Academic literature on the topic 'Nontronita'

AbstractThe synthesis of clay minerals has been studied for decades in an attempt to better understand their formation in natural environments and more recently to obtain clay minerals with controlled compositions and properties. Even though nontronite has been synthesized successfully since 1935, the process is not a straightforward and has been poorly documented. In the present review concerning the synthesis of nontronite and other Fe-rich smectites, the experiments attempted in the past are discussed critically in light of the most recent data. Most notably, the application of relationships established recently, thanks to synthetic smectitic series, have allowed us to refine the chemical compositions of some nontronites synthesized previously.

AbstractFive Fe–bearing dioctahedral smectites (three nontronites and two Fe-rich smectites) were purified using a variety of physical and chemical procedures. The structural formulae indicate one nontronite and one Fe-rich smectite to be montmorillonitic, whereas the other three smectites are beidellitic. Mössbauer spectra showed Fe to be exclusively trivalent and were fitted with three doublets, two of which had quadrupole splittings characteristic of Fe3+ in octahedral coordination, whereas the third had a distinctly lower quadrupole splitting. Although the position of the Si–O stretching band in the infrared spectra could reflect tetrahedral Fe3+, the lack of distinctive features prevented a definitive attribution of this component to tetrahedral Fe3+. The 18O/16O data suggest that fractionation of nontronite-water at ambient temperatures (1000 lnα = 23 ± 2‰) is lower than that of Fe-rich smectite (1000 lnα = 27 ± 2‰). The estimated formation temperatures of the samples are below 70°C.

AbstractLateritic weathering profiles developed on serpentinized peridotites of Murrin Murrin (Western Australia) exhibit thick smectite zones (10–15 m). The smectites from plasma and fissures were characterized by XRD, chemical analyses (ICP-AES, SEM-EDX and TEM-EDX) and Mo¨ssbauer spectroscopy. These Fe-rich smectites, previously described as nontronites, are in fact more complex. Their layer charges originate from both the tetrahedral and octahedral sheets. Plasma and notably fissure smectites exhibit, from the bulk sample scale to the particle scale, large and continuous Al for (Fe+Cr) substitutions, covering a chemical gap previously described for dioctahedral smectites ranging between nontronite and beidellite end-members. Lastly, they exhibit an octahedral occupancy slightly above 2, due to a low (Mg+Ni) trioctahedral contribution. Thus, the smectites occurring in weathering profiles of ultrabasic rocks can have actual chemistries intermediate between four dioctahedral end-members (beidellite, nontronite, montmorillonite and previously rarely described ferric-montmorillonite) and a trioctahedral one ((Mg+Ni)-saponite).

O presente trabalho teve por objetivo caracterizar, física, química e mineralogicamente, os solos localizados nas várzeas de Sousa (Sertão da Paraíba), bem como verificar o efeito dos cátions alcalinos e alcalino-terrosos na estabilidade das substâncias húmicas. Procurou-se, ainda, identificar os critérios de distinção de ambientes utilizados pelos pequenos agricultores e as diferentes formas de uso dos solos da região estudada. Para isso, foram selecionados, amostrados e analisados perfis de solos das classes: Neossolo Flúvico, Luvissolo, Planossolo Nátrico e Vertissolo Cromado. Constatou-se que, além do sódio, o magnésio teve participação efetiva na dispersão de argila, principalmente nos Vertissolos. Os teores de Fe2O3 foram baixos em todos os perfis, com provável predomínio das formas menos cristalinas, identificadas pelas altas relações Feo/Fed. A mineralogia cálcio-sódica da fração silte é condizente com os teores, relativamente elevados, de cálcio, magnésio e sódio, sendo, provavelmente, o principal responsável por esses valores nos solos estudados. Na fração argila de todos os solos, foi observada a presença marcante da vermiculita/esmectita e ilita. Nos Vertissolos, o teor expressivo de ferro na fração argila revela, além da presença da hematita, a ocorrência de mineral 2:1 expansivo rico em ferro, sobretudo a nontronita. O pré-tratamento para eliminação de carbonatos (HCl 0,1 mol L-1), efetuado durante o fracionamento das substâncias húmicas, resultou em aumentos de 300 e 340 % para as frações ácidos húmicos e fúlvicos, respectivamente, e redução de 60 % na fração humina, evidenciando a participação de humatos e fulvatos de cálcio e de magnésio na estabilização da matéria orgânica.

AbstractDifferent types of dioctahedral smectites (nontronite, beidellite, montmorillonite) were investigated by X-ray fluorescence analysis (XRF) and Fourier transmission infrared spectroscopy (FTIR). Starting with the chemical composition of the octahedral sheet, the occupancies within the octahedral sheet were adjusted by computer simulations to fit the occupancies derived from FTIR. For bothcis-andtrans-vacant smectites the AlAl and FeFe pairs are mainly randomly distributed but seem to be aligned along OH-bonded directions. Relative to the chemical composition, AlFe pairs are enriched incis-vacant smectites and depleted in nontronites. This behaviour can be explained by the necessity to dehydrate and hydrolyse cations when they become incorporated into the structure during crystal growth. The first and second hydrolysis steps are necessary for incorporating cations intrans-vacant smectites, whereas only the first hydrolysis step is necessary forcis-vacant smectites. The corresponding difference in energy may explain why mostlycis-vacant smectites occur in low-temperature environments.

The catalytic power of Ca-nontronite (0.2-2 μm) in the polymerization of hydroquinone was studied. The polymerization reaction proceeded abiotically, since there was no evidence of microbial growth in the system studied. The polymerization of hydroquinone in the presence of Ca-nontronite was substantially higher in air than in an N2 atmosphere, indicating the synergistic effect of Ca-nontronite and O2 in enhancing the reaction. After a sodium metaphosphate treatment to block the edges of Ca-nontronite, both absorbances at 472 and 664 nm of the supernatant and yield of humic macro-molecules in the Ca-nontronite-hydroquinone system were significantly decreased. However, the treatment did not eliminate the catalytic effect of Ca-nontronite. The results indicate that both Fe(III) on the edges and other Lewis acid sites of Ca-nontronite contributed to promoting the polymerization of hydroquinone. IR and ESR spectra of FA (MW > 1000) and HA (MW > 1000) formed in the supernatants of the Ca-nontronite-hydroquinone system were similar to those of natural humic substances. Key words: Catalysis, nontronite, iron(III), Lewis acid, oxygen, formation of humic macromolecules

Studies of the extraction of nickel from low-grade laterite ores require a much better quantitative understanding of the poorly ordered mineral phases present, including turbostratically disordered nontronite. Whole pattern refinements with nontronite X-ray diffraction data from a Western Australian nickel deposit (Bulong) using a nontronite lattice model (Pawley phase) with two space groups (P3 andC2/m) and a peaks phase group model were performed to improve the accuracy of quantitative X-ray diffraction of nickel laterite ore samples. Modifications were applied when building the new models to accommodate asymmetric peak shape and anisotropic peak broadening due to the turbostratic disorder. Spherical harmonics were used as convolution factors to represent anisotropic crystal size and strain and asymmetric peak shape when using the lattice model. A peaks phase group model was also developed to fit the anisotropic peak broadening in the nontronite pattern. The quantitative results of the new Pawley phase and peaks phase group models were compared and verified with synthetic mixtures of nontronite, quartz and goethite simulating various West Australian laterite ore compositions. The models developed in this paper demonstrate adequate accuracy for quantification of nontronite in the synthesized reference materials and should be generally applicable to quantitative phase analysis of nontronite in nickel laterite ore samples.

Estudos de caracterização de solos em regiões ainda pouco exploradas, além de disponibilizarem e ampliarem a base de informações sobre as mais distintas ordens de solos do território nacional, também permitem sistematizar informações sobre suas propriedades, que poderão servir de subsídio para o desenvolvimento de práticas de manejo e uso sustentável das terras. Entre os principais solos recorrentes na região semiárida pernambucana, destacam-se os Neossolos Regolíticos, os quais perfazem aproximadamente 27 % da superfície do Estado e recobrem importantes áreas voltadas à produção agrícola, especialmente à agricultura familiar. Considerando a possibilidade de ocorrência de Neossolos Regolíticos com distintas propriedades físicas, químicas ou mineralógicas, em razão da existência de distintos contextos geológicos e climáticos ao longo do Estado de Pernambuco, o presente trabalho teve como objetivo caracterizar física, química e mineralogicamente Neossolos Regolíticos ao longo da região semiárida do Estado de Pernambuco, bem como relacionar os solos com sua litologia. Para isso, foram selecionados cinco perfis de Neossolos Regolíticos em diversos municípios do Estado de Pernambuco (P1=São Caetano, P2=Lagoa do Ouro, P3=Caetés, P4=São João e P5=Parnamirim). Os perfis foram descritos morfologicamente, coletando-se amostras de todos os horizontes do solo e da rocha do embasamento. Foram realizadas análises físicas e químicas para fins de classificação de solos, análises mineralógicas das frações grossas (cascalho e areia) por microscopia óptica e das frações silte e argila por difração de raios X, além de análises petrográficas das amostras de rochas. De acordo com os resultados, observou-se a ocorrência de solos semelhantes e com pequeno grau de desenvolvimento pedogenético, variando de medianamente a muito profundos, com sequência de horizontes A-AC-C e Cr e textura arenosa a média. Dois perfis apresentaram caráter solódico em profundidade. Todos os solos apresentaram baixos teores de matéria orgânica e P disponível. Apesar dos baixos teores de cátions trocáveis, todos os perfis são eutróficos. A assembleia mineralógica das frações cascalho, areia e silte é constituída essencialmente por quartzo, seguido de feldspatos e mica, corroborando a constituição petrográfica analisada. A caulinita é o principal argilomineral da fração argila em todos os perfis e horizontes estudados, indicando um importante processo de monossialitização em solos autóctones, em clima caracteristicamente semiárido. No perfil P2, devido à posição mais baixa do solo na paisagem, ocorreram minerais esmectíticos com misturas de fases entre montmorilonita, beidelita ou nontronita, identificados pela análise de DRX, empregando o teste de Greene-Kelly.

Two calibration-based quantitative X-ray diffraction (XRD) models for turbostratically disordered Bulong nontronite, the PONKCS (partial or no known crystal structure) approach and the supercell structural model, were compared in terms of the accuracy and refinement error from Rietveld quantitative phase analysis. The PONKCS approach achieved improved nontronite quantitative results with synchrotron diffraction patterns compared with those achieved with laboratory XRD data as a result of better data quality and the use of Debye–Scherrer geometry with significantly reduced preferred orientation effects. The introduction of a peak shape modifier (spherical harmonics) to correct the quantification result is mainly useful for laboratory XRD patterns containing nontronite collected from Bragg–Brentano geometry with appreciable preferred orientation effects. A novel calibration approach for the nontronite supercell model was developed, based on the Rietveld quantitative formula in theTOPASsymbolic computation system. The calibrated supercell model achieved better accuracy (deviation within 1 wt%) and lower refinement error than the PONKCS approach because the physically based description of turbostratic disorder requires fewer refinable parameters than the PONKCS approach. The drawbacks and limitations of the supercell approach are also discussed.

Orientador: Raquel Fernandes Pupo Nogueira
Banca: Clovis Augusto Ribeiro
Banca: Maria Valnice Boldrin
Banca: Emerson Henrique de Faria
Banca: Renato Falcão Dantas
Resumo: Este trabalho descreve um estudo comparativo da atividade catalítica de material obtido com imobilização de ferro em vários suportes argilominerais: Argila natural modificada com amido (AN+A) Vermiculita (V) e Nontronita (N) para processo Fenton heterogêneo. A atividade catalítica foi avaliada pela degradação dos antibióticos sulfatiazol (STZ) e cefalexina (CFX) utilizando dispositivos LED-UV (360 nm) e LED-Vis (460 nm) como fonte de irradiação, bem como solar. Os materiais usados como suportes de ferro passaram previamente por processo de moagem, secagem e peneiragem (≤ 180 μm). Foram realizadas diversas impregnações de Fe em diferentes condições e com posterior tratamento térmico (450, 600 e 750 °C). Os materiais foram caracterizados pelas técnicas de Fluorescência de raios X, Difração de Raios- X, Espectroscopia de Reflectância Difusa, Espectrometria de absorção ultravioleta-visível e infravermelho próximo, área superficial específica, Microscopia Eletrônica de Varredura de Alta Resolução e Potencial Zeta. Foi observado que o aumento do pH natural da solução (pH < 1) para 5,0 proporcionou uma maior impregnação de Fe passando de 7,4% (m/m) para 49% Fe no caso AN+ A, e para 45% Fe para a N. Os materiais apresentaram em sua composição química SiO2, Al2O3, Fe2O3, K2O, TiO2, MgO como óxidos maioritários, e mostraram alta absorção na faixa UVA, UVB e Vis e energias de banda proibida de 1,9 eV. O Potencial Zeta em pH 3,0 mostrou comportamentos opostos para os dois materiais sendo... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work describes a comparative study of the catalytic activity of material obtained with iron immobilization in several clay minerals: Natural clay modified with starch (AN + A) Vermiculite (V) and Nontronite (N) for heterogeneous Fenton process. The catalytic activity was evaluated by the degradation of the antibiotics sulfathiazole (STZ) and cefalexin (CFX) using LED-UV (360 nm) and LED-Vis (460 nm) devices as irradiation source as well as solar. The clay minerals used as iron supports were previously crushed, dried and sieved (≤ 180 μm). Several iron impregnations were carried out under different conditions and with subsequent thermal treatment (450, 600 and 750 °C). The materials were characterized by the techniques of X-ray Fluorescence, X-ray Diffraction, Diffuse Reflectance Spectroscopy, Ultraviolet-Visible and Near Infrared Absorption Spectrometry, specific surface area, High Resolution Scanning Electron Microscopy couple to Energy dispersive X-ray spectroscopy. It was observed that the increase inthe natural pH of the solution (pH <1)to 5.0 provided an improved Fe impregnation from 7.4% (m / m) to 49% Fe in the AN + A case, and to 45% Fe in the case of N. The materials presented in the chemical composition SiO2, Al2O3, Fe2O3, K2O, TiO2, MgO as major oxides, and showed high absorption in the UVA, UVB and Vis range, and bandgap energies of 1.9 eV. The Zeta Potential at pH 3.0 showed opposite behaviors for the two materials with -12.7 mV for AN + A 49% Fe and 7.2 mV ... (Complete abstract click electronic access below)
Doutor

La nontronite mineral argileux ferrifere presente un deficit de charge tetraedrique du a des substitutions si#4#+(al#3#+, fe#3#+). Malgre cela elle possede des proprietes d'adsorption de l'eau ou de solvants polaires analogues a celles des argiles de meme architecture mais possedant un deficit de charge octaedrique. L'etude du mineral de reference internationale, a la fois par microscopie electronique (m. E. T. ), par spectroscopie infrarouge et mossbauer et par fluorescence et diffraction des rayons x (d. R. X. ) fait ressortir quelques points importants: a - le mineral est inhomogene. Il presente deux populations de particules n'ayant pas la meme morphologie, ni exactement la meme composition chimique. B - du fait de cette inhomogeneite le mode de purification de l'argile enrichit l'echantillon en l'un ou l'autre des constituants. Ceci permet d'expliquer les contradictions apparentes existant entre les resultats publies anterieurement par differents auteurs. C - les anomalies d'hydratation sont a relier au caractere plus electro-accepteur de fe#3#+ que celui de l'al#3#+. D - la modelisation des spectres experimentaux de d. R. X. Obtenus a differentes humidites relatives permet de montrer que l'echantillon de nontronite est en fait constitue de population de particules presentant differents etats d'hydratation

Comme tous les pays produisant de l’électricité par la filière nucléaire, la France envisage d’enfouir les déchets radioactifs en site géologique profond. Le concept comprend l’enrobage des radionucléides dans une matrice vitreuse et son confinement dans un conteneur en acier. Ce conteneur doit résister plus de 1000 ans dans un environnement anoxique saturé en eau, contenant des espèces carbonatées et argileuses. De précédentes études sur menées sur des expériences de laboratoire (<4 ans) et sur des analogues archéologiques (450 ans) ont mis en évidence la présence de couches de produits de corrosion (CPC) constituées d’oxyde, silicate et carbonate de fer distribués de manière hétérogène à l’échelle nanométrique.La connaissance de l’influence de ces différentes phases formées sur les mécanismes de corrosion et in fine sur les vitesses de corrosion doit encore être améliorée. Plus particulièrement, la localisation de la réaction cathodique dans ces systèmes de corrosion multi-couches doit encore être établie.Ce travail de thèse considère les interactions entre le fer et l’eau porale du Cox sur deux échéances de corrosion courtes (1 et 3 mois) en comparaison des durées des expériences préalablement mises en place. Deux matériaux métalliques ont été comparés: un acier ferrito-perlitique et un fer pur afin de comprendre l’influence de la cémentite sur la cinétique de corrosion.La morphologie et la nature des phases ont été caractérisées de l’échelle micrométrique (MEB-EDS, μ-Raman) à nanométrique (STEM, MET-SAED,STXM/XANES). Le transport d’espèces dans les CPC a été étudié à l’aide d’expériences en milieux isotopiques marqués (²H et ¹³C) détectés par ToF-SIMS.Enfin, les transferts électroniques ont été étudiés en surface par conductimétrie et en coupe transversale par C-AFM.Les résultats montrent qu’après 1 mois dans l’eau du Cox, les CPC sont formées d’une bicouche de sidérite calciée (10%m Ca) isolante avec des îlots nanométriques de magnétite dans la couche interne et nano à micrométrique à l’interface M/CPC. Il a été montré que l’interface entre les deux couches délimite la surface d’origine des substrats métalliques. La couche interne comporte des canaux conducteurs connectés au métal permettant d’évacuer les électrons produits par la réaction anodique. Ces canaux diffèrent selon la matrice métallique et correspondent à la cémentite pour l’acier ferrito-perlitique et à des canaux nanométriques de magnétite pour le fer pur.Après 3 mois de corrosion, les processus de corrosion continuent de manière hétérogène à l’interface M/CPC. Une couche discontinue de sidérite faiblement conductrice est identifiée à l’interface M/CPC. Sous cette couche apparait également localement une couche de nontronite isolante ainsi qu’une couche de magnétite continue. En ce qui concerne les déplacements électroniques, ils ont toujours lieu par la cémentite pour l’acier ferrito-perlitique.En revanche, pour le fer pur, la faible conductivité de la sidérite pourrait affecter l’évacuation électronique ; impacter la cinétique de la réaction cathodique et ainsi la vitesse de corrosion du fer pour des durées supérieures.Ces résultats fondamentaux pourraient être reliés avec la formation de lacouche de passivation des aciers observée lors d’expériences de laboratoire de plusieurs années. Des perspectives de recherche combinant étude des transferts électroniques M/CPC et passivation des aciers peuvent être envisagées
As all countries producing power by nuclear industry, France plansto bury radioactive waste in a deep geological site. The concept includes embedding the radionuclides in a glassy matrix and confining them in a steelcontainer. This container should last over 1000 years in a water satured anoxic environment, containing carbonate and clay species. Previous studies onlaboratory experiments (<4 years) and on archaeological analogues (450years) have demonstrated the presence of layers of corrosion products (CPL) consisting of iron oxide, silicate and carbonate distributed heterogeneously at nanoscale. Knowledge of the influence of these different phases formed on corrosion mechanisms and ultimately on corrosion rates must be further improved. More particularly, the location of the cathodic reaction in these multilayer corrosion systems has yet to be established.This thesis considers the interactions between iron and Cox pore water over two short corrosion periods (1 and 3 months) in comparison with the durations of the experiments previously set up. Two metallic materials were compared:a ferrito-pearlitic steel and a pure iron in order to understand the influence of cementite on the corrosion kinetics.The morphology and nature of the phases were characterized from micrometric (SEM-EDS, μ-Raman) to nanometric (STEM, TEM-SAED,STXM/XANES) scale. Mass transport in the CPL was studied using experiments in labelled isotopic media (²H and ¹³C) detected by ToF-SIMS. Finally, the electronic transfers were studied at the surface by conductimetry and in cross section by C-AFM.The results show that after 1 month in the Cox water, the CPL are formed ofan insulating Ca-siderite bilayer (10%m Ca) with nanometric islets of magnetite in the inner layer and nano to micrometric islets at the M/CPL interface. The interface between the two layers has been shown to delimit the original surface of both metal substrates. The inner layer has conductive channels connected to the metal to evacuate the electrons produced by theanodic reaction. These channels differ depending on the metal matrix and correspond to cementite for the ferritic-pearlitic steel and to nanoscale magnetite channels for the pure iron.After 3 months of corrosion, corrosion processes continue heterogeneously at the M/CPL interface. A discontinuous layer of weakly conductive siderite is identified at the M/CPL interface. Under this layer also appears locally an insulating layer of nontronite as well as a continuous magnetite layer. As far as electronic transports are concerned, they always take place through the cementite for the ferrito-pearlitic steel. In contrast, for the pure iron, the low conductivity of siderite may affect electrons evacuation; influence the kinetics of the cathodic reaction and the corrosion rate of iron for longer durations.These fundamental results may be related to the formation of the steel passive layer observed in laboratory experiments of several years. Research perspectives combining studies of M/CPL electronic transfers and steelspassivation can be considered

Les smectites riches en fer appelées nontronite jouent un rôle majeur dans de nombreux processus biogéochimiques à la surface de la Terre. La compréhension de ces processus requiert une caractérisation cristallochimique détaillée de ces minéraux, avec notamment une connaissance précise du statut du fer. Les signatures spectrales du fer structural des nontronites ont été étudiées par spectroscopie infrarouge (IR), Mössbauer et XPS. La mise en évidence de ces signatures a été possible grâce à la synthèse hydrothermale à 150°C d’une série de nontronites avec une large gamme de teneur en [4]Fe(III). Les caractéristiques spectrales IR permettent d'effectuer une estimation robuste de la quantité de [4]Fe(III) tétraédrique présente dans la structure de la nontronite. Ces synthèses ont également permis de faire le lien entre la cristallochimie des nontronites synthétiques et la spéciation aqueuse du Si, Fe et Na. Les calculs de la spéciation aqueuse du Si montrent que l'augmentation des espèces anioniques H3SiO4-(aq) et H2SiO42-(aq) liée à l'augmentation du pH, favorise l'incorporation du Fe(III) dans les sites tétraédriques de la nontronite. La stabilité de ces nontronites dans les conditions de synthèse a ensuite été étudiée en fonction du temps. Une transformation minéralogique a été mise en évidence, amenant à la dissolution de la nontronite au profit d'un assemblage aegirine et hématite. Ces résultats montrent clairement que les nontronites synthétisées sont transitoires dans le système étudié
Iron-rich smectites named nontronite are playing a great role in lot of biogeochemical processes at the Earth's surface. To better understand these processes a characterization of iron status in nontronites is required. Spectral iron features in the nontronite structure were studied by infrared (IR), Mössbauer, and XPS spectroscopies. IR characteristic fingerprints of Fe(III) allowed to obtain a detailed overview of the crystal-chemistry of this minerals, notably a robust estimation of the tetrahedral [4]Fe(III) content of the nontronite. This study was possible thanks to an experimental approach using hydrothermal synthesis (150°C) of a series of nontronites with a wide range of [4]Fe(III) content. These syntheses allowed to assess the link between the crystal-chemistry of synthetic nontronites and the aqueous speciation of Si, Fe, and Na. The aqueous speciation calculations indicated that the increase in anionic species H3SiO4-(aq) and H2SiO42-(aq) linked to the increase in pH, favored the incorporation of Fe(III) in the tetrahedral sites of nontronites. The stability of nontronites versus time was also studied. A mineral transformation was evidenced with the formation of the aegirine and hematite through the dissolution of nontronite. These results revealed that the synthetic nontronite are transitional in this experimental syntheses

Although interfacial electron transfer has been shown to occur for sorbed Fe(II) and Fe-oxides, it is unclear if a similar reaction occurs between sorbed Fe(II) and Fe(III)-bearing clay minerals. Here, we use the isotope specificity of 57Fe Mössbauer spectroscopy to demonstrate electron transfer between sorbed Fe(II) and structural Fe(III) in a nontronite clay mineral (NAu-2). Appearance of an Fe(II) doublet in the NAu-2 spectra after reaction with aqueous 56Fe(II) (56Fe is transparent in Mössbauer spectra) provided evidence for reduction of structural Fe(III). Mössbauer spectra using enriched 57Fe(II) reveal that Fe(II) is oxidized upon sorption to NAu-2, and the oxidation product of this reaction is a ferric oxide with spectral parameters similar to lepidocrocite. The reduction of structural Fe(III) by Fe(II) induces electron delocalization in the clay structure, which we observe by variable-temperature Mössbauer spectra and macroscopic color change indicative of Fe(II)-Fe(III) pairs. The extent of structural Fe(III) reduction in NAu-2 is equal to the amount of Fe(II) sorbed until approximately 15% reduction, after which point reduction is no longer concomitant with the amount of sorbed Fe(II).

The objective of this thesis study is to recover nickel and cobalt at maximum efficiency from column leach liquor of lateritic nickel ores existing in Gö
rdes region of Manisa by performing various hydrometallurgical methods under the optimum conditions. This column leach solution of nontronite type lateritic nickel ore was initially neutralized and purified from its basic impurities by a two stage iron removal process under the optimum conditions determined experimentally. Then, nickel and cobalt were precipitated in the form of mixed hydroxide precipitate from the purified leach solution by a two stage precipitation method called &ldquo
MHP&rdquo
and a manganese removal process was carried out also under the optimum conditions determined. By decreasing Mn concentration with this process to an acceptable level yielding at most 10% Mn in hydroxide precipitate, it was possible to produce a qualified MHP product suitable to the current marketing and standard conditions. As a result of this thesis study, the experiments conducted showed that by recycle leaching with sulfuric acid about 81% of Ni and 63% of Co in the lateritic nickel ore (9.72 kg Ni / ton of ore and 0.28 kg Co / ton of ore) could be extracted as mixed hydroxide precipitate by MHP method. The MHP product contains 41.9% Ni, 1.0% Co, 2.3% Mn, 0.06% Al, 1.5% Mg, 0.02% Fe, 0.01% Cr, 0.25% Zn, 0.03% Cu and 4.73% S.