•The predominance of kaolinite in the sample contributes to its application in geopolymer synthesis.•The best synthesis parameters were determined through Box-Behnken design: 3.4–3.8Si/Al, ...1–1.1Na/Al, and temperature of 100 °C.•Mechanical strength of up to 47.78 MPa was obtained by geopolymers.•Immersion in water for 24 h does not affect the mechanical strength of the geopolymers.
The exploitation of bauxite deposits in the Amazon region is well known. Mining begins with the temporary or even permanent removal of an extensive surface layer of clayey material (Belterra clay) that can reach a thickness of up to 20 m. The mineralogical composition of this material has already been described in the literature and consists mainly of kaolinite. The extensive surface distribution of Belterra clay in the Amazon region and its composition is of interest in the evaluation of its viability for the synthesis of geopolymers. For the present study, a sample of Belterra clay (BTC-1) from the bauxite deposits of Rondon do Pará was selected, in addition to microsilica (MCR-1) (Ecopowder) and Sigma P.A. reagent (NaOH). The Belterra clay sample was characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), and thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. To determine the physical and mechanical properties of Belterra clay, geopolymers were synthesized using BTC-1, MCR-1, and NaOH with different Si/Al and Na/Al ratios according to the Box-Behnken design (BBD). Technological tests, including water absorption, apparent porosity, and compressive strength tests, were performed. Based on the BBD, the highest compressive strength was 47.78 MPa, and the lowest compressive strength was 7.05 MPa. BTC-1 showed potential for the synthesis of geopolymers with high mechanical strength and an acceptable percentage of water absorption.
•The waste clay from beneficiation of bauxite ore has high alumina contents.•The waste can be used to produce calcium sulphoaluminate eco-cements.•32% less CO2 is generated in their process ...production compared to traditional cements.•Produced mortars developed higher strength compared to a Portland cement.
The beneficiation process of bauxite (Al-ore) generates over 10 mi tons of waste clay disposed of in tailing ponds. The purpose of this work was to test this material to produce CSA–based cements. Raw mixtures with the clay were formulated to maximize ye’elimite contents in the clinkers. A CSA-belite clinker composed of 46% of ye’elimite, 40% of belite, and minor amounts of Fe-perovskite and brownmillerite was produced. Cement pastes using clinker to gypsum ratios of 90:10, 85:15, and 75:25 developed compressive strength higher than a Portland cement. The pastes have major contents of ettringite and kuzelite depending on the sulfate additions, besides straetlingite, aluminium hydroxide and hemicarboaluminate. The waste clay is as a potential raw material for CSA-belite low-CO2 cements.
Gastric cancer is one of the most frequent types of neoplasms worldwide, usually presenting as aggressive and difficult-to-manage tumors. The search for new structures with anticancer potential ...encompasses a vast research field in which natural products arise as promising alternatives. In this scenario, piperine, an alkaloid of the
species, has received attention due to its biological activity, including anticancer attributes. The present work proposes three heating-independent, reliable, low-cost, and selective methods for obtaining piperine from
L. (Black pepper). Electronic (SEM) and optical microscopies, X-ray diffraction, nuclear magnetic resonance spectroscopies (
C and
H NMR), and optical spectroscopies (UV-Vis, photoluminescence, and FTIR) confirm the obtention of piperine crystals. The MTT assay reveals that the piperine samples exhibit good cytotoxic activity against primary and metastasis models of gastric cancer cell lines from the Brazilian Amazon. The samples showed selective cytotoxicity on the evaluated models, revealing higher effectiveness in cells bearing a higher degree of aggressiveness. Moreover, the investigated piperine crystals demonstrated the ability to act as a good cytotoxicity enhancer when combined with traditional chemotherapeutics (5-FU and GEM), allowing the drugs to achieve the same cytotoxic effect in cells employing lower concentrations. These results establish piperine as a promising molecule for therapy investigations in aggressive gastric cancer, both in its isolated form or as a bioenhancer.
In the Carajás Mineral Province, gossan formation and lateritization have produced numerous supergene orebodies at the expense of IOCG deposits and host rocks. The Alvo 118 deposit comprises massive ...and disseminated hypogene copper sulfides associated with gossan and mineralized saprolites. The hypogene reserves are 170 Mt, with 1% Cu and 0.3 ppm Au, while the supergenes are 55 Mt, comprised of 30% gossan and 70% saprolite, with 0.92% Cu and 0.03 ppm Au. The gossan includes goethite, malachite, cuprite, and libethenite zones. The saprolite comprises kaolinite, vermiculite, smectite, and relics of chlorite. In the hypogene mineralization, Ag, Te, Pb, Se, Bi, Au, In, Y, Sn, and U are mainly hosted by chalcopyrite and petzite, altaite, galena, uraninite, stannite, and cassiterite. In the gossan, Ag, Te, Pb, Se, and Bi are hosted by Cu minerals, while Au, In, Y, Sn, and U are associated with iron oxyhydroxides, in addition to Zn, As, Be, Ga, Ga, Mo, Ni, and Sc. As supporting information, δ65Cu values indicate that the gossan is immature and, at least partly, not affected by leaching. In the saprolite, Ga, Sc, Sn, V, Mn, Co, and Cr are associated with the iron oxyhydroxides, partially derived from the host rock weathering. The δ56Fe values indicate that hypogene low contribution of the hypogene mineralization to the saprolite iron content. The association of Al2O3, Hf, Zr, Th, TiO2, Ce, La, Ba, and Sr represents the geochemical signature of the host rocks, with dominant contributions from chlorites, while In, Y, Te, Pb, Bi, and Se are the main pathfinders of Cu mineralization.
Abstract The objective of this work was to investigate changes in soil chemical characteristics, phosphorous concentrations in maize leaves, and the agronomic efficiency (AE) of magnesium ...thermophosphates produced from rocks of the Maicuru complex in the Brazilian Amazon Basin, in comparison with triple superphosphate (TSP). The thermophosphates consisted of a mixture of raw material from apatite, dunite, and quartz sandstone from Maicuru, aiming to adjust the contents of P, Mg, and Si. The mixture was melted, ground, and subjected to the analysis of solubility, chemical characteristics, and granulometry. The experiment consisted of two rates of dolomitic lime (0 and 2.4 Mg ha-1), three rates of P (20, 60, and 100 mg kg-1 soil), and four sources of P (TSP and three Mg thermophosphates), as well as of two control treatments, with and without lime. Three replicates were carried out per treatment in pots containing plants of the BR 5107 maize hybrid. Phosphorous concentration was determined in maize leaves at 45 days after sowing. The Mg thermophosphates showed a high AE and a higher neutralizing effect with the application of lime, which improved soil chemical characteristics and AE. The thermophosphates obtained from rocks of the Maicuru complex can be an alternative P fertilizer in maize production.
Resumo O objetivo deste trabalho foi investigar mudanças em atributos químicos do solo, concentrações de fósforo em folhas de milho e eficiência agronômica (EA) de termofosfatos magnesianos produzidos com rochas do complexo de Maicuru, na bacia da Amazônia brasileira, em comparação ao superfosfato triplo (SFT). Os termofosfatos consistiram de mistura de matéria-prima de apatita, dunita e arenito quartzoso de Maicuru, para ajuste dos conteúdos de P, Mg e Si. A mistura foi fundida, moída e submetida à análise de solubilidade, características químicas e granulometria. O experimento consistiu em dois níveis de calcário dolomítico (0 e 2,4 Mg ha-1), três níveis de P (20, 60 e 100 mg kg-1 de solo) e quatro fontes de P (TSP e três termofosfatos magnesianos), além de dois controles, com e sem calcário. Foram realizadas três repetições para cada tratamento, em vasos com plantas de milho do híbrido BR 5107. A concentração de P foi determinada nas folhas de milho aos 45 dias após a semeadura. Os termofosfatos magnesianos apresentaram alta EA e maior poder neutralizante com a aplicação de calcário, o que melhorou as características químicas do solo e a EA. Os termofosfatos obtidos de rochas do complexo Maicuru podem ser alternativa de fertilizante fosfatado na produção de milho.
A 200 cm-long high resolution macro-charcoal and pollen record from the Lagoa da Cachoeira in Serra Sul dos Carajás (Serra Sul) in southeast Amazonia reveals insights into local palaeofire over the ...last 26,200 years. Local fires in Serra Sul were most frequent in transition periods from dry to wet environmental conditions between 11,000 and 10,200 years ago, and under seasonal climatic conditions after 5,000 years ago. During pronounced dry periods fires were not a substantial component of the environment in Serra Sul. An anthropogenic influence on fire in Serra Sul may have played a role since the beginning of the Holocene, but is not a likely driver of palaeofire variability. Charcoal records for southern Amazonia coupled with proxy data for precipitation and changing Atlantic Sea Surface Temperature (SST) suggest that Holocene palaeofires in southern Amazonia are driven by changes in climate.
Eco-friendly binders are among the opportunities to reduce the approximately 8% global CO2 emissions generated by the cement industry, with calcium-sulphoaluminate (CSA) -based cements standing as a ...potential low-CO2 alternative to the world most used ordinary Portland cements (OPC). Belterra Clay (BTC), an abundant low-cost alumina-rich clay overburden on the huge bauxite reserves of the Brazilian Amazon was tested to produce CSA-based binders. Successive Designs of Experiments were used to prepare mixtures containing BTC, CaCO3, and gypsum, seeking the maximum BTC and minimal CaCO3 consumption under the lowest possible temperature to maximize CSA's main phase ye'elimite, Ca4Al6(SO4)O12, in the clinkers. X-ray powder diffraction accompanied by Rietveld phase quantifications, X-ray fluorescence, and scanning electron microscopy were used to characterize the obtained products and guide the experimental work. CSA-belite and CSA-ternesite clinkers were successfully sintered at 1250 °C using up to 42% of BTC. The hydration of selected clinkers was investigated by isoperibolic heat flow calorimetry after blending with gypsum at 95:5 and 90:10 mass ratios. The main hydrations of the clinkers were faster (within 24 h) when using 5% of gypsum. Ettringite was the main hydrated phase, followed by kuzelite, straetlingite, and hemicarboaluminate. Produced mortars reached up to 40 Mpa after 28 days of curing, a strength development comparable to that of an OPC (46 Mpa) tested under the same conditions. BTC, currently a drawback during bauxite mining and rehabilitation of mined areas, was successfully used to produce clinkers that generate ca. 30% less CO2 during calcination when compared to OPC, with further CO2 and energy savings expected because of the required lower sintering temperature.
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•Bauxite clay overburden to produce CSA eco-friendly binders•Design of experiments to reduce extensive laboratory work•XRPD mineralogical quantifications and SEM-EDS to investigate the products•CSA-belite and CSA-ternesite cements were successfully produced.•Similar strength to Portland cements but with ca. 30% less CO2 generated.
Transition zones between forest and savanna in northern South America are important areas for improving our understanding of ecosystem dynamics and climate change. The uniquely available mid-Holocene ...sediment deposits from the Serra do Tepequém plateau in Roraima State, northwestern Brazil, were used to analyze past forest-savanna dynamics through pollen, spores, microcharcoal and loss on ignition (LOI). In this newly studied landscape, two distinct periods of vegetation, fire and climate dynamics have been recorded. The first phase from ca. 7,570 to 6,190 cal bp, with the dominance of savanna vegetation in particular with Poaceae and Cyperaceae and some small forest patches with Moraceae/Urticaceae, Alchornea and Schefflera, indicates a relatively dry period. Based on the microcharcoal concentration and influx data, frequent regional fires occurred at that time. The second phase from ca. 6,190 to 4,900 cal BP shows a change in the vegetation composition with an increase of Ilex, Schefflera and Fabaceae. In this period forest expanded, while savanna became reduced, reflecting an increase of wetter conditions. The fire frequency was markedly lower. The first occurrence of Mauritia flexuosa palm was at ca. 7,300 cal BP and an early expansion occurred at around 6,600 cal BP. This early expansion of M. flexuosa showed a development that was in opposition to the increase of fire and savanna expansion found in other regions in northern South America. The increase of wetter conditions in Serra do Tepequém in the mid-Holocene confirms other results found in savannas of Colombia and Venezuela between 7,000 and 6,600 cal BP.
Abstract Cenozoic world-class bauxite deposits developed on sedimentary sequences of the Parnaíba and Amazon Basins. The Décio pilot mine, excavated in the Rondon do Pará bauxite deposit, exposes a 3 ...m thick bauxite-bearing lateritic profile on the top of a 350 m high plateau. From the base to the top, this profile is composed of clayey bauxite; porous microcrystalline bauxite; spherulitic ferro-aluminous duricrust, fragmentary on the top; as well as loose ferro-aluminous spherulites and nodules, embedded in clay. The lower horizons represent a classic lateritic succession, while the top of the profile was produced through post-lateritic reworking. During this process, Ga, Cr, Mo, As, Pb, Hg, Sb, Zn, V and Sc were captured by the iron oxi-hydroxides; and REE, Hf, Nb, Ta, Y remained carried by relict zircon. Isocon diagram and mass balance demonstrate the affinity of the bauxite with claystone from Itapecuru Formation.
Several occurrences and deposits of aluminum-phosphate-sulfate (APS) minerals have been discovered during the last century, and most are closely related to lateritic weathering formations. These ...deposits have been found all over the world but are more common in the present intertropical climate zone. Only one such deposit is mined for phosphate. However, a second, the Bonito deposit, has recently started to be mined in the Amazon region. The deposit is located in one of the most important provinces for APS minerals in the world, the Gurupi region, which lies in the northeastern Amazon region and still remains relatively unexplored. The Bonito APS deposit comprises a complete mature laterite profile, and the APS minerals are exposed at the top of the profile in the form of an aluminum phosphatic-sulphatic crust and an aluminum phosphatic-sulphatic iron-oxyhydroxide crust. The phosphate-sulphatic ore is composed of crandallite-goyazite, woodhouseite-svanbergite, and wardite-millisite, as well as some quartz, kaolinite, hematite and goethite. The ore is high in phosphor (>18% P2O5) and is rich in SrO, BaO and LREEs. The mineralogy and geochemistry of the whole profile show a complete lateritic evolution, with increasing enrichment in Fe, Al, Ti, P, S, Ca, Na, Ba, Sr, REEs, Th, U, Zr, Hf, Y, Sc, V, Ga, As, Se, etc., upwards in the profile. The mineralogy, geochemistry, and chemical element contents indicate a lateritic phosphate-sulphate sequence derived probably from Ca-phosphate-bearing sedimentary rocks from the Paleozoic Parnaíba Basin.
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