Synthesis and Characterization of Blended Cellulose Acetate Membranes

The casting and preparation of ultrafiltration ZnO modified cellulose acetate membrane (CA/ZnO) were investigated in this work. CA membranes were fabricated by phase inversion using dimethylformamide (DMF) as a solvent and ZnO as nanostructures materials. Ultrafiltration (UF) performance, mechanical stability, morphology, contact angle, and porosity were evaluated on both CA- and ZnO-modified CA samples. Scanning electron microscopy (SEM) was used to determine the morphology of the membranes, showing different pore sizes either on rough surfaces and cross-sections of the samples, an asymmetric structure and ultra-scale pores with an average pore radius 0.0261 to 0.045 µm. Contact angle measurements showed the highest hydrophobicity values for the samples with no ZnO addition, ranging between 48° and 82.7° on their airside. The permeability values decreased with the increasing CA concentration in the casting solution, as expected; however, ZnO-modified membranes produced lower flux than the pure CA ones. Nevertheless, ZnO modified CA membranes have higher surface pore size, pore density and porosity, and improved surface hydrophilicity compared with pure CA membranes. The results indicated that the incorporated nano-ZnO tends to limit the packing of the polymer chains onto the membrane structure while showing antifouling properties leading to better hydrophilicity and permeation with consistent UF applications.

Synthesis of ActivaTED Carbon from Plant Raw Materials by a Self-Activation Modified Method

In order to increase environmental safety and reduce the cost of production, a modified method of self-activation for the synthesis of activated carbon from plant wastes - cherry stones and wheat straw. A 5% solution of orthophosphate acid was used as an additional activator. Synthesis of activated carbon at temperatures of 600 °C, 700 °C and 800 °C was performed. It was found that coal from cherry stones has a production of 1.3-1.6 times higher than the production of activated carbon from wheat straw. The obtained coal was studied by electron microscopy and the method of isothermal adsorption / desorption of nitrogen. It is shown that all synthesized coal has a well-developed porous structure, which is determined mainly by micropores. An increase in the synthesis temperature leads to an increase in the specific surface area, the volume of micro-and mesopores and a decrease in the average pore radius. The reduction of the average pore radius for activated carbon from cherry stones occurs at lower temperatures compared to coal from wheat straw.

HIGHLY EFFICIENT REMOVAL OF COPPER(II) IONS FROM AQUEOUS SOLUTION BY NICKEL 2-ETHYLIMIDAZOLATE

Nickel 2-ethylimidazolate was obtained and characterized, which is used in this work as a sorbent for the removal of copper (II) ions. The sample characterization was carried out by scanning electron microscopy, low-temperature nitrogen adsorption. It was found that the obtained sorbent is a microheterogeneous material with the size of individual particles in the range of 0.4-0.7 μm. Nitrogen adsorption isotherms in the pores of nickel 2-ethylimidazolate were obtained. It was found that when processing the experimental data in linear coordinates of TVFM, linearization is reached in coordinates lnV-lnPs/P, which indicates the predominance of mesopores in the structure of nickel 2-ethylimidazolate. The total pore volume was determined from the TVFM linear coordinates. It was 0.21 cm3/g. According to obtained differential pore size distribution, the most probable average pore radius corresponds to 7.5 nm. One of the main characteristics of nickel 2-ethylimidazolate as a sorbent, the surface area was determined by the A.V. Kiselev method and amounted to 703.56 m2/g. The efficiency verification of using nickel 2-ethylimidazolate in the heavy metal ions sorption processes was carried out by removal of copper(II) ions from aqueous solutions by the limited solution volume method at different contact times. The copper(II) sorption kinetics in the presence of nickel 2-ethylimidazolate was studied by processing experimental data in the first and second orders linear coordinates. It was found that the adsorption kinetics of copper(II) ions is described by a second order model, which indicated ion-exchange adsorption. Equilibrium adsorption capacity in the sorbent-solution system is reached at a contact time of 90-120 min.

Impact of water–rock interaction on the pore structures of red-bed soft rock

The physical and mechanical properties of the reservoir bank slope are affected by the water–rock interaction. However, few studies considered the impact of long-term water–rock interaction on the evolution law of mesostructure. Therefore, in this study, the water–rock interaction test was conducted on a slightly weathered red-bed soft rock from the Three Gorges Reservoir area, considering the fluctuation in the reservoir water level. The corresponding pore structure parameters were measured and analyzed based on a scanning electron microscope (SEM) and digital image processing technology. The study showed that: (1) The pore size has been gradually increased, while the number of pores was increased initially and then decreased. Within 12 cycles, the maximum and average pore radius of the rock specimens was increased by 101.02% and 43.32%, respectively, and the porosity has been increased by 26.59%, whereas the number of pores decreased by 22.65%. This indicates the effect of water–rock interaction on the propagation of pores. (2) The pores were changed from oblate to slender by the water–rock interaction. The shape factor was decreased by about 15.79% within 12 cycles. In the meantime, the fractal dimension was increased from 1.20 to 1.28, and more complex structures of pores were observed. (3) The porosity evolution model for the red-bed soft rock was established based on the curve fitting technique. The results can be used as a reference to conceptualize the mesostructure damage of rocks under water–rock interaction.

Experimental Study on the Effect of Long-Term Water Injection on Micropore Structure of Ultralow Permeability Sandstone Reservoir

During the long-term waterflooding (LTWF) in oil reservoirs, the formation is subject to permeability reduction as clay release and fine migration. At present, the mechanisms of permeability impairment in both macroscopic and microscopic pore structures in ultralow permeability reservoirs under LTWF are unclear. This statement epitomizes the main objective of this work: to understand how long-term waterflood changes porous structures and thus compromises permeability. The standard core flow experiments in conjunction with a couple of tests consisting of online nuclear magnetic resonance (NMR), high-pressure mercury intrusive penetration (HPMIP), X-ray diffraction (XRD), and scanning electron microscope (SEM) were performed to determine the mineral compositions, macrophysical properties, and micropore structures of two kinds of cores with different natures of pore distribution (i.e., unimodal and bimodal) before and after LTWF in Yan Chang field China. Results showed that the permeability decreased while the porosity increased after the LTWF. With respect to the pore size distribution, the small pores (SPs) decreased and the large pores (LPs) increased for both cores. For the unimodal core, the distribution curve shifted upwards with little change in the radius of the connected pores. For the bimodal core, the curve shifted to the right with an increasing radius of connected pores. With respect to the characteristic parameters, the average pore radius, median pore radius, structural coefficient, and tortuosity increased, while the relative sorting coefficient decreased. The relative changes of the parameters for the unimodal core were much smaller than those for the bimodal core. With respect to the clays, chlorite accounted for a majority proportion of the clays, and its content increased after LTWF. According to these changes, the mechanism of LTWF at different stages was interpreted. At the early stages, the blockage of the released clays occurred in SPs. Some of the middle pores (MPs) and LPs became larger due to the release and some of them became smaller due to the accumulation. At the middle stage, the blockage of SPs weakened. Some flow channels formed by MPs and LPs became dominant flow channels gradually. The effluxes of particles occurred, resulting in a significant increase in porosity. At the late stage, the stable flow channels have formed. The higher response of the bimodal core to LTWF could be attributed to its higher content of chlorite, which was more likely to accumulate. This study clarifies the mechanism of fine-migration-induced formation damage in microscopic pore structures and the migration pattern of clay minerals in ultralow permeability reservoirs. The work provides potential guidance for optimizing waterflood strategies in ultralow permeability reservoirs.

Dielectric Properties of Cr3+ Doped Al2O3 of a Hierarchical Nanostructure Synthesized Using a Highly Porous Precursor of Tubular AlO(OH)⋅αH2O Fibers

Herein, we have developed a Cr3+ doped Al2O3 of a hierarchical nanostructure by a simple two-step synthesis. A pure AlO(OH)⋅αH2O, as synthesized in forms of small tubular fibers by hydrolysis of Al-metal sheets, is easily doped with selective Cr3+ dosages up to 2.0 mol% using an aqueous CrO3. As-synthesized samples exhibit XRD of a single phase Cr3+: Al2O3 of a rhombohedral crystal structure. Average pore-volume is decreased as 98.1, 89.8, and 61.5 cm3-g-1 in the 0.5, 1.0 and 2.0 % Cr% doped samples, with average pore radius of 1.70, 2.17 and 1.90 nm, respectively, as measure from BET specific surface area. Local Al-O vibrations exhibit IR bands of 400 to 1200 cm-1 intrinsic of oxygen polygons. At room temperature, a duly tailored dielectric permittivity of 480 is obtained in a 2.0 mol% Cr3+:Al2O3 and that is enhanced progressively on heating it over 25 to 300 °C, showing a value 6700 at 300 °C in phonon induced dynamics of charge carriers, useful for solid-state electronics.

Study of activated carbon characteristic from ketaping fruit shell (Terminalia Catappa) as supercapasitors electrode

Studi karakteristik karbon aktif dari cangkang buah ketaping (Terminalia Catappa) sebagai elektroda superkapasitor telah diteliti. Karbon aktif dari cangkang buah ketaping (CBK) disiapkan dengan proses karbonisasi pada suhu 400oC dan Proses aktivasi KOH pada suhu 800oC di bawah aliran gas N2. Karbon aktif CBK memiliki kandungan karbon dengan massa atomik sebesar 97,52%. Karbon aktif CBK memiliki struktur amorf dengan dua buah puncak yang lebar pada sudut 2θ yaitu 24,93o dan 42,93o yang bersesuaian dengan bidang (002) dan (100). Karbon aktif CBK yang dihasilkan memiliki pola serapan dengan jenis ikatan OH, C-H, C=O, dan C=C. Adanya ikatan OH dan C=O menunjukkan bahwa arang aktif yang dihasilkan cenderung bersifat lebih polar. Morfologi permukaan karbon aktif CBK menunjukan distribusi ukuran pori yang merata dan luas permukaan yang besar. Luas permukaan spesifik karbon aktif dari CBK adalah 799,892 m2×g-1 dengan volume total pori 0,080 cm3×g-1 dan jari-jari pori rata-rata 1,9072 nm. Kapasitansi spesifik dari karbon aktif dari CBK adalah sebesar 125,446 F×g-1. Studies on the characteristics of activated carbon from ketaping fruit shells (Terminalia Catappa) as supercapacitor electrodes have been studied. Activated carbon from ketaping fruit shells (KFS) prepared by carbonization process at 400oC and the KOH activation process is carried out at 800oC under N2 gas flow. Activated carbon KFS has a carbon content with 97.52% of atomic mass. Activated carbon KFS has an amorphous structure with two wide peaks at an angle of 2θ 24.93ᵒ and 42.93ᵒ corresponding to the plane (002) and (100). Activated carbon KFS produced has an absorption pattern with OH, C-H, C = O, and C = C bond types. The presence of OH and C = O bonds indicates that the activated charcoal produced tends to be more polar. The surface morphology of activated carbon KFS shows an even distribution of pore size and large surface area. The specific surface area of activated carbon KFS is 799.892 m2×g-1 with a total pore volume 0.080 cm3×g-1 and an average pore radius of 1.9072 nm. The specific capacitance value of activated carbon KFS is 125.444 F×g-1.Keywords: Ketaping, Activated Carbon, Supercapacitor, Activator, Capacitance.

Dynamic Evaluation Method of Caprock Microscopic Sealing in CO2 Sequestration Project

The existing statistical evaluation methods of caprock sealing ability in CO2 sequestration engineering only take into account the sealing ability of caprocks before sequestration but cannot reflect the retained sealing ability of caprock after hydrochemical reactions. A microscopic sealing evaluation method of caprock was established based on the microscopic mechanism of chemical reaction and the breakthrough pressure of caprock which, changes with the time of CO2 sequestration, was taken as the dynamic evaluation index. The results show that the change of microstructure parameters such as the average pore radius after dissolution is the essential reason that affects the variation of the caprock microscopic sealing property. Dissolution or precipitation of different caprock minerals during the chemical reaction process is the key factor that determines the decrease or increase of caprock microscopic sealing property. The evaluation method can reflect the change of microscopic sealing property of the caprocks in different areas as the sealing time goes and provides an efficient and practical quantitative evaluation method for the initial formation site selection and safety sealing in the later stage.

The Production and Characterization of Activated Carbon Electrodes from Pineapple Leaf Fibers for Supercapacitor Application

Elektroda karbon aktif berbasis serat daun nanas (SDN) telah berhasil diproduksi dengan proses tiga langkah berikut ini, yaitu: (i) aktivasi kimia, (ii) karbonisasi, dan (iii) aktivasi fisika. Aktivasi kimia dilakukan dengan menggunakan agen pengaktif KOH dengan konsetrasi 0,3 M. Karbonisasi dilakukan dalam lingkungan gas N2 pada temperatur 600oC dan diikuti oleh aktivasi fisika pada temperatur 850oC menggunakan gas CO2 selama 2,5 jam. Luas permukaan spesifik elektroda 512,211 m2×g-1 dengan volume total pori sebesar 0,093 cm3×g–1, dan jari-jari pori rata-rata 1,199 nm. Morfologi permukaan elektroda karbon aktif menunjukkan adanya serat karbon dengan diameter serat dalam kisaran 101 - 185 nm dan memliki kandungan karbon dengan massa atomik sebesar 84,33%. Elektroda karbon aktif memiliki struktur amorf, yang ditunjukkan oleh dua puncak difraksi yang lebar pada sudut hamburan 24,64 dan 43,77o yang bersesuaian dengan bidang (002) dan (100). Kapasitansi spesifik, energi spesifik dan daya spesifik sel superkapasitor yang dihasilkan masing-masing sebesar 110 F×g-1, 15,28 Wh×kg-1 dan 36,69 W×kg-1. Pineapple leaf fiber (PALF) based activated carbon electrode has been successfully produced using three-step process, i.e. (i) chemical activation, (ii) carbonization, and (iii) physical activation. The chemical activation was carried out using KOH activating agent with a concentration of 0.3 M. The carbonization process is conducted out in N2 gas environment at 600oC and followed by physical activation at a temperature of 850oC by using CO2 gas for 2.5 h. The specific surface area of the electrode is 512.211 m2×g-1 with a total pore volume of 0.093 cm3×g-1, and average pore radius of 1.199 nm. The surface morphology of the electrode shown the carbon fibers with diameter in the range of 101 - 185 nm and carbon content with 84.33% of atomic mass. The activated carbon electrode has an amorphous structure, which is shown by two wide diffraction peaks at scattering angles of 24.64 and 43.77o which correspond to the plane (002) and (100), respectively. The specific capacitance, energy and power of the electrode are 110 F×g-1, 15.28 Wh×kg-1 and 36.69 W×kg-1, respectively.Keywords: Serat daun nanas, Kalium hidroksida, Elektroda karbon aktif, Kapasitansi spesifik, Superkapasitor

Analysis of a flat capillary evaporator with a bi-layered porous wick

A numerical evaluation of the heat and mass transfer concerning a flat capillary evaporator provided by a bi-layered porous wick is presented. The wick has a shape of a flat disc and is assembled between the liquid feeding channel and the vapor chamber. An external heat input is applied into the upper surface of the bi-layered wick, where the working fluid evaporates. The mass and heat transfer are modeled using the mass and energy conservation equations. The model allows to verify the effect of design variables, such as working fluids, dimensions, permeability, average pore radius and thermal conductivity of the wick, in the performance of the capillary evaporator. It can be used as a predictive tool to design similar capillary pumping systems for thermal control of satellite or electronics systems in general.