Brazilian Journal of Chemical Engineering最新文献

The core-shell structured nanomaterial of MgCo₂O₄@MnO₂ on nickel foam (MCMNA/NF) was synthesized via a two-step hydrothermal method. It can be used as a self-supported electrode, which was constructed to an electrochemical sensor for sensitive measurement of glucose. The core-shell structure with a MnO₂ shell significantly enhances the material’s specific surface area and accelerates the electron transport process. Electrochemical catalytic oxidation tests were conducted on core-shell structured MCMNA/NF nanocomposite as a working electrode. The sensitivity is determined to be 9.37 μA·mM⁻¹·cm⁻² and the detection limit is 0.02 mM. These test results demonstrate that the material exhibits excellent stability and selectivity as a glucose sensor. The synergistic effect of MgCo₂O₄ and MnO₂ can effectively promote the application performance of the electrode materials. The MgCo₂O₄@MnO₂ glucose sensor material also exhibits exceptional resistance to interference, demonstrating no interference from Urea, Citric acid (CA), Ascorbic acid (AA), or specific inorganic salts during blood glucose detection.

Graphical abstract

Azo dyes have emerged as a critical category of dyes in most sectors where color is essential. These dye classes are preferred in businesses because of their favorable properties, albeit at the expense of the environment and ecosystem. Various treatment methodologies are being investigated to degrade these azo dyes via different wastewater treatment approaches. Chemical approaches, especially those involving advanced oxidation processes, are preferred for rapid degradation, whereas biological approaches are widely preferred for various reasons, including their cost-effectiveness and sustainability. While, bio-chemical approaches can overcome the hurdles of both chemical and biological approaches. This review primarily centers on various chemical, biological, and biochemical methodologies and the critical elements involved in those processes. It employs bibliometric and scientometric studies to elaborate on azo dye degradation via the approaches above. Additionally, VOSviewer was used to demonstrate bibliometric mapping.

Priming is a technique widely used by seed technologists to improve seed vigor and stress tolerance. The underlying principle of all priming techniques is seed imbibition, which triggers pre-germinative metabolism. The present study aims to analyze the hydration process of Cariniana estrellensis seeds using the diffusion model with variable effective diffusivity in combination with micro-CT images to identify the different imbibition stages and the temperature effect on the hydration process. Hydration curves were obtained at temperatures of 25, 35, and 45 °C. Adjustments showed Chi-squared ≤ 2.82 × 10⁻⁴ for all temperature ranges. The analysis of the effective diffusivity variations allowed us to identify the three stages of the hydration process. Although temperature has a effect on hydration kinetics, it does not affect the moisture content at which each stage occurs. The micro-CT images allowed us to identify the moisture range at which germination processes begin, which corroborates the data observed from the effective diffusivity variations. Therefore, the combination of the variable diffusivity diffusion model and the analysis of micro-CT images represents a promising tool for the development of priming techniques, as it allows for the systematic evaluation of the different hydration stages.

Current multivariate statistical process monitoring is mostly based on data-based models with the principal aim of detecting faults promptly. To increase fault detection performance, various methods, such as novel learners, sliding window-based methods, subspaces based on query point estimation residuals, and feature/component selection methods have been proposed. On the other hand, hierarchical and combined modeling have only been recently considered; furthermore, the online sampled observations, once assessed by the monitoring scheme, are not usually used again for fault detection. In the current study, we show how to obtain valuable information on faults via re-examining the recently sampled points in a conveniently built hierarchical monitoring scheme. The top level consists of a combination of a novel query point estimation method based on multilinear principal component analysis (PCA) and PCA model of the estimation residuals. Upon a warning signal from the upper level, the bottom level is implemented, that consists of retrospective PCA monitoring of the recently sampled observations, scaled with respect to estimation residuals. Implementation of the proposed scheme on a demonstrative process and Tennessee Eastman Plant data exhibits decrease both in fault detection delay and missed detection rate compared to both traditional and the recently proposed methods.

Diclofenac (DCF), ranitidine (RNT), and simvastatin (SVT) are emerging pollutants that occur in low concentrations (ng L^–1 to µg L^–1) in different environmental matrices. They are not completely removed in sewage treatment plants. Therefore, this work assesses the photo-Fenton process after an anaerobic–aerobic one to degrade DCF, RNT, and SVT (50 µg L^–1, each) in domestic sewage. A photoreactor (1654 mL) with 7 blacklight blue lamps (8 W) was used. Batch degradation in biologically-treated domestic sewage (pH 7.2 ± 0.3, 25 °C) was optimized by 2³ full factorial design (two lamps on, 3 mg L⁻¹ Fe(III), and 40 mg L⁻¹ H₂O₂), degrading 100% of RNT and DCF, 97.5% of SVT, and 72% mineralization in 10 min. Parallel processes (adsorption, photolysis, direct oxidation with H₂O_2, and UV/H₂O₂) were not observed. In continuous mode (72 mL min^–1, hydraulic retention time 10 min), 97%, 90%, and 68% of RNT, DFC, and SVT, respectively, were degraded, and 55% DOC removed. The combined system was relatively stable for, at least, 10 days. Capital and operating costs were estimated: US$ 11,565.00 and US$ 1.97 m^–3, respectively, being electric energy consumption responsible for up to 98% of the total operating cost.

Graphical Abstract

Carbon dioxide (CO₂) hydrogenation to higher added-value products has been reported as a promising alternative to adapt the current industry to produce high-valuable chemicals via lower CO₂ emission processes. The CO₂ hydrogenation to formic acid via the tertiary amine & diol route was investigated in the present study. This process requires two reactors, and the tertiary amines’ size strongly influences both reactors’ performances. The present study investigated the thermodynamic influence of tertiary amines in each reactor and presented the most suitable amines’ size on each reactor’s performance. Suitable predictive thermodynamic models were assessed, and the most accurate ones were applied to estimate all species missing properties and systems equilibrium. This set of models is suggested to be used on further developments of similar processes. Eight tertiary amines, ranging from trimethylamine (C₁) to tri-octylamine (C₈), were studied. The thermochemical evaluation indicated that the amines’ size influences the two reactions inversely: small-sized tertiary amines were more efficient in the first reaction, whereas higher chain ones increased the second reaction’s conversion. Tertiary amines with radicals sized from ethyl (C₂) to hexyl (C₆) presented the most equilibrated performances in both reactions. Thermodynamic analysis revealed that high pressures and low temperatures favor the first reaction, and low pressures and high temperatures favor the second. Notably, triethylamine (C₂) demonstrated high conversions in both reactors, exceeding 90% conversion in both reactions.

The processing of carbon sources as precursors for the production of eco-friendly sustainable carbon dots (CDs) has attracted attention in the literature due to the outstanding antibacterial, antioxidant, and fluorescent properties, which are associated with intrinsic high stability, biocompatibility, hydrophilicity, and low toxicity. This review summarizes the recent advances in green carbon dots using biomass waste and antibiotics as precursors. The general mechanisms associated with the antibacterial activity of CDs are discussed based on the generation/scavenging of reactive oxygen species (ROS) that results in damage of vital components/processes of the bacteria in a process that can be tuned by functionalization of the carbon core/CD’s surface, allowing that photodynamic/chemodynamic processes can be activated by different excitation sources applied in the optimization of reactive oxygen species generation. Furthermore, a compilation of toxicity reports for different carbon dots is presented, highlighting the relevance of ecotoxicity, cytotoxicity, genotoxicity, and mutagenicity tests as a central topic to ensure safety for the large-scale use of green carbon dots-based products.

Several products of great importance in the food and pharmaceutical industries are produced by biotechnological processes, using high conversion and high specificity chemical reactions carried out by microorganisms. Such processes can be conducted in airlift reactors (ALRs), which are capable of operating multiphase systems. The ALRs are pneumatically agitated, have a high surface area of contact between the phases and have satisfactory homogenization, favoring the transfer of mass and energy. However, thus yet, the comprehensive investigation of the relationships among flow patterns, dead zones, gas holdup, phase velocity profiles, and the loop recirculation has not been extensively investigated. The purpose is to analyze the dynamics of multiphase flow at a local level, which is scarcely explored in the literature. This will provide a complete understanding of the recirculation pattern found in the ARL reactor. In this work, Computational Fluid Dynamics (CFD) technique was used to study the effects of different air inlet velocities (0.27 m/s, 0.36 m/s, 0.45 m/s and 0.54 m/s) and the average Sauter diameter of the bubbles injected by the sparger (12 mm, 15 mm, 18 mm and 21 mm) on the type of flow (stagnant, recirculation and preferential path zones), gas holdup, alpha parameter (α) and phase velocity profiles. The model was validated through experimental data. The simulation results indicated that the higher the air velocity injected by the sparger, the greater the amount of gas in the riser relative to the downcomer, which results in a lower alpha parameter (useful information for reactor sizing). It was also observed that the velocity profile of the liquid phase is closely related to that of the gas phase. The operating conditions that provided the most satisfactory results (better mixing time, more effective homogenization, and better establishment of the recirculation circuit) were obtained for an inlet air velocity of 0.54 m/s and an average Sauter bubble diameter of 21 mm.

This work aimed to evaluate the lipases from Yarrowia lipolytica as a biocatalyst for synthesizing fatty acid ethyl esters (FAEE). The Yarrowia lipolytica lipases were evaluated in three distinct forms: firstly, as the crude enzymatic liquid extract derived from the submerged fermentation process of Y. lipolytica (YLL); secondly, as YLL immobilized on silica-alumina (YLL-S40); and thirdly, as the fermented solid material obtained from solid-state fermentation of Y. lipolytica (SEP-YLL). The highest FAEE content (54 wt.%) was obtained after 240 h in transesterification reactions using SEP-YLL. The influence of temperature, biocatalyst concentration, and reaction time was studied in the ethyl oleate synthesis. The SEP-YLL also showed better results compared to YLL and YLL-S40. The reaction catalyzed by SEP-YLL achieved 81% conversion at 30 °C. The SEP-YLL was evaluated in a batch-stirred reactor (BSTR) and a continuous packed-bed reactor (PBR), obtaining an oleic acid conversion of 80% and 70%, respectively. The low-cost biocatalyst (SEP-YLL) demonstrated potential for application in biodiesel production by reducing free fatty acids from an acid oil source through PBR and BSTR.

Enzyme immobilization allows the reuse of the biocatalyst more than once without excessive loss of its catalytic activity and conveys operational and storage stability. In this work, β-glucosidase produced extracellularly by the filamentous fungus Moniliophthora perniciosa was immobilized by adsorption on Celite, silica, and chitosan. Celite was the chosen carrier for immobilization due to the high activity yield and maintenance of 65% ± 1.9 of its initial activity after seven reuses. The activity of the immobilized β-glucosidase peaked at pH 4 at a temperature of 60 °C. Moreover, the immobilized enzyme retained 23.7% ± 4.85 of the initial activity when incubated at a temperature of 90 °C during 60 min. Additionally, it retained more than 70% of the initial activity after 20 min of incubation at 50–70 °C.