مجله مواد نوین
سال دوازدهم شماره 4 (پیاپی 46، زمستان 1400)

In this study, multi wall carbon nanotubes (MWCNTs) were utilized as powerful nanoadsorbants for efficient removal of Omeprazole (OMP) from water samples and comprised with graphite (GR). Effective parameters on removal efficiency including, pH, contact time and ionic strength were optimized by using one factor at a time optimizing method. Results showed that maximum removal of OMP was occurred at pH=5.0 after 30.0 min for both MWCNTs and GR. Kinetic models were employed to investigate the data corresponding to the adsorption of OMP on the surface of MWCNTs and Gr. Results revealed that the pseudo second-order model for adsorption of OMP on the surface of both MWCNTs and GR indicate the high ability of this model for representation of the data. Adsorption equilibrium studies indicated that the Langmuir isotherm efficiently represented both MWCNTs and GR adsorption data. Maximal adsorption capacity for 25.0 mg L-1 of OMP was calculated about 166.706 mg g-1 and 16.321 mg g-1 for MWCNTs and GR, respectively. The thermodynamic of adsorption process was investigated. Results exhibited that adsorption of OMP on the adsorbents is an exothermic process. As a result, this study can be used to remove ibuprofen from hospital and domestic wastewater.

The lack of an appropriate dispersibility of Graphene Nanoplatelets (GNP) in different hydrophilic and hydrophobic media and their poor interaction to form bundles is one of the most important problems of this material. Therefore, in the present study, in order to perform covalent functionalization of GNP as well as increase the dispersibility in aqueous media, firstly it is created carboxylated with oxidation method on the GNP (Gr). Then, polyvinyl alchol (PVA) with the long chain can be a good candidate to functionalize on the surface of Gr for decorating divalent cations as a linkage and/or bridge and to solve the problem of lack of dispersibility. Also, it can provide good colloidal stability in aqueous media. So, after performing a reaction between PVA and Gr structure, structure and morphology of functionalized PVA-Gr to covalently were investigated by Raman spectroscopy and transmission electron microscopy (TEM), respectively. after covalently-functionalized nanofluids (PVA-Gr/water), with different weight concentrations of 0.025%, 0.05% and 0.1% were prepared. The stability and thermophysical properties such as thermal conductivity, viscosity and density of the above nanofluids have been studied. Then, the convective heat transfer coefficient, pressure drop, performance index and pumping power of the prepared nanofluids for different weight concentrations under turbulent flow regime (0.03-0.12 lit/s) were studied. The results show that as the flow rate and weight concentration of PVA-Gr in nanofluids increase, the convective heat transfer coefficient enhances, which PVA-Gr/water nanofluids illustrate the maximum enhancement in the heat transfer coefficient for all weight concentrations in comparison with pure water.

One of the main problems in oil and gas pipelines is abrasion corrosion on the edges of the flow channel in the plug and ball valves. Under normal conditions, the gas is moving at a pressure of about 145 bar and an approximate speed of 70 feet per second; The suspended particles in the gas collide with the edges of the flow channel and cause severe erosion on them. Abrasion resistance of steels depends mainly on their surface properties and can be increased by increasing the surface hardness by friction stir processing (FSP). In this study, A216-WCB steel, which is used in the manufacturing of casting parts for valves, flanges and fittings, was processed using a friction stir process for one and three passes. The microstructure, hardness and wear properties of the processed area were investigated. The results showed that two distinct zones, the stir zone (SZ) and the thermo-mechanical affected zone (TMAZ), are formed in the processed zone. Due to the friction stir process, the ferrite grain size in the stirring region decreased from 25 microns to about 3 microns. The hardness of the stir zone increased from 165 Vickers to about 780 HV. Also, the abrasion resistance of the stirring area increased up to 2.5 times.

In this study a direct electrochemical copolymerization of pyrrole-formyl pyrrole (Py-co-FPy) was carried out by copolymerization of formyl pyrrole and pyrrole in LiClO4 aqueous solution under constant current of 480 µA for 200 s. The (Py-co-FPy) copolymer was characterized using field emission scanning electron microscope (FESEM), energy-filtering transmission electron microscope (EFTEM), thermal gravimetric analysis (TGA) and Electrochemical Impedance Spectroscopy (EIS). The FESEM images showed that the synthesized copolymer had a hollow whelk-like helixes structure. Moreover, the whorls on the bodies of (Py-co-FPy) copolymer whelk have well-ordered periodic nanostructures that provides a great high ratio of surface to volume. The Impedance study results confirm that (Py-co-FPy) copolymer layer can improve the electron conduction 2.5 times higher than PPy. The conjugated structure between Py and FPy in the presence of methine group can cause the enhancement of conductivity compared to polypyrrole. TGA analysis reveals that the Py-co-PPy copolymer has more thermal stability compared to polypyrrole.

Bismuth vanadate is one of the most widely used semiconductors for photoelectrochemical water splitting using sunlight due to its activity in the presence of visible light, stability, and cost-effectiveness. In addition to having a suitable band gap, this semiconductor has disadvantages such as high electron-hole recombination. In this research, with the aim of reducing electronhole recombination and increasing the efficiency of bismuth vanadate photoelectrodes, templated mesoporous titanium dioxide prepared by P123, F127, and Brij 58 copolymers were used.

The effect of three and two-block copolymers on the properties of prepared mesoporous synthesized titanium dioxide and their effect on the bismuth vanadate photoelectrode was investigated by FE-SEM, XRD, UV-vis, and BET analyses. These copolymers changed the porosity by creating cavities of different sizes, resulting in different loads of bismuth vanadate on titanium dioxide.

To evaluate the photoelectrochemical results, LSV and electrochemical impedance spectroscopy were performed on the photoelectrodes. Absorption in the visible region showed an increase in current at a potential of 1.23V vs RHE and a low charge transfer resistance in Meso TiO2 / BiVO4 samples. The results showed that the templated mesoporous titanium dioxide increases the activity of bismuth vanadate up to 2.5 times.