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The Intex laterite deposit in Mindoro, Philippines is derived from the weathering of the ultramafic rocks under a tropical climate. This study investigates the several types of serpentines and the effect of the degree of chemical weathering of ultramafic rocks and laterites on the enrichment of Ni in the deposit. The five types of serpentines are differentiated based on their textural features and Raman spectral data. Type I, type II, type III, and type IV serpentines contain a low amount of NiO (average 0.15 wt%), and their formation is linked to the previous exhumation of the ultramafic body. Conversely, type V serpentines show the highest NiO contents (average 1.42 wt%) and have the composition of serpentine-like garnierites, indicating a supergene origin. In the limonite horizon, goethite is the main ore mineral and shows high NiO contents of up to 1.68 wt%, whereas the Mn-oxyhydroxides (i.e., asbolane and lithiophorite-asbolane intermediate) display substantial amounts of CoO (up to 11.3 wt%) and NiO (up to 15.6 wt%). The Ultramafic Index of Alteration (UMIA) and Index of Lateritization (IOL) are used to characterize the different stages of weathering of rocks and laterites. The calculated index values correspond to a less advanced stage of weathering of the Intex laterites compared with the Berong laterites. The Berong deposit is a Ni-Co laterite deposit in the Philippines, which is formed from the weathering of the serpentinized peridotite. The less extreme degree of weathering of the Intex laterites indicates less advanced leaching, and thereby the re-distribution of Ni, Si, and Mg from the limonite towards the saprolite horizon may have resulted in the poor precipitation of talc-like (kerolite-pimelite) and sepiolite-like (sepiolite-falcondoite) phases in the studied saprolite horizon. Nickel in the Intex deposit has undergone supergene enrichment similar to other humid tropical laterite deposits.

In natural environments, ferrihydrite (Fh) reacts readily with the contaminant and nutrient oxyanions through surface complexation. While previous experiments showed that the transformation of Fh to Gt and Hm under oxic conditions at 70 °C is controlled by the type and strength of oxyanion surface complexes, the impact of surface loading on this process is only partly understood. Synchrotron scattering methods and chemical analysis were used to develop a kinetic model that describes the impact of oxyanion surface loading on the rate and pathway of Fh transformation by using arsenate (AsO43-) and phosphate (PO43-). Kinetic modeling showed that AsO43- and PO43- adsorption decreased the rate of transformation and favored Hm formation over Gt. Higher surface loadings increasingly inhibited Fh transformation with a greater effect for PO43- compared with AsO43-. This information has implications for understanding the impacts of oxyanions on the transformation of natural Fe to Gt and Hm in environmental systems.

The presence of arsenic in drinking water above the permissible limits is one of the current problems facing modern engineers in the field of separations and it has not yet been satisfactorily resolved, because the permissible concentrations of arsenic in drinking water are constantly reduced by the World Health Organization (WHO). Among the various processes for arsenic removal, adsorption has a special place as one of the most efficient and cheap process. Many natural and artificial materials are tested for adsorption processes, and adsorption on metal powders is particularly interesting because they represent adsorbents with fast kinetics and relatively high adsorption capacities. However, the application of powder adsorbents is difficult due to their separation from the mixture after adsorption. In order to solve that problem, metal powders may be immobilized into particles obtained by gelling natural polymers. In this way, it is easier to separate the adsorbent from the mixture, however this must be achieved without losing the adsorption capacity and rate compared to pure metal powders. In this study, the use of metal oxide (iron oxide nanoparticles) immobilized within the alginate gel showed good potential for arsenic (V) ions removal. The obtained results showed that arsenic adsorption by obtained composite has fast kinetic, following pseudo-second-order model, and that it is conducted in several steps, according to the Weber-Morris model. It was suggested that external diffusion is the dominant mechanism at the beginning of the arsenic adsorption, followed by intraparticle diffusion. The obtained results confirmed that gelling with alginate did not significantly affect the adsorption process, that is, it does not interfere with the adsorption capacity of metal oxides, which is a very important factor. Arsenic (V) removal was successfully performed using the investigated composite.

Oxide minerals (include oxides, hydroxides, oxyhydroxides and hydrated oxides) are primary and secondary minerals of Si, Fe, Mn, Al and Ti. Secondary oxides, particularly of Fe, Al and Mn, are perhaps the most reactive and important components in many soils due to their high specific surface area and strong sorption capacity for many essential and potentially toxic elements. Iron and Mn oxides also play key roles in many redox reactions and have major influence on the transformation and availability of organic and inorganic contaminants in soils. This chapter provides an overview of the oxide minerals in soils, with an emphasis on their structure and composition, environmental conditions for their formation and their properties.

The combination of biochar (BC) and iron minerals improves their pollutant adsorption capacity. However, little is known about the reactivity of BC-iron mineral composites regarding their interaction and change in the pore structure. In this study, the mechanism of cadmium (Cd) adsorption by BC-iron oxide composites, such as BC combined with ferrihydrite (FH) or goethite (GT), was explored. The synergistic effect of the BC-FH composite significantly improved its Cd adsorption capacity. The adsorption efficiencies of BC-FH and BC-GT increased by 15.0% and 10.8%, respectively, compared with that of uncombined BC, FH, and GT. The strong Cd adsorption by BC-FH was attributed to stable interactions and stereoscopic pore filling between BC and FH. The scanning electron microscopy results showed that FH particles entered the BC pores, whereas GT particles were loaded onto the BC surface. FTIR spectroscopy showed that GT covered a larger area of the BC surface than FH. After loading FH and GT, BC porosities decreased by 9.3% and 4.1%, respectively. Quantum chemical calculations and independent gradient mode analysis showed that van der Waals interactions, H-bonds, and covalent-like interactions maintained stability between iron minerals and BC. Additionally, humic acid increased the agglomeration of iron oxides and formed larger particles, causing additional aggregates to load onto the BC surface instead of entering the BC pores. Our results provide theoretical support to reveal the interfacial behavior of BC-iron mineral composites in soil and provide a reference for field applications of these materials for pollution control and environmental remediation.

Adsorption and transport of levofloxacin (LEV) and ofloxacin (OFL) enantiomers in a matrix containing goethite and natural organic matter (NOM) were investigated using batch and column experiments. In batch studies, competition and enantioselectivity were observed in the adsorption of LEV and OFL. Enantioselectivity upon adsorption was investigated by comparing changes in the enantiomer fraction (EF) (the ratio of LEV to the sum of LEV and OFL remaining in the solution) after and before adsorption. At pH < 7, there was hardly any selectivity in adsorption of OFL and LEV to goethite. At pH > 7, OFL showed a stronger adsorption than LEV to goethite, and this preference remained when NOM samples of Leonardite humic acid (LHA) and Elliott Soil fulvic acid (ESFA) were added. However, when Suwannee River NOM (SRNOM) was added, the preference was reversed, and LEV was adsorbed more strongly. In single systems, the presence of different types of NOM increased adsorption of LEV and OFL, especially LEV. In column studies, preloaded NOM decreased the transport of LEV and OFL through goethite-coated sand. The EF values in the effluent increased with retention time and reached the largest values (0.59–0.72) at around 1.5 pore volume (PV), and then decreased again, reaching a stable value at 5.0–30.0 PV. Both batch and column experiments showed that, fractionation of LEV and OFL occurred during adsorption and transport in the presence of NOM-goethite complexes, which would eventually affect their environmental fate

Boreal forests store the majority of their carbon in the soil and play an important role in the global carbon cycle. However, the mechanisms that control carbon storage in boreal soils are not well understood. In recent studies, there has been a specific focus on how ectomycorrhizal (ECM) fungi influence carbon dynamics in boreal forests, particularly through their nitrogen acquisition. A major part of the nitrogen in boreal forests is present in organic form, as proteins, and adsorbed on soil minerals. However, it is generally unknown whether the ECM fungi can access this nitrogen. In this study, a laboratory method development was carried out. This provided useful information for future studies which can investigate if ECM fungi can acquire nitrogen from proteins adsorbed on two common iron oxide minerals in boreal forests. Concretely, the maximum adsorption of the protein Bovine serum albumin (BSA) on ferrihydrite and goethite was investigated. The result of this study showed that goethite is saturated at 0,58 mg BSA/ml goethite and ferrihydrite at approximately 1,25-1,3 mg BSA/ml ferrihydrite. This result was consistent with the hypothesis which stated that ferrihydrite, with its larger surface area compared to goethite, would have a greater capacity to adsorb proteins. These results can subsequently be used to create films with different protein loadings on minerals which then can be used to study if ECM fungi can acquire nitrogen from protein-mineral complexes. By studying this, we can increase our understanding of soil carbon storage and tree growth in boreal forests, as nitrogen is a limiting nutrient for tree growth., Marken är en viktig spelare när det kommer till att lagra kol, särskilt i boreala skogar. Dessa skogar lagrar nämligen största delen av sitt kol i jorden och fungerar som en viktig kolsänka. Men vi vet faktiskt inte helt vad det är som styr detta. Ny forskning har dock lyft ektomykorrhizasvampar som en viktig faktor. Mer konkret så föreslås nu ektomykorrhizasvampars förmåga att frigöra grundämnet kväve från organiskt material vara en viktig mekanism som påverkar kollagringen i marken. I denna studie genomfördes en metodutveckling som ska kunna hjälpa oss att förstå detta bättre. Den boreala skogen sträcker sig över norra delen av jordklotet och är hem för en speciell typ av svamp som kallas ektomykorrhizasvamp. Denna sorts svamp har en unik förmåga att bilda ett nära samspel (symbios) med träden i skogen. Symbiosen innebär att svampen ger näring åt trädet i utbyte mot kol. Ett viktigt ämne som ektomykorrhizasvampen bidrar med, är kväve, som är nödvändigt för att träden ska växa. I den boreala skogen förekommer det mesta av kvävet i organisk form som protein. Dessutom är proteinet ofta adsorberat (fäst på ytan) på mineralerna i jorden. Dock vet vi inte om ektomykorrhizasvampen kan frigöra kvävet som är bundet till dessa mineral. I denna studie genomfördes en metodutveckling som bidrog med viktig information för framtida studier av ektomykorrhizasvampars förmåga att frigöra kväve från protein som adsorberats på två vanliga järnoxidsmineraler i boreala skogar. Mer konkret så undersöktes den maximala adsorptionen av protein på järnoxidsmineralerna ferrihydrit och goethit. Detta undersöktes genom att addera olika mängder utav proteinet BSA (Bovint serumalbumin) och sedan observera vid vilken koncentration som mineralerna var mättade och alltså inte kunde adsorbera mer protein. Studiens resultat visade att goethit var mättat vid 0,58 mg BSA/ml goethit och ferrihydrit var mättat vid 1,25-1,3 mg BSA/ml ferrihydrit. Detta resultat bekräftade studiens hypotes om att ferrihydr

In this study, iron oxide nanoparticles immobilized within alginate gel exhibited promising potential for the removal of arsenic (V) ions. The preparation of the polymer-oxide composite was achieved by the ionic crosslinking of an alginate/iron oxide solution with a calcium (II)ions solution. The maximum amount of arsenic adsorbed by the investigated composite under the experimental conditions was slightly above 26 mg/g in 120 min. The results indicated that arsenic adsorption by this composite material follows a fast kinetic profile, adhering to a pseudo-second-order model. The adsorption process occurs in multiple stages, as suggested by the Weber-Morris model, with external diffusion dominating initially, followed by intraparticle diffusion. Importantly, the results confirmed that the use of alginate gel does not significantly impact the adsorption process, preserving the adsorption capacity of the metal oxides. Overall, the investigated composite successfully removed arsenic (V) from the solution, addressing a critical issue in water treatment. (1) (PDF) Application of Natural Polymer and Metal Oxide Composite for Removal of Arsenic(V) Ions from Aqueous Solutions. Available from: https://www.researchgate.net/publication/378821317_Application_of_Natural_Polymer_and_Metal_Oxide_Composite_for_Removal_of_ArsenicV_Ions_from_Aqueous_Solutions [accessed Mar 12 2024]."

In this study, iron oxide nanoparticles immobilized within alginate gel exhibited promising potential for the removal of arsenic (V) ions. The preparation of the polymer-oxide composite was achieved by the ionic crosslinking of an alginate/iron oxide solution with a calcium (II) ions solution. The maximum amount of arsenic adsorbed by the investigated composite under the experimental conditions was slightly above 26 mg/g in 120 min. The results indicated that arsenic adsorption by this composite material follows a fast kinetic profile, adhering to a pseudo-second-order model. The adsorption process occurs in multiple stages, as suggested by the Weber-Morris model, with external diffusion dominating initially, followed by intraparticle diffusion. Importantly, the results confirmed that the use of alginate gel does not significantly impact the adsorption process, preserving the adsorption capacity of the metal oxides. Overall, the investigated composite successfully removed arsenic (V) from the solution, addressing a critical issue in water treatment

Naphthalene (NAP) has received particular attention due to its impact on the environment and human health, mandating its removal from water systems. In this work, the abatement of NAP in the aqueous phase was achieved using persulfate (PS) activated by Fe (III) and monochromatic LED light at a natural pH. The reaction was carried out in a slurry batch reactor using goethite as the Fe (III) source. The influence of the PS concentration, goethite concentration, irradiance, temperature and presence of organic matter, chloride, and bicarbonate on the abatement of NAP was studied. These variables were shown to have a different effect on NAP removal. The irradiance showed a maximum at 0.18 W⋅cm−2W·cm−2 where the photonic efficiency was the highest. As for the concentration of goethite and PS, the influence of the first one was negligible, whereas for PS, the best results were reached at 1.2 mM due to a self-inhibitory effect at higher concentrations. The temperature effect was also negative in the PS consumption. Regarding the effect of ions, chloride had no influence on NAP conversion but carbonates and humic acids were affected. Lastly, this treatment to remove NAP has proved to be an effective technique since minimum conversions of 0.92 at 180 min of reaction time were reached. Additionally, the toxicity of the final samples was decreased., Comunidad de Madrid, Ministerio de Economía y Competitividad, Ministerio de Ciencia, Innovación, Depto. de Ingeniería Química y de Materiales, Fac. de Ciencias Químicas, TRUE, pub

Iron(III) oxides and oxyhydroxides are among the most reactive minerals in the environment, with surfaces that become charged when immersed in water. The governing role of surface charge over interfacial processes such as metal sorption is well understood. However, its role in interfacial redox reactions, such as when metal sorption is coupled to interfacial electron transfer (ET), is not. This is mainly because surface charge affects not only the types and densities of surface complexes formed but also their respective driving forces for ET. An important case is Fe(II)-catalyzed recrystallization of Fe(III)-oxyhydroxides, in which Fe(II) sorption and interfacial ET are closely linked. In this study, we used replica-exchange constant-pH molecular dynamics simulations (Zarzycki, P.; Smith, D. M.; Rosso, K. M. J. Chem. Theory Comput. 2015, 11, 1715–1724) to calculate the distance-dependent electrostatic potential at charged (110) surfaces of goethite particles, assessing its effect on previously computed Fe(II) sorption and interfacial ET free energies (Zarzycki, P.; Kerisit, S.; Rosso, K. M. J. Phys. Chem. C 2015, 119, 3111–3123). We show that Fe(II) adsorbs preferentially as an inner-sphere complex on the negatively charged surface, and as an outer-sphere complex on the positively charged surface because of both electrostatic repulsion and high energy barriers that arise from ordered water layers at the interface. The separation distance between adsorbed Fe(II) and the surface largely dictates adiabatic versus nonadiabatic ET regimes for this interface. The findings help unravel the pH dependence of Fe(II)-catalyzed recrystallization of goethite.

Recent studies have suggested that a chromian spinel can be formed under natural hydrothermal conditions; however, the required conditions, process, and associated redistribution of Cr are still poorly understood. Here, chromian spinel formation was performed by Fe-Cr hydroxides alteration with an Fe-(aq)(2+) supply at 150, 170, and 200 degrees C and 5 MPa simulating the diagenetic process. The flow-through system enabled the Fe-(aq)(2+) supply to be leached from the magnetite by an acidic solution to synthesize Fe-Cr hydroxides as the starting material with two reaction cells, flow lines, heaters, and a high-performance liquid chromatography (HPLC) pump. The accuracy of the temperature measurement was confirmed based on the amorphous silica solubility. Mineralogical analysis of solid samples recovered from the reaction cell indicated that the chromian spinel was formed between 150 and 170 degrees C from Fe-Cr hydroxides through goethite with a simultaneous hematite formation, while Mossbauer spectra showed that a large quantity of Fe-Cr ferrihydrites still remained after the experiments probably because of the Cr addition to the stability of ferrihydrites. The Cr/Fe ratio of the chromian spinel was smaller than that of the bulk of the Fe-Cr ferrihydrites and equivalent to Cr-rich magnetite, suggesting a redistribution of Cr during the transformation from goethite to synthesized spinel under the hydrothermal conditions.

Anthropogenic emissions of vanadium (V) into terrestrial and aquatic surface systems now match those of geogenic processes, and yet, the geochemistry of vanadium is poorly described in comparison to other comparable contaminants like arsenic. In oxic systems, V is present as an oxyanion with a +5 formal charge on the V center, typically described as H x VO4 (3-x)-, but also here as V(V). Iron (Fe) and manganese (Mn) (oxy)hydroxides represent key mineral phases in the cycling of V(V) at the solid-solution interface, and yet, fundamental descriptions of these surface-processes are not available. Here, we utilize extended X-ray absorption fine structure (EXAFS) and thermodynamic calculations to compare the surface complexation of V(V) by the common Fe and Mn mineral phases ferrihydrite, hematite, goethite, birnessite, and pyrolusite at pH 7. Inner-sphere V(V) complexes were detected on all phases, with mononuclear V(V) species dominating the adsorbed species distribution. Our results demonstrate that V(V) adsorption is exergonic for a variety of surfaces with differing amounts of terminal -OH groups and metal-O bond saturations, implicating the conjunctive role of varied mineral surfaces in controlling the mobility and fate of V(V) in terrestrial and aquatic systems.

Current demand on adsorbent materials is in constant growth, hence scientific society is in ceaseless research subjecting cheap and optimal adsorbent. Abundant raw materials which may be utilized as adsorbent of cation species are mica minerals, and vermiculite as one of them is widely examined. Since wastewater may contain anion or/ and non-ionic pollutants it is needed to functionalize adsorbent so it may attract those species as well. Goethite and ferrihydrite are potential candidates for such modification since they: have large specific surface area (SSA), possess hydroxide group and they are not toxic to the environment. Goethite/ expanded vermiculite (Goe/EV) and ferrihydrite/ expanded vermiculite (Fer/EV) are successfully prepared and those composites have showed better adsorption related chemical properties than expanded vermiculite (EV) itself. Utilizing BET methodology, it is determined that Fer/EV possess five-time larger SSA than EV, while Goe/EV is two times larger. Measuring cation exchange capacity (CEC) it is determined that modified samples have only ~10% smaller values of CEC. Summary, both composites have shown higher affinity toward cationic dye, malachite green and also showed their adsorbent potential toward anionic dye, tartrazine. Thanks to facile preparation of such materials and its cost, it may be concluded that they are prospective choice as adsorbents, in first order of heavy metals and dyes.

Recent studies have suggested that a chromian spinel can be formed under natural hydrothermal conditions; however, the required conditions, process, and associated redistribution of Cr are still poorly understood. Here, chromian spinel formation was performed by Fe-Cr hydroxides alteration with an Fe-(aq)(2+) supply at 150, 170, and 200 degrees C and 5 MPa simulating the diagenetic process. The flow-through system enabled the Fe-(aq)(2+) supply to be leached from the magnetite by an acidic solution to synthesize Fe-Cr hydroxides as the starting material with two reaction cells, flow lines, heaters, and a high-performance liquid chromatography (HPLC) pump. The accuracy of the temperature measurement was confirmed based on the amorphous silica solubility. Mineralogical analysis of solid samples recovered from the reaction cell indicated that the chromian spinel was formed between 150 and 170 degrees C from Fe-Cr hydroxides through goethite with a simultaneous hematite formation, while Mossbauer spectra showed that a large quantity of Fe-Cr ferrihydrites still remained after the experiments probably because of the Cr addition to the stability of ferrihydrites. The Cr/Fe ratio of the chromian spinel was smaller than that of the bulk of the Fe-Cr ferrihydrites and equivalent to Cr-rich magnetite, suggesting a redistribution of Cr during the transformation from goethite to synthesized spinel under the hydrothermal conditions.

The production and degradation of plastic remains can result in nanoplastics (NPs) formation. However, insufficient information regarding the environmental behaviors of NPs impedes comprehensive assessment of their significant threats. In this study, the transport behavior of unmodified NPs (PSNPs), carboxyl-modified NPs (PSNPs−COOH), and amino-modified NPs (PSNPs−NH2) was investigated using column experiments in the presence and absence of goethite (GT) and diethylhexyl phthalate (DEHP). Quantum chemical computation was performed to reveal the transport mechanisms. The results showed that GT decreased the transport of NPs and the presence of DEHP decreased it further. Van der Waals forces and small electrostatic interactions coexisted between the PSNPs and GT and caused deposition. Ligand exchange caused greater deposition of PSNPs−COOH on GT-coated sand than that of PSNPs. Although hydrogen bonding existed between the DEHP and NPs with functional groups, an increase in the positive charge and chemical heterogeneity of the collector was the main reason for DEHP promoting the deposition of NPs. Because of low absolute negative zeta potential values, PSNPs−NH2 was sensitive to chemical heterogeneity, and thus fully deposited (over 96.9%) in GT and GT-DEHP-coated columns. Generally, the deposition of NPs due to chemical heterogeneity was more significant than that due to the formation of chemical bonds and van der Waals, electrostatic, and hydrogen interactions. Our results highlight that the surface charge and functional groups significantly influence the transport behaviors of NPs and elucidate the fate of NPs in the terrestrial environment.

Assessing the surface reactivity of metal (hydr)oxides in soils is essential for quantifying ion adsorption phenomena that control the availability of nutrients and pollutants. Despite the high natural abundance of Fe and Al (hydr)oxides in intensively weathered environments, the surface reactivity of these pedogenic materials has not been consistently characterized for weathered tropical soils. Here, we used a novel probe-ion methodology combined with state-of-the-art surface complexation modelling (SCM) to derive the reactive surface area (RSA) of the soils, as well as the amount of phosphate (PO4) that can be potentially desorbed (R-PO4) from the natural fraction of metal (hydr)oxides and thereby controlling the solid-solution partitioning of PO4. We applied this methodology to a series of weathered topsoils from the sub-Saharan region. The results showed that nanocrystalline ferrihydrite (Fh) is a better proxy than well-crystallized goethite for describing with SCM the reactivity of the natural metal (hydr)oxides, even though well-crystallized materials dominate the mass fraction of metal (hydr)oxides of these weathered tropical soils. Using Fh as a proxy in the SCM, the RSA ranged from ∼2 to 40 m2 g−1 soil. Nanoparticles with a mean diameter of ∼1.5–5.0 nm dominate the reactive fraction of metal (hydr)oxides in these tropical topsoils. Our SCM in conjunction with soil extractions indicates that only a fraction of the total PO4 associated with the metal (hydr)oxides is reversibly adsorbed, whereas the majority of the total PO4 pool, on average ∼64%, is occluded in the crystalline Fe and Al (hydr)oxide fraction. Only this smaller reversibly adsorbed fraction is thus available for participating in sorption reactions that determine the solid-solution partitioning of PO4. Overall, this research provides new insights into the reactivity of the metal (hydr)oxide fraction in weathered tropical soils and highlights the relevance of these pedogenic materials in determini

There is significant environmental concern about chlorinated organic compounds (COCs) in wastewater, surface water, and groundwater due to their low biodegradability and high persistence. In this work, 1,2,4-trichlorobenzene (124-TCB) was selected as a model compound to study its abatement using wet peroxide oxidation at neutral pH with goethite as a heterogeneous catalyst, which was enhanced with visible monochromatic light-emitting diode (LED) light (470 nm). A systematic study of the main operating variables (oxidant and catalyst concentration and irradiance) was accomplished to investigate their influence in the abatement of 124-TCB in water. The reaction was carried out in a well-mixed reactor of glass irradiated by a visible LED light. The hydrogen peroxide concentration was tested from 0 to 18 mM, the goethite concentration within the range 0.1–1.0 g·L−1 and the irradiance from 0.10 to 0.24 W·cm−2 at neutral pH. It was found that this oxidation method is a very efficient technique to abate 124-TCB, reaching a pollutant conversion of 0.9 when using 0.1 g·L−1 of goethite, 18 mM of H2O2, and 0.24 of W·cm−2. Moreover, the system performance was evaluated using the photonic efficiency (ratio of the moles of 124-TCB abated and the moles of photons arriving at the reactor window). The maximum photonic efficiencies were obtained using the lowest lamp powers and moderate to high catalyst loads., Comunidad de Madrid, Ministerio de Economía, Industria y Competitividad, European Union’s Horizon 2020, Depto. de Ingeniería Química y de Materiales, Fac. de Ciencias Químicas, TRUE, pub

Goethite (FeOOH)-based ore has become attractive to be utilized in ironmaking. As mildly dehydrated to remove its high combined water (CW), it changes to a nanoporous hematite ore. The nanopore contributes a significant increase in ore reduction reactivity due to the nanocontact between iron oxide and reducing agents such as C, CO, or H-2. However, the long dehydration time of goethite ore is still one problem. This study revealed the effect of vacuum condition on the mild-dehydration of goethite-based ore significantly reduces the ore dehydration time. The dehydration is finished within one hour at 300 degrees C under high-vacuum condition (P=1.7 Pa), producing nanoporous hematite ore that is similar to under atmospheric one for 24 h. However, no significant decrease in the dehydration temperature under the high-vacuum condition. In contrast, in-situ heating TEM observation reveals that nanopore generation can occur at low temperatures under ultra-high vacuum conditions (P = 5.6 x 10(-6) Pa). Slit pore generates at low temperatures that then eventually disappear by merging to bigger pores at the higher temperatures.

The concentration of total dissolved mercury (HgT) in surface and groundwater resources in the coastal parts of Urmia aquifer (NW of Iran) was investigated to identify the possible sources and sinks of mercury and the geochemical mechanisms controlling its mobilization. The distribution of water samples on the Piper diagram demonstrates that most samples have the Ca-Mg-HCO3 facies. From 62 water samples collected in this area, one sample contained HgT concentrations exceeding the maximum contaminant level recommended by the WHO (6 μg/L). The principal component analysis (PCA) produced five principal components. The positive moderate correlation of HgT with EC, Cl, K, Mg, and Na indicated that the weathering of geological formations was one of the main sources of mercury in groundwater samples. Position of water samples in Eh-pH regions where microorganisms involved in mercury methylation and mineralization were potentially active demonstrated that the aquifer had undergone sulfate reduction and had reached the final stage of the terminal electron accepting process (TEAP) sequence in the methane production processes which are limited to only 37% of the water samples that have anaerobic conditions. Some Hg-bearing species are in nonequilibrium geochemical conditions. The supersaturation of water samples with magnetite and goethite indicated that these Fe-bearing minerals could act as the strong reducing agents for the reduction of Hg(II) to Hg(0)., QC 20210423

Iron(III) oxides and oxyhydroxides are among the most reactive minerals in the environment, with surfaces that become charged when immersed in water. The governing role of surface charge over interfacial processes such as metal sorption is well understood. However, its role in interfacial redox reactions, such as when metal sorption is coupled to interfacial electron transfer (ET), is not. This is mainly because surface charge affects not only the types and densities of surface complexes formed but also their respective driving forces for ET. An important case is Fe(II)-catalyzed recrystallization of Fe(III)-oxyhydroxides, in which Fe(II) sorption and interfacial ET are closely linked. In this study, we used replica-exchange constant-pH molecular dynamics simulations (Zarzycki, P.; Smith, D. M.; Rosso, K. M. J. Chem. Theory Comput. 2015, 11, 1715–1724) to calculate the distance-dependent electrostatic potential at charged (110) surfaces of goethite particles, assessing its effect on previously computed Fe(II) sorption and interfacial ET free energies (Zarzycki, P.; Kerisit, S.; Rosso, K. M. J. Phys. Chem. C 2015, 119, 3111–3123). We show that Fe(II) adsorbs preferentially as an inner-sphere complex on the negatively charged surface, and as an outer-sphere complex on the positively charged surface because of both electrostatic repulsion and high energy barriers that arise from ordered water layers at the interface. The separation distance between adsorbed Fe(II) and the surface largely dictates adiabatic versus nonadiabatic ET regimes for this interface. The findings help unravel the pH dependence of Fe(II)-catalyzed recrystallization of goethite.

Two ore blends containing substantial channel iron deposit (CID) and Marra Mamba (MM) ores were assessed. The blends granulated well with addition of hydrated lime, which was found to improve the morphology and strength, and consequently the bed permeability of the resultant green granules. Compared with Blend 2 (a simulated industry blend), Blend 1, containing more MM and less CID ores was slightly less permeable but required similar moisture to achieve its optimum permeability. Both blends showed similar sintering characteristics as evidenced by sintering productivity and sinter quality, suggesting that Blend 1 was comparable to Blend 2. This was further supported by observations of sinter macro- and microstructure. Addition of hydrated lime improves the bed permeability and the formation and fluidity of sinter melt, consequently leading to improved sinter yield and strength along with sintering productivity. To achieve sinter return balance, the sinter return ratio had to decrease as the coke addition increased. (Authors.), Two ore blends containing substantial channel iron deposit (CID) and Marra Mamba (MM) ores were assessed. The blends granulated well with addition of hydrated lime, which was found to improve the morphology and strength, and consequently the bed permeability of the resultant green granules. Compared with Blend 2 (a simulated industry blend), Blend 1, containing more MM and less CID ores was slightly less permeable but required similar moisture to achieve its optimum permeability. Both blends showed similar sintering characteristics as evidenced by sintering productivity and sinter quality, suggesting that Blend 1 was comparable to Blend 2. This was further supported by observations of sinter macro- and microstructure. Addition of hydrated lime improves the bed permeability and the formation and fluidity of sinter melt, consequently leading to improved sinter yield and strength along with sintering productivity. To achieve sinter return balance, the sinter return ratio had to decrease as the coke addition increased. (Authors.)

A reactor model has been built to simulate the goethite process for iron removal. A three-factor designed set of boundary conditions was applied to determine the effect of stirring speed, gas inlet flow rate, and Fe2+ concentration. The two-phase flow velocity field, gas volume fraction distribution, mass transfer rate, and Fe2+ concentration were obtained as simulation results. The results showed that stirring has a significant effect on the distribution of the fluid field. The reaction rate and mass transfer were greatly influenced by the gas inlet flow rate. Based on the results, the following suggestions can be made for the goethite process for iron removal in this system: the number of stirrers should be increased, and the type and size of stirring paddle should be changed to enhance the fluidity of the solution; the rate of gas inlet flow should be increased to enhance the mass transfer and accelerate the iron removal reaction. (Authors.), A reactor model has been built to simulate the goethite process for iron removal. A three-factor designed set of boundary conditions was applied to determine the effect of stirring speed, gas inlet flow rate, and Fe2+ concentration. The two-phase flow velocity field, gas volume fraction distribution, mass transfer rate, and Fe2+ concentration were obtained as simulation results. The results showed that stirring has a significant effect on the distribution of the fluid field. The reaction rate and mass transfer were greatly influenced by the gas inlet flow rate. Based on the results, the following suggestions can be made for the goethite process for iron removal in this system: the number of stirrers should be increased, and the type and size of stirring paddle should be changed to enhance the fluidity of the solution; the rate of gas inlet flow should be increased to enhance the mass transfer and accelerate the iron removal reaction. (Authors.)

In zinc hydrometallurgy, hot-acidic leaching of calcines leads to Fe/Zn solutions in sulphuric acid medium. Three distinct processes have been previously developed to remove iron: jarosite, goethite and haematite. Each process displays their own drawbacks: important loss of zinc (jarosite, goethite), significant environmental impact of residue (jarosite) or economic cost (haematite). The work reported herein investigated the possibility of using phytic acid, a compound extractable from cereals, to remove iron. Precipitation was studied first at the laboratory-scale using DOE methodology and then with a laboratory pilot. At pH = 2.1, it is shown that it is possible to remove up to 99.5% of iron with a loss of zinc equal to 0.6% and a residual concentration of Fe(III) of 130 mg/l. Even if the amount of residue is more important than in the jarosite process, leaching tests showed that iron phytate could be stored in less drastic conditions than jarosite., In zinc hydrometallurgy, hot-acidic leaching of calcines leads to Fe/Zn solutions in sulphuric acid medium. Three distinct processes have been previously developed to remove iron: jarosite, goethite and haematite. Each process displays their own drawbacks: important loss of zinc (jarosite, goethite), significant environmental impact of residue (jarosite) or economic cost (haematite). The work reported herein investigated the possibility of using phytic acid, a compound extractable from cereals, to remove iron. Precipitation was studied first at the laboratory-scale using DOE methodology and then with a laboratory pilot. At pH = 2.1, it is shown that it is possible to remove up to 99.5% of iron with a loss of zinc equal to 0.6% and a residual concentration of Fe(III) of 130 mg/l. Even if the amount of residue is more important than in the jarosite process, leaching tests showed that iron phytate could be stored in less drastic conditions than jarosite.

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zhou, P., Ireland, T., Murray, R. W., & Clift, P. D. Marine sedimentary records of chemical weathering evolution in the western Himalaya since 17 Ma. Geosphere, 17(3), (2021): 824–853, https://doi.org/10.1130/GES02211.1., The Indus Fan derives sediment from the western Himalaya and Karakoram. Sediment from International Ocean Discovery Program drill sites in the eastern part of the fan coupled with data from an industrial well near the river mouth allow the weathering history of the region since ca. 16 Ma to be reconstructed. Clay minerals, bulk sediment geochemistry, and magnetic susceptibility were used to constrain degrees of chemical alteration. Diffuse reflectance spectroscopy was used to measure the abundance of moisture-sensitive minerals hematite and goethite. Indus Fan sediment is more weathered than Bengal Fan material, probably reflecting slow transport, despite the drier climate, which slows chemical weathering rates. Some chemical weathering proxies, such as K/Si or kaolinite/(illite + chlorite), show no temporal evolution, but illite crystallinity and the chemical index of alteration do have statistically measurable decreases over long time periods. Using these proxies, we suggest that sediment alteration was moderate and then increased from 13 to 11 Ma, remained high until 9 Ma, and then reduced from that time until 6 Ma in the context of reduced physical erosion during a time of increasing aridity as tracked by hematite/goethite values. The poorly defined reducing trend in weathering intensity is not clearly linked to global cooling and at least partly reflects regional climate change. Since 6 Ma, weathering has been weak but variable since a final reduction in alteration state after 3.5 Ma that correlates with the onset of Northern Hemispheric glaciation. Reduced or stable chemical weathering at a time of falling sedimentation rates is not consistent with models for Cenozoic global climate change that invoke greater Himalayan weathering fluxes drawing down atmospheric CO2 but are in accord with the idea of greater surface reactivity to weathering., This study was made possible by samples provided by the IODP. The work was partially funded by a grant from The U.S. Science Support Program (USSSP), as well as additional funding from the Charles T. McCord Jr. Endowed Chair in petroleum geology at LSU.

The uptake of the fission product technetium (Tc) by chukanovite, an Fe(II) hydroxy carbonate mineral formed as a carbon steel corrosion product in anoxic and carbonate-rich environments, was studied under anoxic, alkaline to hyperalkaline conditions representative for nuclear waste repositories in deep geological formations with cement-based inner linings. The retention potential of chukanovite towards Tc(VII) is high in the pH range 7.8 to 12.6, evidenced by high solid-water distribution coefficients, log Rd ~ 6, and independent of ionic strength (0.1 or 1 M NaCl). Using Tc K-edge X-ray absorption spectroscopy (XAS) two series of samples were investigated, Tc chukanovite sorption samples and coprecipitates, prepared with varying Tc loadings, pH values and contact times. From the resulting 37 XAS spectra, spectral endmembers and their dependence on chemical parameters were derived by self-organizing (Kohonen) maps (SOM), a neural network-based approach of machine learning. X-ray absorption near-edge structure (XANES) data confirmed the complete reduction of Tc(VII) to Tc(IV) by chukanovite under all experimental conditions. Consistent with mineralogical phases identified by X-ray diffraction (XRD), SOM analysis of the extended X-ray absorption fine-structure (EXAFS) spectra revealed the presence of three species in the sorption samples, the speciation predominately controlled by pH: Between pH 7.8 and 11.8, TcO₂-dimers form inner-sphere sorption complexes at the surface of the initial chukanovite as well as on the surface of secondary magnetite formed due to redox reaction. At pH ≥11.9, Tc(IV) is incorporated in a mixed, chukanovite-like, Fe/Tc hydroxy carbonate precipitate. The same species formed when using the coprecipitation approach. Reoxidation of sorption samples resulted in a small remobilization of Tc, demonstrating that both the original chukanovite mineral and its oxidative transformation products, magnetite and goethite, contribute to the immobilization

The primary objectives of this study is mineralogical characterization of two sludge samples with different initial content of iron derived by hydro-cyclone overflow generated during the processing of iron ore in the Omarska mine. Also, a comparative study of the mineral composition and its connection with some properties important for the sludge flocculation process was done. Studied sludge samples are composed of major goethite and quartz; less clay minerals; and minor magnetite, hematite, clinochlore and todorokite. They have quite similar qualitative, but different semi-quantitative compositions. There are similar particle size distributions between the samples, and highest contents of about 50% belongs to the finest classes of <6 m. Among size classes within the samples, almost identical iron contents are present; indicating to their similar mineral compositions, which make this system very complex for further separation processes. Sludge II has higher natural settling rate, due to its higher density and mineral composition. With addition of the flocculant, settling rates increases significantly with the increase of the liquid component in both of the samples. The effect of flocculant on the settling rate is different between samples, and depends on their mineral composition. The time of settling does not play a role in selectivity, to the ratio of the mass of floating and sinking parts, and iron content does not change with time. The content of iron partially increases by flocculation; therefore, this method should be considered as an appropriate one. Zeta potential values for sludge are mostly between those for goethite and quartz, indicating their particle mixture and intricately association.

Biochar works as a green catalyst for the dechlorination of chlorinated ethylenes (CEs) by green rust (GR). Although the GR-biochar composite shows great potential for groundwater remediation, its performance under simulated field conditions has not been investigated. In this study, a composite of chloride GR and bone char (BC) was used to investigate the effect of groundwater solutes (Cl-, SO42-, HCO3-, and H4SiO4) and the co-existence of one or two CE(s) on GR-BC reactivity with CEs. Furthermore, a contaminant-free groundwater and five CE-contaminated groundwaters were collected to test the reactivity of the GR-BC composite under real groundwater conditions. Among all tested groundwater solutes, HCO3- affected CE dechlorination rates the most, exemplified by a 6.7-fold decrease in trichloroethylene (TCE) reduction rate constant, k(mass), to 0.16 L g(-1) h(-1) in the presence of 10 mM HCO3- solution when compared to the solute free experiment. Silicic acid led to a 1.7-fold decrease in k(mass) at concentrations of 0.5 and 1 mM and a 5.3-fold decrease at 2 mM. TCE reduction rate was also decreased by the co-existence of PCE (by a factor of 1.6), while cDCE had very little impact. Natural groundwater matrices led to up to 52-fold decrease in k(mass)(TCE), depending on the complexity and pollutant profile of the groundwater. However, relatively fast dechlorination with k(mass)(TCE) >= 0.021 L g(-1) h(-1) was seen in all tested CE-contaminated groundwaters where CE concentrations were comparable. For hard groundwaters, HCO3- is recognized as the main inhibitor for dechlorination, while the impact of the other tested solutes is minor. The study provides practical information for the application of the GR-BC composite for remediation of CE-contaminated groundwaters.

The occurrence of dark subsurface horizons rich in organic matter (OM) associated with polychrome in the B horizon (yellowish over reddish hue) is common in soils from Southern Brazil. The formation of these horizons and the combination with such morphological attributes has not been properly documented, and neither has the cause effect relationship. Four soil profiles with such sombric-like horizons with a yellowish color at the upper part of the B horizon over red subsoil were studied in Southern Brazil. Results from micromorphology, extractable sesquioxide minerals, clay mineralogy and isomorphic substitution of Fe by Al in iron minerals showed that melanization, xanthization, bioturbation, moderate shrinking/swelling and moderate ferralitization were the most evident pedogenetic processes in role. Xanthization is closely related to the sombric-like horizon formation. In the studied area the findings demonstrated that no clay and OM illuviation had taken place. Therefore, the classification of these soils was revisited, so as to take into account the processes that underlie their genesis with emphasis on xanthization, clay illuviation and soil aggregation. The results suggest that the sombric horizon may need redefinition, unless profiles can be found in which illuviation of clay and/or OM can be proven.

Background: Mercury (Hg) is recognized as one of the 10 most toxic elements in nature and is much more persistent in soils than in other environmental compartments. However, an effective, environmentally friendly, economical, and large-scale applicable technology for the remediation of soils contaminated by Hg has not yet been established. This study evaluates the feasibility of a new carbon foam-based product for the remediation of three soils contaminated with Hg, and infers the mobilization or immobilization mechanism through a detailed study of Hg speciation. Results: Soil treatment with carbon foams, one of them impregnated with goethite, reduced Hg availability by 75–100%. The proportion of mercury associated to humic acids (Hg–HA) determined the mobility and the availability of Hg when soils were treated with carbon foams. The drop of pH promotes changes in the structure of HA, a consequence of which is that Hg–HA becomes part of the unavailable fraction of the soil along with HgS. The carbon foam impregnated with goethite did not mobilize Fe as occurred with zero valence iron nanoparticles. The presence of acidic groups on the surface of the foam (carboxyl, quinone and phenolic groups) can strongly improve the binding of metal cations, enhancing Fe immobilization. Conclusions: A novel carbon foam-based amendment was efficient in immobilizing Hg in all the soils studied. The carbon foam impregnated with goethite, in addition to not mobilizing Fe, had the additional advantage of its low effect on the electrical conductivity of the soil. This novel approach could be considered as a potential amendment for other industrial and/or abandoned mining areas contaminated with Hg and/or other metal(loid)s.

More knowledge of the geochemical behavior of tungsten (W) and associated contamination risks is needed. Therefore, weathering of scheelite (CaWO4) and secondary sequestration and transport of W to groundwater in historical skarn tailings and surface water downstream of the tailings were studied. The tailings contained 920 mg/kg W, primarily in scheelite. Mineralogical and geochemical analyses were combined to elucidate the geochemical behavior of W in the tailings, and water samples were taken monthly during 2018 to monitor its mobility. In the tailings, a large peak of W was found at 1.5 m depth. There, 30 wt%. of W was present in easily reducible phases, indicating former scheelite weathering. Currently, W is being released from scheelite to water-soluble phases at 2.5 m depth. The release of WO42− is hypothetically attributed to anion exchange with CO32− released from calcite neutralizing acid produced from pyrrhotite oxidation in the upper tailings and transported downwards to pH conditions > 7. Higher concentrations of dissolved W were found in the groundwater and particulate W in downstream surface water than in reference water, but they were lower than current contamination thresholds. Tungsten showed correlations with hydrous ferric oxides (HFO) in both the tailings and surface water., Validerad;2020;Nivå 2;2020-03-18 (alebob);Artikeln har tidigare förekommit som manuskript i avhandling.

Many lateritic soils contain goethite and hematite, which have a low thermal expansion coefficient and also enhance the formation of soil aggregates. The influence of these minerals on the thermo-mechanical soil behaviour, however, has not been well understood. In this study, cyclic thermal strain of a small number of specimens of saturated lateritic clay was investigated over a temperature range of 5 to 70 °C, using a thermal oedometer equipped with an invar ring. Both compacted and reconstituted specimens, which were expected to have different degrees of aggregation, were tested. The soil was characterised in terms of its mineralogy and microstructure determined respectively using x-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that a semi-empirical equation over-estimated the thermal expansion coefficient of normally consolidated (NC) lateritic clay by about 3 times. The discrepancy is mainly because the goethite and hematite in the lateritic clay enhance the formation of aggregates and stiffen the specimen. Even the reconstituted specimen contains many aggregates, as clearly revealed by the result SEM tests. Goethite and hematite have much lower thermal expansion coefficient (TEC) than many clay minerals. On the other hand, it was found that both NC compacted and reconstituted specimens showed an accumulation of irreversible contraction under cyclic heating and cooling, but at a decreasing rate, where for a given number of thermal cycles, the measured thermal strain of NC reconstituted specimens was about 30% lower than that of the NC compacted specimens. This is mainly because the density of NC reconstituted specimen is much higher than the NC compacted specimen, even though they had experienced the same effective stress. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

A comparative study of polyacrylamide and potato starch as selective flocculants for the beneficiation of low-grade iron-ore slimes (head sample: 52.6% Fe) from Barsua mines, Sundergarh, Odisha, India is presented. Characterisation of the slimes is performed using chemical analyses, particle size distribution, optical microscopy, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis and scanning electron microscopy/energy-dispersive X-ray spectroscopy. Using a feed size of -75 micrometres, the effects of pulp density, flocculant dosage and pH on the settling rate, grade, recovery, and separation efficiency are described. The results indicate that, under optimum conditions of pH 9, pulp density 20% and polyacrylamide dosage 45 ppm, an iron grade of 65.90% and recovery of 91.04% with a separation efficiency of 69.59% are achieved. A statistical analysis of the experimental data using ANOVA and a mechanistic investigation of the adsorption of the flocculants on the mineral surfaces (haematite and goethite) by measuring the FTIR spectra and XRD patterns of the feed sample and concentrates are discussed., A comparative study of polyacrylamide and potato starch as selective flocculants for the beneficiation of low-grade iron-ore slimes (head sample: 52.6% Fe) from Barsua mines, Sundergarh, Odisha, India is presented. Characterisation of the slimes is performed using chemical analyses, particle size distribution, optical microscopy, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis and scanning electron microscopy/energy-dispersive X-ray spectroscopy. Using a feed size of -75 micrometres, the effects of pulp density, flocculant dosage and pH on the settling rate, grade, recovery, and separation efficiency are described. The results indicate that, under optimum conditions of pH 9, pulp density 20% and polyacrylamide dosage 45 ppm, an iron grade of 65.90% and recovery of 91.04% with a separation efficiency of 69.59% are achieved. A statistical analysis of the experimental data using ANOVA and a mechanistic investigation of the adsorption of the flocculants on the mineral surfaces (haematite and goethite) by measuring the FTIR spectra and XRD patterns of the feed sample and concentrates are discussed.

The present study demonstrates the effect of the different morphological types on the cold crushing strength (CCS) of heat-treated iron ore pellets. Blends with different morphologies of iron ore oxides were subjected to grinding, filtering and pot grate tests on industrial scale trials. Results of grinding tests showed the haematite-goethite aggregates had the most effect on energy consumption. The martitic-haematite content was straightly related to the final moisture and filtration productivity. The goethite content in haematite-goethite aggregates influences CCS, i.e., the lower the goethite content, the higher the values of CCS., The present study demonstrates the effect of the different morphological types on the cold crushing strength (CCS) of heat-treated iron ore pellets. Blends with different morphologies of iron ore oxides were subjected to grinding, filtering and pot grate tests on industrial scale trials. Results of grinding tests showed the haematite-goethite aggregates had the most effect on energy consumption. The martitic-haematite content was straightly related to the final moisture and filtration productivity. The goethite content in haematite-goethite aggregates influences CCS, i.e., the lower the goethite content, the higher the values of CCS.

The loss of iron-bearing minerals to the tailings, especially in the finest fractions (−44 micron), is a problem that must be endured due to the depletion of deposits containing high-Fe haematite. The two main mechanisms for iron mineral loss in the froth in reverse cationic flotation are hydrodynamic dragging and true flotation. This last one being attributed to failures in the conditioning processes regarding the depression of iron mineral by starch. In this work, two industrial mechanical flotation circuits located in Minas Gerais—Brazil, namely Conceição Itabiritos II and Pico, operating with mineralogically distinct iron minerals, had their tailings analysed in order to attribute reasons for the iron-bearing minerals losses. Liberation studies excluded losses due to the presence of composite particles where haematite was combined to silica or goethite. The method known as two-liquid flotation was applied to the several particle fractions present in the tailings to evaluate the particles surfaces hydrophobicity/hydrophilicity. The results indicated that for Conceição Itabiritos II, the loss of iron minerals was due to a combination of true flotation and hydrodynamic dragging. True flotation probably took place because of depression failure. For Pico, the results revealed that most of the iron-bearing particles were lost due to hydrodynamic dragging. The shape factor and terminal velocity, both obtained via permeametry, confirmed the two-liquid flotation results. Two-liquid flotation was shown to be a fast and simple method to qualitatively assess the hydrophobicity of particles in froth flotation, thus allowing quick improvements in the process. (Authors.), The loss of iron-bearing minerals to the tailings, especially in the finest fractions (−44 micron), is a problem that must be endured due to the depletion of deposits containing high-Fe haematite. The two main mechanisms for iron mineral loss in the froth in reverse cationic flotation are hydrodynamic dragging and true flotation. This last one being attributed to failures in the conditioning processes regarding the depression of iron mineral by starch. In this work, two industrial mechanical flotation circuits located in Minas Gerais—Brazil, namely Conceição Itabiritos II and Pico, operating with mineralogically distinct iron minerals, had their tailings analysed in order to attribute reasons for the iron-bearing minerals losses. Liberation studies excluded losses due to the presence of composite particles where haematite was combined to silica or goethite. The method known as two-liquid flotation was applied to the several particle fractions present in the tailings to evaluate the particles surfaces hydrophobicity/hydrophilicity. The results indicated that for Conceição Itabiritos II, the loss of iron minerals was due to a combination of true flotation and hydrodynamic dragging. True flotation probably took place because of depression failure. For Pico, the results revealed that most of the iron-bearing particles were lost due to hydrodynamic dragging. The shape factor and terminal velocity, both obtained via permeametry, confirmed the two-liquid flotation results. Two-liquid flotation was shown to be a fast and simple method to qualitatively assess the hydrophobicity of particles in froth flotation, thus allowing quick improvements in the process. (Authors.)

Laboratory (balling disc and rising hearth furnace) and pilot-scale (basket trial) pelletisation investigations to increase the strength of roasted iron-ore pellets by optimising the induration furnace firing cycle for 100% high-loss on ignition (LOI) iron-ore fines (57.7% Fe; 8.80% moisture; 8.85% LOI), and to optimise the use of high-LOI iron-ore fines in a pellet-plant induration cycle are presented. The laboratory results indicate that, in order to obtain the required pellet properties, the induration firing cycle needs to be increased from 54 to 62 min (drying 5 min; pre-heating 3 min) and the firing temperature should be increased by 20 degrees C. This procedure reduces the pellet production from 12 000 to 10 459 tons/d and increases the raw-material consumption from 12 720 to 13 344 t/d. The pilot-scale results show that up to 20% high-LOI iron ore can be mixed in the low-LOI/high-LOI ore blend without affecting the pellet properties or the pellet-plant-machine operating conditions., Laboratory (balling disc and rising hearth furnace) and pilot-scale (basket trial) pelletisation investigations to increase the strength of roasted iron-ore pellets by optimising the induration furnace firing cycle for 100% high-loss on ignition (LOI) iron-ore fines (57.7% Fe; 8.80% moisture; 8.85% LOI), and to optimise the use of high-LOI iron-ore fines in a pellet-plant induration cycle are presented. The laboratory results indicate that, in order to obtain the required pellet properties, the induration firing cycle needs to be increased from 54 to 62 min (drying 5 min; pre-heating 3 min) and the firing temperature should be increased by 20 degrees C. This procedure reduces the pellet production from 12 000 to 10 459 tons/d and increases the raw-material consumption from 12 720 to 13 344 t/d. The pilot-scale results show that up to 20% high-LOI iron ore can be mixed in the low-LOI/high-LOI ore blend without affecting the pellet properties or the pellet-plant-machine operating conditions.

Voluminous piles of mine waste generated over several decades of iron ore mining (c.17 Mt) are dumped near the Oraghat iron ore mine, Bonai-Keonjhar belt, Odisha, causing immense environmental and disposal problems. The pile of waste containing low Fe (c.51%) and high Al2O3 (c.13%) with SiO2 (c.6%) is not suitable for iron-making and hence considered as waste. The major minerals identified under a reflected light microscope and XRD are haematite, goethite/limonite and gibbsite with minor kaolinite and quartz. Size classification of mine-dump samples shows enrichment of gibbsite and kaolinite in finer fractions smaller than 1 mm. The bulk sample was ground below 1 mm size and deslimed using a hydrocyclone. The cyclone overflow (c.21%) was rejected and the underflow material (c.79%) was processed through a wet high-intensity magnetic separator. The feed having 51% Fe was upgraded to 63% Fe with 40% yield and 49% recovery. The final product can suitably be utilised as a sinter feed. (Authors.), Voluminous piles of mine waste generated over several decades of iron ore mining (c.17 Mt) are dumped near the Oraghat iron ore mine, Bonai-Keonjhar belt, Odisha, causing immense environmental and disposal problems. The pile of waste containing low Fe (c.51%) and high Al2O3 (c.13%) with SiO2 (c.6%) is not suitable for iron-making and hence considered as waste. The major minerals identified under a reflected light microscope and XRD are haematite, goethite/limonite and gibbsite with minor kaolinite and quartz. Size classification of mine-dump samples shows enrichment of gibbsite and kaolinite in finer fractions smaller than 1 mm. The bulk sample was ground below 1 mm size and deslimed using a hydrocyclone. The cyclone overflow (c.21%) was rejected and the underflow material (c.79%) was processed through a wet high-intensity magnetic separator. The feed having 51% Fe was upgraded to 63% Fe with 40% yield and 49% recovery. The final product can suitably be utilised as a sinter feed. (Authors.)

Organic binders have been used as alternative to bentonite in the iron ore pelletising process mainly because it burns without leaving residue in the pellet. There are two main types of organic binders, those based on cellulose and those based on polyacrylamide structures. The purpose of this investigation was to explore how an organic binder based on carboxymethyl cellulose structure improves the compressive strength of wet and dry pellets. Thus, the interaction between the binder Peridur and the mineral surface and the content of goethite in two Brazilian pellet feed were investigated. This work has found that the same organic binder performs differently depending on the type of iron ore processed. (Authors.), Organic binders have been used as alternative to bentonite in the iron ore pelletising process mainly because it burns without leaving residue in the pellet. There are two main types of organic binders, those based on cellulose and those based on polyacrylamide structures. The purpose of this investigation was to explore how an organic binder based on carboxymethyl cellulose structure improves the compressive strength of wet and dry pellets. Thus, the interaction between the binder Peridur and the mineral surface and the content of goethite in two Brazilian pellet feed were investigated. This work has found that the same organic binder performs differently depending on the type of iron ore processed. (Authors.)

The North and South Flank deposits are located on the flanks of the Weeli Wolli anticline at Mining Area C in the central Hamersley Province. Supergene martite-goethite mineralisation is hosted within the Marra Mamba Iron Formation and is developed over a strike length of more than 60 km. This multibillion metric ton resource has been drilled out on a 150- × 50- to 50- × 50-m grid, thus providing us with an unprecedented data set for analysis. This study synthesises the drill hole data and presents a physical process model that can account for the observed distribution of mineralisation. A fluid and mass flux model is proposed which envisages a three-stage process: leaching of Fe from banded iron formation (BIF) in the vadose zone by reduced, acidic, meteoric-derived fluids; penetration of an Fe-rich supergene-fluid plume, driven by gravity and focused by bedding-parallel permeability into the body of ambient alkaline groundwater, effecting nonredox, mimetic replacement of magnetite by haematite and of the gangue minerals (carbonate, silicate, and chert) by goethite coupled with the release of silica into the fluid phase; and a change from silica leaching to silica deposition on the downdip margins of the system before the ore-fluid plume is eventually diluted and becomes indistinguishable from the surrounding body of groundwater. Based on this physical process model, the development of a large-scale martite-goethite mineralising system requires continued delivery of unleached BIF (and, perhaps ultimately, previously mineralised martite-goethite ore) into the vadose zone. The combination of ongoing uplift since at least 60 Ma and a wet, temperate climate is likely to be the key to the widespread formation of martite-goethite deposits in the Hamersley Province., The North and South Flank deposits are located on the flanks of the Weeli Wolli anticline at Mining Area C in the central Hamersley Province. Supergene martite-goethite mineralisation is hosted within the Marra Mamba Iron Formation and is developed over a strike length of more than 60 km. This multibillion metric ton resource has been drilled out on a 150- × 50- to 50- × 50-m grid, thus providing us with an unprecedented data set for analysis. This study synthesises the drill hole data and presents a physical process model that can account for the observed distribution of mineralisation. A fluid and mass flux model is proposed which envisages a three-stage process: leaching of Fe from banded iron formation (BIF) in the vadose zone by reduced, acidic, meteoric-derived fluids; penetration of an Fe-rich supergene-fluid plume, driven by gravity and focused by bedding-parallel permeability into the body of ambient alkaline groundwater, effecting nonredox, mimetic replacement of magnetite by haematite and of the gangue minerals (carbonate, silicate, and chert) by goethite coupled with the release of silica into the fluid phase; and a change from silica leaching to silica deposition on the downdip margins of the system before the ore-fluid plume is eventually diluted and becomes indistinguishable from the surrounding body of groundwater. Based on this physical process model, the development of a large-scale martite-goethite mineralising system requires continued delivery of unleached BIF (and, perhaps ultimately, previously mineralised martite-goethite ore) into the vadose zone. The combination of ongoing uplift since at least 60 Ma and a wet, temperate climate is likely to be the key to the widespread formation of martite-goethite deposits in the Hamersley Province.

A study has been carried out to compare wet ball milling with the new HPGR processing technology for haematite-goethite ores. Bench and pilot scale simulations were undertaken for green-pellet ball milling and induration. It was found that recirculation in the HPGR gave a Blaine specific surface area (BSA) increase suitable for pelletising applications. The percentage of particles smaller than 45 microns showed an increase of only 5% after the third recirculation cycle and then remained constant until the end of the process. The ballability tests showed good seed formation and steady pellet growth and a higher percentage of green pellets sized between 10 and 16 mm was obtained. The high BSA led to a need for more water to balance the pellet growth. The fired pellets performed will in terms of cold crushing strength (CCS) in every test with the ore blend ground in HPGR., A study has been carried out to compare wet ball milling with the new HPGR processing technology for haematite-goethite ores. Bench and pilot scale simulations were undertaken for green-pellet ball milling and induration. It was found that recirculation in the HPGR gave a Blaine specific surface area (BSA) increase suitable for pelletising applications. The percentage of particles smaller than 45 microns showed an increase of only 5% after the third recirculation cycle and then remained constant until the end of the process. The ballability tests showed good seed formation and steady pellet growth and a higher percentage of green pellets sized between 10 and 16 mm was obtained. The high BSA led to a need for more water to balance the pellet growth. The fired pellets performed will in terms of cold crushing strength (CCS) in every test with the ore blend ground in HPGR.

Hybrid adsorbent, based on the cross-linked copolymer impregnated with hydrous iron oxide, was applied for the first time for Se(VI) adsorption from water. The influence of the initial solution pH, selenate concentration and contact time to adsorption capacity was investigated. Adsorbent regeneration was explored using a full factorial experimental design in order to optimize the volume, initial pH value and concentration of the applied NaCl solution as a reagent. Equilibrium state was described using the Langmuir model, while kinetics fitted the pseudo-first order. The maximum adsorption capacity was found to be 28.8 mg/g. Desorption efficiency increased up to 70%, and became statistically significant with the reagent concentration and pH increase, while the applied solution volume was found to be insignificant in the investigated range. Based on the results obtained, pH influence to the adsorption capacity, desorption efficiency, Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analysis of loaded adsorbent, it was concluded that the outer- and inner-sphere complexation are mechanisms responsible for Se(VI) separation from water. In addition to the experiments with synthetic solutions, the adsorbent performances in drinking water samples were explored, showing the purification efficiency up to 25%, depending on the initial Se(VI) concentration and water pH. Determined sorption capacity of the cross-linked copolymer impregnated with hydrous iron oxide and its ability for regeneration, candidate this material for further research, as a promising anionic species sorbent.

Hybrid adsorbent, based on the cross-linked copolymer impregnated with hydrous iron oxide, was applied for the first time for Se(VI) adsorption from water. The influence of the initial solution pH, selenate concentration and contact time to adsorption capacity was investigated. Adsorbent regeneration was explored using a full factorial experimental design in order to optimize the volume, initial pH value and concentration of the applied NaCl solution as a reagent. Equilibrium state was described using the Langmuir model, while kinetics fitted the pseudo-first order. The maximum adsorption capacity was found to be 28.8 mg/g. Desorption efficiency increased up to 70%, and became statistically significant with the reagent concentration and pH increase, while the applied solution volume was found to be insignificant in the investigated range. Based on the results obtained, pH influence to the adsorption capacity, desorption efficiency, Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analysis of loaded adsorbent, it was concluded that the outer-and inner-sphere complexation are mechanisms responsible for Se(VI) separation from water. In addition to the experiments with synthetic solutions, the adsorbent performances in drinking water samples were explored, showing the purification efficiency up to 25%, depending on the initial Se(VI) concentration and water pH. Determined sorption capacity of the cross-linked copolymer impregnated with hydrous iron oxide and its ability for regeneration, candidate this material for further research, as a promising anionic species sorbent.

Fluviatile sediments comprising a 600‐m‐thick sequence of the Lower and Middle Siwaliks in the Karnali area in Nepal exhibit a distinct zonation revealed by magnetic and geochemical properties. Four magneto‐chemical zones (MCZ1–MCZ4), each about 150 m thick and 400 kyr in duration, provide new insights into Himalayan tectono‐climatic events during the Tortonian (Miocene) stage. They exhibit contrasting magnetic susceptibility and isothermal remanence due to differences in magnetic mineral types (magnetite, haematite, and goethite) and concentrations. Odd‐numbered zones with higher goethite/(goethite + haematite) ratio, a moisture proxy, indicate wetter conditions in the source area, while the even‐numbered zones, virtually without goethite, suggest drier conditions. Chemical indices of alteration/weathering and proxies for hydraulic sorting and mobility derived from the major element compositions also reveal contrasts among these zones. The middle of the MCZ2–MCZ3 zone, with a transitional magneto‐chemical signature, is the best candidate for the Lower‐to‐Middle Siwaliks contact, rather than the field‐based boundary placed 18 m up‐section at the base of the thick salt‐and‐pepper sandstone bed. The transition records an increase in river energy and associated accelerated erosion of the Himalayan gneiss zone as the source of coarse‐grained material. We suggest a scenario, whereby climate change from drier to wetter (with higher precipitation) conditions affects erosional processes (i.e., weathering, disaggregation and particle transport on the hillslope) prevailing in a large catchment and influencing the depositional modes.

The Intex laterite deposit in Mindoro, Philippines is derived from the weathering of the ultramafic rocks under a tropical climate. This study investigates the several types of serpentines and the effect of the degree of chemical weathering of ultramafic rocks and laterites on the enrichment of Ni in the deposit. The five types of serpentines are differentiated based on their textural features and Raman spectral data. Type I, type II, type III, and type IV serpentines contain a low amount of NiO (average 0.15 wt%), and their formation is linked to the previous exhumation of the ultramafic body. Conversely, type V serpentines show the highest NiO contents (average 1.42 wt%) and have the composition of serpentine-like garnierites, indicating a supergene origin. In the limonite horizon, goethite is the main ore mineral and shows high NiO contents of up to 1.68 wt%, whereas the Mn-oxyhydroxides (i.e., asbolane and lithiophorite-asbolane intermediate) display substantial amounts of CoO (up to 11.3 wt%) and NiO (up to 15.6 wt%). The Ultramafic Index of Alteration (UMIA) and Index of Lateritization (IOL) are used to characterize the different stages of weathering of rocks and laterites. The calculated index values correspond to a less advanced stage of weathering of the Intex laterites compared with the Berong laterites. The Berong deposit is a Ni-Co laterite deposit in the Philippines, which is formed from the weathering of the serpentinized peridotite. The less extreme degree of weathering of the Intex laterites indicates less advanced leaching, and thereby the re-distribution of Ni, Si, and Mg from the limonite towards the saprolite horizon may have resulted in the poor precipitation of talc-like (kerolite-pimelite) and sepiolite-like (sepiolite-falcondoite) phases in the studied saprolite horizon. Nickel in the Intex deposit has undergone supergene enrichment similar to other humid tropical laterite deposits.

Many lateritic soils contain goethite and hematite, which have a low thermal expansion coefficient and also enhance the formation of soil aggregates. The influence of these minerals on the thermo-mechanical soil behaviour, however, has not been well understood. In this study, cyclic thermal strain of a small number of specimens of saturated lateritic clay was investigated over a temperature range of 5 to 70 °C, using a thermal oedometer equipped with an invar ring. Both compacted and reconstituted specimens, which were expected to have different degrees of aggregation, were tested. The soil was characterised in terms of its mineralogy and microstructure determined respectively using x-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that a semi-empirical equation over-estimated the thermal expansion coefficient of normally consolidated (NC) lateritic clay by about 3 times. The discrepancy is mainly because the goethite and hematite in the lateritic clay enhance the formation of aggregates and stiffen the specimen. Even the reconstituted specimen contains many aggregates, as clearly revealed by the result SEM tests. Goethite and hematite have much lower thermal expansion coefficient (TEC) than many clay minerals. On the other hand, it was found that both NC compacted and reconstituted specimens showed an accumulation of irreversible contraction under cyclic heating and cooling, but at a decreasing rate, where for a given number of thermal cycles, the measured thermal strain of NC reconstituted specimens was about 30% lower than that of the NC compacted specimens. This is mainly because the density of NC reconstituted specimen is much higher than the NC compacted specimen, even though they had experienced the same effective stress. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

The adsorption and desorption of boric acid onto reactive materials such as metal (hydr)oxides and natural organic matter are generally considered to be controlling processes for the leaching and bioavailability of boron (B). We studied the interaction of B with ferrihydrite (Fh), a nanosized iron (hydr)oxide omnipresent in soil systems, using batch adsorption experiments at different pH values and in the presence of phosphate as a competing anion. Surface speciation of B was described with a recently developed multisite ion complexation (MUSIC) and charge distribution (CD) approach. To gain insight into the B adsorption behavior in whole-soil systems, and in the relative contribution of Fh in particular, the pH-dependent B speciation was evaluated for soils with representative amounts of ferrihydrite, goethite, and organic matter. The pH-dependent B adsorption envelope of ferrihydrite is bell-shaped with a maximum around pH 8-9. In agreement with spectroscopy, modeling suggests formation of a trigonal bidentate complex and an additional outer-sphere complex at low to neutral pH values. At high pH, a tetrahedral bidentate surface species becomes important. In the presence of phosphate, B adsorption decreases strongly and only formation of the outer-sphere surface complex is relevant. The pH-dependent B adsorption to Fh is rather similar to that of goethite. Multisurface modeling predicts that ferrihydrite may dominate the B binding in soils at low to neutral pH and that the relative contribution of humic material increases significantly at neutral and alkaline pH conditions. This study identifies ferrihydrite and natural organic matter (i.e., humic substances) as the major constituents that control the B adsorption in topsoils.

The occurrence of dark subsurface horizons rich in organic matter (OM) associated with polychrome in the B horizon (yellowish over reddish hue) is common in soils from Southern Brazil. The formation of these horizons and the combination with such morphological attributes has not been properly documented, and neither has the cause effect relationship. Four soil profiles with such sombric-like horizons with a yellowish color at the upper part of the B horizon over red subsoil were studied in Southern Brazil. Results from micromorphology, extractable sesquioxide minerals, clay mineralogy and isomorphic substitution of Fe by Al in iron minerals showed that melanization, xanthization, bioturbation, moderate shrinking/swelling and moderate ferralitization were the most evident pedogenetic processes in role. Xanthization is closely related to the sombric-like horizon formation. In the studied area the findings demonstrated that no clay and OM illuviation had taken place. Therefore, the classification of these soils was revisited, so as to take into account the processes that underlie their genesis with emphasis on xanthization, clay illuviation and soil aggregation. The results suggest that the sombric horizon may need redefinition, unless profiles can be found in which illuviation of clay and/or OM can be proven.