Brazilian Journal of Chemical Engineering最新文献

Acid mine drainage (AMD) is one of the most significant environmental liabilities of the mining industry. Biological AMD treatment is proposed as an alternative remediation method, but it is typically employed at neutral pH, which influences its costs. This study evaluated the influence of carbon sources (lactate, acetate, and ethanol) on the start-up of three upflow anaerobic sludge blanket (UASB) reactors, inoculated with non-adapted biomass. A synthetic AMD with an acidic pH of 3.0 and the addition of metals (iron, zinc, and copper) was used. The ethanol-fed reactor was the only one capable of treating AMD and stabilizing sulfate removal, achieving efficiencies higher than 90% over 55 operational days, with metals removal efficiencies of 96% for copper, 98.4% for zinc, and 86% for iron. The lactate-fed reactor, after a long acclimation period of 55 days, produced sulfide and was capable of removing copper and zinc. However, 45 days after the acclimation period, the metabolic sulfidogenic pathway ceased, and lactate fermentation began. The acetate-fed reactor was not capable of utilizing this carbon source for sulfate reduction. This reactor suffered from the acetic acid decoupling effect, which caused the collapse of biomass cells by disrupting biomass granules and also allowed fungal growth. It was evident that the choice of carbon source is also influenced by the pH of the acid drainage to be treated, as pH values lower than the pKa value can lead to the failure of the treatment process.

The highly selective reaction concerning catalytic glycerol dehydration to acetol was studied using Zn, Al and Cu oxide catalysts. The diffractograms and Raman spectroscopy revealed the presence of Al₂O₃, ZnO, CuO, ZnAl₂O₄ and CuAl₂O₄ phases with crystallite nanometer size (8–22 nm). ^AlNMR profiles showed the octahedral, pentacoordinate and tetrahedral coordination of the Al species The redox properties obtained by TPR indicated that at 250 °C, due to SMSI effects, the copper phase is reduced and ZnO is more resistant to reduction while alumina is metastable. The N₂ adsorption/desorption isotherms exhibited the formation of materials in the micro-mesopore range with specific surface area between 90 and 224 m² g⁻¹. The SEM micrographs showed a sponge-like morphology with cavity sizes between 60 and 70 nm. The best catalytic performance occurred with average yield and selectivity to acetol of 26% and 97%, respectively. The catalyst was quite selective to acetol during reuse tests and was almost completely reactivated after regeneration. The ex-situ analyzes investigated the changes that occurred in the Cuⁿ⁺ sites during the reaction, which confirmed the sintering of the copper species by increasing the crystallite size from 25.3 to 36.3 nm. The simple computational theoretical study identified the most exposed sites in planes (hkl), supporting the proposed mechanism. Considering that they are little explored, a brief discussion on the mechanisms involved in the catalyst deactivation by coke was also proposed. Thus, the presence of Cu⁰ and Cu⁺ sites combined with Zn–Al species and their synergy enhances the high selectivity and yield to acetol, while unreduced Cu²⁺ has inferior catalytic performance.

The deformation scale prior to breakage and time behavior, including the maximum deformation time and the time of the total breakage cascade of two different oil drops in the turbulent field of a stirred tank, was analyzed by high-speed imaging coupled to image processing software. The effects of Reynolds number and the physical properties of drop on the deformation scale and breakage time were quantified and discussed. Different shape descriptors were used to characterize the deformation scale at the impeller vicinity, such as drop projection circularity, projection area increase, and projection perimeter extension, using image processing software. Through flow visualization, new findings concerning the effect of physical properties and Re on the critical deformation scales and breakage time were obtained. The results revealed that drop A, with a lower viscosity, experiences a lower critical deformation scale and a lower breakage time, resulting in a higher number of daughter drop at breakage. Higher viscosity drop (B) exhibited a higher critical deformation scale and higher breakage time, taking longer for breakage. About 90% of the drop deformation scale occurred at the blade’s tip. The breakage time was found to be considerably influenced by physical properties of the drop. A higher impact of impeller Re on the deformation and time behavior of drop A was observed due to the lower surface stability against turbulent stresses. A highly branched morphology of deformed drop A was observed, while drop B exhibited larger elongation.

The extensive use of salt in the food industry, especially in sea fishing, generates saline waste, such as sludge from salted fish effluent stations. Improper waste disposal contributes to significant environmental problems, such as inhibiting the natural microbiota and affecting the biogeochemical cycle. The study suggests using composting, with the addition of halotolerant bacteria, to address the issues related to the treatment of sludge from saltwater aquaculture to make the process more efficient and viable. The study's objectives included the application of halotolerant bacteria in the treatment of saline waste via controlled composting, its feasibility for treating this waste, and the compost quality after the composting process. The results indicated a reduction in electrical conductivity, maintenance of pH within legal standards, an insignificant decrease in carbon content, and adequate humidity in the treatments with the inoculums. Despite the drop in nitrogen levels due to denitrification caused by bacteria, mineral matter increased due to microbial action. The saline fish sludge obtained better results with the addition of inoculants, indicating improvements such as the introduction of nitrogen-rich waste, modifications to the volume/structuring material, and a more extended composting period. It is important to note that the results met the standards of Brazilian legislation despite the observations made.

Carbonates are expected to be reactive during the injection of fluids as a secondary recovery method in an oilfield reservoir. Desulphated seawater is usually chosen to reduce scaling potential for barium and strontium sulfates at the producer wells. However, desulfation presents some operational difficulties, often limiting the platform injection’s capacity. The chemical interactions between seawater and carbonate reservoirs affect produced water composition and must be considered for scaling predictions. Reactive transport models had shown that dolomitization increases anhydrite precipitation, reducing sulphate concentration in the produced water. This paper studied the reaction between calcite and three different fluids: seawater, seawater without sulphate and seawater without magnesium. All tests were performed in the presence of CO₂ and using a semi-batch reactor. The focus was to analyze the effects of possible dolomitization on sulfate concentration in reservoir conditions. As the scale potential is strongly related to the sulphate concentration, the previous knowledge of this behaviour plays a key role at the water quality decision. Experimental results confirmed simulation predictions.

Metal–organic frameworks (MOFs) are porous materials composed of metal ions, clusters and organic ligands. Due to their outstanding chemical, thermal, and solvent stability, as well as numerous unsaturated metal sites, they have proven to be useful catalysts. In this study, MOFs were synthesized using hydrothermal methods with terephthalic acid and Ca, Mg, Al, and Cr nitrates. Subsequently, they were functionalized with diethylamine. The formation of MOF-Al and MOF-Cr structures was confirmed through characterization via XRD, FT-IR, and CHN analyses. However, the synthesis did not yield MOF structures with Ca and Mg as metal ions; instead, phthalates of Ca and Mg were obtained. SEM images revealed the particle size and morphology of the particles, which ranged between 0.2 and 1 μm. TGA/DTA curves revealed that the functionalized MOFs were the most thermally stable. Textural analysis by N₂ adsorption/desorption showed that MOF-Cr and MOF-Cr-NH₂ had high BET area values of 1,769.67 and 998.22 m²g⁻¹, respectively. MOFs were employed as catalysts in Knoevenagel condensation reactions to synthesize (E)-ethyl 2-cyano-3-phenylacrylate and (E)-methyl 2-cyano-3-phenylacrylate, indicating their potential for reactions requiring acidic or basic sites.