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A nanocatalyst of CaO supported by Fe3O4 magnetic particles was prepared by a chemical precipitation method. It was characterized by various techniques including X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM); Fourier transforms infrared spectroscopy (FTIR), and Hammett indicator. It has been found that the catalyst consists of CaO and Fe3O4 accompanied by CaFe2O4. This composite catalyst was used for the catalytic transesterification of palm seed oil. The results revealed that the highest biodiesel yields for palm seed oil of 69.7% can be obtained under the conditions of (65 °C reaction temperature, 300 min reaction time, 20 methanol/oil molar ratio, and 10 wt.% of CaO/Fe3O4 catalyst loading). The physicochemical properties of the biodiesel produced from palm seed oil were further studied and compared with the ASTM and the EN biodiesel specifications. The results showed that the properties of the biodiesel produced comply with the international standard specifications.

The melting of a phase change material (PCM) inside a horizontal concentric two-pipe heat exchanger is experimentally investigated. The PCM RT-42 (Rubitherm) is contained in the annular space between the inner tube of diameter 25 mm and outer insulated shell of diameter 75mm. The hot water as a heat transfer fluid (HTF) flows inside the inner tube at different temperatures, 60, 70 and 80 °C. The experimental setup involves twelve thermocouples to record the transient temperatures of PCM at different locations. Also, the progress of the solid-liquid front during the melting process is tracked photographically by a digital camera. The experimental findings revealed that the heat conduction, accompanied by the same melting rate around the inner tube of the heat storage unit, is predominant at the beginning of the melting process. As time progresses, the natural convection role is strengthened and causes a higher melting at the top part than is shown at the lower part, which is still dominated by conduction. Also, the melting rate is directly affected by the temperature of the HTF. The melting time is reduced by about 27% and 46% when the HTF temperature varies from 60 to 70°C and 80°C, respectively. The variation of the Nusselt number during the melting process is evaluated. There is a positive influence of the HTF temperature on the energy stored by the PCM.

Electro-Coagulation (EC) method is the most effective electrochemical treatment of the wastewater that contains heavy metals as pollutants such as (lead compounds). It is consumed less energy compared with the other conventional methods. In this work, the Computational Fluid Dynamics (CFD) modeling approach for the simulation of the EC unit was studied. Transport of species, current-voltage distribution, and fluid flow were simulated using the diffusion, Nernst-Planck, and Navier-Stokes equations, respectively. The commercial software (COMSOL 5.4) was used to solve the system of equations that govern this problem. The influence of different parameters such as Hydraulic Retention Time (HRT) (15-45 min), applied voltage (2-10v) rotating speed of electrode (0-150 rpm) on the EC reactor also has been studied. The extracted results from the simulation show how the voltage, current, velocity and concentration of the pollutant and coagulant are distributed in the reactor. Besides, the transient behavior of the lead removal from the water was demonstrated in this work. The obtained results from this study were compared with experimental results. The theoretical results showed a good prediction of lead removal from water by electrocoagulation system and they showed good agreement between predictive and experimental data.

Gas separation membranes are one of the most important processes in purifying natural gas. CO2 reduction of natural gas is essential for purifying the gas and increasing its calorific value. A covalent organic framework (COF) has been developed as a filler in mixed-matrix membranes (MMM) to separate gases. COF materials were chosen because of their economical rate, good thermal and chemical stability, and flexible microporous structure. Mixed matrix membranes (MMMs) have received significant interest for their improved permeability and selectivity in natural gas purification. The results of using COF combined with other chemicals added to MMM. It has been observed that CO2 permeability increases as the COF content in the MMM increases, which enhances the gas-separation performance of the MMM. This review evaluated and analyzed the current scientific and the technical breakthroughs in developing MMMs, especially the unique type of organic fillers, which has been the basis of numerous new research for CO2 separation.

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