نشریه پژوهش های کاربردی مهندسی شیمی - پلیمر
سال ششم شماره 3 (پیاپی 21، پاییز 1401)

Research subject:

Low biodegradation rate of plastics, especially different grades of the polyethylene leads to many environmental problems. To reduce these effects, pro-oxidant added to the polyethylene to increase the photo-degradation and subsequently the bio-degradation rate of the polymer matrix. Besides the pro-oxidant, it seems that the photocatalysts can affect on the photo-degradation of the polyethylene and the subject of this study is to examine this idea.

Research approach: 

Photodegradable films of LDPE were prepared by melt blending of the polymer with cadmium selenide (CdSe) and trisilver phosphate (Ag3PO4) as photo-catalysts and manganese stearate as pro-oxidant. The samples were irradiated with visible and ultra-violet light. Scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC) and viscometry measurements were used to investigate the microstructure of the films.

FTIR spectra indicated to increment of the carbonyl index (CI) and vinyl index (VI) of the samples with photo-catalysts. In addition, SEM imaged confirmed higher and more homogeneous photo-degradation for these samples in comparison with other ones. Also, the dynamic-mechanical-thermal analysis showed that the polyethylene samples without the additives had higher modulus compared to other samples. However, the crystallinity of the samples with photo-catalysts increased due to nucleating agent effects of their particles. The viscosity of the samples containing the photo-catalysts and  pro-oxidants decreased significantly and the modeling results showed that this decrement  was due to the polymer chain degradation and reduction of their molecular weights. In general, the results showed that the combination of the photo-catalysts and the pro-oxidants had synergistic effect on the photo-degradation of the LDPE and accelerates its degradation process a lot more in comparison when only the pro-oxidant was used.

Research subject:

 Investigation of the effect of temperature on the polymer flooding performance at the pore scale, leads to an understanding of the behavior of the polymer solution in porous media with varying permeability.

Research approach:

 In this study, the effect of temperature on flooding of polyacrylamide polymer on enhanced oil recovery in two homogeneous micromodels at 25 and 70 °C was investigated. The polymer solution and DW were injected at the injection rate of 1 μl/min up to 1 PV into the micromodel and the amount of produced oil and the movement of the injected fluid in the porous medium were analyzed. In addition, polymer rheology and injected fluid viscosity were measured for better analysis of results. Then the results were compared with flooding of distilled water as the control test.

Examining the flood results, it was found that on the one hand, the temperature factor helped to increase oil recovery by reducing the viscosity of the oil. On the other hand, it has reduced the role of injected fluid viscosity in oil extraction by reducing the viscosity of the polymer. The results showed that the phenomenon of fingering decreases in the case of polymer injection, and the rate of improvement of oil recovery during polymer and water flooding in both micromodels increases with increasing temperature. Also, the rate of improvement of oil recovery during polymer flooding in the A micromodel increased from about 43% at ambient temperature to more than 51% and in the B micromodel from about 51% to more than 60% at 70 °C. In fact, it can be said that the flow pattern and stability of the polymer solution front and consequently the ultimate oil recovery are significantly affected by the morphology of the pores, the shape and the throats pores.

Research subject: 

Poly (2-oxazoline) (PEOX) polymers are a family of synthetic macromolecules with biodegradable and biocompatible features. They resemble polypeptides in structure and therefore, have recently taken put to use in drug delivery. Nonetheless, these polymers suffer from relatively low thermal and mechanical performance and thus are reinforced with nanoparticles as nanocomposites. The molecular details of the reinforcement mechanism of PEOX have not yet been elucidated.

Research approach: 

This research work was done to reach an understanding on interaction of 2-oxazoline-based polymers with 2D nanoscale reinforcements and to shed light on the mechanism of reinforcing the respective nanocomposites. To this end, conformation and dynamics of poly (2-ethyl-2-oxazoline), as a known representative member of this family, near a functionalized graphene nanosheet were studied via classical molecular dynamics for a period of 10 ns. The effects of various temperatures and polymer chain lengths on polymer conformation and dynamics were assessed.

Molecular dynamics snapshots exhibited effective interaction of the polymer chain with the graphene nanosheet leading to adsorption, whereby conformation and dynamics of the chain underwent transition. The adsorbed polymer chain adopted a flat, folded arrangement parallel with the graphene plane. Also, the gyration radius was found to increase, when the polymer chain approached the graphene nanosheet. Pair correlation function curves revealed that the adsorption correlation length was on the order of the repeating unit end-to-end distance. Mean-square-displacement of the polymer chain decreased as it moved towards graphene. An increase in temperature led to a change in structure and dynamics of the adsorbed polymer chain.

Subject:

In this study, the steam reforming of the methanol process was analyzed based on three different inputs including temperature, pressure, and H2O/CH3OH ratio with the use of different Artificial Intelligence methods.

In the first step, Cu-Zn/ZrO2 catalysts were synthesized via the co-precipitation method, and then experimental tests of steam reforming of methanol were performed at a temperature range of 180 –500 °C, the pressure of 1-11 bar, and the H2O/CH3OH ratio of 0.75-3.75 on the Cu-Zn/ZrO2 catalyst in a fixed bed reactor. Afterward, three different methods of Mamdani fuzzy type-1, Mamdani fuzzy type-2, and Sugeno fuzzy were applied in order to develop the models. Using these methods, the developed models only required the heuristics derived from the expert’s knowledge and some experimental data, without needing the calculation of complex kinetic as well as thermodynamic parameters related to the corresponding process. In addition, the structures of the developed fuzzy models were optimized to improve the model performance according to the analysis of the initial results. The model developments didn’t require a high number of experimental data, and this feature is especially interesting when dealing with the process conditions in which data gathering is expensive or the accuracy of data is low.

The overall accuracy as well as the properties of the developed models were compared. The type-2 Mamdani fuzzy model proved to be the best model, using which, the methanol conversion, H2 yield, and CO yield were predicted with accuracies of 67%, 91%, and 83%, respectively.

Research subject: 

Osmosis membrane bioreactor is one of the best industrial wastewater treatment methods. The main advantage of using osmosis process is its operation at low hydraulic pressures which has a better performance in removing pollutants and low energy consumption than other methods                        

Research approach: 

In this research, Nano porous Titanium dioxide powder with a specific surface area and anatase wall was synthesized through a thermal process using cetyltrimethylammonium bromide (CTAB) as a surfactant directing agent and a pore-creating agent.Ultrafiltration nanocomposite membranes were made using modified titanium dioxide (TiO2) (MT) and polysulfone (PSf) by phase the inversion method. The morphology and structure of the prepared membranes and nanoparticles were investigated using by atomic fourier transforms infrared spectroscopy(FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). In this research, bovine serum albumin (BSA) was used as simulated wastewater for the feed solution. The fabricated ultrafiltration membranes were tested in osmosis membrane bioreactor (OMBR) system due to lower energy and fouling. 0.6 % solution of poly (sodium 4-styrene sulfonate) was used as an osmotic solution. Comparative separation performance and antifouling properties of both nanocomposites in several analyzes such as water contact angle measurement, pure water flux and filtration of different concentrations of bovine serum albumin solution. BSA and fouling resistance have been investigated.

 TThe results that Due to the addition of MT nanoparticles to the polymer matrix, the hydrophilicity and surface energy of the membrane increased, which led to the improvement of the membrane performance. The membrane containing 1% titanium oxide nanoparticles showed the best result. For example, for feeding with a concentration of 200 ppm, the water flux increased from 20 to 38.5 L/ m2 h, and the percentage of returning lethal solution decreased from 19.6 to 30 g/ m2 h. The flux recovery in this membrane was 96%, which indicates the antifouling property of the modified nanocomposite membrane.

Research Subject: 

Because of the constant deterioration of environmental conditions, the world faces energy and clean water shortage. To address the water crisis issue, the solar steam generation system has been considered as a suitable technology for seawater desalination due to its competitive features, such as no carbon dioxide emission, low energy consumption, and high efficiency. In modern solar steam generation systems, solar energy is harvested by a photothermal absorber and then converted into thermal energy to heat a certain volume of water and produce steam. Then, the generated steam condenses on the inner surface of the cover, and clean water is collected. The five key features required for solar steam generation system are: high light absorption, low heat losses and heat localization, proper water transfer, and the ability to float on the water surface.

In this study, a solar steam generation system based on a graphite absorber layer is built, and its performance is improved using nickel plasmonic nanoparticles.
In order to investigate the dependency of the performance on the structure, two different layers including cotton and polyester felts are used to transfer water controllable. In this study, the water evaporation rate, surface temperature, and efficiency of the devices are evaluated.

Thermal efficiency and evaporation rate for the system based on the pure graphite absorber is 68.17% and 0.97 kg/m2.h, which increases to 93.57% and 1.37 kg/m2.h, respectively by adding nickel nanoparticles. Using two cotton and PS water managers reveals the importance of the thermal energy and mass transfer balancing in the systems, which strongly affects the devices performance.