Scientia Iranica
Volume:29 Issue: 3, May & Jun 2022

In this study, an eco-friendly approach has been introduced for the synthesis of pyrimido[4,5-b]quinolones and indenopyrido[2,3-d]pyrimidines. This synthesis was done via a three component coupling of 6-amino-2-(methylthio)pyrimidin-4(3H)-one, 1,3-indanedione/dimedone and aromatic aldehydes using Fe3O4@nano-cellulose/Sb(V) as catalyst under solvent-free condition at 70 °C by electrical mortar-heater. The catalyst was separated from the reaction mixture by an external magnet and reused for subsequent reactions. The present procedure offers many advantages such as high yield, easy work-up, simple isolation of catalyst by external magnet and high reusability of the it. The structure of the obtained pyrimido[4,5-b]quinolones and indenopyrido[2,3-d]pyrimidines products were studied by FT-IR, 1H-NMR and 13C-NMR spectroscopic data.

Fluorescence spectroscopy due to its high sensitivity continues to be of extensive attention to analytical chemists. Spectra recording at several interval times while the reaction is preceded, or at various concentrations of complexing agent, are cases of policies by which one can create second-order data by the spectrofluorometric technique. In this case, fluorescence spectra of a mixture of two caffeic acid (CA) and ellagic acid (EA) target analytes were recorded as a function of γ-cyclodextrin (γ-CD) (as an inclusion complexing agent) concentration to produce second-order data. At this point, bilinear least squares/residual bilinearization (BLLS/RBL), as a second-order calibration technique, due to its benefits of rapidity, accuracy, simplicity, suitable spectral resolution, and concentration estimation even in the presence of the unknown interference (Second-order advantage), was exploited for deconvolution of trilinear data to obtain fluorescence spectra and concentration profiles of the CA and EA as a function of γ-CD concentrations. A calibration set comprising 10 reference samples was employed to build BLLS/RBL model. The resulting model predictive ability was validated by a test set including 6 samples. The suggested model was effectively exploited to simultaneously quantify the content of CA and EA in 4 fruit juice samples.

The UV-Vis absorption spectra of the discrete magnetic molecules [py.H]3[FeBr4]2Br were calculated based on density functional theory with B3LYP exchange-correlation functional in acetonitrile solution. The molecule was dissolved dilutely in acetonitrile to ensure that its experimental response can be attributed to a single dispersed molecule without significant interaction to other molecules. The experimental UV-Vis absorption spectra show four typical peaks in UV region and three peaks in visible region. A number of different basis sets are employed to compare the experimental data with the theoretical absorption spectra on different levels of basis sets. The comparison of experimental data with theoretical computation shows that choosing 6-311++G** improves computational results mainly in visible region and makes little differences between results based on DFT and TDDFT in other wavelength domains, especially in UV wavelengths. The simulated results are of importance in simulating the response of these molecular magnets as a discrete asymmetric unit to applied light.

A computational investigation of some novel charge transfer complexes, prepared by the adsorption of dyes on SnO2 and ZnS, was carried out using semiempirical PM3 method. Natural dyes Chlorogenic acid (DTC) and Flavone (PHC) were adsorbed on 1  1  1 SnO2 and ZnS crystals to form SnO2-DTC, SnO2-DTC-PHC, and ZnS-DTC adsorption complexes. The electronic absorption spectra calculated using PM3 method showed a large bathochromic shift to 958 nm and 577 nm for SnO2-DTC and SnO2- DTC-PHC, respectively, suggesting the charge transfer complex formation. Moreover, the bandgap was reduced to 1.29 and 2.15 eV as compared to 3.4 eV of pristine SnO2. Subsequently, the adsorption of DTC on ZnS was accomplished and calculations were performed to determine the spectroscopic properties of the complex, where a considerable red shift was observed for ZnS-DTC as well. The semiempirical PM3 calculations pointed to stability of SnO2-DTC, SnO-DTC-PHC, and ZnS-DTC as predicted from negative adsorption energy values. The energies of Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) determined from single-point energy calculations were concomitant with the proposed photocatalytic mechanisms.

Designing a catalyst that combines the activity, selectivity, simple recovery, and follows the green chemistry instructions is of great importance. In the present study, Fe3O4@Pectin~Imidazole~SO3H-Cu(II) was synthesized as an efficient and biopolymer-based magnetic catalyst for the oxidation of benzyl alcohols to aldehydes using tert-butyl hydroperoxide (TBHP) as an oxidant under solvent-free conditions. The catalyst was characterized using Fourier Transform Infrared Spectroscopy (FT-IR), Powder X-Ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM), Field Emission scanning electron microscopy (FE-SEM), Energy dispersive spectroscopy (EDX), Transmission electron microscopy (TEM), and inductively coupled plasma (ICP) atomic emission spectroscopy. The results indicated that our catalyst was quite active in oxidizing the benzyl alcohols to their corresponding aldehydes in the presence of TBHP. The efficiency with low catalyst loading, convenient work-up, isolation of pure products, use of inexpensive metal instead of precious metals, solvent-free condition, use of eco-friendly support, and also the sustainability of catalyst up to at least 5 consecutive runs without a special drop-in activity are some of the remarkable advantages of this protocol.

In the present study, activated carbon prepared from cedar wood was synthesized, ‎via NaOH activation, and optimized to be used as the adsorbent for Pb2+ removal ‎from aqueous solutions in a batch process mode. The physicochemical properties ‎of the synthesized adsorbent were examined by SEM, FTIR and BET analysis. In ‎order to determine the optimum operational conditions, the effects of different ‎parameters including pH, adsorbent dosage, contact time, temperature, and initial ‎Pb2+concentration on the adsorptive performance of synthesized samples were also ‎investigated. According to the obtained results, the highest Pb2+ ion adsorption ‎capacity (971.9 mg/g) took place at the optimum operational condition of pH=4, ‎adsorbent dosage of 0.025 g/L, contact time of 60 minutes, 300 ppm of Pb2+ and ‎‎30 ℃. The results showed that among Langmuir, Freundlich, and Temkin ‎isotherms, the obtained data were fitted the best with the Freundlich model. ‎Additionally, the process of Pb2+ adsorption was consistent with the pseudo-‎second-order kinetics model, indicating that chemical adsorption was the dominant ‎mechanism of adsorption. Finally, according to the calculated thermodynamic ‎parameters, i.e., ∆H°, 〖∆S〗^° & 〖∆G〗^°, Pb2+ adsorption on activated cedar ‎wood can be considered as an exothermic and spontaneous process.‎

The adsorption of methylparaben (MP) on Calgon carbon (F400) and Norit-type granular activated carbons (GACs) from aqueous solutions was examined. The influence of humic acid (HA) on adsorption of MP under different pH conditions was evaluated. The adsorption isotherm results are well described by Freundlich model. The MP adsorption capacity on F400 and Norit GACs was found to be of 150 mg/g. In the presence of 2.357 mg/L HA total organic carbon (TOC), the maximum MP adsorption capacity on F400 GAC at pH 7 was increased to 2.2 folds. The Norit-type GAC had a comparatively higher uptake capacity of MP than F400 GAC. The key mechanism for MP adsorption onto the F400 GAC was through the hydrogen interaction between –OH functional group of the MP molecules. The MP adsorption capacity on Norit GAC was increased from 5 to 100 mg/g at pH 7.

This research aims to investigate the parameters affecting the electromagnetic (EM) stimulation of an oil well. To hit the target, the CST simulator and Box-Behnken were implemented to find the sensitivity of the EM stimulation regarding rock and fluid properties. Seven factors of the frequency, brine water salinity, water saturation, oil dielectric constant, rock dielectric constant, porosity, and initial temperature were analyzed by employing 62 simulation runs. The dielectric constants of brine water were obtained using the Stogryn model as a function of brine salinity, frequency, and initial temperature. Based on the distance far from the wellbore, the wellbore region was divided into four sections of 5-6, 6-10, 10-20, and 20-100cm. The most affecting parameter in the domain of 5-20 cm is the brine salinity. The frequency and water saturation were obtained as the next affecting parameters, respectively. The most affecting parameter in the section of 20-100 cm is the frequency. In the section of the 20-10cm, the second and third affecting parameters were found to be the brine water salinity and water saturation, respectively. The highest power loss density at the 5-6cm obtained 4300 watts/m3 while the highest density was almost 1 watt/m3 at the section of 20-100 cm.

In this study, the separations of praseodymium (Pr) and neodymium (Nd) from model NdFeB Magnet-leaching solution were evaluated by two different mixtures, namely Aliquat 336/toluene (system I) and Cyanex 272/kerosene (system II). The operational parameters such as Aliquat 336 concentration (0.30-0.85 mol/L), Cyanex 272 concentration (0.23-0.57 mol/L), pH (2.0-5.0), organic to aqueous phase (O/A) ratio (1-3), and ammonium nitrate (AN) concentration (2.2-5.6 mol/L) were investigated. The impact of the studied parameters on the separation factor were modeled, compared, and optimized by response surface methodology (RSM) based on the central composite design (CCD). The parameters had relatively consistent impact on the extraction efficiency and selectivity of the system I but inconsistent impact for the system II. According to the optimization results of the operational selectivity, the system I was more fitted in which the extraction efficiencies of Pr and Nd were obtained 74.8% and 61.2%, respectively, and the separation factor was 2.10. The obtained values for Aliquat 336 concentration, O/A ratio, pH, and AN concentration were 0.85 mol/L, 1, 5.0, 3.9 mol/L, respectively. Finally, the stripping of metal ions from the loaded organic phase was effectively conducted with 0.1 M hydrochloric acid solution within a contact time of 5 minutes.

The stone-carving robotic manipulators (SCRM) find a broad range of applications due to their high efficiency, wide range of processing and strong flexibility. However, the features of strong disturbance, uncertainty and variation in the parameters make the design of SCRM control systems more complicated. This paper introduced the inverse linear quadratic (ILQ) theory into the SCRM control system. First, we deduced the dynamic equation and state-space equation of the SCRM system with the Lagrange method. Then, the ILQ theory was used to achieve the desired closed-loop poles assignment of the system. To simplify the design process and meet the requirement of practical use, the state feedback optimal control law was determined by an improved ILQ design method. The proposed control scheme has the explicit capacity to achieve the desired joint angle and joint torque control performances, with fewer external disturbances and no sensitivity to changing model parameters. The effectiveness of the proposed control scheme compared with the traditional control strategies is shown in the simulation results. Thus, the vibration of the joint torque during the manufacturing process can be greatly reduced.

Deeper understanding of all aspect of biomass thermochemical conversion is necessary as researchers pursue multiple avenues for energy and environmental sustainability. In this paper, the agglomerative accumulation of soot observed, captured on the inner surface of the exhaust pipe, during the operation of a top-lit updraft biomass gasification system was evaluated to understand its nature and qualities. The soot was evaluated using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy with Energy Dispersion Spectroscopy (SEM-EDS) and Brunauer–Emmett–Teller (BET) analyses. The combustion fuels were bamboo (Bambusa vulgaris) stalk and stem of African balsam (Daniellia olivieri). FTIR analysis revealed the presence of hydroxyl, aromatic double bond, aldehyde, thyiol and carbonyl functional groups. EDS analysis revealed that the elemental carbon content of the soot was found to be 75.05% carbon with 15.13% oxygen. SEM analysis revealed that the soot has a hollow morphology and a lustrous appearance with white tiny grit grains of carbon nano-spheres. The BET analysis revealed that the specific surface area of the soot was 500 m2/g while the pore volume and pore diameter were measured to be 0.218 cc/g and 2.113 nm respectively. The material can find use in water purification purposes, and as an additive in lubricating oils