained by analysis of the solution using the inductively coupled plasma with optical emission spectroscopy technique, which demonstrated that the electrodeposition method exhibits anomalous behaviour. The amount of deposited nickel ions is related to the composition of the sulfamate bath. The presence of manganese in the electrodeposits is due to the precipitation of Mn(OH)2, and Zn(OH)42− does not undergo reduction in the investigated potential range. The electrodeposited material contains Ni, Co, CoO, Co(OH)2, and Mn3O4. A charge efficiency of 83.7% was attained for the electrodeposits formed by the application of −1.1 V vs. Ag/AgCl at a charge density of −90 C cm−2. The dissolution of the electrodeposits depends on the applied potential.