•Comparison of imidazolium-based IL as catalysts for biodiesel production.•Reaction parameters optimization by Response Surface Methodology.•High conversion and high Fatty Acid Methyl Ester content ...were obtained.•Low activation energy value for esterification reaction with HMIMHSO4.
In this study, 1-methylimidazolium hydrogen sulfate, HMIMHSO4, ionic liquid, was successfully applied as a catalyst in the biodiesel production through the esterification reaction of oleic acid with methanol. A response surface methodology (RSM) known as Box-Behnken Design (BBD) was applied to optimize the main experimental reaction conditions, using a set of 27 experiments. This optimization was based on the maximization of both the conversion of oleic acid and the Fatty Acid Methyl Esters (FAME) content of the obtained biodiesel samples. It was concluded that the two most relevant parameters for both the conversion and the FAME content were the molar ratio between oleic acid and methanol and the catalyst dosage. Accordingly to the model, the optimum condition for the maximum conversion was determined as being 8 h, 110 ± 2 °C, 15:1 M ratio methanol/oleic acid and a catalyst dosage of 15 wt%, resulting in a 95% conversion and for the maximum FAME content were 8 h, 110 ± 2 °C, 14:1 M ratio and a catalyst dosage of 14 wt%, leading to a FAME content of 90%. The kinetics of the esterification reaction was also evaluated, and the experimental results were well described using a third-order reaction model. The kinetic parameters were experimentally determined, and the value of the activation energy was 6.8 kJ/mol and the pre-exponential factor was 0.0765 L2.mol−2.min−1 confirming that the ionic liquid, HMIMHSO4, is a good alternative for replacing traditional catalysts for biodiesel production through esterification reaction.
This paper presents the results of studies on reducing the amount of vibrations in different frequency ranges generated by a combustion engine through the use of different types of engine mounts. ...Three different types of engine supports are experimentally and numerically analyzed, namely an elastomeric engine mount, an elastomeric engine mount with a hydraulic component and standard decoupling, and an elastomeric engine mount with a hydraulic component and a modified decoupler-with this engineering design being a novelty in the literature. Experimental tests that considered different excitation frequencies were performed for the three types of engine mounts. Experimental data for stiffness and damping were used to obtain nonlinear mathematical models of the two systems with hydraulic components through the use of an Artificial Neural Network (ANN). For the results, all of the mathematical models presented coefficients of determination, R
, greater than 0.985 for both stiffness and damping, showing an excellent fit for the nonlinear experimental data. Numerical results using a quarter-car suspension model showed a large reduction in vibration amplitudes for the first vibration model when using the hydraulic systems, with values ranging between 48.58% and 66.47%, depending on the tests. The modified system presented smaller amplitudes and smoother behavior when compared to the standard hydraulic model.
In the present work, a study was carried out on the dosage of wastes from the chemical industry (tannery sludge) and civil construction (concrete and plaster) in mixtures used in concrete blocks’ ...production. The objective was the application of these blocks in paving. The characterization of the materials used was performed employing X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The effect of the different residues on the blocks’ properties was evaluated through compressive strength, flexion-traction, water absorption, abrasion resistance, and leaching tests. The results indicated that the concrete paving blocks produced with the addition of residues did not obtain gains in the values of mechanical resistance to compression and traction in bending compared to blocks made with standard raw material. However, the blocks produced with construction waste presented satisfactory results for application in street paving after 7 days of concrete curing, reaching values between 36.54 and 44.6 MPa for the mentioned properties. These values also increased to 21.4% within 28 days of curing. The blocks produced with plaster showed values between 37.03 and 39.85 MPa after 28 days of curing, allowing their use for street paving. On the other hand, the blocks containing residues from the chemical industry had lower strengths, reaching a maximum of 29.36 MPa after 28 days of curing. In addition, it was also noted that the blocks produced with recycled concrete showed an improvement in performance for a composition of 50% recycled material.
The biosorption of orange solimax TGL 182% (OS-TGL) textile dye onto new and low cost biossorbent (malt bagasse) in aqueous solutions was investigated. The malt bagasse was characterized by Fourier ...transform infrared spectroscopy and specific surface area (BET method).Batch biosorption experiments were conducted in order to determine the following parameters: particles size, pH, agitation speed, temperature, contact time, biomass dosage, influence of the ionic strength and, finally, the influence of other textile dye on the OS-TGL biosorption. The optimum conditions for OS-TGL removal were obtained at pH 1.5, agitation speed of 150rpm, contact time of 180min and biomass dosage 2, 8gL−1. The results show that the kinetics of biosorption followed a pseudo-second-order model and by increasing the temperature from 293 up to 313K, the biosorption capacity was improved. The Langmuir model showed better fit and the estimated biosorption capacity was 23.2mgg−1. The negative values of Gibbs free energy, ΔG°, and positive value of enthalpy, ΔH°, confirm the spontaneous nature and endothermic character of the biosorption process. The results of the ionic strength effect indicated that the biosorption process under study had a strong tolerance in high salt concentrations. The removal capacity (>95%) was not affected with the presence of other textile dyes.
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•Malt bagasse a potential biosorbent for dye removal.•Removals higher than 95% without any treatment.•Isotherm, kinetic and thermodynamic studies for dye biosorption onto malt bagasse.
The oxidation of As(III) to As(V) in aqueous solution was evaluated using heterogeneous photocatalysis and photolysis. The influence of TiO2 as catalyst in different crystalline (rutile, anatase) and ...commercial forms was evaluated in a batch reactor and an insignificant difference was observed between them. The process by photocatalysis reached up to 97% As(III) oxidation and no significant difference was observed comparing to results obtained by photolysis. The photolysis experiments (UV radiation only), also carried out in a batch system, showed a high oxidation rate of As(III) (90% in 20min). The influence of different matrices (well water, river water and public water supply) were evaluated. Additionally, the effect of As(V) concentration, generated during the oxidation process, was studied. Continuous photolysis experiments using only UV radiation were performed, resulting in a high As(III) oxidation rate. Using a flow rate of 5mLmin−1 and an initial concentration of As(III) 200µgL−1, gave an oxidation percentage of As(III) of up to 72%, showing a simple and economical alternative to the oxidation step of As(III) to As(V) in the treatment of water contaminated with arsenic.
•High efficiency of a continuous flow process for As(III) oxidation by photolysis.•High As(III) oxidation rates in a short time of UV radiation exposure.•Evaluation of matrices effect in the As(III) to As(V) oxidation.
In this paper, a mathematical model was developed to describe the dynamic behavior of a bioreactor in which a fermentation process takes place. The analysis took into account the bioreactor ...temperature controlled by the refrigerant fluid flow through the reactor jacket. An optimal LQR control acting in the water flow through a jacket was used in order to maintain the reactor temperature during the process. For the control design, a reduced-order model of the system was considered. Given the heat transfer asymmetry observed in reactors, a model considering the fractional order heat exchange between the reactor and the jacket using the Riemann–Liouville differential operators was proposed. The numerical simulation demonstrated that the proposed control was efficient in maintaining the temperature at the desired levels and was robust for disturbances in the inlet temperature reactor. Additionally, the proposed control proved to be easy to apply in real life, bypassing the singularity problem and the difficulty of initial conditions for real applications that can be observed when considering Riemann–Liouville differential operators.
This paper presents the results of investigating the dynamics of an economic system with chaotic behavior and a suboptimal control proposal to suppress the chaotic behavior. Numerical results using ...phase portraits, bifurcation diagrams, Lyapunov exponents, and 0-1 testing confirmed chaotic and hyperchaotic behavior. The results also proved the effectiveness of the control, showing errors below 1%, even in cases where the control design is subject to parametric errors. Additionally, an investigation of the system in fractional order is included, demonstrating that the system has periodic, constant, or chaotic behavior for specific values of the order of the derivative.
Chlorophyll Sensitization of TiO2: A Mini-Review Fuziki, Maria E. K.; Tusset, Angelo M.; dos Santos, Onélia A. A. ...
Reactions (Basel, Switzerland),
12/2023, Volume:
4, Issue:
4
Journal Article
Peer reviewed
Open access
Recent studies have shown that chlorophyll sensitization can improve the performance of semiconductors like TiO2 in photocatalytic reactions and light-harvesting technologies, such as solar cells. ...Faced with the search for renewable energy sources and sustainable technologies, the application of this natural pigment has been gaining prominence. The present work addresses some of the main possibilities of chlorophyll-TiO2 combination, presenting the most relevant aspects affecting chlorophyll extraction and TiO2 sensitization.
TiO2-based semiconductors are formidable photocatalysts for redox reaction applications. Although N-doped TiO2-Nb2O5 catalysts have already been explored in the literature, studies on their ...antioxidant activity are scarce, and systematic investigations on the effects of synthesis parameters over a wide range of %Nb and NH4OH concentrations are limited. In addition, the relationship between optimal pH and %Nb has not yet been adequately explored. In the present work, the sol–gel synthesis of N-doped TiO2-Nb2O5 catalysts was optimized using a design of experiments approach focused on photocatalysis, adsorption, and antioxidant applications. The samples were characterized by TGA, SEM/EDS, XRD, PZC tests, photoacoustic spectroscopy, and N2-adsorption/desorption experiments. The salicylic acid (SA) degradation tests and DPPH radical scavenging assays demonstrated the superior photocatalytic activity (up to 72.9% SA degradation in 30 min, pH 5) and antioxidant capacity (IC50 = 88.9 μg mL−1) of pure TiO2 compared to the N-doped TiO2-Nb2O5 catalysts. The photocatalytic activity, however, proved to be intensely dependent on the pH and %Nb interaction, and at pH 3, the 25Nb-1N-400 catalyst promoted more significant SA degradation (59.9%) compared to pure TiO2 (42.8%). In the methylene blue (MB) adsorption tests, the catalysts N-doped TiO2-Nb2O5 showed removals at least seven times greater than TiO2 catalysts without Nb.
The present work explored the adsorptive capacity and catalytic activity of rock powders from basaltic and granitic rocks in the discoloration of synthetic and industrial effluents containing the ...yellow dye Basic Yellow 96. The rock powders were characterized with scanning electron microscopy associated with energy-dispersive spectroscopy, photoacoustic spectroscopy, N2 physisorption and X-ray diffraction, the latter confirming the abundant presence of silica in the four materials studied. The basaltic powders presented specific surface areas between 7 and 10 times greater than those of granitic materials, which allowed up to 92% removal of the dye in 3 h of test using the basaltic powder. Despite the smaller area, the granitic materials showed considerable photocatalytic activity in 3 h, 94%, the same as that of the basaltic materials in the photocatalysis. Granitic and basaltic photocatalysts proved to be efficient in the discoloration of synthetic and industrial effluents, although TOC analyses indicated that it was not possible to promote the pollutant mineralization in the industrial effluent. Both artificial light and sunlight were effective in the photocatalysis of the dye, although the former was slightly faster.
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