The wide application of beneficial microorganisms in agriculture as inoculants to combat pests and diseases and/or to improve soil fertility and the nutrients availability for plants has been considered as an effective and more sustainable alternative than chemical fertilizers and agricultural defensives. However, it is necessary to examine all processing steps of these bio-based products under a more integrated view including the type of microorganisms and the whole production process in order to reduce dependence on synthetic chemical inputs. Here, recent developments on the production and formulation technologies of microbial inoculants and the main types of inoculants currently applied in agriculture are addressed. The different types of microbial formulations are compared with emphasis on the encapsulation technology. Moreover, the application of biofertilizers in seed coating and a new approach to apply biocomposites as fertilizers are discussed, presenting the main challenges and future perspectives to promote more sustainable agriculture practices.

Tin oxide (SnO2) nanoparticles were synthesized by the co-precipitation method and mechanically modified by high-energy ball milling. The experimental results demonstrate that the collision with zirconia balls produces slight changes in the crystalline, electronic, morphological, and surface properties of SnO2, which lead to an increase in the redox potential of the energy level and the formation of the hydroxyl group on the SnO2 surface. Moreover, these changes are intensified over the milling up to 90 min, directly affecting the photocatalytic performance, which was monitored by the rate of rhodamine B (RhB) degradation driven by ultraviolet (UV) irradiation. As a result, all ground samples showed better photocatalytic activity than pristine SnO2 (Sn-cop). The maximum degradation of rhodamine B was ca. 75%, achieved with 90 min-milled SnO2 nanoparticles (Sn-M90), compared to the Sn-cop sample induced a 1.67 times higher degradation rate. The reaction mechanism suggests that its better photocatalytic activity may be associated with the higher increased redox potential of the valence and conduction bands and the formation of hydroxyl active sites on the catalyst surface principal oxidizing agent generated. Therefore, we conclude that the ball milling process is an efficient way to induce stable activation of oxide metal for photocatalytic applications.

The development of visible-light active photocatalysts is vital to harvest the solar irradiation and build efficient photoelectrochemical devices. Bismuth oxyhalide (BiOCl, BiOBr and BiOI) materials stand out due to their remarkable properties, e.g., the band gap energy can be tuned from 1.9 to 3.4 eV depends on the halide employed. However, the hydrothermal synthesis of this material class was not properly investigated and compared. Then, we evaluated the effect of the hydrothermal treatment in the BiOX’s structural, electronic, morphological and textural properties and the relationship with their photocatalytic performance. Methylene blue (MB) dye was used as probe for photocatalytic performance evaluation under ultraviolet (UV) and visible (Vis) radiation. BiOCl and BiOBr samples showed a good photoactivity under both UV and visible radiation, on other hand the BiOI samples was not active, likely due to the fast charge recombination. BiOCl and BiOBr samples exhibit a favorably interaction with MB dye, because their surfaces are negatively charged. BiOCl samples were able to promote around 40 and 80% of the MB dye degradation under visible and UV radiation, respectively. The samples were also employed as photoanode for O2 evolution, BiOI sample exhibited the best performance, due to the synergistic effect of photocatalysis and electrocatalysis.

CO2 REDUCTION TO HYDROCARBONS AND OXYGENATES: FUNDAMENTALS, STRATEGIES AND CHALLENGES. The development of renewable energy sources (e.g., solar and wind) moves foward, the tendance for replacing fossil fuels increases. However, these technologies have as primary barriers to industrial processes’ efficiency and especially storage. Thus, CO2 reduction routes using these energy sources could chemically store part of the energy as fuels or chemicals, offering alternatives to current oil and gas industry. This process is inspired by photosynthesis, e.g., photochemical or electrochemical processes, using homogeneous or heterogeneous catalysts. Nevertheless, this reaction is thermodynamically unfavorable and has very slow kinetics, given the high stability of the CO2 molecule and the complexity of the redox reactions involved. Therefore, this review addresses this process’s kinetic and thermodynamic challenges, and the fundamental concepts of the photo(electro)chemical processes for CO2 reduction, besides presenting and discussing the materials with the potential to act as catalysts. The main reaction mechanisms and advances in the understanding of such processes are discussed, as well as future perspectives

Resumo: O objetivo deste trabalho foi avaliar a solubilização de fósforo de rocha fosfática por Aspergillus niger, em cultivo em estado sólido (CES) em bagaço de cana-de-açúcar (Saccharum officinarum), por meio da maximização da eficiência de produção de ácido cítrico. A rocha fosfática (IPR) escolhida para o estudo é um tipo de rocha ígnea com solubilização de fósforo muito baixa, obtida da empresa Itafós, em Arraias, no estado do Tocantins. Utilizou-se o delineamento composto central rotacional (DCCR) como ferramenta estatística para avaliar o efeito das concentrações da fonte de carbono (sacarose) e da IPR no meio para CES como estratégia para melhorar a solubilização de P. Para o processo sem a IPR, houve produção de ácido cítrico de até 300 g por quilograma de substrato. Os experimentos em DCCR mostraram que a adição da IPR afetou a produção de ácido cítrico, com valores de P solubilizado de 1,44 a 2,72 g por quilograma de substrato e rendimento de P solubilizado de 12,96 a 48,94%. Além disso, a análise da razão P solubilizado/sacarose mostrou condições favoráveis para solubilização de P e produção de ácido cítrico. Os valores de P solubilizado são promissores, ao se considerar que a IPR apresenta baixa solubilização, com apenas 8,6% de P2O5. No geral, esses resultados podem contribuir para o desenvolvimento de processos biotecnológicos, para a produção de fertilizantes fosfatados ambientalmente favoráveis, como alternativa para uma agricultura mais sustentável.

Abstract: The objective of this work was to evaluate the solubilization of phosphorus from a phosphate rock by Aspergillus niger, under solid-state cultivation (SSC) in sugarcane (Saccharum officinarum) bagasse, by maximizing the efficiency of citric acid production. The phosphate rock (IPR) chosen for the study is a type of igneous rock with a very low phosphorus solubility, obtained from the Itafós company, in Arraias, in the state of Tocantins, Brazil. The rotatable central composite design (RCCD) was used as a statistical tool to evaluate the effect of the concentrations of the carbon source (sucrose) and of the IPR on the SSC medium as a strategy to improve P solubilization. In the process without the IPR, there was a citric acid production of up to 300 g per kilogram of substrate. The experiments in the RCCD showed that the addition of the IPR affected citric acid production, with values of solubilized P ranging from 1.44 to 2.72 g per kilogram of substrate and of solubilized P yield from 12.96 to 48.94%. The analysis of the solubilized P/sucrose ratio showed favorable conditions for P solubilization and citric acid production. The obtained solubilized P values are promising considering that the IPR has a very low solubilization, with only 8.6% P2O5. Overall, these findings could contribute to the development of biotechnological processes for producing eco-friendly phosphate fertilizers, as an alternative for a more sustainable agriculture.

ABSTRACT: Urea is a common non-protein supplement used in ruminant feed; however, excessive consumption may lead to poisoning by NH3. Although the slow release of urea into the rumen has shown to be an essential aspect for ruminant feed, to date only a few studies have addressed this matter. In this study we examined the influence of five different NH3-N slow release systems based on clay-urea nanocomposites on the fiber digestibility of low-quality forage (sugarcane straw) in vitro. Physical properties of nanocomposites were evaluated and their effects on digestibility were tested in vitro using pristine urea as a positive control (level of 1 % of DM of sugarcane straw sample) and sugarcane (with no additives) as a negative control. Ammonia release and digestibility were evaluated at 12, 24, 36, 48, 72 and 96-h. Generally, all nanocomposites increased (p < 0.05) digestibility of fiber over control under all the conditions stipulated, but the samples with hydrogel content were more expressive. We concluded that an ideal release rate and optimum environment for microbial synthesis are necessary to maximize the digestion of sugarcane.

ABSTRACT: Polymer coatings are used to control the rate of release of plant available nutrients from fertilizers as well as to reduce nutrient losses such as ammonia (NH3) volatilization. Although the literature presents several examples of materials used to coat urea, little is known about nitrogen (N) release properties such as the mechanism involved and phenomena (e.g., pore opening) in the polymer coating. Thus, this study investigated urea release from polyurethane (PU) derived from two renewable raw materials (castor oil and soybean oil), to explain how the oil structure and coating microstructure influence release and urea-N dynamics in soil. The results demonstrated that the profile of urea release and the urea-N mineralization in the soil could be controlled by altering the thickness of the coating on the urea granules. Coating by eco-friendly polymer was efficient in controlling urea release in soil to reduce volatilization of ammonia and increase the availability of N in the soil.

Heterostructured semiconductors are materials with unique features formed by combination of two or more semiconductors with suitable interface between them. The study of the heterostructures aim the development of physico-chemical and photocatalytic properties higher than their isolated phases, which makes it possible to obtain higher efficiency and lower cost in several technological processes. Recently the heterostructured materials have been extensively used in the development of alternative technologies either for environmental pollution control or for renewable energy production, among other applications. However, the obtaining of a heterostructure with suitable features is not trivial. In this way, this review article presents a broad discussion about methods of obtaining heterostructures formed by semiconductors and their applications in the photochemical processes, mainly in the environmental field. It will be addressed the use of the heterostructures in photocatalytic application for the organic pollutants degradation, heavy metals removal, the inactivation of pathogenic microorganisms, beyond of the volatile organic compounds (VOC’s) photooxidation and the photocatalytic abatement of nitrogen oxide (NOx) in gaseous phase. Finally, a discussion about the carbon dioxide (CO2) photoreduction and hydrogen (H2) production focusing mainly in the chemical energy production will be presented.

Eutrophication is an undesirable environmental process that occurs in water bodies affected by high concentrations of phosphate. Different economic sectors are responsible for discharge effluents with extremely high phosphate content. Therefore, is important to develop technologies capable of remove phosphate from these effluents, before that reach other and larger water bodies. This work proposes the use of layered double hydroxide (LDH) as an adsorbent matrix for phosphate removal from aqueous solution. Different isomorphic structure of LDH ([Mg-Al]-LDH and [Zn-Al]-LDH) were employed to incorporate loadings of phosphate by ion exchange. The obtained materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and thermal analysis (TG/DTG). The crystalline structure of [Mg-Al]-LDH was preserved after phosphate adsorption, however the performance was low in comparison to [Zn-Al]-LDH, for which a high phosphate removal efficiency of 116.07 mg P. g-1 of LDH was achieved. The [Zn-Al]-LDH material showed good potential for use as matrix for the adsorption of phosphate in effluents.

Conventional single superphosphate (SSP) is known as one of the most important and common sources of phosphorus in agriculture. Despite SSP has been widely produced as a fertilizer, a few studies have been done to describe the fundamental aspects of this P-fertilizer, i.e., phase composition, thermal degradation behavior, and solubility kinetics. Therefore, this paper reports on the detailed characterization of SSP powders by correlating their properties with particle size and surface area. Commercial SSP fertilizers were milled under different conditions and the resulting powders were characterized by X-ray diffraction, thermogravimetric analyses, scanning electron microscopy, FT-IR spectroscopy, and solubilization tests. It was observed that short milling times favored the solubilization kinetics, whereas long milling times were deleterious due to agglomeration effects. It was pointed out that agglomeration plays an important role in phosphate availability. These results provided a deeper understanding of SSP powders in microstructural terms, and may be used as a foundation for the development of novel strategies of alternative production of phosphorus fertilizers.

Despite the fact that Brazil is the world’s largest niobium mineral producer, governmental interest in exploration of the mineral leading to more valuable derived materials is scarce, which has reduced the country’s knowledge about a wider range of technological applications for this metal. Niobium pentoxide stands out due its remarkable electronic, structural, and textural properties. Therefore, this review aims to highlight its main properties, synthetic methods, and applications, with a particular focus on photocatalysts based on Nb2O5. This review will highlight the potential of Nb2O5 and encourage the study of niobium and its compounds in technological and environmental applications.

Herbicides have great importance in agricultural productivity for weed control, given their competition with crops. However, inadequate application of herbicides may lead to environmental problems, which can be minimized through controlled release of the active compounds. This may be achieved by protecting the herbicide in a structure with adequate porosity, where the diffusional behavior can determine release. Thus, in this study we evaluated a novel structure, a composite based on activated carbon bonded by polyvinyl alcohol (PVA) as pellets, to deliver a triazine herbicide. The product obtained was shown to be adequate for its purpose, since it was possible to process regular pellets, where the PVA percentage determined the properties.

Plants absorb phosphorus from the soil, which has low levels of this element due to the poor solubility of these compounds in soil and high adsorption capacity of the element by soil particles. Therefore, the purpose of this study was to assess, using hydroxyapatite nanoparticles synthesized in the laboratory, the amount of phosphorus available under different conditions. The results showed that the phosphorus compound had highest solubility in hydroxyapatite sintered at 300°C in an oven for 2h and diluted to 0.05M with MilliQ water, corroborating the theory that the stronger the agglomeration of the nanoparticles, the fewer the pores and the poorer their solubility.

Foram produzidas amostras de amido termoplástico (TPS) reforçadas com materiais de alta área superficial, com o intuito de verificar a variação nas propriedades do polímero, com especial enfoque na sua permeabilidade a vapor d'água. Foram utilizadas como carga a sílica coloidal (área superficial de 122,7 m²/g) e uma zeólita do tipo ZSM-5, produzida em laboratório (área superficial de 261,3 m²/g), em teores de 2 a 10% em massa. Os resultados demonstraram que a adição de ambos os materiais melhorou as propriedades mecânicas do TPS, embora nos maiores teores houve redução da qualidade das interfaces e dessas propriedades, principalmente para a ZSM-5. Em todos os casos a introdução da carga inorgânica reduziu a permeabilidade ao vapor d'água em até 20% quando comparada à permeabilidade do TPS, porém a melhor dispersão da sílica coloidal na matriz permitiu as maiores reduções, apesar da área superficial inferior.

Compositions of thermoplastic starch (TPS) reinforced by high surface area materials were produced, intending to study the variation in polymer properties, focusing on the permeability to water vapor. Colloidal silica (surface area 122.7 m²/g) and a ZSM-5 zeolite (surface area 261.3 m²/g) were used, in loadings from 2 to 10% weight. The results demonstrated that the addition of both materials was favorable to the TPS mechanical properties, however in higher loadings the quality of polymer interfaces and these properties were negatively affected, especially for ZSM-5. In all the cases the inorganic particles reduced the permeability to water vapor in levels below 20% when compared to pure TPS, although the best dispersion of colloidal silica determined better reductions, despite its lower surface area.

The development of analytical procedures to evaluate transesterification process is still a challenge in biodiesel production. Then, this paper shows an electroanalytical methodology to transesterification process assessment, proposing the application of nanostructured TiO2 electrodes. The results showed, for sunflower oil - methanol reaction catalyzed by KOH, a reduction peak in - 1050 mV and the gradual appearance of a second peak at - 1160 mV. This peak was observed as originated by the transesterification process and is probably related to intermediates. By measuring the intensity of this peak a kinetic profile was determined, showing that the conversion is almost finished in 2 h.