Volume 7, Issue 1

In the present work, synthesis of iron oxide nanoparticles (NPs) using continuous flow microreactor (MR) and advanced flow™ reactor (AFR™) has been investigated with evaluation of the efficacy of the two types of MRs. Effect of the different operating parameters on the characteristics of the obtained NPs has also been investigated. The synthesis of iron oxide NPs was based on the co-precipitation and reduction reactions using iron (III) nitrate precursor and sodium hydroxide as reducing agents. The iron oxide NPs were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, and X-ray diffraction (XRD) analysis. The mean particle size of the obtained NPs was less than 10 nm at all flow rates (over the range of 20−60 ml/h) in the case of spiral MR, while, in the case of AFR™, the particle size of NPs was below 20 nm with no specific trend observed with the operating flow rates. The XRD and TEM analyses of iron oxide NPs confirmed the crystalline nature and nanometer size range, respectively. Further, magnetic properties of the synthesized iron oxide NPs were studied using electron spin resonance spectroscopy; the resonance absorption peak shows the g -factor values as 2.055 and 2.034 corresponding to the magnetic fields of 319.28 and 322.59 mT for MR and AFR™, respectively.

The search for less time-consuming and inexpensive methods for the synthesis of disulfides continues to be a hot subject of research. Herein, we report that diisopropylamine ( i Pr 2 NH) can act as a very effective catalyst for this process. The oxidative coupling of aryl thiols was carried out in the presence of catalytic amount of i Pr 2 NH in air (room temperature) in acetonitrile, without metal catalyst, additives, or external activators. This procedure opens a low-cost, green, and industrially applicable synthetic pathway to obtain aryl disulfides.

(NH 4 ) 2 RuCl 6 is an important precursor in the synthesis of Ru powder with high-purity requirement. In this study, high-purity (>99.999 wt%) micro-sized (NH 4 ) 2 RuCl 6 pieces were synthesized by distillation and precipitation from crude Ru powder. Then, the thermal decomposition behavior of the (NH 4 ) 2 RuCl 6 pieces was investigated. The decomposition process included two stages. First, (NH 4 ) 2 RuCl 6 was decomposed from 255.0°C to 314.0°C, with the endothermic peak located at 309.4°C. At this stage, HCl and NH 3 were released, while the dense micro-pieces were transformed to loosened micro-pieces due to the thermal decomposition. Then, the solid phase [(NH 3 ) 4 Ru 3 Cl 12 ] kept decomposing from 314.0°C to 352.7°C, HCl and N 2 were released, and agglomerated Ru particles were achieved. Thermogravimetric analysis-differential thermal analysis-mass spectrum coupling (TG-DTA-MS) was used to monitor the thermal decomposition process and identify the released gaseous phases, respectively. The solid phases in different stages were characterized by high-temperature X-ray diffraction (HTXRD). A good understanding of the processing and thermal decomposition of (NH 4 ) 2 RuCl 6 is crucial in the creation of Ru products.

Abstract: Zeolite NaY was successfully synthesized by a dynamic hydrothermal crystallization method with water glass and kaolin from Yunnan Provice of China. The products were modified to serve as hydrocracking catalysts. The influences of aging conditions of the structure-directing agent and crystallization methods were examined. The compositions and microstructures of zeolites were characterized by field emission scanning electron microscopy, X-ray diffraction and Brunauer-Emmett-Teller (BET). The catalytic performance for hydrocracking was briefly evaluated. The results showed that appropriate aging temperature and time of structure-directing agent were beneficial to nucleation. Combined with static crystallization, the yield of zeolite NaY prepared by the dynamic crystallization method was significantly improved, relative crystallinity increased from 46.91% to 74.18%, and conversion in hydrocracking accordingly increased from 39.58% to 55.93%.

Abstract: An environmentally benign method to synthesize silver nanoparticles (SNPs) using the leaf extract of Bridelia retusa was developed. The UV-Vis absorption spectrum of the synthesized SNPs displayed a surface plasmon peak at 420 nm. Scanning electron microscopy (SEM) revealed the irregular shaped nanoparticles, and energy dispersive X-ray (EDX) ascertained the presence of metallic silver by showing a strong signal at 3 eV. The crystalline structure of metallic silver was confirmed by X-ray diffraction (XRD). The mean size of the SNPs was calculated as 16.21 nm. Fourier infrared (FT-IR) spectroscopic studies displayed specific bands for various functional groups and affirmed the function of reduction and stabilization of SNPs. The stability was endorsed by the zeta potential value of −18.1 mV. The results evidenced that this leaf extract-mediated synthesis method is eco-friendly, rapid, and cheap. The catalytic power of the SNPs was investigated for Rhodamine B dye degradation. The SNPs completely degraded Rhodamine B within 9 min; thus, the dye degradation process was very rapid. The pseudo-first order degradation constant was found out to be 0.1323 min −1 . This paves the way for the future development of novel nano-catalysts to reduce environmental pollution.

Edible mushroom ( Agaricus bisporus ) extract was used to synthesize gold nanoparticles (AuNPs) through hydrothermal process (at a pressure of 15 psi and a temperature of 121°C for 15 min). Response surface methodology was applied to monitor the influence of the synthesis parameters, namely: the mushroom extract concentration (1–9 gr DP/100 ml distilled water) and the amount of HAuCL 4 ·3H 2 O solution (8–12 ml) on the particle size and concentration of fabricated AuNPs. The obtained results demonstrated that while the main and quadratic terms of the synthesis parameters had significant (p<0.05) effects on the response variables, their interactions had insignificant effect on them. The results indicated that spherical synthesized AuNPs using 10 ml of HAuCl 4 ·3H 2 O solution (1 m m ) and 1 ml of mushroom extract with concentration of 5 gr DP/100 ml had mean particle size (25 nm) and maximum concentration (534 ppm) and stability (zeta potential of –45.8 mV). The results revealed that mushroom extract could act as both reducing and stabilizing agents due to its bioactive compounds. Fourier-transform infrared analysis showed that polyols and carbonyl groups in mushroom extract had strong effects on formation of stable AuNPs. The fabricated AuNPs exhibited high antifungal activity against Aspergillus flavus as compared to the Aspergillus terreus .

The effect of waste carbonized eggshell and silicon carbide (SiC) wt.% on the dry sliding wear behavior of AA2014 alloy green composites produced by electromagnetic stir casting method was investigated. The percentage of waste carbonized eggshell particles and SiC particles varied from 2.5% to 12.5%. The tribological behavior of AA2014/waste carbonized eggshell/SiC hybrid green metal matrix composites (MMCs) was investigated on a pin-on-disc apparatus. The weight percentages of waste carbonized eggshell and of SiC, normal load, and sliding speed and distance were taken as input process parameters, and wear rate was taken as a response. Response surface methodology was used to plan and analyze the experiment. Minimum wear rate was found to be 8.89×10 −5 mm 3 /m with desirability one at optimum parameters of 1.75 m/s (sliding velocity), 6.5 (carbonized eggshell wt.%), 34.24 N (normal load), 1219.63 m (sliding distance), and 11 wt.% (SiC wt.%). In the confirmation experiment, the experimental wear rate of the hybrid green MMC at optimum parameters was found to be 9.5×10 −5 . Results showed that the experimental wear rate and density of the hybrid green MMC were reduced by about 36.66% and 0.35%, respectively, compared with the matrix.

Several advanced oxidation processes have been performed for the decomposition of ester nitrates (ENs), such as nitroglycerine (NG) and pentaerythritol tetranitrate (PETN). The reaction kinetics for removing NG and PETN by some of the advanced oxidation processes (e.g. UV-H 2 O 2 , Fenton, UV-Fenton) followed the pseudo-first-order model. The reaction rates in different systems followed the sequence ENs/UV<ENs/H 2 O 2 <ENs/UV-H 2 O 2 <ENs/Fenton<ENs/UV-Fenton. The effect of various parameters, such as pH, concentration of hydrogen peroxide, and temperature, on the degradation of NG and PETN were studied.

A mathematical model for modeling solid-liquid extraction from plants was developed. Two extraction systems, System I Nicotiana tabacum L.- water and System II Geranium sanguineum L.- water , were investigated. The effect of agitation rate on the mode of the extraction process was studied, as the limit values in the case of internal diffusion for System I and System II were determined. The kinetics of extraction for both systems at determined technological parameters (temperature and solid/liquid ratio) was experimentally investigated. The values of the partial mass transfer coefficient, k , were determined by the Regular regime method. A four-parameter empirical model for prediction of the effective diffusivity, D eff , was also presented. The model adequacy is verified with the experimental data and shows very good coincidence.

This study compares the capacity of Rhodotorula sp. and Bacillus megaterium for Cd(II) removal considering the influence of operating parameters (pH, biosorbent dosage, contact time, temperature, initial metal concentration in solution). The highest Cd(II) uptake of 14.2 mg/g by Rhodotorula sp. was exhibited at 30°C, when working at pH 6 and with 5 g/l biosorbent dosage, after 48 h of contact time. In these conditions, a removal efficiency of 85% was obtained. Similar outcomes were obtained for B. megaterium (15.1 mg/g, 90%) at 35°C, pH 4 and 3 g/l biosorbent dosage, considered as the optimum set of parameters, equilibrium being achieved for a contact time of 20 min. The possible interaction mechanisms between the biosorbents and Cd(II) were evaluated through point of zero charge (pH pzc ), Fourier transform infrared (FTIR), spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX). Data were modeled using pseudo-first and pseudo-second order kinetic models and Langmuir and Freundlich isotherms models. Further studies considered a modeling approach based on linear regression with Durbin-Watson statistics, while the accuracy and precision of experiments were evaluated by ANOVA.