Brazilian Journal of Chemical Engineering最新文献

Abstract

This study compared the performance of microbial fuel cells (MFCs) using parchment paper as a separator to a CMI7000 proton exchange membrane. The MFCs were operated in two chambers with whey solution as the substrate. Parameters such as COD removal, internal resistance, power density, current density, and Coulombic efficiency ratio (CE) were evaluated. The CMI7000 membrane exhibited the highest COD removal at 92%, while the parchment paper achieved removal percentages ranging from 72 to 91%. The internal resistance was lower for the parchment paper separator for the first run, the internal resistances were 68 Ώ and 84 Ώ for parchment paper and CMI7000, respectively. The maximum energy densities were 219 mW/m² (5.74 mA/m²) and 421 mW/m² (8.24 mA/m²) for parchment paper and CMI7000 membrane, respectively. The CE values for parchment paper were 36.32% and 33.5%, while for the CMI7000 membrane, they were 42.73% and 32.0%, for the two runs. Overall, the study demonstrated that the parchment paper separator performed reasonably well in terms of COD removal, internal resistance, energy density, and Coulombic efficiency ratio compared to the CMI7000 membrane in microbial fuel cells.

Abstract

Over the past few decades, environmental contamination from the wastewater industry has gravely threatened the environment and public health. According to reports, thousands of different dyes and pigments are used in a range of industries around the world each year, producing more than 7 × 10⁵ tonnes of synthetic dyes. Environmental contamination can be prevented by using semiconductor metal sulfide nanostructures (MSNSs) with doping and heterojunction as photocatalysts for the long-term, economical removal of hazardous organic dyes. The current review focuses on the degradability of hazardous dyes in the environment by metal sulfide nanoparticles such as ZnS, CdS, CuS, Ag₂S, CoS, and FeS.

Vanadium pentoxide (V₂O₅) thin films were grown on porous silicon (PS) layer by electron beam evaporation technique under an oxygen partial pressure. The morphology of the porous surface before and after V₂O₅ deposition for different evaporation times was observed by the Scanning Electron Microscope (SEM). The predicts changes of the chemical composition and bonds at the porous surface have been studied by FTIR and Raman spectroscopies. Photoluminescence (PL) spectroscopy was carried out to study the effect of vanadium pentoxide thickness on the optical properties of V₂O₅/PS nanocomposites. The PL spectrum of PS show a red-shift of 90 nm following the deposition of vanadium pentoxide while a quenching of the PL intensity was observed. Referring to FTIR and Raman results, the origin of this shift can be attributed to the formation of oxidized vanadium elements at PS surface as well as the creation of localized states by V₂O₅ molecules inside the band gap of PS. The wavelength dependence of optical transmittance, reflectance and absorption coefficients were investigated. An increase in the optical band gap from 1.95 to 2.18 eV was obtained due to Moss-Burstein effect as well as the presence of vacancy defects in V₂O₅ film.

Phycobiliproteins (PBPs) are light collecting pigments of cyanobacteria that attract growing interest for several industrial applications. Each step of the extraction process is crucial for yield, concentration and quality of obtained pigments. In the current work, we present an optimization scheme of major limiting steps for PBPs extraction from Arthrospira platensis biomass. As first step, the effects of pretreatment, extraction time, and separation conditions on the recovery of PBPs were compared. Subsequently, the influence of pH and concentration of the extraction buffer as well as the addition of preservatives (Polyethylene glycol (PEG), Magnesium chloride (MgCl₂), and Calcium chloride (CaCl₂)) was studied. In addition, the effect of the biomass type (dried vs wet) and its concentration in the extraction buffer was also investigated. Optimal extraction required the use of dry biomass at relatively low ratio (1:50, solvent:biomass), without previous treatment. The use of concentrated phosphate buffer (100 mM) at a neutral pH gave the highest PBPs recovery and concentration after 6 h of extraction followed with a separation at 6000 rpm during 15 min. Calcium chloride used at 1.5% improved by 30% both PBPs recovery and concentration in the crude extract. The optimized protocol allowed the recovery of 464.5 mg/g PBPs from spirulina biomass with concentration of 15.9 mg/ml. The crude PBPs obtained with this extraction method reduced the stable radical DPPH with a percentage scavenging activity of 86.45 ± 1.2%. This protocol could reduce both PBPs time and cost extraction and is easily scalable for industrial application.

The worldwide crisis of the fossil fuels and the current environmental issues have led for the search of new alternative for the energy industrial sector. In this scenario, the production of second-generation ethanol, from the exploitation of lignocellulosic biomasses fractions, has presented itself as a prominent alternative. Thus, the present work aimed to develop a combined process for the sugarcane bagasse (SCB) fractionation using a deep eutectic solvent (DES), a new class of ecofriendly solvents, and diluted acid hydrolysis. The DES delignification process was able to reduce the SCB lignin content in about 48% and, at the optimum hydrolysis conditions (1.1% v v⁻¹ of sulfuric acid and 59 min of hydrolysis time), the delignified material was converted into a solid fraction rich in cellulose (51.11 ± 0.95%, increment of 41.46%) and into a liquor product rich in xylose (18.26 ± 3.14 g L⁻¹). The data statistical analysis proved that the combined strategy was superior to the single and direct acid hydrolyzation of SCB. The structural changes of the material after all investigated pretreatments were confirmed by FTIR and DRX techniques, what reinforce the relevance of the results here reported.

The markers commonly used to detect fraud and adulteration in fuels are conventional organic molecules. Recent developments in nanotechnology have gained an important role in this field. The novelty of this work is the application of multicolor semiconductor fluorescent nanocrystals, CdSe quantum dots (QDs), as gasoline nanomarkers. QDs with fluorescence emissions ranging from green to red were evaluated as gasoline nanomarkers. They retained their colloidal and fluorescence stability after more than 5 years, as verified by visualization under UV light and by absorption and fluorescence spectra. Additionally, they were clearly detected in gasoline concentrations of around 40 ppm. Advantages of this class of nanomarkers over traditional organic molecules markers are: the simpler production process, the high photostability and the ease and sensitivity of detection based on fluorescence emission in multicolored wavelengths. Thus, the application is potentially useful for different gasoline matrices. For instance, CdSe quantum dots could be used to differentiate regular gasoline from gasoline with additives, or differentiate gasolines produced in different sources and thus subjected to different commercial taxation. Therefore, this study presents nanomaterials such as CdSe QDs and their optical properties, used as gasoline nanomarkers, as a technological innovation in the field of Chemical Engineering.

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Pesticides are chemical compounds widely used in crop pest control, ensuring high productivity and product quality control. However, pesticides are toxic and can be bioaccumulative. Their excessive use causes environmental and health impacts. In this study, the potential of glow discharge plasma to degrade diazinon present in water was investigated. For the degradation process, a glow discharge plasma (GDP) system was used to process diazinon at several plasma flow rates (10, 20, and 30 mL/min) and exposure times (10, 20, and 30 min). The degradation levels and the identification of the by-products were analyzed by gas chromatography coupled to mass spectrum (GC-MS). GDP processing efficiently degraded diazinon, reaching a maximum potential degradation of 8.19 ± 0.92 mg/L, sufficient to bring diazinon-contaminated waters to safe levels. Two parallel degradation routes were proposed for diazinon degradation by cold plasma.

In this work, the degradation of the fast green dye FCF (FG) by means of photocatalysis under natural solar and UVC radiation was studied. The following degradation parameters were evaluated: catalyst type, catalyst dosage, initial dye concentration and pH. Phytotoxicity evaluation was also carried out using Lactuca sativa seeds. ZnO promoted better degradation rates in both radiations, under the best experimental conditions (0.06 g of catalyst, 10 mg L⁻¹ of FG and pH = 6). A generalist kinetic model was developed in order to allow its broad use in a wide range of photodegradation systems. The developed kinetic model was able to fit to the total set of generated data with a coefficient of determination R² = 0.95. The phytotoxicity tests showed an increase in the relative growth of the roots after treatment, indicating a reduction in toxicity of the solution and the efficiency of the process.

One of the main promises of Industry 4.0 is the incorporation of computational intelligence techniques in industrial process control. For the chemical industry, the efficiency of the control strategy can reduce the production of effluents and the consumption of raw materials and energy. A possible, although currently underutilized approach is reinforcement learning (RL), which can be used to optimize many sequential decision making processes through training. This work used Van de Vusse kinetics as an evaluation environment for controllers based on reinforcement learning and comparison with conventional solutions like non-linear model predictive control (NMPC). These kinetics contain characteristics that make it difficult for classic controllers such as PID to handle, such as its non-linearity and inversion point. The investigated algorithms showed excellent results for this notable chemical process control benchmark. This study was divided into two experiments: setpoint change and operation around the inversion point. The former showed the ability of RL controllers to adjust the controlled variable and simultaneously maximize production. The latter revealed the excellent management capability of the reinforcement learning algorithms and NMPC at the inversion point. In this study, the RL algorithms performed similar to NMPC but with lower computational cost after training.

Mixed metal oxide-based nanocomposites (NCs) have remained broadly used for photocatalysis-facilitated elimination of harmful substances from the aquatic ecosystem. Nowadays, searching for an improved photocatalyst looks plentiful; metal oxide-based materials have begun to emerge from studies. In the present work, the use of ZnO/NiO NCs as photocatalytic treatment of wastewater utilizing oxides of metals as photocatalysts has become a subject of major concern. The way of coupling with other semiconductors for improved photodegradation in the presence of UV-visible light. NCs were mainly characterized by XRD, FT-IR, UV-DRS, morphological studies such as SEM and TEM, and elemental composition by EDAX, which all affirmed the effective synthesis of NCs. For instance, ZnO/NiO NCs having a bandgap of about 3.11 eV achieved outstanding degradation activity toward 100% photodegradation of methylene blue (MB) within a short period of time. Further, prepared ZnO/NiO NCs have excellent antibacterial activity against both Gram-negative and Gram-positive bacteria. This behavior is primarily caused by the accumulation of ZnO/NiO NCs on the bacteria’s surface, which results in cytotoxic bacteria and a relatively increased ZnO, resulting in cell death. Also, ZnO/NiO NCs exhibit essential, harmless effects on human red blood cells and their intervention with the action of clotting on both PPP and PRP in human erythrocytes. As an outcome, the studies have shown that Phyllanthus Niruri (L) mediated synthesis by combustion methods performs well as a good capping agent to synthesize ZnO/NiO NCs with important multi-disciplinary applications.

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