Extraction Of Sulfur Research Articles

Właściwości gleb technogenicznych wykształcających się z substratów neogeńskich i czwartorzędowych na zrekultywowanych terenach po odkrywkowej eksploatacji siarki i piasków podsadzkowych

Właściwości gleb technogenicznych wykształcających się z substratów neogeńskich i czwartorzędowych na zrekultywowanych terenach po odkrywkowej eksploatacji siarki i piasków podsadzkowych

Geology and genesis of the Debao Cu polymetallic skarn deposit, southwestern China

The Debao deposit, with stratiform orebodies in Middle-Upper Cambrian carbonate rocks, is a rare Early Paleozoic skarn copper deposit in the South China Block. Garnet U-Pb dating yielded a lower intercept 206Pb/238U date of 438.8 ± 7.3 Ma, which is coeval with the related granite (439 ~ 441 Ma). Skarns contain garnets with andraditic compositions (Ad53~93Gr4~46Py1~8) and clinopyroxene (Hd5~11Di89~94Jo0~1 and Hd52~85Di13~46Jo1~4) with low Mn/Fe ratios (<0.1), showing typical mineral compositions of Cu skarn deposits. The proximal garnet skarn mainly developed at the bottom and both sides of the orebody, while distal pyroxene skarn developed in its interior and upper parts. The garnets in the bottom of the orebodies contain more andraditic compositions than their upper parts. The prograde skarn minerals have a range of δ18Ofluid values from 8.81 to 9.53‰, and the sulfide minerals of the main ore stage have a range of δ34S values from −2.40 to 2.57‰, both suggesting a magmatic origin of the ores. In the Debao deposit, hydrothermal magnetite from different skarn zones contains substantial amounts of Al, Sn, Ga, Mn, Mg, Ti, Zn, Co, V, and Ni. The content of Al and Ti in the magnetite, which was considered to derive from the wall rock due to fluid-rock interaction, was positively correlated with temperature. Magnetite in the retrograde skarn stage from the proximal garnet skarn zone contains more Ti and V than that from the distal pyroxene skarn zone, indicating a gradual decrease in temperature and increase in oxygen fugacity of the ore-forming fluid in this stage. The magnetite has higher Sn content (mainly hundreds to thousands of ppm) than normal skarn deposits, implying that high oxygen fugacity occurs during the retrograde skarn stage. Subsequently, the formation of magnetite led to a decrease in the oxygen fugacity of the ore-forming fluid. The decrease of oxygen fugacity and temperature provided favorable conditions for subsequent precipitation of Cu sulfides. Minor vein-type Cu mineralization related to late magmatic fluid extraction of sulfur from the sedimentary strata was recognized. All geologic and geochemical data suggested that the deep skarn in the region transformed from Early Paleozoic carbonate has copper mineralization potential.

Application of superheated water as a soil remediation media: a review

Water is a unique solvent cause its highly hydrogen-bonded structure, and at room temperature it has a high boiling point for its mass, a high dielectric constant and high polarity. At the higher temperatures, its permittivity, viscosity and surface tension decreases, but diffusion rate increases. Superheated water is a general term to denote the region of the condensed phase between 100°C and the critical point. Liquid water at elevated temperatures above its boiling point has been used for many years as an industrial solvent and cleaning agent in applications ranging from enhancing the extraction of oil shale, the extraction of sulphur from ore bodies in the Frasch process, to degreasing. In recent years, there has been an interest in using superheated water for soil remediation. In this paper, a review on this area of application has been performed.

ПРИМЕНЕНИЕ НЕОРГАНИЧЕСКИХ РЕАГЕНТОВ-МОДИФИКАТОРОВ ДЛЯ ИЗВЛЕЧЕНИЯ СЕРОСОДЕРЖАЩИХ ПРИМЕСЕЙ ПРИ ФЛОТАЦИИ ГАЗОВЫХ УГЛЕЙ

The relevance of the research lies in the need to remove sulphur-containing compounds from coal raw materials at the lowest cost to reduce the environmental load in the areas of coal use. The object of the study is coals of the “G” brand of the Kuznetsk basin of the Kirov mine. The subject of the study is the petrographic and chemical composition of coals, the content of sulphur impurities. The aim of the study is to develop selective reagent flotation modes using inorganic reagents-modifiers. Research objectives: – to determine the petrographic and chemical composition of coals; – to conduct flotation studies using the foam flotation method; – to evaluate the effect of inorganic reagents-modifiers on the φ - potential and hydration of the coal surface; – to determine the mechanism of modifiers’ action on the depression of sulphur-containing impurities of coals. Methodology and methods of research. A complex of physical, chemical and physico-chemical research methods has been used in the work. The degree of scientific development of the topic. A promising direction for reducing sulphur-containing emissions is to increase the selectivity of the flotation process by modifying the coal surface. Results: petrographic analysis of the studied coals has showed that the main micro-component is vitrinite (85 %); chemical analysis indicates that the humidity of the coals is 2.27 %, the ash content is 17.82 %, the yield of volatile substances is 32.90 %, the mass fraction of inorganic sulphur is 0.38 %, organic sulphur is 0.43 %. A comparative analysis of qualitative and quantitative indicators of coal flotation shows that the use of non-organic reagents-modifiers can significantly increase the extraction of sulfur into flotation waste. The analysis of the kinetics of changes in the electrode potential of pyrite indicates an increase in the potential values in the presence of these reagents and a decrease in the hydration of the pyrite surface. The obtained results indicate the expediency of using inorganic salts as modifier reagents that contribute to reducing the sulfur content in coal concentrates due to the depression of pyrite-containing impurities due to an increase in the hydration of their surface

Chemical conversion synthesis of magnetic Fe1-xCox alloy nanosheets with controlled composition.

Chemical conversion provides a versatile platform for the synthesis of advanced nanomaterials with targeted phase, composition, and architecture. Here, we report a trioctylphosphine (TOP)-driven chemical conversion route to transform lamellar Fe1-xCoxS1.2-DETA (x = 0.1, 0.3, 0.5, 0.7, DETA = diethylenetriamine) inorganic-organic hybrid solid solutions into two-dimensional (2D) single-crystal Fe1-xCox alloy with controllable composition and dimensionality. Synergetic transformation coupled with DETA removal and sulfur extraction of lamellar Fe0.9Co0.1S1.2-DETA hybrids was examined in detail. The highest magnetization of 175 emu g-1 was recorded for the prepared Fe0.7Co0.3. Our results not only provide a new lamellar inorganic-organic hybrid solid solution but also extend the chemical conversion strategy to the synthesis of previously unavailable magnetic alloy nanosheets.

PROCESSING OF PYRITE CONCENTRATES WITH THE EXTRACTION OF NONFERROUS METALS: NICKEL AND COBALT TECHNOLOGY ELABORATION

The paper presents the results of the development of a technology for processing of pyrite concentrates with the extraction of nonferrous metals, iron and sulphur using the technology of two-stage dissociating roasting with hydrometallurgical processing of cinder. Hydrometallurgical processing of cinder was studied. It comprised of two steps - cinder leaching and extraction for processing multi-component solutions. Based on the results of laboratory tests, balance experiments were conducted on the chemical enrichment of nickel-poor and cobaltpyrite concentrates. The experiments included (i) Thermal decomposition of pyrite concentrate at a temperature of 660 - 700° C and a duration of 60 minutes, an oxygen flow rate of 30-50% of the stoichiometric; (ii) Leaching of the cinder with a HCl solution at a temperature of 90°C, liquid: solid = 8:1, pH 2,7 and a duration of 60 minutes; (iii) Filtration of pulp and precipitation of nickel and cobalt from solutions with iron sulphide. During leaching, mainly iron is transferred to the solution; nickel and cobalt remain in a small amount of cake (the cake weight is reduced by almost ten times compared to the thermal decomposition product). As a result, up to 99% of non-ferrous metals are extracted into the concentrate, and the solution becomes more concentrated in iron.

Extractive desulfurization using choline chloride-based DES/molybdate nanofluids; Experimental and theoretical investigation

Recently, greater attention is being paid for desulfurization by deep eutectic solvents as an efficient extractive desulfurization agent. Deep desulfurization is a critical process to reach fuel with an ultra-low percentage of less than 10 ppm sulfur. Deep eutectic solvents (DESs) are eutectic mixture formed of Lewis or Brønsted acids and bases and have a lower melting point than individual components. Interaction strength among molecules in the DES affects their characteristics and applications. In this work, four DESs were prepared and characterized. The extractive desulfurization affinities of the DESs were evaluated using n-octane solvent as a model fuel containing thiophene as a sulfur compound. The DES consisted of choline chloride and ethylene glycol (ChCl-EG) exhibited the highest desulfurization affinity ~37% using the low volumetric ratio of DES: model fuel (1: 2). Moreover, molybdate nanofluid (0.02 wt%) based on ChCl-EG was prepared and analyzed by XRD, TGA, DLS, and TEM. The sulfur extraction of simulated fuel consisting of thiophene was conducted by MoO3-based DES nanofluid, which exhibited a high extraction efficiency of 98.01% in a single step, so considered as a deep desulfurization process. The concentration of sulfur in the model oil reached less than 4 ppm in one cycle. Furthermore, Molecular dynamics (MD) simulation and computational chemistry were implemented to evaluate the thiophene removal and oil desulfurization by deep eutectic solvent, in addition to investigating the intermolecular interactions between the DES and thiophene. The obtained results provide insights into the desulfurization mechanism by the DES solvents.

Extractive desulfurization of fuels using diglycol based deep eutectic solvents

Abstract In this work, the effect of Deep Eutectic Solvents (DESs) on sulfur extraction of organo-sulfur compounds was investigated. Different DESs were prepared using a common hydrogen bond donor, Diglycol, and different hydrogen bond acceptors. The effects of experiment variables such as temperature, DESs/feed ratio, and the time on desulfurization efficiency of different organo-sulfur compounds were also studied. Results show that Tetra butyl ammonium bromide based DES showed relatively higher sulfur removal capabilities (Dibenzothiophene (DBT): −92 %, 2- Methylthiophene (2-MT): −86 % and Thiophene (T): −71 %)) as compared to other DESs. Also, all DESs have higher DBT extraction efficiency followed by 2-MT and T. Further, non-random two liquids (NRTL) thermodynamic model was employed to model liquid-liquid equilibrium.

Effective extraction of high purity sulfur from industrial residue with low sulfur content

In this work, toluene and carbon disulfide have been employed as solvents to obtain sulfur out of sulfur concentrate. Sulfur concentrate is produced as residue in the flotation of zinc industry, coming from the leaching process of zinc concentrate. Up to 86.7% of sulfur is recovered using toluene at 100 °C, and a 96.3% of high purity sulfur recovered at room temperature using carbon disulfide as solvent. The X-ray diffraction of the obtained sulfur is very similar to the commercial sulfur, and the diffraction data of the residue show no peak of sulfur. The results are compared to the evaporation-condensation method previously used with similar samples.

Energy, exergy and economic analyses of new coal-fired cogeneration hybrid plant with wind energy resource

A novel configuration of a coal-fired cogeneration plant is proposed in this paper. This novel system is composed of combustion chamber, Rankine cycle, absorption chiller, alkaline electrolyzer, and methanation plant. In the proposed configuration, the heat of exhaust gas from the combustion chamber can be used in a Rankine cycle to produce electricity. The heat of exhaust gas also powers the absorption chiller to provide cooling. The exhaust gas flows through a sulfur extraction unit to separate sulfur from CO2 gas. To supply electrical power, wind turbines alongside the Rankine cycle are considered. A part of the produced electricity from both the Rankine cycle and the wind turbines can be used by an alkaline electrolyzer to produce hydrogen and oxygen. The CO2 gas from sulfur unit and hydrogen gas (H2) provided by the electrolyzer can be delivered to a methanation unit to produce syngas (CH4) for different applications. The oxygen from the electrolyzer is injected into the combustion chamber to improve the combustion process. Results show that by using 80 units of 1 MW Nordic wind turbine to generate electricity, all of the CO2 in the exhaust gas is converted to syngas. The whole system energy and exergy efficiencies are equal to 16.6% and 16.2%. The highest and lowest energy efficiencies of 85% and 30.1% are related to compressor and steam power plants. The energy and exergy efficiencies of the wind turbine are 30.7% and 11.9%. The system can produce 40920.4 MWh of electricity and 180.5 MWh of cooling. As CO2 is consumed to produce syngas, the proposed system is capable of avoiding a significant amount of 2776 t CO2 emissions while producing 1009.4 t syngas annually. Based on economic analysis, the payback period of the system is 11.2 y, and internal rate of return is found to be 10%, which can prove the viability of the proposed configuration.

Flotation extraction of elemental sulfur from gold-bearing cakes

Currently, in the development of the raw materials base of the gold mining industry, there is a tendency to reduce the quality of the initial mineral raw materials due to the depletion of reserves of rich gold-bearing ores. The article discusses the technology of extraction of refractory gold-bearing concentrates based on low-temperature leaching of pyrite concentrate. A decrease in the parameters of the autoclave oxidation of sulfide minerals, such as pyrite and arsenopyrite, leads to the incomplete extraction of gold into the solution and, consequently, its losses during subsequent cyanidation. As a possible option for a more complete extraction of gold using low-temperature oxidation technology, a method of flotation separation of elemental sulfur from leaching cakes is proposed. According to the basic process flow chart, the flotation process designed for gold extraction is carried out after autoclave oxidation, but before cyanidation. A series of experiments were carried out with varying reagent conditions and the dependence of gold losses on the extraction of elemental sulfur in the flotation tailings was established. As determining factors, pH and solid content in the initial pulp were considered. The paper justifies the separation of elemental sulfur from autoclave cake to enriched sulfur concentrate. The cake flotation modes after autoclave oxidative leaching of pyrite concentrate are investigated. The distribution of elemental sulfur and gold by flotation products makes it possible to conduct the tailings cyanidation process with acceptable indicators.

Light-Induced Sulfur Transport inside Single-Walled Carbon Nanotubes.

Filling of single-walled carbon nanotubes (SWCNTs) and extraction of the encapsulated species from their cavities are perspective treatments for tuning the functional properties of SWCNT-based materials. Here, we have investigated sulfur-modified SWCNTs synthesized by the ampoule method. The morphology and chemical states of carbon and sulfur were analyzed by transmission electron microscopy, Raman scattering, thermogravimetric analysis, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopies. Successful encapsulation of sulfur inside SWCNTs cavities was demonstrated. The peculiarities of interactions of SWCNTs with encapsulated and external sulfur species were analyzed in details. In particular, the donor–acceptor interaction between encapsulated sulfur and host SWCNT is experimentally demonstrated. The sulfur-filled SWCNTs were continuously irradiated in situ with polychromatic photon beam of high intensity. Comparison of X-ray spectra of the samples before and after the treatment revealed sulfur transport from the interior to the surface of SWCNTs bundles, in particular extraction of sulfur from the SWCNT cavity. These results show that the moderate heating of filled nanotubes could be used to de-encapsulate the guest species tuning the local composition, and hence, the functional properties of SWCNT-based materials.

Extraction of Sulfur from Commercial Gasoline Using 1-Butyl-3-Methylimidazolium Tetrafluoroborate [BMIM] [BF&lt;sub&gt;4&lt;/sub&gt;] as the Extraction Solvent

This study aims to demonstrate the importance of using the 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM] [BF4] ionic liquid (IL) as a green solvent in the extractive desulfurization of commercial gasoline, as a complementary technology to conventional hydrodesulfurization (HDS), which has limitations in the removal of sulfur aromatic compounds. The extractive desulfurization of gasoline was evaluated by means of a factorial design to determine the best extraction conditions, considering temperature (25 and 35 °C), feed/solvent mass ratio (3/1 and 1/1) and number of extraction stages (1 and 3 stages). The results show a maximum sulfur removal efficiency of 40%. In addition, the selectivity of [BMIM] [BF4] in the removal of aromatic sulfur compounds from gasoline, its extraction mechanism and the effects of desulfurization using IL regenerated by means of washing cycles with water and/or diethyl ether was investigated.

Unraveling the Effects of Melt–Mantle Interactions on the Gold Fertility of Magmas

The oxidation state of the Earth’s mantle and its partial melting products exerts a fundamental control on the behavior and distribution of sulphur and chalcophile and siderophile elements between the mantle and crust, underpinning models of ore deposit formation. Whether the oxidized nature of magmas in inherited from the asthenospheric mantle source or acquired during ascent and differentiation is vigorously debated, limiting our understanding of the mechanisms of extraction of sulphur and metals from the mantle. Here, we focused on the redox-sensitive behavior of sulphur in apatite crystallized from quenched alkaline basaltic melts preserved within a peridotite xenolith from the El Deseado Massif auriferous province in southern Patagonia. We took advantage of this unique setting to elucidate the redox evolution of melts during their ascent through the subcontinental lithospheric mantle, and grasp the inner workings of the Earth’s mantle during gold metallogenesis. Our data reveal that an initially reduced silicate melt (ΔFMQ -2.2 to -1.2) was oxidized to ΔFMQ between 0 and 1.2 during percolation and interaction with the surrounding peridotite wall-rock (ΔFMQ 0 to +0.8). This process triggered changes in sulphur speciation and solubility in the silicate melt, boosting the potential of the melt to scavenge ore metals such as gold. We suggest that large redox gradients resulting from the interaction between ascending melts and the surrounding mantle can potentially modify the oxidation state of primitive melts and enhance their metallogenic fertility. Among other factors including an enriched metal source and favorable geodynamic conditions, redox gradients in the mantle may exert a first-order control on the global-scale localization of crustal provinces endowed with gold deposits.

Investigating of Nitric Acid Leaching of High-Sulfur Copper Concentrate

This article describes the problems of deterioration of the quality of processed raw materials due to depletion of mineral resources. It is proposed to use nitric acid for the processing of complex refractory low-grade concentrates containing non-ferrous and noble metals. It was found that the studied concentrate contains: sphalerite (26.9 %), pyrite (22.0 %), chalcopyrite (19.9 %), silica (13.9 %), alumina (5.5 %), galena (1.7 %), oxidized forms of iron (Fe2O3) (12 %). Gold and silver are associated with sulfide minerals. Typical reactions of interaction of these minerals with nitric acid are considered. A sufficiently high thermodynamic probability of these reactions in a wide temperature range is established. With the use of mathematical methods, the optimal conditions of the process of nitric acid leaching are selected: the ratio of L:S = 5:1; the concentration of nitric acid 10 mol/L; the duration of the process is 60 minutes. In this case, the extraction of copper, zinc, iron and sulfur into the solution was 99.00 %, 99.84 % 98.60 %, 88.51 %, respectively.

Optimization of Extractive Desulfurization of Diesel Oil in a Continuous Oldshue–Rushton Column Pilot Plant

In this study, a continuous sulfur extraction process in a pilot plant Oldshue-Rushton column has been studied and its operating cost has been optimized, where the feed of the column was earlier produced in an oxidative desulfurization reactor. Dimethylformamide was used as a polar solvent to remove the sulfur-containing compounds of the oxidized diesel in the extraction column. The effects of agitation speed (100-200 rpm) and inlet flow rate of the solvent to the column (33-165 mL/min) on the holdup, sulfur removal, diesel recovery, and solvent recovery were investigated utilizing the response surface methodology. The operating cost during the continuous-flow extraction process, consisting of the chemical cost, electricity cost, and the health cost related to the SO2 emission, was also applied as a criterion to optimize the process. The best performance of the extraction process was achieved at ambient temperature, where inlet flow rate of the oxidized diesel was 99 mL/min, agitation speed was 107 rpm, a...

DCA]-based ionic liquids for the extraction of sulfur and nitrogen compounds from fuels: Activity coefficients at infinite dilution

Some petroleum processes need the removal of low level aromatic-sulfur and nitrogen compounds for many products, which are extremely important according to the new strict environmental regulations to reduce sulfur and nitrogen content compounds in liquid fuels. Thus the new, alternative solvents such as ionic liquids (ILs) have been proposed. ILs reveal a high selectivity and capacity of extraction of sulfur- and nitrogen-compounds from alkanes with little solvent loss during the process. The measurements of activity coefficients γ13∞ at infinite dilution of different solutes in the IL shows the effect of interactions between organic solutes, or water on the interfacial and bulk properties of the IL. The new (3-cyanopropyl)pyridinium dicyanamide, [N–C3CNPy][DCA] and (3-cyanopropyl)methylpyrrolidinium dicyanamide, [N–C3CNMPyr][DCA] were investigated in this work. The data were obtained using the gas-liquid chromatography technique. Measurements were undertaken at six temperatures, in 10 K intervals, in the range of (318.15–368.15) K. The solutes studied included both non-polar and polar compounds, as alkanes, alkenes, alkynes, as well as aromatic hydrocarbons, alcohols, water, ethers, ketones, and esters. The most important solutes used were thiophene, pyridine, and 1-nitropropane. Densities, ρ, measurements for a range of temperatures, T (298.15–368.15) K for the chosen ILs were undertaken at pressure, p = 101 kPa. The gas-liquid partition coefficients, KL at infinite dilution were calculated. The fundamental thermodynamic functions such as partial molar excess Gibbs energy, enthalpy and entropy at infinite dilution were calculated from the experimental data measurements to discuss the interaction between solutes and the ILs. The values of selectivity and capacity for three separation cases, viz. heptane/thiophene, heptane/pyridine, and heptane/1-nitropropane were calculated from γ13∞ values and compared to literature data for dicyanamide-based ILs. The Abraham solvation parameter model was presented for all solutes. The obtained results indicated that [N–C3CNPy][DCA] has large selectivity and capacity values for all three of the separation cases studied.

A new type of isotopic anomaly in shergottite sulfides

AbstractThe isotopic composition and abundance of sulfur in extraterrestrial materials are of interest for constraining models of both planetary and solar system evolution. A previous study that included phase‐specific extraction of sulfur from 27 shergottites found the sulfur isotopic composition of the Martian mantle to be similar to that of terrestrial mid‐ocean ridge basalts, the Moon, and nonmagmatic iron meteorites. However, the presence of positive Δ33S anomalies in igneous sulfides from several shergottites, indicating incorporation of atmospherically processed sulfur into the subsurface, complicated this interpretation. The current study expands upon the previous work through analyses of 20 additional shergottites, enabling tighter constraints on the isotopic composition of juvenile Martian sulfur. The updated composition (δ34S = −0.24 ± 0.05‰, Δ33S = 0.0015 ± 0.0016‰, and Δ36S = 0.039 ± 0.054‰, 2 s.e.m.), representing the weighted mean for all shergottites within the combined population of 47 without significant Δ33S anomalies, strengthens our earlier result. The presence of sulfur isotopic anomalies in igneous sulfides of some meteorites suggests that their parent magmas may have assimilated crustal material. We observed small negative Δ33S anomalies in sulfides from two meteorites, NWA 7635 and NWA 11300. Although negative Δ33S anomalies have been observed in nakhlites and ALH 84001, previous anomalies in shergottites have all shown positive values of Δ33S. Because NWA 7635 has formation age of 2.4 Ga and is much more ancient than shergottites analyzed previously, this finding expands our perspective on the continuity of Martian atmospheric sulfur photochemistry over geologic time.

Sulfur extraction via carbonated melts from sulfide-bearing mantle lithologies – Implications for deep sulfur cycle and mantle redox

Transport of sulfur via mantle-derived partial melts from deep Earth to the surface reservoirs is a critical step in the deep global sulfur cycle. Given that sulfur is stored mostly in sulfide phases in mantle lithologies, the critical parameter is sulfur concentration at sulfide saturation (SCSS) of mantle-derived magmas. CO2 ± H2O-induced melting beneath oceanic and continental mantle produces incipient CO2-rich melts. Although, SCSS of silicate melts of a variety of compositions is extensively studied, the SCSS of carbonatitic and carbonated silicate melts have not received much attention. Here we present experiments in graphite capsules at pressures (P) of 2.5–6.0 GPa and temperatures (T) of 1350–1650 °C investigating the SCSS of carbonatitic and carbonated silicate melts. All experiments produced quenched Fe ± Ni-sulfide melt blobs + carbonated melt matrix ± ol ± cpx ± opx ± gt, with melt composition on a CO2-free basis varying from 7 to 40 wt.% SiO2, 0.5 to 7 wt.% Al2O3, and 9 to 17 wt.% FeO* (total FeO). SCSS measured using EPMA increases with SiO2 and T but is not affected by P; the effect of composition being more pronounced than P-T. The composition of sulfide melt phase also affects SCSS. With increasing Ni in the molten sulfide phase, the SCSS changes from 2000 to 4000 ppm (Ni-free) to is 800–3000 ppm (33 wt.% Ni). Comparison of our measured SCSS with the existing SCSS models for nominally CO2-free silicate melts and with one study for carbonated melts show that these parameterizations fail to capture the sulfide saturation values in CO2-rich melts from our study. Using our new SCSS data and previous SCSS data for melt compositions that span the range from carbonatite to basalts via carbonated silicate melts, we develop a new empirical SCSS parameterization. Unlike a previous model, which suggested SCSS of carbonated melt is only affected by melt FeO* (other than P-T) and did not constrain how SCSS evolves from low-silica carbonatitic melt to low-CO2 basaltic melt, our new parameterization captured complex effects of many melt compositional parameters, including silica on SCSS. Using our new SCSS model, we constrained the efficiency of S extraction from the mantle beneath mid-oceanic ridges and continents via low-degree carbonated melts. Deep carbonated melts beneath ridges are expected to mobilize 5–15% of the initial sulfur before nominally-volatile-free peridotite melting begins. In continental mantle, deep kimberlitic melt can act as an agent to mildly enrich the shallow mantle in sulfide as it evolves to a carbonatitic melt upon reactive cooling. Application of our data to subduction zones suggests that low degree carbonatitic melt is not an efficient agent to extract residual sulfide from the subducting oceanic crust.

EXTRAÇÃO E EXPORTAÇÃO DE MACRONUTRIENTES EM LAVOURAS DE MILHO DE ALTA PRODUTIVIDADE

O conhecimento da variabilidade da nutrição de plantas e da produtividade em áreas cultivadas com plantas de milho que apresentam alta produtividade pode fornecer importantes subsídios na racionalização do uso de insumos e auxiliar no manejo da fertilidade do solo. Essa pesquisa tem como objetivo determinar os padrões de extração e de exportação de nitrogênio (N), fósforo (P), potássio (K), cálcio (Ca), magnésio (Mg) e enxofre (S) por lavouras de milho de alta produtividade. Quinze talhões de milho cultivados sob sistema convencional e que apresentavam alto potencial produtivo foram amostrados no ano agrícola 2014/2015 na região do Alto Paranaíba (MG) e avaliaram-se a produtividade e a extração e exportação de N, P, K, Ca, Mg e S. Os acúmulos de N, P, K e S em grãos e extração total tiveram efeitos positivos na produtividade da cultura do milho. A massa de mil grãos foi o componente de produtividade mais importante na definição da produtividade. A extração e exportação de N, P, K e S aumentaram linearmente com o aumento da produtividade. Os resultados fornecem dados importantes sobre a absorção e partição de nutrientes dos híbridos atuais e permitem aprimorar as recomendações de adubação para produção de grãos de milho.