Brazilian Journal of Chemical Engineering最新文献

Nanoparticles are useful for immobilization due to their size and physical properties. The present study aimed to synthesize herbal silver nanoparticles (SNPs) to immobilize the lipase from Candida rugosa covalently on the nanoparticles as well as to examine the biochemical parameters of the immobilized enzyme. SNPs were synthesized using Cydonia oblonga leaf extract and were characterized. Lipase enzyme was immobilized on synthesized SNPs and the immobilization efficiency was calculated. The biochemical properties of immobilized and free enzymes, including the temperature effect and pH on enzymatic activity, thermal stability, storage stability, and reusability of the immobilized enzyme were specified. Electron microscopy, DLS measurements, and Raman spectroscopy confirmed the 50 nm SNPs and the immobilization of lipase enzyme on them. The efficiency of lipase enzyme immobilization on nanoparticles was estimated to be 48%. The free enzymes and immobilized enzymes had the highest activity at 37°C and 55°C, respectively. Also, the optimal pH was 7 for the free enzyme and 6 for the immobilized enzyme. A comparison of thermal and storage stability of free and immobilized enzymes suggested that immobilized enzymes had more stability and resistance than free enzymes as they also could be reused up to 12 times. The kinetic parameters of the immobilized enzyme compared to the free enzyme indicated a slight decrease in the maximum rate of the enzyme. Immobilized enzymes can be used in industries and are also very crucial for commercial use as they are cost-effective.

Production xylanases at low cost and their storage stability are of utmost importance for the animal feed industry. This work aimed to produce fungal xylanases by solid-state cultivation and to immobilize the enzymes in agricultural residues by spray-drying. The enzymes were obtained by cultivating Myceliophthora thermophila I-1D3b in sugarcane bagasse and wheat bran at 45 °C and 75% moisture content (w.b.) and the titres were as high as 864 U per gram of dry solids. The physical–chemical activity of the enzyme showed to be of interest for the animal feed industry, as the optimal activity was obtained at pH 5.0 and the optimal temperature at 70 °C. The enzymes were spray-dried using soybean meal, wheat bran, and corn bran as carriers, and the most suitable carrier was soybean meal in terms of residual enzyme activity after drying. The operational conditions for soybean meal were optimized, with the outlet temperature, the liquid flow rate, and the total solid content as variables, and only the total solid content was significant. The highest residual enzyme activity was 130.9% after optimization. Experiments for storage of the dry powders of soybean meal showed that the loss of activity was under 30% for storage times up to 45 days. The results here presented are promising for the reduction of costs of xylanases used as feed enzymes and for their preservation for long periods as a dry powder.

Many crude oils have high levels of acidity due to the presence of naphthenic acids, which under certain conditions form insoluble salts in water and/or oil. Chemical additives are a good alternative to avoid formation of these deposits, or at least to cause the formation of a weak film. In this work, four commercial molecules based on ethoxylated nonylphenol were investigated, with varying hydrophilic-lipophilic balances (HLB) (12.3, 13.3, 14.1 and 17.1), to evaluate their action on calcium naphthenate formation. Moreover, the influence of the addition of monoacids (C4, C10 and C18) on the additives’ performance was also evaluated. Tetraprotic acid (ARN) was extracted from an industrial deposit and was characterized for use in the tests. The additives were investigated at 100, 500, 1000 and 2000 mg. L⁻¹. The performance was evaluated by the biphasic mixture test and oscillatory interfacial rheology (using a Du Noüy ring), being characterized by the reduction of precipitate amount and the time for the formation of the film, respectively. The performance increased with rising additive HLB and concentration within the range tested. Concerning the monoacid, the best result was obtained using butyric acid. By using the additive with HLB of 17.1 and butyric acid together, a synergistic effect was observed, with better performances at lower additive concentrations. Moreover, the surfactant:monoacid ratio played an important role in the formulations’ performance, with the best result achieved at 75:25 wt/wt.

V₂O₅ and TiO₂ have been supported on FCC waste catalyst by modified impregnation method. The composition and morphology of the materials obtained by the characterization results. The relationship between reaction conditions and structure, as well as the close relationship between structure and electrochemical performance were analyzed from the micro level. TiO₂-V₂O₅/FCC has a good porous structure. Using TiO₂-V₂O₅/FCC samples, a three-electrode system was constructed, and the electrode was electrocatalyzed to investigate the degradation efficiency and cycle life of methylene blue dye. The experimental results show that TiO₂-V₂O₅/FCC has good dye degradation and electrocatalytic oxidation performance, which can be used in wastewater treatment and other green chemical industry.

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A thorough examination was undertaken to evaluate ZnO nanostructured films doped with transition metals (M = Fe, Cu, and Cr) and their respective functional attributes, emphasizing their potential applications in optical technology and electronic components. Both pure and M-doped ZnO nanostructured films were synthesized through a co-precipitation and spin coating procedure. Structural investigations revealed that all films exhibited hexagonal wurtzite formation. XRD findings highlighted evident evolution in the lattice parameters of prepared doped samples in comparison to the pure ones. The introduction of M doping led to modifications in various crystalline parameters of the host ZnO layers. Photocurrent density measurements illustrated a range from 2.5 µA/cm² for pristine ZnO to 25, 8 and 19 µA/cm² for Fe, Cu, and Cr-doped samples, respectively, showcasing distinct variations in performance. Notably, this study represents the first reported comparative analysis of the functional properties of three dopants spin coated in ZnO films. These distinctive results position the coated layers as promising candidates for novel optoelectronic applications.

The pre-treatment of waste cooking oil (WCO) by removing free fatty acids (FFAs) is pivotal for biodiesel production. This study develops a low-cost, efficient adsorbent derived from water hyacinth (Eichhornia crassipes), activated with 5 M NaOH, termed WHA-H, for this purpose. Characterization through FT-IR and SEM analyses revealed that NaOH activation significantly enhanced the surface roughness and functional group availability on WHA-H, leading to improved adsorption capabilities. Nitrogen adsorption–desorption isotherms of WHA-H confirmed a complex pore structure with Type II and Type IV isotherms combination, indicating the presence of both meso- and macroporosity. Kinetic studies conformed to the pseudo-second-order model, suggesting chemisorption as the primary FFA adsorption mechanism, while isotherm data were best described by the Langmuir model, indicating monolayer coverage on a homogeneous surface. WHA-H exhibited a maximum FFA adsorption capacity (q_m) of 1666.67 mg g⁻¹. Thermodynamic parameters indicated that the adsorption process is spontaneous and exothermic, with desorption studies establishing diethyl ether as an effective solvent for WHA-H regeneration. Our study not only demonstrates WHA-H’s potential as a sustainable adsorbent for improving WCO quality but also offers an eco-friendly approach to managing the invasive water hyacinth.

Sustainable chemical production through biomass pyrolysis is attractive. This is necessary to suppress massive dependence on fossil resources. Nevertheless, the liquid product as raw bio-crude oil (RBCO) from biomass pyrolysis still contains high water content. In this study, batch vacuum distillation of RBCO from empty fruit bunches (EFB) pyrolysis was performed at 80(-)95 °C and 30(-)45 kPa to produce light distillate. The highest yield of light distillate is acquired at 69.73–88.27% under 95 °C and 30 kPa. The functional groups in RBCO and light distillate indicate the presence of water (O–H bond), acetic acid (C = O bond), and phenol (C = C–C aromatic ring and O–H bond). This is also proven by the results from Karl-Fischer of RBCO that water contained at 66.77% whereas GC–MS of RBCO show the concentrations of acetic acid is 16.02% and phenol is 26.53%. Physically, the light distillate had a light brown color and smoky odor, with density range of 0.96–0.99 g/ml and viscosity range of 0.60–0.93 cP. According to this study, light distillate has water content of 70.57–98.81%. During vacuum distillation, acetic acid and phenol, as the major chemicals contained in RBCO, are also dissolved in the aqueous phase with the highest concentrations of 0.28% and 0.09%, respectively. Looking at its chemical components, this light distillate has the potential for food preservatives or agricultural biopesticides.

This study investigated sulfuric acid leaching of Zn and/or Cu from brass ashes. The material consists of a heterogeneous powder containing ZnO, CuO, SiO₂, Zn₂SiO₄, Zn, and Cu as main phases. Due to the strong exothermic behavior exhibited by changing operating conditions (L/S ratio = 3‒6 mL/g, pH 1‒5), temperature with time behavior was monitored to determine the heat released by leaching reactions. Eh–pH diagrams were drawn to identify regions to leach Zn selectively or simultaneously with Cu. A rich-Zn liquor (62 g/L) with low Cu (0.97 g/L) content was obtained using L/S ratio 3 mL/g and pH 5; a second leaching stage at pH 5 resulted in a liquor with only 10.2 g/L of Zn and 1.5 g/L of Cu. The low efficiency was attributed to the predominance of the refractory Zn₂SiO₄ phase. To increase leaching yield of Zn and Cu, the leaching residue was leached at pH 1 and L/S ratio = 3 mL/g, resulting in a liquor containing 90.5 g/L Zn and 14.4 g/L Cu. Quartz was refractory to H₂SO₄ in all tests, and silica gel formation was not observed. The acquired liquors must be submitted to adequate treatment to produce purified Zn and Cu solutions.

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Electrohydrodynamic (EHD) convective drying is a non-thermal energy-efficient technology to preserve heat-sensitive materials by dehydration. A high-voltage electrode is used to induce corona wind that increases convective heat and mass transfer in the material and air interface. A chamber used for EHD drying with a wire-to-plate configuration and additional air crossflow was modeled considering the finite element method in COMSOL Multiphysics (v.6.1). The concepts of electrostatics, turbulent flow, heat transfer in fluids and moisture and energy transport physics were combined iteratively to solve and predict the electric field strength, airflow, convective heat transfer coefficient and moisture removal. Different electric potential and air crossflow velocities were tested and their impact on the drying rate was quantified. Combining high voltage (0, 10, 15 and 20 kV) and air crossflow velocity (0, 1, and 2 m/s) was found to have a significant effect on the convective heat transfer coefficient and moisture removal; however, the increase in one of the drying factors had a low effect on drying time. The main results show that the proposed model can adequately simulate the EHD airflow phenomena and the drying process and can be used for product quality improvement, energy efficiency analysis and optimization studies.