A novel green synthesis of zero valent iron nanoparticles (NZVI) using three plant extracts and their efficient application for removal of Cr(VI) from aqueous solutions

In the present study, NZVI particles were synthesized from the plant extracts including Rosa damascene (RD), Thymus vulgaris (TV), and Urtica dioica (UD). The FTIR arspectshowed that polyphenols, proteins and organic acids which serve as reducing and stabilizing agents play a significant role in the synthesis of NPs and reduce the possibility of aggregation of NPs compared to chemical techniques of NPs synthesis. The amount and type of compounds in plant extracts affect the structure and also agglomeration of NPs after adsorption process. Based on the results, the highest removal efficiency occurred at pH 2. With increase in contact time and amount of dose, the percentage removal increases. Inversely, increase of initial concentration of Cr(VI) decreases the removal efficiency of the contaminant. These nanoparticles have a high adsorption capacity. Accordingly, by applying a dose of 0.2 g/l and contact time of 10 min, the three NPs yielded >90% removal efficiency. Also, for 1 min contact time, the percentage removal was 94.87%, 83.48% and 86.8% for RD-Fe, UD-Fe and TV-Fe, respectively. By an increase to 25 min, the removal percentage reached to 100% for TV-Fe and UD-Fe. Moreover, 30 min was required to remove Cr(VI) completely by RD-F.     

Bending behavior of empty and foam-filled beams: Structural optimization

Bending crash tests on empty and foam-filled square aluminum beams have been performed. Furthermore, in order to find more details about crash processes, finite element simulations have been done. In terms of improving crash behavior of the aluminum beams, the crashworthiness optimization procedure has been applied to maximize specific energy absorption of the square beams with the target energy absorption. A comprehensive study about the strengthening effect of foam in the filled beam has been performed and finally the optimization technique has been implemented to find the optimum foam-filled beam that absorbs the same energy as optimum empty tubes with lower weight.     

Peroxi-coagulation degradation of C.I. Basic Yellow 2 based on carbon-PTFE and carbon nanotube-PTFE electrodes as cathode

The electrochemical treatment of solutions containing C.I. Basic Yellow 2 (BY2) in aqueous solutions with carbon-PTFE (polytetrafluoroethylene) and carbon nanotube (CNT)-PTFE electrodes as cathode has been studied. The fabricated electrodes were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The amount of electrogenerated H₂O₂ on the surface of these electrodes was investigated, too. The results showed that the amount of H₂O₂ obtained with the CNT-PTFE electrode was nearly three times higher than that of carbon-PTFE electrode. The decolorization efficiency of BY2 in peroxi-coagulation process reached 62% and 96% in the first 10 min by carbon-PTFE and CNT-PTFE electrodes at 100 mA, respectively. The effect of operational parameters such as applied current, initial pH and initial dye concentration was studied in an attempt to reach higher decolorization efficiency. The degradation and mineralization of BY2 using CNT-PTFE electrode were followed by total organic carbon (TOC) and GC–MS analysis. The results of TOC measurements indicated that peroxi-coagulation with carbon-PTFE allowed 81% mineralization after 6 h of electrolysis; whereas peroxi-coagulation with CNT-PTFE yields 92% mineralization under the same conditions. GC–MS analysis verified the identity of intermediates and a reaction pathway based on them was proposed.     

Rapid and efficient diazotization and diazo coupling reactions on silica sulfuric acid under solvent-free conditions

A convenient, rapid, one-pot method for the synthesis of azo dyes has been developed by the sequential diazotization–diazo coupling of aromatic amines with NaNO₂, silica sulfuric acid and coupling agents under solvent-free conditions at room temperature. Using this method, several types of aromatic amine, containing electron-withdrawing groups as well as electron-donating groups, were rapidly converted to the corresponding azo dyes in good yield. The ensuing aryldiazonium salts supported on silica sulfuric acid (aryl diazonium silica sulfates), ArN₂^+?OSO₃–SiO₂, were sufficiently stable to be kept at room temperature in the dry state. The use of mild reaction conditions and an inexpensive procedure are further advantages of this method.     

Computational fluid dynamic simulation of MVG tray hydraulics

The flow pattern and hydraulics of a Mini V-Grid valve (MVG) tray is predicted by using computational fluid dynamics simulation. A 3-D CFD model in the Eulerian framework was used. The simulation results for MVG tray are compared with that of sieve tray. The sieve tray geometry and operating conditions are based on the Solari and Bell’s sieve tray [1]. The MVG tray differs from that of Solari and Bell’s sieve tray solely by the difference in design of available openings for the flow of gas. The simulation results show that the clear liquid height and the pressure drop of MVG tray are lower than that of sieve tray whereas the liquid velocity is higher and contacts of phases are good. The simulation results of sieve tray are in agreement with the experimental data of Solari and Bell [1].     

Latest Developments in Modeling and Characterization of Joining Metal Based Hybrid Materials

Advanced materials consist of several materials systems that exhibit complementary properties for multi‐purpose applications. Joining of dissimilar materials is a critical and challenging advanced manufacturing technique to develop novel hybrid materials with properties fully transferred. The “bonding strength” of a joint is crucial for its integrity and performance. The bonding strength is affected by a range of parameters that can be better understood, controlled, and optimized via both experimental and analytical approaches. In this paper, the authors review the theoretical and experimental studies of the interface inside several metal based composites. The scope includes interface bonding's critical parameters, characterization techniques of joining processes, potential applications, and their future perspectives. The review is significant to develop advanced manufacturing techniques for heterogeneous materials and to design innovative heterogeneous systems for various medical, electrical, electronics, industrial, and other daily life applications that involve the broad range of “joining” processes.

     

CO2/CH4 separation using prepared and characterized poly (ether-block-amide)/ZIF-8 mixed matrix membranes

In this study, poly (ether-block-amide) (Pebax-2533) based mixed matrix membranes were prepared by incorporating various contents of synthesized zeolitic imidazole framework (ZIF-8) nanoparticles into the polymer matrix. The membranes were fabricated via a solution casting–solvent evaporation technique. The results of gas permeation through the membranes revealed that the addition of the ZIF-8 into the polymer matrix enhances both permeability and CO₂/CH₄ selectivity values. As an example, for the mixed matrix membrane comprising 25 wt% of ZIF-8, CO₂ permeability and ideal CO₂/CH₄ selectivity values are 269.73 Barrer and 9.31, respectively, while the corresponding values are 187.54 Barrer and 7.25 for the neat membrane.