Marisa Bezerra de Mello Monte

Yield, Quality Components, and Nitrogen Levels of Silage Corn Fertilized with Urea and Zeolite

The zeolite and urea mixture may be use to improve nitrogen (N)–use efficiency of silage corn. The objective of this study was to evaluate dry-matter yield and nutritional levels of N of silage corn fertilized with urea and zeolite mixture. The experimental design was a 2 × 4 × 4 factorial randomized block design with three replications. Treatments included two types of stilbite zeolite (natural and concentrated), four levels of nitrogen (0, 50, 100, and 200 kg ha−1), and four ratios of zeolite (25%, 50%, and 100% of N level). Treatments were applied 60 days after planting with the topdressing fertilization. The use of concentrated (650 g kg−1 of stilbite) or natural (470 g kg−1 of stilbite) zeolite with urea increased silage corn dry-matter production and leaf N concentrations.

Ammonia Volatilization from Soil, Dry-Matter Yield, and Nitrogen Levels of Italian Ryegrass

Nitrogen (N) loss by ammonia (NH3) volatilization is the main factor for poor efficiency of urea fertilizer applied to the soil surface. Losses can be suppressed by addition of zeolite minerals to urea fertilizer. The objective of this study was to evaluate ammonia volatilization from soil and dry-matter yield and nitrogen levels of Italian ryegrass. A greenhouse experiment was carried out with the treatments of urea, urea incorporated into soil, urea + urease inhibitor, urea + zeolite, ammonium nitrate, and unfertilized treatment. Ammonia was captured by a foam absorber with a polytetrafluoroethylene tape. There were few differences between zeolite and urease inhibitor amendments concerning NH3 volatilization from urea. Results indicate that zeolite minerals have the potential to improve the N-use efficiency and contributed to increasing N uptake. Zeolite and urea mixture reduced 50% the losses by volatilization observed with urea.

Nitrogen, Potassium, and Nitrate Concentrations of Lettuce Grown in a Substrate with KNO3-Enriched Zeolite

Zeolite minerals improve the efficiency of nutrient use by plants by helping to regulate the release of nitrogen and nitrate accumulation in tissues. The main objectives of this research were to evaluate effects of the addition of zeolite enriched with potassium nitrate (KNO3) on the nitrate (NO3-N) and potassium (K) levels of lettuce shoot. Treatments arranged in a completely randomized block design with three replications comprised two types of the natural zeolite: concentrated zeolite, zeolite + KNO3, and a control grown in substrate fertilized with a nutrient solution without zeolite supply. Four levels of enriched zeolite were tested (20, 40, 80, and 160 g per pot). Nitrogen, K, and NO3-N data were evaluated and response equations were fitted. The results indicated that zeolite enriched with KNO3 released the macronutrients N and K to lettuce plants. The concentrations of total N, total K, and NO3-N increased with zeolite levels, and there was a positive correlation between total N and NO3-N forms. To keep levels of NO3-N− in shoots within the safe limit for human consumption, based upon the regression equation for NO3-N the recommended dose of KNO3-enriched zeolite should be up to 78 g per plant.

Concentração por flotação da apatita proveniente de rochas de filiação carbonatítica

The current processing study seeks to improve operations for the direct and reverse flotation of apatite originating from carbonatically-affiliated rocks to obtain an apatite concentrate in accordance with the phosphoric acid industry specifications. The direct flotation of apatite was carried out in two flotation phases, rougher and cleaner. The aim of direct flotation was to generate a product to feed the reverse flotation circuit of apatite. Reverse flotation was performed in three stages (rougher, cleaner and recleaner) and at pH 5.0, using phosphoric acid (H3PO4) as an apatite depressor. Summing up, the results of reverse flotation tests pointed out apatite recovery, which shows that the specific reagents used favored system selectivity. It was possible to obtain an apatite concentrate with 38.11% of P2O5, 50.98% of CaO, 1.07% of Fe2O3, 0.67% of MgO and ratio CaO/ P2O5 of 1.34.

Eletroquímica da pirita e da arsenopirita na presença de amil xantato de potássio

Gold is frequently found in nature associated with sulfides, as pyrite and arsenopyrite. Usually, these sulfides are concentrated by flotation and submitted to posterior hydrometallurgical treatment. The flotability of the sulfide minerals depends on the hydrophilic/hydrophobic balance, which is induced respectively by the oxidation products formed on the minerals surface and by the collector adsorption that can not be completely interrupted by the presence of oxidation products. In the present work, rest potentials measurements for pyrite and arsenopyrite indicated that after the addition of hydrogen peroxide solution 10 % v/v in a 1 mL/min rate, these minerals were oxidized to Fe(OH)3 and FeOOH, respectively. Cyclic voltammetries indicated that ferric xanthate and dixanthogen are the species responsible for the hydrophobicity of pyrite and arsenopyrite respectively. Furthermore, the minerals oxidation leads to the formation of those species at more elevated potentials. Rest potentials measurements indicated that the formation of Fe(OH)3 on the pyrite surface due its oxidation is inhibited when this mineral is connected to arsenopyrite. The rest potential of arsenopyrite in the presence of nitrogen bubbling is more elevated when connected to pyrite, indicating its anodic behavior.

True flotation versus entrainment in reverse cationic flotation for the concentration of iron ore at industrial scale

ABSTRACT The loss of iron-bearing minerals to the tailings, especially in the finest fractions (−44 μm), is a problem that must be endured due to the depletion of deposits containing high-Fe hematite. 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 analyzed in order to attribute reasons for the iron-bearing minerals losses. Liberation studies excluded losses due to the presence of composite particles where hematite 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.

Estudo de interação seletiva de hematita em relação ao quartzo.

Com o objetivo de estudar a interação da hematita com um novo reagente de flotação (Bacillus subtilis), foram realizadas medidas experimentais de ângulo de contato da hematita antes (27,4o) e após condicionamento com o reagente (46,0o). Os experimentos de potencial zeta mostraram interação acentuada entre o reagente e o mineral na faixa de pH alcalina e deslocamento do ponto isoelétrico da hematita. Ensaios de microflotação foram conduzidos em tubo de Hallimond modificado sob concentração conhecida do reagente em pH 6. A hematita apresentou recuperação de, aproximadamente, 80%. As teorias DLVO e X-DLVO foram aplicadas para avaliar as energias de interação entre o reagente e os minerais. As duas teorias foram capazes de prever a interação entre o reagente e a hematita. Os resultados evidenciaram o uso promissor do reagente na flotação direta de hematita.

Adsorption and Catalysis of Nucleotide Hydrolysis by Pyrite in Media Simulating Primeval Aqueous Environments

Metal sulfides have been proposed as physical support for primitive bidimensional metabolism and chiral discriminators. There are controversial data about the possibly coupling between the exergonic pyrite syntheses and the endergonic amino acids syntheses in pyrite pulled metabolic-like processes. However, a role in adsorption and catalysis involving biomonomers — such as nucleotides — cannot be ruled out in an especial aqueous scenario. In an aqueous environment with a vast reservoir of reducing power in the form of, especially, iron (II) and sulfide within and beneath the crust. Our hypothesis is that ancient minerals such as pyrite could have played a role in concentrating mononucleotides and in determining their catalytic routes in later periods, when polynucleotides appeared and evolved (Tessis et al., 1999). Pyrite — as well as other sulfides — could have participated in nucleotide adsorption and in primitive phosphoryl transfer reactions in the less drastic conditions that prevail away from the hot hydrothermal vents, the big sources of starting molecules. In this presentation, we shall briefly comment about our results on the following themes: 1) Adsorption of mononucleotides (AMP and ADP) onto untreated and acetate-treated samples of pyrite in which soluble Fe3+ ions were removed; 2) The influence — on nucleotide adsorption — of the previous adsorption onto the crystal of an oxo acid that could have appeared near the mineral and modified its surface properties (acetate can be formed onto the surface of mixed iron nickel sulfides at high temperature and pressure [Huber and Wachtershauser, 1997]); 3) The role of the interface. In some models, the two-dimensional system represented by a mineral surface would be in a seawater environment having a passive role. The actual conditions prevailing when sulfur materials are in contact with salt solutions are quite complex. The very reactive iron-sulfide immersed in a solution resembling a primitive ocean generates a continuously changing interface with ionic gradients and formation of different oxide layers; 4) Hydrolysis of ATP adsorbed onto pyrite.

Phosphate Immobilization by Primitive Condensers

It is well known that co-precipitation of soluble Fe-oxide precursors with reactive phosphate is the dominant mechanism responsible for the low concentrationsof this organic molecule in contemporary aqueous media. The formation of Fe-oxide precursors requires free oxygen molecules. This feature is well established and it is a common observation that reactive phosphate is more abundant in anoxic, i.e., non-oxidizing aqueous media (Van Cappellen and Ingall, 1996).