Pore Diameter Distribution Research Articles

Removal of Anionic and Cationic Dyes from Wastewater Using Activated Carbon from Palm Tree Fiber Waste

This study focuses on using a facile method for the green preparation of activated carbon (AC) from palm tree fiber (PTF) waste. The synthesized cost-effective AC was investigated for the removal of an anionic dye (Congo red, CR) and a cationic dye (Rhodamine B, RhB) from wastewater. The morphological and structural characterization of the synthesized AC were performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), surface area, Fourier transform infrared spectroscopy (FTIR), total pore volume, average pore diameter and pore size distribution, zeta potential, and zero-point charge. To investigate the adsorption efficiency, different parameters such as adsorbent dosage, solution pH, initial dye concentration, and duration were applied using the batch experiments. Various adsorption isotherm and kinetics models were applied to study the adsorption mechanism and dynamics. The results showed that chemical activation with a weak acid (H3PO4) at 400 °C for 30 min is a fast method for the activation of each precursor and produces a high yield. The result of analysis showed an increase in the adsorption capacity at pH 2. The maximum adsorption capacity was 9.79 and 26.58 mg g−1 at 30 min for CR dye and RhB dye, respectively. The optimum adsorbent dosage for the activated carbon from palm tree fiber (PTFAC) was 0.15 g with a high percentage removal of CR (98.24%) and RhB (99.86%) dyes. The adsorption isotherm and kinetic studies were found to be favorable and feasible for assessing the adsorption of dyes with the Langmuir model and pseudo-second-order reaction, respectively. In addition, the AC showed reusability up to five cycles. The results showed that the synthesized AC was environmentally friendly and successfully removed dyes from wastewater.

Synthesis of sulfated zirconium supported MCM-41 composite with high-rate adsorption of methylene blue and excellent heterogeneous catalyst

Zirconia-based mesoporous MCM-41 was successfully prepared then loaded with different content of sulfate (5, 10, 15, 25, 40 and 50 wt.%) through the wet impregnation method. The prepared samples were characterized by numerous methods like N2 adsorption (T= - 196 °C), FT-IR, XRD and TEM images. FTIR spectra of chemically adsorbed pyridine and non-aqueous potentiometric titration were applied to measure the acidity of SO42−/ZrO2@MCM-41 (SZ/MCM-41) catalysts. XRD results showed that the lattice cell parameter (a0) is increased from 37.8 to 39.5 Ǻ with increasing the sulfate content. TEM images of SZ/MCM-41 samples exhibit ordered arrays of mesoporous structure with light and dark contrast and also the formation of nanorods with a diameter of 50 nm. The resulting materials showed a large surface area with a uniform pore diameter distribution. All samples displayed both Lewis and Brønsted acid sites. The catalytic activity of SZ/MCM-41 samples was examined for the preparation of 7-hydroxy-4-methyl coumarin which dramatically enhanced when compared with MCM-41 and Z/MCM-41 and the reaction continued efficiently with a yield of 99.3–89.8 % after reused four times. Furthermore, the adsorption behavior of as-synthesized samples was examined over methylene blue (MB) in the aqueous solution with varying parameters such as dye concentration, pH of the solution and contact time. The prepared samples have a good ability to eliminate the methylene blue from aqueous solution with adsorption capacity equal to 186 mg/g and the equilibrium time of 60 min.

Microstructure analysis of crust during deep-fat or hot-air frying to understand French fry texture

This study aimed to identify the microstructural parameters of the crust which can explain the crispness of French fries. The French fry microstructure was visualized by X-ray micro-computed tomography (XMT). Analysis of the images provided information on the pore size distribution, global porosity of the French fries and local porosity of the crust region. The results revealed that prefrozen French fries do not practically undergo any volume shrinkage during frying. The total porosity created in French fries corresponds to the volume of water loss during frying. The difference between hot-air fried and deep-fat fried French fries was mainly related to the pore diameter and pore size distribution in the crust. Principal component analysis between the sensory and morphometric parameters showed that the volume of small pores (diameter < 0.15 mm) and the span of the pore size distribution in the first millimetres of the crust correlated with the crispness of the product (r > 0.85, P value < 0.05). Thus, a French fry is crispier if the pores generated in the crust have a small median diameter (diameter < 0.2 mm), as well as a large dispersion of pore diameters. • The French fry crust microstructure revealed by XMT is linked to crispness defined by sensory analysis. • The total porosity created in pre-frozen French fries corresponds to water loss. • A higher porosity in the crust generally results in a higher perceived crispness. • A small pore diameter and heterogeneous pore size distribution in the crust improve the crispness.

Regenerating Anode Materials from Scrapped Lithium-Ion Battery by High-Temperature Treatment

Regenerating anode materials from scrapped LIBs draws a significant role in utilizing spent graphite materials and protecting ecological environment. Heat treatment is an essential step in the regeneration process of spent anode. In this study, we focused on the effect of high-temperature treatment on graphite lattice structural reconstruction and electrochemical performance. Prior to heat treatment at different temperatures (e. g. 700, 900, 1100, 1300 and 1500 °C), spent graphite could be purified in sulfuric acid solution. Then, the structural analysis was performed by using XRD tests before and after regeneration, and the results show that when temperature reaches 900 °C, recovered graphite had already formed a good crystallinity. Additionally, the analysis of size distribution, surface area and pore diameter distribution were performed to characterize physical properties. The results showed that heat-treated graphite at 900 °C (HTT-900) displayed the optimal physical properties, which was close to that of commercial graphite. Furthermore, HTT-900 retained an outstanding initial specific capacity (358.1 mAh/g at 0.1 C) and a remarkable cycle stability (capacity retention of 98.8% after 100 cycles). Moreover, the reversible capacities of HTT-900 at 0.1-2.0 C and another 0.1 C reached up to 356.8, 340.1, 306.1, 242.6, 69.7 and 359.2 mAh/g, respectively.

Mechanical Properties and Micro Structure of Cement Concrete in Freeze-Thaw Environment

In order to find the declay law of mechanical property and the performance difference after salty water and fresh water freeze-thaw cycle, freeze-thaw cycle environments under the salty water and fresh water are simulated. The compressive strength, dynamic elastic modulus and the mass lost are tested. The pore structure parameters are also tested by MIP. Plot the pore diameter distribution curve. The result shows that the compressive strength and dynamic elastic modulus are all decreased. The degree of these two properties decreasing under salty water freeze and thaw recycle is more than the one under fresh water. The parameters of porosity and critical pore diameter become larger. The amount of pores whose diameter is between 100nm and 1000nm increase. The amount of pores whose diameter is under 100nm decrease. The deteriorate degree of pore structure is deeper in salty water than in fresh water.

Электронно-микроскопические исследования распределения пор по диаметрам на сорбционной поверхности ультрафильтрационных мембран УАМ-50, УАМ-100, УПМ-К, УПМ-100

В работе обоснована актуальность заявленной тематики, определено место работы среди дру-гих публикаций в области исследования пористости мембран. На основе литературного обзора изуча-емой области и сформулированной цели проведен выбор исследуемых типов ультрафильтрационных мембран, представлены их основные характеристики (рабочее давление, удельный поток растворителя, коэффициент задерживания, рабочий диапазон рН, максимальная температура). Применена методика электронно-микроскопического исследования распределения пор по диаметрам на поверхности уль-трафильтрационных мембран УАМ-50, УАМ-100, УПМ-К, УПМ-100, включающая в себя фиксацию изображения поверхности мембран с помощью электронного микроскопа, перенос в среду автомати-зированного проектирования AutoCad 2018, визуальный выбор четырех равномерных зон, площадью по 1∙106 нм2 с описыванием окружностью пор при использовании программы, экспорт данных с вычис-лением радиальных размеров на поверхностном (активном) слое мембраны в нм. Посредством про-грамной функции AutoCad 2018 находяться главные характеристики (диаметр, площадь каждого эле-мента), затем определялся коэффициент засоренности. Для оценки погрешности определения размеров пор анализировали 5 электронных изображений, полученных для различных участков поверхности ис-следуемой мембраны. Процедуру обработки каждого электронного изображения повторяли 10 раз. В результате статистической обработки результатов относительное стандартное отклонение не превы-шало 0.1. С помощью функции описательной статистики программой Microsoft Excel 2010 определя-лись среднеквадратичное отклонение, средний диаметр пор и производилось построение гистограмм, графиков функции плотности распределения вероятностей и нормального распределения для исследу-емых мембран от распределения диаметров пор.Установлено, что распределение пор по диаметрам на поверхности активного слоя исследуе-мых ультрафильтрационных мембран описывается законом нормального распределения (закон Гаусса). Получены эмпирические выражения функции нормального распределения пор по диаметрам. Анализ экспериментальных исследований методом электронной микроскопии, стандартных средств обработки данных Microsoft Excel 2010, AutoCad 2018 показал, что для образцов мембран УАМ-50, УАМ-100, УПМ-К, УПМ-100 средний диаметр пор на поверхности находится в интервале от 54 до 70 нм

Relationship Between Capillary Water Absorption Value, Capillary Water Absorption Speed, and Capillary Rise Height in Pyroclastic Rocks

The existence of water is one of the most effective factors in deterioration of natural building stones. In the process of deterioration, capillary water absorption is the most significant procedure of water penetration into the building stones. Pyroclastic rocks have been widely utilized as building stone especially in historical buildings and monuments since ancient times in the Central Anatolia in Turkey. Nowadays, this type of rocks is used in the restoration of historical buildings as well as in the construction of modern buildings. Pyroclastic rocks are highly susceptible to deterioration process. Capillary rise has a significant influence on water penetration into building stones. Therefore, it is quite important to identify the factors affecting the values of capillarity, capillary rising speed, and capillary rise that define capillary water absorption in these rocks. To this end, pyroclastic rock samples in different textures were compiled from the Cappadocia region, in Central Anatolia. First, petrographic, mineralogical, geochemical, physical, and pore diameter distribution properties of the samples were determined in the laboratory. Then, capillarity values with capillary rise and capillary rise speeds dependent on time were established. Based on the data obtained, correlation coefficients between matrix percentage and capillary water absorption rate and capillary rise values of pyroclastic rocks were calculated and found to be as 0.850 and 0.891, respectively. Thus, the article proposes a new empirical equation to practically calculate the capillary rise value depending on the matrix percentage (MP) and median pore diameter (MPD) values.

Pore Network Modeling of Microporous Layers for Polymer Electrolyte Fuel Cells

Liquid water accumulated in the catalyst layer (CL) and gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC, PEMFC) results in performance deterioration due to inhibition of oxygen transport to the cathode CL (Flooding). To enhance the drainage in the GDL, the application of a microporous layer (MPL) is effective to the CL side of the GDL substrate [1, 2]. To elucidate the effects of two-phase flow on the oxygen transport in an MPL for its optimized designs, we model three dimensional porous structures of in-house MPLs with pore network model (PNM) [3, 4] for convective air permeation and oxygen diffusion. Pore diameter distribution derived by a focused ion beam scanning electron microscope (FIB-SEM) is employed in the PNM. Air permeation measurements combined with oxygen diffusion measurements with changing wetting liquid saturation (Galwick, Porous Materials Inc., USA) by using gas chromatography validate the model.AcknowledgmentsThe authors are indebted to graduate students, Messrs. Yuhang Liu, Kentaro Harano, Dingfeng Chen for help in the modeling and experiment. Thanks are offered to Professor Kohei Ito of Kyushu University for valuable discussions. The authors acknowledge Ms. Chie Uryu of International Research Center for Hydrogen Energy, Kyushu University for operating the FIB-SEM.References Nakajima H, Konomi T and Kitahara T. 2007. Direct water balance analysis on a polymer electrolyte fuel cell (PEFC): Effects of hydrophobic treatment and micro-porous layer addition to the gas diffusion layer of a PEFC on its performance during a simulated start-up operation. Journal of Power Sources 171: 457-463. Kitahara T, Konomi T and Nakajima H. 2010. Microporous layer coated gas diffusion layers for enhanced performance of polymer electrolyte fuel cells. Journal of Power Sources 195: 2202-2211. Gostick J, Aghighi M, Hinebaugh J, Tranter T, Hoeh MA, Day H, Spellacy B, Sharqawy MH, Bazylak A, Burns A, Lehnert W and Putz A. 2016. OpenPNM: A pore network modeling package. Computing in Science & Engineering 18: 60-74. http://openpnm.org/. Accessed on September 14, 2020

Direct synthesis of Cerium(Ⅳ)-Incorporated mesostructured cellular foam for immobilization of penicillin G acylase

Cerium-incorporated mesostructured cellular foams (Ce-MCF) as a novel support has been synthesized successfully for immobilizing penicillin G acylase (PGA) through a Lewis acid-base interaction. The PGA was firmly immobilized on Ce-MCF by interacting with the surface robust Lewis acid sites due to the incorporation of Ce, which is the essence of this immobilization method. The Ce-MCF support was synthesized through the direct hydrothermal synthesis technique with citric acid complexant and categorized by XRD, SAXS, nitrogen sorption, XPS, TEM , and pyridine-IR. The results showed that the Ce-MCF samples had ordered long-range structure, large pore diameter, large specific surface area, pore-volume, narrow pore diameter distribution and strong Lewis acid site. According to the results, the PGA/Ce-MCF has high enzymatic activity and improved operational stability greatly. The PGA/Ce-MCF's initial enzymatic activity remains 10,573 U/g to hydrolyze penicillin G potassium salt, similar with that of PGA/Si-MCF. In addition, the Ce-MCF samples have much higher operational stability than PGA/Si-MCF. Followed by recycling for 10 times, PGA/Ce-MCF preserves 90% of its primary enzymatic activity, which is much higher than 77% of PGA/Si-MCF. A novel immobilization method has been developed for penicillin G acylase (PGA) by a Lewis acid-base interaction. The essence of this method lies in utilization of a Ce-MCF (mesostructured cellular foam) nanoporous material. The cerium incorporated into the framework of MCF can significantly enhance the Lewis acidity of MCF. The high operational stability and enzymatic activity of PGA/Ce-MCF achieved during the hydrolysis of penicillin G potassium salt, suggesting that the enzymes can be firmly immobilized by the Lewis acid sites whilst retaining high activity. • PGA can be firmly immobilized on Ce-MCF by the Lewis acid sites whilst retaining high activity. • After recycled for 10 times, PGA/Ce-MCF retains 90% of its initial enzymatic activity, much higher than 77% of PGA/Si-MCF. • The cerium incorporated into the framework of MCF can significantly enhance the Lewis acidity of MCF. • The Ce-MCF support was synthesized by a pH-adjusting hydrothermal synthesis method with addition of citric acid.

Estimation of Cortical Bone Microstructure From Ultrasound Backscatter.

Multichannel pulse-echo ultrasound using linear arrays and single-channel data acquisition systems opens new perspectives for the evaluation of cortical bone. In combination with spectral backscatter analysis, it can provide quantitative information about cortical microstructural properties. We present a numerical study, based on the finite-difference time-domain method, to estimate the backscatter cross section of randomly distributed circular pores in a bone matrix. A model that predicts the backscatter coefficient using arbitrary pore diameter distributions was derived. In an ex vivo study on 19 human tibia bones (six males, 13 females, 83.7 ± 8.4 years), multidirectional ultrasound backscatter measurements were performed using an ultrasound scanner equipped with a 6-MHz 128-element linear array with sweep motor control. A normalized depth-dependent spectral analysis was performed to derive backscatter and attenuation coefficients. Site-matched reference values of tissue acoustic impedance Z , cortical thickness (Ct.Th), pore density (Ct.Po.Dn), porosity (Ct.Po), and characteristic parameters of the pore diameter (Ct.Po.Dm) distribution were obtained from 100-MHz scanning-acoustic microscopy images. Proximal femur areal bone mineral density (aBMD), stiffness S , and ultimate force Fu from the same donors were available from a previous study. All pore structure and material properties could be predicted using linear combinations of backscatter parameters with a median to high accuracy (0.28 ≤ adjusted R2 ≤ 0.59). The combination of cortical thickness and backscatter parameter provided similar or better prediction accuracies than aBMD. For the first time, a method for the noninvasive assessment of the pore diameter distribution in cortical bone by ultrasound is proposed. The combined assessment of cortical thickness, sound velocity, and pore size distribution in a mobile, nonionizing measurement system could have a major impact on preventing osteoporotic fractures.

Comparative Evaluation of Pore Structure Heterogeneity in Low-Permeability Tight Sandstones Using Different Fractal Models Based on NMR Technology: A Case Study of Benxi Formation in the Central Ordos Basin

Based on the NMR T2 spectra of all of the samples, the applicability of the single fractal model and the multifractal model for the quantitative investigation of pore diameter distribution heterogeneity is analyzed. Then, the relationships between pore structures, physical properties, and fractal dimensions calculated by each model are discussed. The following results have been achieved. (1) Model 1 can be used to study the heterogeneity of different fluid states (including saturation and bound water) or partial pore size distribution, and the calculated fractal dimension has the best correlation with permeability. This model is mainly suitable for type I samples with macropores developed. (2) Models 2, 3, and 4 can quantitatively analyze the heterogeneity of the overall pore diameter distribution. These calculated fractal dimensions have a good linear relationship with porosity, T2cutoff, T2gm, and other physical parameters, which are mainly suitable for type II, III, and IV samples with micropores developed. (3) There is a negative correlation between multifractal dimensions calculated by model 4 and single fractal parameters calculated by models 2 and 3. Micropores and macropores are the key pore sizes that affect the variation of single fractal parameters, while mesopores are the key size affecting the variation of multifractal parameters. (4) The selection of a reasonable T2 spectrum range has become a key to determine the calculation accuracy of models 2 and 3. Above all, models 1 and 4 should be given priority in characterizing pore distribution heterogeneity of tight sandstone gas reservoirs.

Efficient dye removal from wastewater by functionalized macromolecule chitosan-SBA-15 nanofibers for biological approaches

Today, one of the major concerns of environmental health is the purification of colored wastewater due to its high contamination. The present study focused on the synthesis and comprehensive characterization of environmentally friendly electrospinning membranes based on Chitosan cross linked with SBA-15 as a novel adsorbent for dye removal. Unlike most micro structured adsorbents, CTS-SBA-15 nanofibers with their special properties such as density, porosity, high surface-to-volume ratio, small and layered structures, etc. have a very high adsorption capacity to remove macromolecular pollution and microorganisms. Adsorbents were synthesized and functionalized, then produced by electrospinning instrument in the form of nanofibers sheets. In this study, FT-IR, XRD, FE-SEM, TEM, and tensile tests were employed to characterize the functional groups, surface morphology and pore diameter distribution of nanofibers. The influence of different analytical parameters was investigated to obtain the optimum conditions for the adsorption process. The optimum conditions for adsorption process obtained as following: type of adsorbent: CTS-SBA-15-NH2, pH: 2, adsorbent dosage: 0.05 g, initial concentration: 60 and 40 mg/l and contact time: 40 min, which followed from the Langmuir and Freundlich isotherms. So, it was found that CTS-SBA-15 can act as inexpensive and efficient adsorbent for the dye removal from the contaminated water.

Influence of Al-B grain refiner on porosity formation of directionally solidified Al-Si alloys

This work aims to present a perspective for porosity formation in three different alloys: A356, A413 and A380.1 by taking into account the addition of Al-B grain refiners: AlTi5B1 and Al3B. The directional solidification method was used, and microstructural changes of the alloys and its correlation with porosity formation were investigated. Pore size, number of pores, average pore length and distribution of pores were statistically analyzed. Also, external shrinkage was examined, and the volume of external shrinkage was calculated. It was found that there was a relationship between external shrinkage and the size and number of pores. As the size and number of pores internally decrease, external shrinkage increases. Additionally, porosity is decreased in all the three Al-Si alloys when Al-B grain refiners are used. The distribution of pore diameters is low when AlTi5B1 is used. Grain refiners have a different effect on porosity formation of Al-Si alloys with regard to their solidification morphology.

Double-pore structure porous Mo–Si–B intermetallics fabricated by elemental powder metallurgy method using NH4HCO3 as pore-forming agent

The multiphase porous intermetallic compounds Mo3Si-Mo5Si3-Mo5SiB2 of a double-pore structure has been successfully fabricated by combining the in situ reaction synthesis with the pore-forming agent method. The effects of NH4HCO3 content and size on porosity, pore diameter distribution, permeability, and compressive strength were investigated systematically. The results show that: with the NH4HCO3 increasing from 0 to 60 vol%, the total porosity increases from 46.6% to 73.2%, the big pores volume increases from 2.3% to 69.4%, the gas permeability increases from 5.34 × 10−7 l/(min · cm2 · Pa) to 1.74 × 10−4 l/(min · cm2 · Pa), and the compressive strength decreases from 392 MPa to 14.8 MPa; on the other side, with the NH4HCO3 size increased from 48 μm to 230 μm, the parameters of this porous intermetallics changed slightly except to the significant increase of big pores diameter. An exponential equation of σ c = σ s (1-ρ)1/0.254 based on generalized mixture rule (GMR) has been put forward to quantitatively describe porosity-compressive strength behaviors. Results from this study indicate the potential applications in various filtration environments by tailoring the shape, contents, and size of the pore-forming agent.

Preparation and characterization of novel thin film composite nanofiltration membrane with PVDF tree-like nanofiber membrane as composite scaffold

In the field of seawater and waste water purification, thin film composite membranes (TFC) have drawn great attention. In this study, a novel TFC membrane was fabricated based on the layer of polyvinylidene fluoride (PVDF) via a one-step process formed tree-like electrospun nanofiber membranes (TENMs). Compared with conventional support membrane, TENMs possessed high surface porosity, low tortuosity, high-proportioned interconnect pore, and minimum average pore size below 200 nm. Therefore, it has great potential in the preparation of high-performance TFC nanofiltration(NF)membrane. The effect of additive Tetrabutylammonium chloride (TBAC) concentration in the morphology and structure of TENMs was also discussed. Results indicated that adding 0.025 mol TBAC in the spinning solution would facilitate the formation of tree-like structure with the smallest pore size of 130–140 nm and narrowest pore diameter distribution, as well as the densely packed branching nanofibers. Furthermore, the effect of TENMs structure and surface morphology on the formation of polyamide film were also studied. It was found that the ultrafine branches embedded into polyamide matrix formed “directed water channels”, which increased water molecules transporting speed. Rejection test revealed that a rejection rate above 97% against MgSO4 solution and 76% against NaCl solution could be achieved, indicating the potential in the application of water purification.

Fiber Foam Tuffcrete Structure and Properties Formation on the Basis of Volcanic Tuff Dusting Waste

The results of studies on the foam concrete and fiber concrete development based on volcanic tuff dusting waste are presented. The foam concrete compositions that can significantly reduce the Portland cement consumption and at the same time increase its strength properties are proposed. To study the dispersed reinforcement parameters’ effect on the properties of fiber-reinforced concrete, an experiment with a second-order composite rotatable plan such as a regular hexagon was conducted. The use of fosta nylon fibers in foam concrete increases their strength properties and positively affects the structure. Dispersed fibers not only reinforce the matrix, but also significantly change its structure indicators, in particular, porosity indicators (uniformity of pore diameter distribution, average pore size), which in turn affects the strength characteristics of the material.

Study on the Preparation and Properties of Talcum-Fly Ash Based Ceramic Membrane Supports.

Ceramic membrane method for moisture recovery from flue gas of thermal power plants is of considerable interest due to its excellent selection performance and corrosion resistance. However, manufacturing costs of commercial ceramic membranes are still relatively expensive, which promotes the development of new methods for preparing low-cost ceramic membranes. In this study, a method for the preparation of porous ceramic membrane supports is proposed. Low-cost fly ash from power plants is the main material of the membrane supports, and talcum is the additive. The fabrication process of the ceramic membrane supports is described in detail. The properties of the supports were fully characterized, including surface morphology, phase composition, pore diameter distribution, and porosity. The mechanical strength of the supports was measured. The obtained ceramic membrane supports displays a pore size of about 5 μm and porosity of 37.8%. Furthermore, the water recovery performance of the supports under different operating conditions was experimentally studied. The experimental results show that the recovered water flux varies with operating conditions. In the study, the maximum recovered water flux reaches 5.22 kg/(m2·h). The findings provide a guidance for the ceramic membrane supports application of water recovery from flue gas.

Compressive Strength and Durability of FGD Gypsum-Based Mortars Blended with Ground Granulated Blast Furnace Slag.

One new flue gas desulfurization (FGD) gypsum-based binder is attempted in this article, which is made up of FGD gypsum, ground granulated blast furnace slag (GGBS) and ordinary Portland cement (OPC). Influences of raw materials, chemical activators, and curing conditions on the compressive strength of this new binder-based mortar, as well as its durability performances and microscopic characteristics, are investigated in consideration of utilizing FGD gypsum as much as possible. Results show that the compressive strength of this new binder-based mortar under normal curing conditions could increase along with GGBS dosages from three days to 90 days. The compressive strength of one selected mix proportion (FG-4550), which contains the highest dosage of FGD gypsum (45 wt.%), is much the same as those containing the highest dosage of GGBS. A better compressive strength of FG-4550 under normal curing conditions could be gained if the fineness of GGBS is improved. The activated effect of CaCl2 on the compressive strength of FG-4550 is superior to that of Ca(OH)2 under steam curing conditions. FG-4550 shows a good capacity for resistance to water, a low shrinkage ratio, but poor compressive strength after 30 freeze-thaw cycles. Based on the mineralogy of X-ray diffraction, the morphology of scanning electron microscopy and the pore diameter distributions of 1H nuclear magnetic resonance, the compressive strength of this FGD gypsum-based mortar mainly depends on clusters of ettringite.

Graded synthesis of highly ordered MCM-41 and carbon/zeolite composite from coal gasification fine residue for crystal violet removal

The utilization of coal gasification slag currently has become a central issue in both coal and environmental science. Coal gasification slag has been used as raw materials to synthesize the porous materials. However, for the synthesis of these materials, the high temperature was needed, and not all coal gasification slag could be converted to. This work developed a new strategy to graded synthesis of MCM-41 and carbon/zeolite composite from coal gasification fine residue (CGFR) under mild conditions. By this way, graded preparations of valuable porous materials from CGFR could realize the efficient conversion and utilization of CGFR. The synthesized MCM-41 exhibited highly ordering feature with hexagonal arrays and the straight 1D channels. The MCM-41 zeolite had large surface areas and narrow pore diameter distribution. The different synthesis conditions of MCM-41 from CGFR, such as acidification process, gel pH, crystallization temperature and crystallization time were discussed. As to the synthesized carbon/zeolite composite, it presented a P-type zeolite with the flower-like shape on the substrate of carbon with low degree graphitization. The carbon/zeolite composite had the total specific surface area of 189.27 m2 g−1 and exhibited thermal stability below 300 °C. Meanwhile, the synthesis of carbon/zeolite composite with different alkali dissolution time was also investigated. Besides, the adsorption experiments of toxic crystal violet in water indicated that these two porous materials had potential applications in adsorption and removal of harmful pollutants.

Experiment and optimization study on the radial graded porous volumetric solar receiver matching non-uniform solar flux distribution

Radial graded porous volumetric solar receiver is designed to match the non-uniform solar flux distribution. Based on the computed tomography and image-processing techniques, uniform and radial graded porous volumetric solar receivers are reconstructed. The 3D printing technique and suitable post processing are implemented to fabricate complex porous samples using super-alloy Inconel 718 as material. Both experimental and numerical studies are conducted to investigate the fluid flow and heat transfer processes in porous volumetric solar receivers. The results present that the 3D printed porous samples are suitable for solar thermal energy absorption and high temperature utilization. As for uniform porous receivers, porous media with small pore diameter has larger thermal efficiency because of enhanced convective heat transfer. Compared with the uniform porous receiver with highest thermal efficiency, the radial graded porous volumetric solar receiver with large pore diameter inside could further relatively increase the thermal efficiency by 4.1% while relatively decreases the flow resistance by 8.6%. The reasonable distribution of pore diameter of porous media could regulate the mass flow distribution and direct more air to the high heat flux region. Moreover, local overheating phenomenon is observed in the uniform porous receiver using air as heat transfer fluid. By applying the coupled optimization method, an optimum pore diameter distribution is determined for the radial graded porous volumetric solar receiver.