Struvite-based composites for slow-release fertilization: a case study in sand

Struvite (St) recovered from wastewaters is a sustainable option for phosphorus (P) recovery and fertilization, whose solubility is low in water and high in environments characterized by a low pH, such as acidic soils. To broaden the use of struvite in the field, its application as granules is recommended, and thus the way of application should be optimized to control the solubility. In this study struvite slow-release fertilizers were designed by dispersing St particles (25, 50, and 75 wt%) in a biodegradable and hydrophilic matrix of thermoplastic starch (TPS). It was shown that, in citric acid solution (pH = 2), TPS promoted a steadier P-release from St compared to the pure St pattern. In a pH neutral sand, P-diffusion from St-TPS fertilizers was slower than from the positive control of triple superphosphate (TSP). Nevertheless, St-TPS featured comparable maize growth (i.e. plant height, leaf area, and biomass) and similar available P as TSP in sand after 42 days of cultivation. These results indicated that St-TPS slow P release could provide enough P for maize in sand, achieving a desirable agronomic efficiency while also reducing P runoff losses in highly permeable soils.info:eu-repo/semantics/publishedVersio

Walking on Vertices and Edges by Continuous-Time Quantum Walk

The quantum walk dynamics obey the laws of quantum mechanics with an extra locality constraint, which demands that the evolution operator is local in the sense that the walker must visit the neighboring locations before endeavoring to distant places. Usually, the Hamiltonian is obtained from either the adjacency or the laplacian matrix of the graph and the walker hops from vertices to neighboring vertices. In this work, we define a version of the continuous-time quantum walk that allows the walker to hop from vertices to edges and vice versa. As an application, we analyze the spatial search algorithm on the complete bipartite graph by modifying the new version of the Hamiltonian with an extra term that depends on the location of the marked vertex or marked edge, similar to what is done in the standard continuous-time quantum walk model. We show that the optimal running time to find either a vertex or an edge is $O(\sqrt{N_e})$ with success probability $1+o(1)$, where $N_e$ is the number of edges of the complete bipartite graph.Comment: 13 page

Sulfur fertilizer based on inverse vulcanization process with soybean oil

Sulfur deficiency in soils has become an increasing concern over the past decades. Despite elemental sulfur (S8) vast utilization as a commercial fertilizer, S8 has to be biologically oxidized for plant assimilation, drastically limiting its efficiency. Therefore, we propose a new fertilizer in which S8 structure is more accessible to oxidizing microorganisms by chemical modification via inverse vulcanization technique, a solvent-free copolymerization method, with soybean oil as comonomer. Sulfur oxidation experiments were performed by A. niger submerged cultivation, confirming that the homogeneous rubbery-like material provides enhanced oxidation, with great potential as multifunctional sulfur-fertilizer

NIOBIUM OXIDES: AN OVERVIEW OF THE SYNTHESIS OF Nb 2

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

ZnO:ZnWO4 heterostructure with enhanced photocatalytic activity for pollutant degradation in liquid and gas phases

Here we report, for the first time, a versatile ZnO:ZnWO4 heterostructure active for photocatalytic degradation of pollutants in liquid and gaseous media, prepared using a simple hydrothermal method driven by the differences in chemical solubility of the components. This heterostructured material was effective in the oxidation of methylene blue dye, caffeine, and amiloride in aqueous solution, and ethylene gas. High photocatalytic performance was attributed to the spontaneous formation of heterojunctions between ZnO and ZnWO4 during the synthesis step, increasing electron/hole pair lifetimes. Recycling experiments revealed that the heterostructure was stable over time, indicating the commercial potential of this material

Evidence For Independent Glycerol Electrooxidation Behavior On Different Ordered Domains Of Polycrystalline Platinum

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)We investigate the electrooxidation of glycerol (GlOH) on polycrystalline Pt. The results obtained in the presence of GlOH were compared with those of fresh and disturbed low-index Pt single crystals [(111), (100) and (110)]. Monitoring of the oxidation currents of GlOH by cyclic voltammetry on the different surfaces revealed that the electrooxidation of GlOH is highly sensitive to the order of the polycrystalline Pt atoms. Interestingly, after being disturbed by the application of voltammetric cycles, the combined responses of the disordered single crystals become similar to that of polycrystalline Pt. The changes in the current values associated with the specific potentials at which each oxidation peak takes place suggest that different ordered domains of Pt oxidize GlOH independently. This simple approach can clearly assist in our understanding of the effect of the order of surface atoms in a given reaction, not only in electrochemical reactions.22263268Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FUNDECT [23/200.583/2012]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPq [405695/2013-6, 313402/2013-2, 305494/2012-0, 474590/2013-5]FAPESP [2014/01362-6, 2013/13749-0

Controlled Release of Phosphate from Layered Double Hydroxide Structures: Dynamics in Soil and Application as Smart Fertilizer

A route is proposed to produce a hydrotalcite-like layered double hydroxide structure ([Mg-Al]-LDH) for phosphate fertilization. The mechanism of controlled phosphate release from the structure was investigated. The preparation strategy resulted in a phosphorus content of around 40 mg·g^–1 LDH, which was higher than previously reported for related fertilizers. The release of phosphate into water from [Mg-Al-PO₄]-LDH continued over a 10-fold longer period, compared to release from KH₂PO₄. Analysis using ³¹P NMR elucidated the nature of the interactions of phosphate with the LDH matrix. In soil experiments, the main interaction of P was with Fe³⁺, while the Al³⁺ content of LDH had no effect on immobilization of the nutrient. Assays of wheat (<i>Triticum aestivum</i>) growth showed that [Mg-Al-PO₄]-LDH was able to provide the same level of phosphate nutrition as other typical sources during short periods, while maintaining higher availability of phosphate over longer periods. These characteristics confirmed the potential of this preparation route for producing controlled release fertilizers, and also revealed fundamental aspects concerning the interactions of phosphate within these structures

High-density nanoparticle ceramic bodies: A study of heating rates in the sinterization of Gadolinium-doped Ceria

An investigation on the sinterization of Gd:CeO2 (Ce 0.85Gd0.15O1.9-δ ceramic system) 3-10 nm nanoparticles in pressed bodies was done. The heating rate was taken as a key parameter and two competing sinterization processes were identified, associated with different diffusional mechanisms. Using heating rates of 113 C min -1, a high-final density (98 % of the theoretical) was obtained by superposing the two aforementioned mechanisms, resulting in a homogeneous microstructure at lower temperatures. © 2012 Akadémiai Kiadó, Budapest, Hungary