Journal of Particle Science and Technology
Volume:5 Issue: 1, Spring 2019

The present study describes two different methods for the preparation of superabsorbent polyacrylamide (PAAm) hydrogels for application in farming of sandy soil. The two methods were employed to induce the crosslinking of the polymer matrix. In the first method a PAAm paste was exposed to gamma rays, while in the second method the polymer was thermally treated in the solid phase. Crosslinked PAAm hydrogel samples prepared by both methods were characterized by gel content, water absorbance, Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The parameters affecting the gel content, including the irradiation dose and temperature, were investigated. The obtained results suggested that the gel content of the PAAm hydrogel crosslinked by radiation and thermal treatments increases as the irradiation dose and temperature increased. Furthermore, the results indicated that the water absorbance reaches the maximum values at an irradiation dose of 30 kGy and a temperature of 120 ºC. SEM showed that the synthesized hydrogels have a porous morphology. The PAAm hydrogel samples were loaded with urea and their release behavior was examined in water. Finally, the effect of hydrogels on the growth of beans (Vicia faba L.) was studied. The radiation crosslinked samples displayed better stability during the farming period and enhanced plant growth in comparison with the samples crosslinked by thermal treatment.

Cobalt oxide is a candidate material for thermochemical heat storage via reversible reduction and re-oxidation reactions.  In this research, the relationship between Gibb’s free energy (ΔG) with reaction temperature (T) and oxygen partial pressure (PO2) and the relationship between equilibrium temperature (Te) and PO2 were investigated theoretically. It was found that an increase in reduction temperature decreases the reduction ΔG. Also, increasing PO2 increases the Te and reduces ΔG. In addition, isothermal reduction kinetics of Co3O4- 5wt% Al2O3 (CA) and Co3O4- 5wt% Y2O3 (CY) were investigated at various temperatures (1040-1130°C) by thermogravimetric analysis. Results showed that the CA sample desorbs more oxygen than the CY sample in similar conditions. A model-free method was used to calculate the reduction activation energies. It was found that activation energy required for reduction of CA and CY samples, depending on conversion fraction (α), is in the range of 40-65 kcal/mol and 25-50 kcal/mol, respectively. Furthermore, results showed that the reduction activation energy of CA and CY samples decreased and increased as the conversion fraction (α) increased, respectively. The difference in the performance of alumina and yttria additions on the reduction of cobalt oxide was attributed to their ionic radii difference, the ability to create new compounds with different decomposition temperatures, and their different effect on the sintering of cobalt oxide particles.

Corrosion can lead to tremendous defects, and several approaches are applied to alleviate the destructive consequences. In this study, two chitosan and gelatin biopolymers with glutaraldehyde applied as a cross-linker were used to cover the surface of carbon steel grade E. Results showed that a cross-linker decreased water and ions from reaching the metal surface; thereby, increased the stability of the coating. The experiment design was performed with Design-Expert 7.0.0 software and Response Surface Method (RSM) was used to optimize the concentration of chitosan, gelatin and glutaraldehyde. The coatings quality was investigated with microscopic image. Results showed that the optimum coating consist of 10 g.L-1 chitosan, 5 g.L-1 gelatin and 1 mL.L-1 glutaraldehyde. Electrochemical Impedance Spectroscopy (EIS) test were done to compare the anti-corrosion property. The results demonstrated that this optimized coating can enhance the corrosion resistance of coated carbon steel up to 6 times. This can be attributed to a homogenous uniform coating on the metal surface confirmed with EIS. The scanning Electron Microscope (SEM) showed coating covered pores and scratches of bare coupon and the Atomic Force Microscope (AFM) corroborated the coverage of this composition on the carbon steel surface.

Multi-walled carbon nanotubes (MWCNTs) containing hydroxylgroups (OH-MWCNT) were modified by functionalization with 3-[2-(2-aminoethylamino)ethylamino]propyl trimethoxysilane (TRI). Adsorption isotherms of pure CO2 and SO2 on the pristine MWCNT, OH-MWCNT, and amine functionalized MWCNT (amine-MWCNT) were measured at two temperatures of 313.2 K and 323.2 K and pressures up to 2.1 bar by a static volumetric method. Capacities of all three types of adsorbents for CO2 adsorption are greater than those of CO2. The performance of amine-MWCNT in adsorpting CO2 is higher than the other two adsorbents. The average saturated capacity of amine-MWCNT for adsorption of pure CO2 at 313.2 K are about 38.6% and 20.8% higher than OH-MWCNT and pristine-MWCNT, respectively. Corresponding values for adsorption of pure CO2 are about 51.3% and 89.65%. Also, the equilibrium adsorption capacity of pristine MWCNT and amine-MWCNT for mixtures for CO2, nitrogen, and water vapor at 299.2 K was obtained. The equilibrium adsorption of CO2 increases as the water content increases in the presence of diluting gas (nitrogen). Freundlich and Langmuir equations were fitted on experimental adsorption isotherms. The Freundlich equation predicts experimental data better than the Langmuir equation. A multi-layer perceptron artificial neural network (ANN) model has been also proposed for predicting adsorption experimental data. The average and maximum difference between experimental data and values predicted by ANN model are about 3% and 24%, respectively.

In this work, the synthesis and characterization of a new magnetically supported Mo6+ complex have been reported as a catalyst for epoxidation of olefins. For this purpose, a new silylating compound containing a birhodanine moiety, i.e. [(E)-5-(3-(3-(trimethoxysilyl)propyl)-4-oxo-2-thioxothiazolidin-5-ylidene)-3-phenethyl-2-thioxothiazolidin-4-one] (TMOS-BIRD) has been synthesized and used for silylation of magnetite nanoparticles (MNPs). The magnetically supported catalyst was then prepared by deposition of dioxomolybdenum(VI) adduct, dichlorobis(dimethylformamide)dioxomolybdenum (MoO2Cl2(dmf)2), on MNP@BIRD. The prepared supported magnetic catalyst was characterized in detail by FT-IR, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and energy-dispersive X-ray (EDX) analyses. Cyclooctene was used as a model substrate to optimize the epoxidation reaction conditions, and the prepared magnetically retrievable catalyst was then used for epoxidation of cyclohexene, cyclooctene, styrene, indene, trans-trans-cis-1,5,9-cyclododecatrien, 1-octene, 1-heptene, α-pinene, 1-dodecene and trans-stilbene using tert-butyl hydroperoxide (TBHP) as oxidant under solvent-free conditions. The catalyst showed excellent conversion, good turn over frequency, and a short reaction time at 95 °C for epoxidation of cyclooctene. the formula is not displayed correctly!

We plan to study the synthesis of Zn2SnO4 nanoparticles via a sol-gel method and evaluate their catalytic activity in the three-component reaction including active enolates, active methylene, and aldehydes leading to the formation of the pyran derivatives. Functionalized pyrano[3,2-c]chromenes and pyrano[4,3-b]pyran derivatives were synthesized via a one-pot, a three-component reaction under ultrasonic irradiation conditions in good to excellent yields. The catalyst was characterized by XRD, FESEM and TEM analyses.