Chemical composition and minerals in pyrite ash of an abandoned sulphuric acid production plant

The extraction of sulphur produces a hematite-rich waste, known as roasted pyrite ash, which contains significant amounts of environmentally sensitive elements in variable concentrations and modes of occurrence. Whilst the mineralogy of roasted pyrite ash associated with iron or copper mining has been studied, as this is the main source of sulphur worldwide, the mineralogy, and more importantly, the characterization of submicron, ultrafine and nanoparticles, in coal-derived roasted pyrite ash remain to be resolved. In this work we provide essential data on the chemical composition and nanomineralogical assemblage of roasted pyrite ash. XRD, HR-TEM and FE-SEM were used to identify a large variety of minerals of anthropogenic origin. These phases result from highly complex chemical reactions occurring during the processing of coal pyrite of southern Brazil for sulphur extraction and further manufacture of sulphuric acid. Iron-rich submicron, ultrafine and nanoparticles within the ash may contain high proportions of toxic elements such as As, Se, U, among others. A number of elements, such as As, Cr, Cu, Co, La, Mn, Ni, Pb, Sb, Se, Sr, Ti, Zn, and Zr, were found to be present in individual nanoparticles and submicron, ultrafine and nanominerals (e.g. oxides, sulphates, clays) in concentrations of up to 5%. The study of nanominerals in roasted pyrite ash from coal rejects is important to develop an understanding on the nature of this by-product, and to assess the interaction between emitted nanominerals, ultra-fine particles, and atmospheric gases, rain or body fluids, and thus to evaluate the environmental and health impacts of pyrite ash materials

Época de paralisação das irrigações na produção de sementes de Cenoura

Three experiments were carried out under soil and climate conditions of Central Brazil to determine the adequate time to stop irrigations for carrot seed production. The treatments consisted of stopping irrigations at 60, 70, 80, 90, 100, 110, 120, 130 and 140 days after planting. Carrot seed production was found to be a quadratic function of time to stop irrigation. Large productivities were found when irrigation was stopped at 121 days after planting. Irrigation costs were optimized at this time. The weight of 1.000 seed and the crop cicle increased with the time to stop irrigations. Seed germination was not affected by the treatments.Foram conduzidos três experimentos, nas condições de solo e clima da região de cerrado do Brasil Central, objetivando determinar a melhor época de paralisação das irrigações na produção de sementes de cenoura, cv. Brasília, pelo sistema raiz-semente. As irrigações foram paralisadas aos 60, 70, 80, 90, 100, 110, 120, 130 e 140 dias após o plantio. A produtividade de sementes apresentou relação quadrática com a época de suspensão das irrgações, sendo observado um valor máximo quando as irrigações foram interrompidas aos 121 dias, época esta que também possibilitou uma otimização dos custos de irrigação. O ciclo da cultura e o peso de 1000 sementes aumentaram linearmente, quanto mais tarde foram paralisadas as irrigações. A germinação de sementes não foi afetada pelos tratamento

Carrot seed production under different soil moisture regimes

Objetivando estabelecer tensões de água no solo que mais favoreçam a produção de sementes de cenoura (Daucus carora L.), foram conduzidos experimentos no CNPH, em Brasília, DF, nos anos de 1984, 1985 e 1986. Os tratamentos consistiram em irrigar quando as tensões, na profundidade de 10 cm até o florescimento e de 20 cm após este estádio, atingiam 25, 50, 100, 200,400, 800 e 1.500 kPa. A análise de regressão indicou que a produtividade máxima de sementes foi obtida com a tensão de 75 kPa, enquanto a tensão ótima econômica foi estimada cm 80 kPa. O estande, a taxa de germinação e o peso de 1.000 sementes não foram influenciados pelas diferentes tensões.Field experiments were carried out at CNPH-EMBRAPA in 1984, 1985, and 1986 with the objective of establishing soil moisture management for carrot (Daucus carota L.) seed production, based on soil water tension. Treatments consisted of refilling the root zone with water as soil water tension reached values of 25, 50, 100, 200, 400, 800 and 1.500 kPa, at 10 cm depth till flowering and at 20 cm depth after that phase. Regression analysis allowed to conclude that maximum seed productivity was obtained when irrigation was applied each time soil water tension reached 75 kPa. Economical water tension was found to be 80 kPa. Stand, germination and weight of 1.000 seeds were found not to be significantly influenced by the treatment

Solution and Asymptotic Behavior for a Nonlocal Coupled System of Reaction-Diffusion

This paper concerns with existence, uniqueness and asymptotic behavior of the solutions for a nonlocal coupled system of reaction-diffusion. We prove the existence and uniqueness of weak solutions by the Faedo-Galerkin method and exponential decay of solutions by the classic energy method. We improve the results obtained by Chipot-Lovato and Menezes for coupled systems. A numerical scheme is presented

Tandem Thio-Michael Addition/Remote Lactone Activation of 5-Hydroxymethylfurfural-Derived δ-Lactone-Fused Cyclopentenones

Funding Information: We thank the Fundação para a Ciência e a Tecnologia (SFRH/BD/120829/2016, SFRH/BD/148211/2019, UIDB/04138/2020, UIDP/04138/2020, PTDC/QUI‐QOR/32008/2017 and GHTM‐UID/04413/2020). The project leading to this application has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 951996. J. A. S. C. thanks the Fundação para a Ciência e a Tecnologia (FCT) for Scientific Employment Stimulus 2020/02383/CEECIND. Publisher Copyright: © 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.The creation of structurally diverse chemical entities from fairly simple biorefinery products remains a challenge. In this work 5-hydroxymethylfurfural (HMF) was identified as a key synthon for preparing highly complex cyclopentenones (CP) via tandem 1,4-addition/elimination/remote lactone activation to external O- and N-nucleophiles in δ-lactone-fused-CPs hotspots. This scaffold was also reactive enough to be incorporated into model cysteine-peptides in low concentrations, paving the way to a potential translation generating complexity in the synthesis of small peptides. The new enones also exhibited activity against intraerythrocytic Plasmodium falciparum (IC50=1.32 μm).publishersversionpublishe

Irrigação por gotejamento com nitrogênio e potássio em tomateiro

Two levels of nitrogen and potassium were combined with drip irrigation system under edaphoclimatic conditions of "cerrado" soil in central Brazil to test their effect on the yield of 'Kada' tomato (Lycopersicum esculentum Mill). The water head was of 0.8, 1.0 and 1.2 levels of the class A evaporation tank settled on bare soil. Results showed no significant difference among treatments for the total fruit production per hectare. On the other hand, production of large fruits was different among treatments. It was observed that higher level of ammonium sulfate increased number and weight of fruits showing "blossom end rot", independently of the water head used. The combination of 0.8 water level with 1.400 kg/ha of ammonium sulfate and 918 kg/ha of potassium cloride proved to be the most effective in water utilization.Estudou-se o comportamento de tomateiro (Lycopersicum esculentum Mill) cultivar Kada, irrigado por gotejamento e adubado com dois níveis de nitrogênio e potássio, sob condições edafoclimáticas de cerrado do Brasil central. Aplicaram-se lâminas de irrigação correspondentes a 0,8, 1,0 e 1,2 da evaporação de um tanque classe A instalado sobre solo nu. Verificou-se não haver diferenças significativas entre tratamentos na produção total de frutos por hectare; entretanto, a produção de frutos graúdos diferiu entre os tratamentos estudados. Doses elevadas de sulfato de amônio aumentaram o número e o peso dos frutos com podridão estilar independentemente da lâmina de irrigação aplicada. A menor lâmina de irrigação combinada com as doses de 1.400 kg/ha de sulfato de amônio e 918 kg/ha de cloreto de potássio apresentaram melhor eficiência do uso de água