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.

Abstract This work presents a modeling procedure for a tall photocatalytic fluidized bed photoreactor used for the photocatalytic oxidation of n-hexane on the anatase TiO2 surface. The modeling strategy split the reactor into two parts: a lower dense phase, with high solids concentration behaving as a bubbling bed treated as a continuous stirred tank reactor (CSTR); and an upper lean phase of low solids concentration behaving as a plug-flow reactor (PFR). The Langmuir-type kinetic parameters were obtained for the flow rate of 1.67 × 10-4 m3 s-1 and catalyst mass of 0.1 kg. The model revealed a good adjustment with experimental data when predicting conversion results for the same experimental conditions, but deviations grew as flow rates and catalyst loads departed from those values in which the model was obtained.

The production of metallic powder by precipitation from solution was studied in laboratory scale as an alternative to the conventionally adopted processes, based on the atomization of molten material, for producing metal powders with small particle size. The process is based on the precipitation of metals from aqueous solutions by reduction under controlled conditions. Results of laboratory scale experiments are presented for the production of copper particles from aqueous solutions of copper sulfate, using formaldehyde as reducing reactant, and EDTA as complexing agent. The effect of the presence of nuclei was studied. Metallic particles with average sizes in the range from about 0.3 µm to about 15 µm were obtained. In the process, large particles are formed mainly by aggregation of submicrometric particles, indicating that the particle size distribution of the product depends on the control of particle agglomeration rate.

Neste trabalho, estuda-se a degradação fotoquímica de defensivos agrícolas presentes em efluentes aquosos, por meio de processos oxidativos avançados (POAs). Tais processos são baseados na ação do radical hidroxila (HO•), oxidante poderoso e não seletivo. Em particular, o processo foto-Fenton é avaliado quanto à redução da demanda química de oxigênio (DQO) e do teor de carbono orgânico dissolvido (COD), e ao aumento de biodegradabilidade dos efluentes. Os resultados abrem perspectivas para emprego de irradiação solar e aplicação em escala comercial a baixo custo.

The photochemical degradation of agrochemicals in aqueous solution by means of advanced oxidation processes (AOPs) was studied. The photo-Fenton process was evaluated in terms of the time evolution of dissolved organic carbon (COD) and chemical oxygen demand (DOC), their total removals, and increase in biodegradability of treated wastewater. Under the experimental conditions studied, the process showed to be superior to other AOPs, at any Fe(II) and H2O2 concentrations. The results pointed towards the use of solar irradiation and low cost commercial application.

Os Linear Alquilbenzenos (LABs) são usados como fluido refrigerante de cabos elétricos. Quando ocorre um vazamento, os LABs ficam basicamente adsorvidos no solo, pois, são compostos bastante hidrofóbicos e com baixa pressão de vapor. Os métodos convencionais de tratamento de solos não são eficientes. A reação de Fenton (solução de ferro II e peróxido de hidrogênio) gera radicais hidroxila, não seletivos, e capazes de oxidar uma grande variedade de compostos orgânicos, chegando a mineralização dos mesmos. Neste trabalho foi estudada a viabilidade de utilização dos reagentes de Fenton para promover a remediação de solos contaminados com LABs. Utilizou-se uma coluna especialmente projetada para estes experimentos, empacotada com um solo arenoso e outro argiloso. O pH do solo não foi alterado. Os resultados obtidos demonstram a viabilidade técnica do processo de injeção dos reagentes de Fenton para o tratamento de áreas contaminadas com LABs.

Linear Alkyl Benzenes (LABs) are used as insulating oil for electric cables. When it happens a spill, LABs they are basically sorbed in the soil, because, these compounds have high hidrophobicity and low vapor pressure. The conventional methods of treatment of soils are not efficient. The Fenton's reaction (reaction between a solution of iron II and hydrogen peroxide) it generates hydroxyl radicals, not selective, and capable of oxidize a great variety of organic compounds. A study was conducted to evaluate the viability of use of the Fenton's reagents to promote the remediation of polluted soils with Linear Alkyl Benzenes. A column was especially projected for these experiments, packed with a sandy and other soil loamy. The pH of the soil was not altered. The obtained results demonstrated the technical viability of the process of injection of the Fenton's reagents for the treatment of polluted areas with LABs.