Iranian Journal of Chemistry and Chemical Engineering
Volume:39 Issue: 1, Jan-Feb 2020

In this research, at first, Ce-substituted barium ferrite, BaCe0.2Fe11.8O19 was prepared via the sol-gel method as a substrate and then Carbon NanoTubes (CNTs) was synthesized on the surface of the substrate by Chemical Vapor Deposition (CVD) technique. The structure, morphology, and electromagnetic performance of the synthesized nanocomposites were characterized by XRD, FE-SEM, and Vibrating Sample Magnetometer (VSM), respectively. The results indicated that the BaCe0.2Fe11.8O19 particles were coated by CNTs, and the nanocomposite has magnetic properties. Therefore, the electromagnetic properties including complex permittivity (εr), the permeability (µr), and microwave absorption properties were investigated using a vector network analyzer. It was found that in the nanocomposite, because of the presence of CNTs, the Reflection Loss (RL) widely increased. The maximum reflection loss in the frequency range of 8-12 GHz for 2.5 mm thickness was -49.61 dB at 9.0 GHz. The results suggest that prepared nanocomposite can be suitable in the microwave absorbing coatings.

Theoretical study of the electronic structure, NonLinear Optical (NLO) properties, and natural bonding orbital (NBO) analysis of 18-crown-6were investigated using Density Functional Theory (DFT) calculations at the B3LYP/6-311G (d,p) level of theory. The optimized structure is a nonlinear compound indicated from the dihedral angles.  Natural bonding orbital analysis has been analyzed in terms of the hybridization of each atom, natural charges (Core, Valence, and Rydberg), bonding and antibonding orbital's second-order perturbation energy (E(2)). The calculated EHOMO and ELUMO energies of the title molecule can be used to explain the charge transfer in the molecule and to calculate the global properties; the chemical hardness (η), softness(S), global electrophilicity index (w), and electronegativity (χ). The NLO parameters: static dipole moment (µ), polarizability (α), anisotropy polarizability (Δα), first-order hyperpolarizability (βtot) and third-order hyperpolarizability ⟨γ⟩), of the studied molecule have been calculated at the same level of theory. The Molecular Electrostatic Potential (MEP) and ElectroStatic Potential (ESP) for the title molecule were investigated and analyzed.  Also, the electronic absorption spectra were discussed by time-dependent density functional theory (TD-DFT) calculations in ethanol and water solvents. From the experimental conductance measurements, the association thermodynamic parameters (KA, ∆GA, ∆HA, and ∆SA) and complex formation thermodynamic parameters (Kf, ∆Gf, ∆Hf, and ∆Sf) of nano-CuSO4 in presence of 18-crown-6 as a ligand in 10% ethanol-waterer solvents at different temperatures (298.15, 303.15, 308.15 and 313.15K) were applied and calculated.

The MWCNTs-COOH Paste Electrode (MCPE) was successfully used to study the electrochemical behavior of temozolomide in 0.2 M H2SO4 solution, phosphate buffer solution (0.1M PBS, pH 7.4) and 0.1M NaOH solution by Cyclic Voltammetry (CV) technique. The results exhibit that MCPE can remarkably enhance sensing and electrocatalytic activity towards the oxidation and reduction of temozolomide in acidic, neutral, and basic solutions. The effect of the scan rate exhibits the adsorption controlling process. The effect of pH range from 2 to 6 was investigated by cyclic voltammetry technique, from cyclic voltammetry study exhibits the peak current was pH-dependent with a slope of 68 mV/pH.  The detection limit (LOD)) at MCPE were found to be 0.056 mM,0.069 mM and 0.065 mM in 0.1M H2SO4, 0.1M PBS (pH 7.4)  and 0.1M NaOH solutions  respectively by Cyclic Voltammetric (CV) technique. Similarly, from Linear Scan Voltammetric (LSV) technique, the detection limits (LOD) were found to be 0.050 mM, 0.021mM and 0.036 mM in acidic, neutral, and basic solution respectively. The proposed method was successfully applied for the determination of temozolomide in the clinical sample.

In this study, proton conductive composite membranes were produced by using a poly(methylmethacrylate-co-maleic anhydride) (P(MMA-co-MAH)) copolymer and phosphotungstic Acid (PWA) as an additive of the proton conductive agent. P(MMA/MAH) 70/30, 50/50, and 30/70 were synthesized using a free radical polymerization reaction. PWA with a concentration of 2% was added to improve the performance of proton exchange membranes. Composite membranes of P(MMA30-co-MAH70)/PWA had the highest performance, and this improvement was attributed to the presence of MAH and PWA. By increasing the ratio of MMA:MAH from 30/70 to 70/30, thermal stability, ion exchange capacity and proton conductivity of membranes enhanced up to 310°C, 0.85 meq/g, and 5.77 mS/cm, respectively. Moreover, the addition of PWA into the membrane matrix improved the membrane characteristics so that thermal stability, ion exchange capacity, and proton conductivity increased to 317°C, 0.98 meq/g, and 14.42 mS/cm. The synthesized copolymer offered the required properties to be used for the fabrication of a proton conductive membrane.

At this study, thallium (I) ion-imprinted polymer, as a novel sorbent for Tl (I) and comparison with Tl(III) ion-imprinted polymer has been synthesized. This sorbent for preconcentration and solid-phase extraction of Tl(I) ions from aqueous solutions, used. Through preparing the binary complex of Tl(I) ions with 5, 7-dichloroquinoline-8-ol (DCQ) the particles of thallium (I) Ion-Imprinted Polymer (IIP) have synthesized. In the presence of 2-methoxyethanole (porogen) and 2, 2ó-azobisisobutyronitrile (initiator, AIBN) Thermal copolymerization of methyl methacrylate (functional monomer, MMA) and ethyleneglycoldimethacrylate(cross-linkingmonomer, EGDMA) have done. The imprinted ion has removed from the polymer by removing the above particles with 1 mol/L HNO3 to obtain the leached IIP particles. Similarly, Control Polymer (CP) particles, have prepared without thallium (I) ions. The characterization of unleached and leached IIP particles was done by, Fourier-Transform InfraRed (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET), surface area analysis, and X-Ray Diffraction (XRD). As a function of pH, the preconcentration of thallium (I) has studied during rebinding with the leached IIP particles, for determination of thallium in aqueous solution, the weight of the polymer material, the elution and preconcentration times, the concentration of eluent(nitric acid), the volume of the aqueous phase and the volume of an eluent. ElectroThermal Atomic Absorption Spectrometry (ETAAS) has utilized. The method's Detection limit was 0.1 mg/ mL, while the relative standard deviation for five times repeat was 3.5%.

Fluoride, a non-essential element, can enter water resources through several natural processes and human activities. The benefits and risks of fluoride depend on the concentration of this anion on drinking waters. In the present study, the performances of graphene and graphene oxide nanoparticles were investigated for the removal of fluoride from aqueous solution. In the present research, effects of pH, contact time, fluoride initial concentration, adsorbents dosage, as well as temperature in performance of graphene and graphene oxide nanoparticles in removal of fluoride from aqueous solution were examined. Also, isotherms and thermodynamics of the adsorption process were evaluated. For both adsorbents, the maximum adsorption capacities observed during the first 15 minutes at pH=3 and an initial fluoride concentration of 10 mg/L. The results also showed that adsorption of fluoride by graphene and graphene oxide fitted well with Freundlich and Langmuir isotherms, respectively. Furthermore, temperature increase resulted in the adsorption capacity decrease, indicating an exothermic adsorption reaction. According to the results of this research, graphene nanoparticles have higher adsorption capacity of fluoride than graphene oxide nanoparticles.

In this research, zeolite Na-Y was synthesized from Kaolin without an organic template under the non-hydrothermal condition to adsorb sulfur compound. Model fuel desulfurization was optimized by employing the Box-Behnken experimental design with 2 center points, the three parameters, and one response value. The objective was to find how sorption capacity is related to alkali fusion temperature, crystallization time, and aging time. Optimal DBT adsorbent was synthesized at 550 °C, minimum crystallization time, and maximum aging time. The zeolite samples were characterized by FT-IR and XRD. The crystallinity of the samples was lower than the crystallinity of commercial zeolite Y. During zeolite preparation, there was a competition between zeolite Na-Y, Na-P, Na-X and Na-A. The equilibrium results were well fitted by the Langmuir and Freundlich isotherms for the best adsorbent. The largest DBT adsorption capacity, 32.67 mg DBT/g, was calculated for the optimal adsorbent. Pseudo-first order and pseudo-second-order models were evaluated to understand the kinetics of the adsorption process. The reduction of DBT obeyed the second-order model of kinetic. Ni-Y and La-Y zeolites were prepared by the liquid-phase ion-exchange method. The maximum DBT adsorption capacity has been observed for Ni–Y (∼72.25 mg DBT/g) and La–Y (∼66.59 mg DBT/g).

ZSM-11 zeolite was synthesized by hydrothermal treatment and cerium ion was incorporated by the ion exchange method.  The catalytic activity of cerium modified ZSM-11 zeolite was tested for the one-pot synthesis of 4H-pyran derivatives by cyclocondensation of aromatic aldehyde, malononitrile, and ethyl acetoacetate. The synthesized catalyst was characterized by Powder-X Ray Diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Fourier Transform Infrared Spectroscopy, Brunauer-Emmer-Teller surface area analysis and Temperature programmed desorption (ammonia) analysis. The present method offers significant advantages over the reported methods like easy separation of catalyst, simple work-up procedure, an excellent yield of desired products, and reusability of catalyst without significant loose in the activity.

This study was conducted to investigate organoclay prepared using montmorillonite clay with zinc oxide (ZnO) nanoparticles and a long-chain organic surfactant hexadecyltrimethylammonium bromide for the removal of nitrate ion from aqueous solutions. Adsorbents were evaluated by X-Ray Diffraction (XRD), Fourier Transform Infra-Red (FT-IR), Transmission Electron Microscopy, Brunauer-Emmett-Teller, Emission Scanning Electron Microscopy, Energy Dispersive X-ray (EDX) spectroscopy devices and adsorption isotherms of nitrate ion on the best adsorbent were measured at the aqueous concentrations of 40 to 150 mg/25 mL. Activated montmorillonite-ZnO showed a much higher adsorption capacity than other materials. The laminated ZnO and modified surfactant enhanced nitrate ion, thus retaining silicates capacity, montmorillonite (17.24 mg/g) < montmorillonite by laminated ZnO (54.05 mg/g) ˂ montmorillonite modified by a surfactant (86.95 mg/g) < montmorillonite loaded by ZnO and surfactant (119.92 mg/g). The adsorbents for the removal of nitrate ion were studied and then regenerated with HCl solution (0.1 M) to be reused in adsorption. Adsorption data of nitrate ion could be interpreted using Langmuir isotherm and pseudo-second-order kinetic model. Therefore, activation of Montmorillonite/ZnO could be used as a suitable adsorbent to separate nitrate ion from wastewater and groundwater.

MEG is extensively applied in the sour gas industry as a hydrate inhibitor. It is toxic in oral drinking and serious injury or death may result from swallowing of pure ethylene glycol and poses a potential hazard to the environment through impact soil. Glycols are harmful to aquatic life. There is little information about the digestion of MEG in the aerobic reactor. Therefore, the feasibility of MEG removal in the aerobic reactor was investigated. Biodegradation of MEG was done in an aerobic SBR reactor with the capacity of 2000 cc and sanitary wastewater as primarily required microorganisms. The experiments were done in the three stages. In stages 1 and 2, 500cc of reactor content was drawn-off and solutions contain 500 cc of 0.073 (wt %) of MEG (for the first stage) and 0.201 (wt %) of MEG (for the second stage) were added to the reactor. In stage 3, 500 cc of wastewater of MEG removal unit in the 2nd refinery of South Pars Gas Company, Iran with a concentration of 4.021 (wt %) of MEG was added to 1500 cc of reactor content. The feed of stage 1 was pure MEG that was diluted in demineralized water but Feed of stage 2 was a dilution of industrial feed of stage 3. In stage 1, after four days, the removal efficiency of more than 80% was obtained. In stage 2 after six days, the efficiency of 20% was obtained. In stage 3, after seven days, more than 70 percent of MEG removal was obtained. by increasing residence time, the removal efficiency of the reactor could be increased acceptably. Therefore, the MEG solution of more than 4 (wt %) of MEG can be treated biologically.

Herein we report, the robustness of UV/H2O2/Fe2+ system for efficient decolorization of azo-dye Acid Yellow (AY17) solution. It has been found that 88% AY17 decolorized by UV/H2O2/Fe2+ system in 25 minutes under the following optimized conditions; [dye] = 0.14 mM, [H2O2] =1.0 mM, [Fe2+ ] = 0.09 mM, stirring velocity =100 rpm, and pH = 3.0. The decolorization of AY17 by UV/H2O2/Fe2+ system exhibits second-order reaction kinetics. Thermodynamic parameters, activation enthalpy, rH*, (13.76 kJ/mol1), and entropy rS*, (0.034686 J/K) of the dye decolorization were also determined. It was ascertained that electrolytes such as HCO3−, CO32−, Cl−, and SO42− decrease the decolorization efficiency by scavenging the hydroxyl radical generation in the dye solution. Finally, the AY17 decolorization in the tape water sample by UV/H2O2/Fe2+ system was also examined.

Diclofenac is a drug with an analgesic effect that accumulates and results in adverse consequences if it enters the human body more than needed. Low concentrations of diclofenac have been detected in different water sources through leachates of landfills and agricultural areas, human and animal excreta expired drug discharge, and hospital effluents. To eliminate diclofenac from the aquatic environment, different removal methods such as membrane filtration, ozonation, advanced oxidation, Fenton oxidation, electrochemical oxidation, photocatalysis, soil aquifer treatment, ion exchange, and adsorption are studied. Adsorption is considered to be more effective and economical than other methods in case of wastewater treatment. In this review paper, studies on diclofenac removal applying different methods, especially adsorption, are inquired and the adsorbents are divided into two main categories; carbonaceous and other adsorbents. The effect of different parameters such as contact time, pH, adsorbent dosage, initial concentration, and temperature on the adsorption process in the related studies is also mentioned. Furthermore, the equilibrium isotherms, and the adsorption kinetics of the studies were also noted. By studying the literature, it was clear that the pH value was a key parameter among all because it has a main effect on the removal efficiency and it is dependent on the pKa of diclofenac and the pHZPC of the adsorbent.

Aerosol filtration in fibrous filters is one of the principal methods of removal of solid particles from the gas stream. The classical theory of depth filtration is based on the assumption of existing single fiber efficiency, which may be used to the recalculation of the overall efficiency of the entire filter. There are several reasons for inappropriate estimation of the single fiber efficiency including the assumption of the negligible effect of the presence of neighboring fibers and perpendicular orientation of the homogenous fibers. This work aims to investigate the influence of mesoscale inhomogeneity on fibrous filter performance using Computational Fluid Dynamics in models of filters differed by internal structure.

There is a need for knowledge, experience, laboratory, materials, and time to conduct chemical experiments. The results depend on the process and are also quite costly. For economic and rapid results, chemical processes can be modeled by utilizing data obtained in the past. In this paper, an artificial neural network model is proposed for predicting the removal efficiency of Cr (VI) from aqueous solutions with Amberlite IRA-96 resin, as being independent of chemical processes. Multiple linear regression, linear and quadratic particle swarm optimization are also used to compare prediction success. A total of 34 experimental data were used for training and validation of the model. pH, amount of resin, contact time, and concentration were used as input data. The removal efficiency is considered as output data for each model. The statistical methods of root-mean-square error, mean absolute percentage error, variance absolute relative error and the coefficient of determination were used to evaluate the performance of the developed models. The system has been analyzed using a feature selection method to assess the influence of input parameters on the sorption efficiency. The most significant factor was found in pH. The obtained results show that the proposed ANN model is more reliable than the other models for estimating removal efficiency.

In this research, Activated Carbon (AC) was modified using a sodium hydroxide solution for CO2 adsorption. Adsorption experiments were carried out in a batch reactor at a temperature range of 20-80°C and a pressure range of 2-10 bars to investigate kinetic, isotherm, and thermodynamic of the CO2 adsorption process. Activated carbon was modified with NaOH solution concentration in the range of 10-40%. Response Surface Methodology (RSM) was used to assess the combined effect of adsorption CO2 pressure and temperature on CO2 adsorption capacity. Also, RSM was used to obtain the optimum operational conditions. The results showed that modified activated carbon with 30% NaOH concentration (30SH-AC) provided the best performance for CO2 adsorption. The optimum CO2 adsorption capacity was obtained 104.32 mg/g for 30SH-AC at a temperature of 20°C and pressure 6 bars. The sips model was found to be the best for fitting the CO2adsorption isotherm. Also, the kinetic study indicated that the pseudo-second-order model is well-fitted with the experimental data. The thermodynamics parameter shows that the CO2 adsorption process is exothermic.

There are several examples of heuristic rules first proposed from empirical observation, which eventually earned physicochemical validity after the fundamental derivation of a posteriori. This may be the case of Sherwood’s plot – for which a sound rationalization from first principles, entailing enthalpy and mass balances, is provided here; it applies to (fine) chemicals undergoing concentration followed by purification at large, where such costs override the whole processing.

The metal chloride of LaCl3 was chosen to modify the Au-Cu/AC to decrease the noble metal of gold and enhance the catalytic performances. Then a mercury-free catalyst of Au-Cu-La/AC was prepared by the impregnation method, and the fresh Au-Cu-La/AC and Au-Cu/AC catalysts were also characterized in comparison. The catalytic performances of mercury-free catalysts for acetylene hydrochlorination were carried out for 3500 hours in a multi-tubular fixed bed reactor. The additives of La can make the active species dispersed well and retard the aggregation of particles. And the acetylene conversion rate remained stable over 98.5% with the fluctuations, less than 1%, and the selectivity of vinyl chloride maintained the stability of 99% or higher, which indicated that the mercury-free catalyst has excellent catalytic performances for acetylene hydrochlorination.

Water injection is used as a widespread IOR/EOR method and promising formation damages (especially mechanical ones) is a crucial challenge in the near-wellbore of injection wells. The magnesium oxide (MgO) NanoParticles (NPs) considered in the article underwater flooding experiment tests to monitor the promising mechanical formation damage (size exclusion) in lab mechanistic scale include micro-scale classical deep bed filtration model, permeability, and pore size distribution. The averaged upper-scale equations were constructed on the water injection basis on the presence of NPs. The model validation to adjust the equation of state was obtained based on fluid samples from the laboratory and simulation tests. The permeability decline (up to 50% initial permeability) was important when the optimum value of capturing the probability coefficient (pa) is 0.7 mismatched on the conventional simulation results. Pore size distribution in each simulation time step based on retention concentrations determined in the sandstone samples. Formation damage analyses on the presence of NPs showed that modification of the static reservoir models has excellent potential regarding porosity and permeability maps, in large-scale simulation. This study displays an improved approach to NPs’ movement through a porous medium which will act as a benchmark for future waterflooding EOR projects in sandstone oil reservoirs or similar basins all over the world.

Water is the main pillar of human life, which experiencing widespread pollutions that turn clean waters to a non consumption form gradually. Contaminating resources of the clean waters are the human and industries have been made by the human. Because the available water resources for humans and organisms are limited, we must seek recovery of contaminated waters. Some novel oxime and azo dye-based compounds from spiro dihydrofurans were synthesized. All structures were characterized by IR, 1H, and 13C NMR spectroscopy techniques. Some pollutant metal cations of Ni2+, Cu2+, Co2+, Mn2+, and Zn2+ in water and industrial wastewater were examined in the presence of novel ligands. The UV-visible spectral data indicated that 4a selectively absorbed Ni2+ at room temperature and natural pH conditions. Instead, 4b absorbed all cations with exception of Ni2+ under the same condition.

Biological Electronic, Optical Properties, and Vibrational Analysis of 1-benzyl-4-formyl-1H-pyrrole 3carboxamide are studied by using a combination of DFT/B3LYP method and 6-311G (d, p) basis set. Optimized parameters of the title molecule are well-matched with the experiments. The NLO properties of 1-benzyl-4-formyl-1H-pyrrole 3carboxamide have been examined with the help of Polarizability and Hyper-Polarizability. The electronic properties of 1-benzyl-4-formyl-1H-pyrrole 3carboxamide are described with the help of HOMO, LUMO composition. The UV spectra suggest that a strong excitation line occurs at 2.03 eV (160 nm) due to H-2→LUMO (30%). NBO analysis shows that hyper conjugative interaction energy has higher value during LP→ π*, π→ π* transitions. Several biological activities are calculated by PASS software. Docking of the molecule is performed with 5P4Q protein and FF score is -1051.65A.U.

Genus Origanum is an aromatic plant used in folk medicine and as a culinary herb, whose composition of volatile compounds is influenced by the type of species and geographical locations. This research evaluates the effect of altitude on the composition of volatile compounds and the contents of carvacrol and thymol of Origanum x majoricum Cambess and Origanum majorana L. fifty samples of both species were recollected from different altitudes (2500 - 3500 MASL) of the Southern Perú and analyzed by solid-phase microextraction integrated to gas chromatography-mass spectrometry. The principal component analysis was used to differentiate the plants rich in thymol and carvacrol. Peruvian oregano presented 30 different volatile compounds between some monoterpenes (>30%) and some sesquiterpenes (>5%).  The thymol and carvacrol contents of O. majorana and O. majoricum varied between 0.38 and 16.47% and 0.44 and 11.16%, respectively. Interestingly an inverse correlation of the concentration of thymol and carvacrol with their precursors (p-cymene and ɣ-terpinene) was also observed. Altitudes between 3000 and 3200 MASL favors the high proportions of volatile compounds. The data obtained contribute to planning programs for the selection of species and agricultural conditions that allow obtaining a better quality of oregano essential oil.

In this work, the dry reforming of methane was studied using a corona and gliding discharge plasma microreactors. A chemical kinetic model was developed to describe the experimental behavior observed. The kinetic model is proposed based on the assumption that the reactant molecules CH4 or CO2 are attacked by active species produced by the plasma discharges, and the production of this active species are a function of the plasma power. The modelization allowed the prediction of the conversion of the reactants (CH4 and CO2) according to the energy transfer to the gas (). The value is characteristic of the energy cost; the lower β value indicated better efficiency. The value of CH4 was found to be 10.42 and 58.25 J and for CO2 equal to 12.24 and 27.77 J for corona and gliding discharge plasma, respectively. The kinetic model also demonstrated that the methane and carbon dioxide conversion was an exponential function of the plasma energy, and were a linear function of the input energy for a CH4 and CO2 inlet concentration. Our Model also implied that a plasma reactor with a smaller input discharge power has better energy efficiency for CO2 andCH4 conversion.

Although various investigations of Atkinson cycle have been carried out, distinct output power and thermal efficiencies of the engine have been achieved. In this regard, thermal efficiency, Ecological Coefficient of Performance (ECOP), and Ecological function (ECF) are optimized with the help of NSGA-II method and thermodynamic study.  The Pareto optimal frontier which provides an ultimate optimum solution is chosen utilizing various decision-making approaches, containing fuzzy Bellman-Zadeh, LINMAP, and TOPSIS. With the help of the results, interpreting the performances of Atkinson cycles and their optimization is enhanced. Error analysis has also been performed for verification of optimization and determining the deviation in the study.

Polyvinylpyrrolidone/polyaniline emeraldine salt (PVP/PANI) with additives (TiO2, ZnO, NaCl, and Na2SO4) was synthesized via oxidative in situ polymerization. Because of using PVP/PANI as a protective membrane layer and its applications in an electrical device, we investigated the mechanical and rheological properties of PVP/PANI and other composites in order to spread the application of this composite. Mechanical properties of PVP/PANI, PVP/PANI/TiO2, PVP/PANI/ZnO, PVP/PANI/NaCl, and PVP/PANI/Na2SO4 films were studied using the tensile test to obtain tensile strength, elongation at the break, and Young’s modulus. To gain some comprehensive information, rheometry tests were implemented and the storage modulus, loss modulus, and complex viscosity were measured. Interactions between additives and polymers were investigated by NBO analysis. Results from experimental and computational methods show that TiO2, ZnO, and Na2SO4 increase the interactions in the polymer matrix, respectively. However, NaCl weakens these interactions

The most important characteristic of stevia is its high sweetness with zero calories which is due to the presence of Steviol glycosides (SVglys). This research aims to address the effect of salicylic acid (SA) and microelements viz. iron (Fe) and zinc (Zn) under different soil water potentials (-0.5, -3.5, -6.5 and -10 atm) on the production of SVglys and total sugar content in the leaves of stevia. The obtained results indicated that the soil water content and the exogenous application of SA and microelements significantly changed the accumulation of these sweet chemicals in the stevia leaves. The highest values of Stevioside (Stev), Rebaudioside C (Reb C), total SVglys and SVglys yield were obtained in SA + Fe + Zn treatment under the potential of -3.5 atm (76. 82, 2.82, 116.71 mg/g DW and 0.836 mg/g plant, respectively). Also, the HPLC results indicated that the highest rates of Rebaudioside A (Reb A) and the Reb A/Stev ratio (sweetness quality) belonged to SA + Zn treatment under the potential of -3.5 atm (28.63mg g-1 DW and 0.433). The application of SA + Fe + Zn was the most effective in terms of Rebaudioside B (Reb B), Dulcoside A (Dulc A), and total sugar (2.31, 5.73 and 335.8 mg/g DW, respectively). In general, our results suggest that it can be possible to improve the rate of secondary metabolites (SVglys) and hence the sweetness property in stevia leaves by applying SA, Fe, and Zn and particularly by the integrated application of these three agents.

Recently, many economic studies of poly(3-hydroxybutyrate) PHB production on an industrial scale, and the impact of replacing petrochemical polymers by PHB were carried out, clearly indicating that the most crucial factors to reduce the cost of producing biopolymers are allotted to the application of microbial production strains capable of high productivity in inexpensive carbon sources, high cell density cultivation methods, cheap yet effective methods for the extraction of PHB and other polyhydroxyalkanoates (PHAs), and gene transfer from bacteria to plants. We present current strategies to reduce the production price of biological PHA. Because an important part of the PHA production cost is related to the cost of carbon source, the article focuses on the use of natural gas as an inexpensive and readily available C1-carbon source. Since the first and foremost point in PHA production is biomass growth, we discuss different types of bioreactors to be potentially used for efficient biomass production from natural gas, which facilitates the subsequent selection of the ideal bioreactor for PHA production from this substrate. Nowadays, process simulation software can be used as a powerful tool for analysis, optimization, design, and scale up of bioprocesses. Controlling the process design by in silico simulations instead of performing an excessive number of lab-scale experiments to optimize various factors to save in time, material and equipment. Simulation of PHA production processes to find the optimal conditions can play a decisive role in increasing the production efficiency. Computational fluid dynamics and mathematical modeling helps us to achieve a better understanding of the role of different nutrients, flow parameters of gaseous substrates, efficient feeding strategies, etc. This finding leads to higher productivity by prediction of parameters e.g. nutrient supply and biomass concentration time profile and their respective yields.