Brazilian Journal of Chemical Engineering最新文献

This study aimed to optimize two cell disruption methods, i.e., high-speed homogenization (Ultra-turrax) and cold plasma, to efficiently recover microbial lipids from Rhodotorula mucilaginosa CCT 7668. A previously optimized medium composed of agro-industrial byproducts (70 g/L sugarcane molasses and 3.4 g/L corn steep liquor) was used for producing lipids at 25 °C, 180 rpm for 144 h. Different pretreatments of biomass (wet, dry, and/or frozen) were evaluated; 7.0% of lipid content and 0.50 g/L total lipids resulted from the use of dry and frozen biomass. An experimental design methodology was applied to study the following variables: biomass:solvent ratio (0.3:100–1.2:100), operation time (0.6–7.4 min) and rotation speed (9280–22,720 rpm), when high-speed homogenization was used. Lipid contents ranged from 9.6 to 35.2% while total lipids ranged from 0.80 to 2.96 g/L. Regarding the cold plasma technology, biomass (0.5–0.7 g), operation time (20–40 min) and power (8–14 W) were evaluated. Lipid contents ranged from 20.6 to 34.9% while total lipids ranged from 1.81 to 3.06 g/L. Therefore, this study defined optimal conditions to efficiently produce microbial lipids with low toxicity, which represent potential sources that may be applied to food and pharmaceutical industries.

Structural and functional properties of a membrane describe its quality necessary to achieve the defined performance. Preparation of mixed matrix membrane (MMM) was performed considering the non-solvent induced phase separation (NIPS) method, relied immersion precipitation technique using dimethylformamide (DMF) and tetrahydrofuran (THF) solvents. Nanoclay particles (NCPs) at a certain weight were dispersed within the PVC polymer. Four different membranes were structurally characterized using FTIR, XRD, and EDS methods. Further analyses were on surface morphology using FESEM, and AFM. Nanofiltration experiment was conducted and functionality of the novel membranes was evaluated in terms of flux of water permeation (FWP), hydrophilicity character (contact angle determination), and salt rejection (SR) behavior. With use of 2 wt% NCPs, porosity and hydrophilicity characteristics of the resultant membrane increased by 15%, and 17%, respectively. Crystallinity nature of the composite membrane did not change considerably (XRD results). Pure water flux (PWF) and calculated salt rejection were 118.35 kg m⁻² h⁻¹, and 95%, respectively.

Graphical abstract

The synthesis of pure titanium dioxide (TiO₂) nanomaterials from naturally occurring ilmenite (FeTiO₃), which is present in black sands, is highly desirable due to its numerous industrial and technological applications. In this study, nanostructured rutile nanorods were synthesized using Egyptian ilmenite concentrate through a simple mechanical/chemical route, comprising two stages: the first stage involved the reduction of ilmenite by activated carbon as a reducing agent during milling, while the second stage involved the decomposition of FeTiO₃/carbon and the selective dissolution for iron and silica using a mixture of HCl/H₂O₂ and NH₄F/HF, respectively. The results indicated that the optimal conditions for hydrothermal leaching of the milled ilmenite/carbon are achieved at a solid/liquid ratio of 167 g/L, 4 h at 170 °C. The amorphous titanium dioxide could be converted to ~ 95% pure rutile-phase nanorods by annealing at 700 °C followed by additional leaching processes to simply remove silica from the synthesized rutile.

This article focuses on synthesizing dual-functional adsorption-ion exchange material (Fe-Ca/225H) by precipitation method on 225H cation exchange resin for the treatment of phosphate and hardness in water. Materials were analyzed through methods such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction studies (XRD), and scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). For the phosphate adsorption, suitable conditions were experimentally found to include reaction time (48 h), pH (6.5), adsorbent dosage (10 g/L), and HCO₃⁻ ions as the most impact ion on the phosphate adsorption. When calcium and magnesium were present in a solution containing phosphate, the phosphate adsorption capacity increased by 1.24 times. This was due to the combination of calcium and magnesium with phosphate on the surface of the material, which improves the adsorption efficiency. Besides, when compared with materials containing only iron (Fe/225H), the adsorption capacity of Ca-Fe/225H materials is still higher in both synthetic wastewater and domestic wastewater. The durability of the material after 10 regenerations was still over 80% effective. The material is effective in simultaneously treating both phosphate and hardness in the solution, with a much higher hardness treatment efficiency than amphoteric resin on the market (MB6SR).

Propionic acid (PA) is industrially produced using raw materials derived from petroleum. In search of more sustainable processes, this work investigated the production of propionic acid (PA) by fermentation using whey permeate (WP) and corn steep water (CSL), with the strain Propionibacterium freudenreichii subsp ATCC 6207. Two strategies of fermentation were compared: one in batch and the other fed batch, carried out in a 5 L bioreactor at 30 °C, with pH control. Furthermore, in fed-batch fermentation, lactose concentration was controlled. The study revealed that batch fermentation was more efficient in producing propionic acid (PA). After 72 h, the concentration reached 13.10 g L⁻¹, with a yield of 0.335 g g⁻¹ and productivity of 0.182 g L⁻¹ h⁻¹. The research addressed the PA purification by ion exchange chromatography, using cryogels functionalized with taurine (Tau-cryogel). Tests at different pH (4 to 7) showed greater PA adsorption on the cryogel at pH 4 (256.13 mg g⁻¹), with recovery of 59.7% and lower adsorption of acetic acid (29.34 mg g⁻¹), indicating promising selectivity in purification. This study shows the feasibility of using byproducts such as WP and CSL in the production of PA and the potential of applying ion exchange cryogels in its purification.

Graphical Abstract

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.