Brazilian Journal of Chemical Engineering最新文献

In this work, the effect of the sonification time on the stability of styrene and styrene/butyl acrylate (50/50) miniemulsions was investigated by centrifugation. Octadecyl methacrylate (ODMA) miniemulsion was used as a comparative system owing to its degradation by monomer diffusion being minimum. The droplet and particle size distributions were also evaluated by capillary hydrodynamic fractionation (CHDF) and dynamic light scattering (DLS) for the various sonification times. For the styrene/butyl acrylate miniemulsions, the most stable were those formed with the shortest sonification times tested, 1 and 2 min. For the styrene miniemulsions, longer sonification times were required than for the styrene/butyl acrylate miniemulsions and the most stable sample was formed by the use of 4 min of sonification. It was observed that larger droplets (300 to 1000 nm) were formed at shorter sonification times, although the numbers of these were reduced significantly after polymerization owing to monomer diffusion from these larger “reservoir” droplets to the smaller droplets and particles.

Toxic chemical release is the major issue of concern of the industrial effluents. Hence, recovery of chemicals from effluent stream is of great research interest. Present investigation was focused on recovery of pyridine-2-carboxylic acid (picolinic acid) from aqueous streams by reactive extraction using corn oil as a non-toxic diluent. Attempts have been made to estimate the recovery of picolinic acid by chemical extraction and to investigate its kinetic parameters. The kinetic modeling was also carried out for chemical extraction by the law of mass action. Extraction equilibria had been reported and effect of acid concentration, agitation speed and extractant-diluent composition were studied at room temperature. Kinetic study reveals very slow, first order reaction in acid concentration and zero order in extractant, tri-butyl phosphate. The reaction rate constant of 0.191 s⁻¹ suggests a slow type of reaction. The diffusivity of picolinic acid in corn oil was found to be 7.0170 × 10^–11 m² s⁻¹. Although the distribution coefficient is very low and reaction is infinitely slow, the non-toxicity of corn oil used in this study is the key parameter for its use as diluent.

Copper oxide supported on a biochar could suffer from a low nitrogen-selectivity and carbon combustion, despite the sustainability prospect it provides in replacing the utilization of non-renewable materials as the catalyst support to reduce nitric oxide. Bimetallic catalysis is a means to improve catalytic properties including conversion and selectivity. Therefore, this work investigates the enhancement of carbon-supported copper oxides in nitric oxide selective reduction using hydrogen by co-impregnating iron or manganese with copper. The bimetallic catalysts were prepared via sequential incipient wetness method where copper oxide was impregnated and calcined prior to the impregnation and calcination of the co-catalyst. As iron was paired with copper, the nitrogen selectivity was enhanced by 20% (almost 100% selective) at 200 °C while reducing the carbon combustion rate by 20% at a higher temperature (300 °C). This improvement was regarded as the synergistic effects obtained by the bimetallic oxide catalysts as a result of the altered elemental composition (from 60% carbon content to 50%), catalyst acidity (from 12 mmol NH₃ desorbed/g to 16 mmol NH₃d/g) and redox properties (from 5 mmol H₂ consumed/g to 3 mmol H₂/g). Flash elemental analyser showed that this catalyst has lower carbon content but higher oxygen amount (30% compared to 19%) which is correlated to the higher acidic sites, as confirmed via temperature-programmed desorption analysis and Fourier-Transform infra-red spectroscopy. Varying the ratio between the two catalysts revealed that different mechanisms govern the reaction that could be the key to understanding the enhancement of the nitrogen-selectivity. Nevertheless, further studies are required to ensure the applicability of this catalytic system in the industry.

The difficulty of removing low-concentration heavy metals from wastewater and the impact of coexisting anions on adsorption and regeneration performance has been widely recognized. To address this challenge, we synthesized a new adsorbent called porous boron nitride (PBN) and characterized it with X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and nitrogen isothermal adsorption–desorption isotherms. Then, the adsorption kinetics and equilibrium models of PBN for Cd(II) and Ni(II) with a concentration as low as 10 mg/L, along with the impact of anions on adsorption performance and the regeneration of PBN, were investigated. The findings indicated that PBN achieved adsorption equilibrium for Cd(II) and Ni(II) in just 5 min. Furthermore, the adsorption processes fit better with the pseudo-second order kinetic model and the Freundlich isothermal model. Especially, we found that the presence of SO₄²⁻ inhibited the adsorption of Cd(II) and Ni(II), whereas SiO₃²⁻, CO₃²⁻, and PO₄³⁻ promoted adsorption by forming a PBN-anion-metal ternary complex. We determined that the adsorption mechanism involved electrostatic attraction and chemisorption. After regeneration, PBN retained its crystal structure and typical pore distribution, demonstrating excellent adsorption performance for heavy metals.

Abstract

Lignocellulosic biomass and agricultural residues rich in carbohydrates, lipids, and proteins are promising sources for renewable energy production, particularly in the field of biofuel. Goat manure (GM) is a suitable raw material for the anaerobic digestion process owing to its high total nitrogen content, besides providing stability to fermentation. However, its utilization results in a relatively low biogas production yield. This yield can be significantly increased by co-digesting animal manure with co-substrates such as cheese whey (CW). Therefore, this study applied the Simplex Lattice experimental design to verify the biomethane production through different mixture concentrations of goat manure and cheese whey using bench reactors in batch mode. The volumetric compositions (CW₁₀₀/GM₀, CW₇₅/GM₂₅, CW₅₀/GM₅₀, CW₂₅/GM₇₅, CW₀/GM₁₀₀) were evaluated by adjusting linear and quadratic models. The results presented COD removal efficiencies between 40.07 and 63.73% and total volatile solids removal between 22.87 and 58.99%. According to the statistical analysis of the Simplex Lattice design, co-digestion showed favorability for methane production compared to goat manure alone. Furthermore, the maximum methane production yield (MY_COD) was 319.89 mL-CH₄/gCOD, with a productivity rate (MYPR) of 3.39 mL-CH₄/gCOD.d. These maximum values were observed in the CW₇₅/GM₂₅ condition. The quadratic model exhibited the best fit for the design adopted.

Nuclease P1 can hydrolyze nucleic acid into four 5'-mononucleotides, which are widely used as food additives and pharmaceutical intermediates. Nuclease P1 is mainly obtained by microbial fermentation and the low fermentation efficiency of microorganisms for enzyme production is the limit of its application. In order to improve the productivity of nuclease P1, a semi-continuous fermentation of Penicillium citrinum TKZY02 using free-cell was established and the residual sugar, retention volume and air–liquid ratio were optimized. The results indicated that at least 6 fermentation times was performed under the optimum semi-continuous fermentation condition, and the average enzyme activity was up to 518.2 U/mL, which were 16.5% and 9.7% higher than those of batch fermentation and original semi-continuous fermentation, respectively. The average productivity reached 20.9 U/mL/h, which was 42.4% and 21.5% higher than those of batch fermentation and original semi-continuous fermentation, respectively. These findings indicated that Penicillium citrinum TKZY02 was suitable for the production of commercially acceptable levels of nuclease P1 in semi-continuous culture.

All species on this planet, both living and non-living, require water. It is well known that the availability of clean water sources is dwindling and that the rapid development of industry and technology has increased the number of hazardous effluents released into the environment. Before being released into the environment, industrial, agricultural, and municipal wastewater must be treated to remove dangerous contaminants such as organic colours, pharmaceutical wastes, inorganic compounds, and heavy metal ions. They pose major threats to human health and can pollute our environment if not controlled. Membrane filtration is a tried-and-true technique for removing germs and numerous hazardous substances from water. Carbon nanoparticles are used in wastewater treatment because of the promising surface area of sorbents. With the growth of nanotechnology, carbon nanomaterials (CNM) are being created and used in membrane filtration (MF) for effluent treatment before being terminated. To remove wastewater contaminants, this paper investigates using CNMs such as fullerenes, graphene’s, and CNTs. By examining sorption rate, selectivity, permeability, antimicrobial disinfectant properties, and environmental compatibility, we concentrate on these CNM-based membranes and this approach due to its attributes and utilization and how they can improve the performance of the frequently used membrane filtration system.

Concrete is a common construction material used to support structures around the world. However, the durability of concrete is affected by weathering action, abrasion, and chemical attack and this may lead to reduction in desired material properties necessary to support structures. Electromigration is the transport of material in a conductor under the influence of an applied electric field. All conductors are susceptible to electromigration; therefore it is important to consider the effects the electrical current resulting from the applied field may have on the conductor. The net force exerted on a single metal ion in a conductor has two opposing contributions: a direct force and wind force. Electrochemical engineering is the branch of chemical engineering dealing with the technological applications of electrochemical phenomena, such as electrosynthesis of chemicals, electrowinning and refining of metals, flow batteries and fuel cells, surface modification by electrodeposition, electrochemical separations and corrosion. This paper presents results of two small-scale tests using electromigration process as a means of transporting nanosilica to recover cement matrix integrity of aged 32 MPa concrete samples extracted from a 40-year-old structure. A set up with two vessel was proposed, with 12 Vdc electrical font working for 48 h generating transportation of nanosilica (12 nm in diameter) into the aged concrete samples. The experiments were performed in two distinct laboratories. One at Flowtest in Brazil and one at the Research Laboratory of the George Mason University Department of Civil Engineering in the US. Thus, repeatability and reproducibility of the process can be proven under laboratory conditions. The success of the electromigration process was verified with electronic microscope (qualitative analysis), scanning electronic microscope, and X ray dispersive energy spectroscopy. The results showed that an electromigration of nanosilica into the cement matrix occurred and resulted in reduction of micro fissures. Additionally, deposition of silica on the sample surface was observed. Reduction of calcium in the matrix was verified with the development of hydrated calcium silicate, providing the recovery of cement matrix in increasing cement mechanical properties like strength and also decreasing the porosity of the concrete matrix. Another important phenomenon is the rehabilitating of the chloride contaminated concrete structure to extend its service life, an electrochemical chloride extraction (ECE) treatment with simultaneous migration of silicate ion was performed. Based on referenced literature, it can be assumed that the extraction of chlorine ions occurs simultaneously with the recovery of cement matrix by nanosilica.

Abstract

In the present research, the Tin dioxide/Titanium dioxide (SnO₂/TiO₂) composite has been successfully fabricated by a chemical co-precipitation method. SnO₂/TiO₂ composite precursors were calcined at different temperatures (400 °C, 500 °C 600 °C, 700 °C). The degradation experiment of methylene blue (MB) dye using SnO₂/TiO₂ composite material was conducted to analyze the electrocatalytic performance. The degradation efficiency of the composite material can reach 96.6% (calcination at 500 °C). The logarithm of methylene blue concentration exhibits a strong linear relationship with reaction time, and the correlation coefficient R for each curve exceeds 0.99. This suggests that the electrocatalytic degradation process of methylene blue follows quasi-first order reaction kinetics. The ⋅OH present in the whole system can oxidize methylene blue (MB) into CO₂ and H₂O, and the reaction is accompanied by oxygen evolution reaction. The inactive electrode has weak adsorption to the free ⋅OH, so the SnO₂/TiO₂ electrode in the system has obvious advantages. The composite material electrode calcinated at 500 °C has the fastest electrocatalytic decolorization reaction rate and the highest catalytic capacity, which is consistent with the results of degradation efficiency.