Brazilian Journal of Chemical Engineering最新文献

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.

This research involved the implementation of steam-assisted dry reforming (SDR) on methane utilizing a CoMo/Al₂O₃ nanoflake catalyst under microwave irradiation. The CoMo/Al₂O₃ nanoflakes demonstrated superior catalytic activity for reforming reactions, attributed to their enhanced surface exposure to incident microwaves and heightened microwave absorption capability. Fischer–Tropsch (F–T) synthesis was employed for the production of liquid fuels, with the predicted syngas ratio (H₂/CO) easily adjustable by varying the steam-to-carbon ratio (S/C) supplied to the reactor. Achieving an H₂/CO ratio greater than one was feasible with an intake S/C ratio below 0.1 and 200 W of microwave power. In comparison to carbon-based catalysts, the CoMo nanoflakes exhibited significantly higher catalytic stability after 16 h of time-on-stream (TOS) during the SDR process under microwave irradiation. The utilization of microwaves in this process opens novel routes for methane reforming to fuel, offering distinct advantages.

Abstract

Anaerobic co-digestion of organic wastes and plant biomass generates an environmentally friendly energy source. Anaerobic co-digestion of cow dung (CD), goat manure (GM), and cactus cladodes (CC) was investigated under mesophilic laboratory conditions. A 14-day-long daily biogas production potential and methane content were evaluated for the three substrates co-digested at different mix ratios. Physicochemical properties showed significant differences between the raw and digested substrates. Biogas production started after the first day of anaerobic digestion for all substrates, with the peak observed near day fourteen. The anaerobic co-digestion of 66.7% GM and 33.3% CC substrate mixture produced the highest biogas yield. The cumulative biogas production study also revealed that the same substrate combination achieved better biogas yield. The anaerobic digestion of CD, GM, and CC showed a significant increase in biogas yield followed by a reduction in volatile and total solid contents. The 100% CC, 33.3% CC + 66.7% CD, 33.3% CC + 66.7% GM, and 33.33% CC + 33.33% CD + 33.33% GM anaerobic digestions achieved biogas with methane content (%) of 56.02, 72.6, 56.65, and 67.95, respectively. The 33.33% CC + 33.33% CD + 33.33% GM anaerobic co-digestion achieved the highest methane content compared to other substrates. The CC + CD + GM and CC + GM mixtures had a C/N ratio ranging from 20 to 30, contributing to better biogas yield with more methane content than substrates deviating from such a ratio. For all substrates, the methane content of the biogas ranged from 50 to 72.6%. The study also revealed that the co-digestion of CC with GM resulted in a better cummulative biogas yield and cumulative methane content.

Biotechnology has increasing relevance worldwide in the mining sector, either as a response to the recovery of metals (gold, silver, copper, zinc, nickel, among others) as well as an alternative in the bioremediation of contaminated soil and water, frequent problems directly linked to mining activities. Hence, acidophilic microorganisms are of special scientific and industrial interest for the sustainable use of mineral resources. Nowadays, a wide variety of acidophilic chemolithotrophic microorganisms (MOs) are recognized, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Acidithiobacillus caldus, and Leptospirillum ferrooxidans, among others; those MOs grow in culture medium at pH ≤ 3 and obtain cellular energy from the oxidation of inorganic compounds, such as sulfur and iron. These microorganisms have different abilities to act on the mineral, converting insoluble metal sulfides into soluble metal sulfates of those species that are of interest, or that prevent optimal recovery of a specific mineral. Such microorganisms have been applied in biomining operations and are internationally known for the recovery of valuable metals from low-grade ores and refractory ores. Likewise, these acidophilic MOs can bioremediate soils contaminated with metals, extract metals from sludge generated as a byproduct in wastewater treatment, detoxify hazardous waste and recover metals from electronic waste; so the main interest of biomining processes lies in the economic impact that has benefited the world, since it is known that 5% of the gold and 20% of the copper that has been extracted worldwide are using this type of bacteria in bioleaching processes. The objective of this review is to expand the knowledge of the characteristics and applications of the main acidophilic microorganisms used in the solubilization/extraction of minerals, whether for the recovery of metals, bioremediation, or reduction of metals in different systems.

Graphical abstract

The role of acidophilic bacteria in several industrial sectors. Created with BioRender.com.

Abstract

Gluconic acid is a chemical raw material widely used in the food and chemical industries that can be produced by oxidizing glucose and available sugar-rich substrates such as biomass. The abundance of glucose and fructose in industrial waste from lignocellulose and inverted sugar makes them a promising sustainable feedstock. In this work, the catalytic conversion of a glucose and fructose mixture into gluconic acid in an alkaline medium using Pd (4%)—Pt (1%)—Bi (5%)/C catalysts under flowing air was studied. Previously, the traditional chemical conversion of glucose into gluconic acid produced large amounts of by-products. In this work, we combined glucose and fructose to investigate the latter's influence on conversion. The selectivity to gluconic acid was significantly improved by fructose, indicating a new approach for using biomass and by-products such as glucose and fructose syrup. The first step was to conduct a series of experiments at different temperatures and pH levels. The second step was to experiment with adding fructose under optimal conditions. The gluconic acid was about 90%. The yield was approximately 79% at 55 °C and pH 9.5 using the same method with only glucose. Combining experimental data, we propose a kinetic model with a TOF (turnover frequency) between 1.0 and 5.5.