Effect of Division Methods of the Adsorption Isotherm on the Fractal Dimension of Clay Minerals Calculated Based on the Frenkel–Halsey–Hill Model

2021 ◽  
Author(s):  
Jiaqing Cui ◽  
Xiaohong Niu ◽  
Guorui Feng ◽  
Yanna Han ◽  
Zhu Li
Keyword(s):  
Fractal Dimension ◽  
Adsorption Isotherm ◽  
Clay Minerals ◽  
Hill Model

scholarly journals Total Organic Carbon Enrichment and Its Impact on Pore Characteristics: A Case Study from the Niutitang Formation Shales in Northern Guizhou

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1480 ◽  
Author(s):  
Liu ◽  
Tang ◽  
Xi
Keyword(s):  
Fractal Dimension ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Vitrinite Reflectance ◽  
Guizhou Province ◽  
Type I ◽  
Pore Characteristics ◽  
Hill Model ◽  
Recovery Coefficient ◽  
Niutitang Formation

This study analyzes samples from the Lower Cambrian Niutitang Formation in northern Guizhou Province to enable a better understanding of total organic carbon (TOC) enrichment and its impact on the pore characteristics of over-mature marine shale. Organic geochemical analysis, X-ray diffraction, scanning electron microscopy, helium porosity, and low-temperature nitrogen adsorption experiments were conducted on shale samples. Their original TOC (TOCo) content and organic porosity were estimated by theoretical calculation, and fractal dimension D was computed with the fractal Frenkel–Halsey–Hill model. The results were then used to consider which factors control TOC enrichment and pore characteristics. The samples are shown to be dominated by type-I kerogen with a TOC content of 0.29‒9.36% and an equivalent vitrinite reflectance value of 1.72‒2.72%. The TOCo content varies between 0.64% and 18.17%, and the overall recovery coefficient for the Niutitang Formation was 2.16. Total porosity of the samples ranged between 0.36% and 6.93%. TOC content directly controls porosity when TOC content lies in the range 1.0% to 6.0%. For samples with TOC < 1.0% and TOC > 6.0%, inorganic pores are the main contributors to porosity. Additionally, pore structure parameters show no obvious trends with TOC, quartz, and clay mineral content. The fractal dimension D1 is between 2.619 and 2.716, and D2 is between 2.680 and 2.854, illustrating significant pore surface roughness and structural heterogeneity. No single constituent had a dominant effect on the fractal characteristics.

scholarly journals Experimental Study of the Adsorption of Nitrogen and Phosphorus by Natural Clay Minerals

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Tingyu Fan ◽  
Miao Wang ◽  
Xingming Wang ◽  
Yingxiang Chen ◽  
Shun Wang ◽  
...  
Keyword(s):  
Adsorption Isotherm ◽  
Clay Minerals ◽  
Removal Rate ◽  
Ammonia Nitrogen ◽  
Order Kinetic ◽  
Natural Clay ◽  
Nitrogen And Phosphorus ◽  
Adsorption Capacities ◽  
Adsorption Of Nitrogen ◽  
Kinetics And Isotherms

Nitrogen and phosphorus are commonly recognized as causing eutrophication in aquatic systems, and their transport in subsurface environments has also aroused great public attention. This research presented four natural clay minerals (NCMs) evaluated for their effectiveness of NH4+ and PO43- adsorption from wastewater. All the NCMs were fully characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), BET analysis, and adsorption kinetics and isotherms to better understand the adsorption mechanism-property relationship. The results show that the adsorption efficiency of the four NCMs for phosphate was better than that for ammonia nitrogen. The removal rate of phosphate was higher than 65%, generally in the range of 80%-90%, while the removal rate of ammonia nitrogen was less than 50%. The adsorption kinetic behavior followed the pseudo-second-order kinetic model. The ammonia nitrogen adsorption isotherm was in good agreement with the Freundlich isotherm equilibrium model, and the phosphate adsorption isotherm matched the Langmuir model. Among all the NCMs studied, bentonite (7.13 mg/g) and kaolinite (5.37 mg/g) showed higher adsorption capacities for ammonia nitrogen, while zeolite (0.21 mg/g) and attapulgite (0.17 mg/g) showed higher adsorption capacities for phosphate. This study provides crucial baseline knowledge for the adsorption of nitrogen and phosphate by different kinds of NCMs.

scholarly journals TECHNIQUE FOR DETERMINATION OF SURFACE FRACTAL DIMENSION AND MORPHOLOGY OF MESOPOROUS TITANIA USING DYNAMIC FLOW ADSORPTION AND ITS CHARACTERIZATION

2010 ◽  
Vol 9 (1) ◽  
pp. 13-17
Author(s):  
Silvester Tursiloadi
Keyword(s):  
Fractal Dimension ◽  
Adsorption Isotherm ◽  
Surface Morphology ◽  
Average Pore Size ◽  
Fractal Dimensions ◽  
Nano Particles ◽  
Dynamic Flow ◽  
N2 Adsorption ◽  
Surface Fractal Dimension ◽  
Surface Fractal

A technique to determine the surface fractal dimension of mesoporous TiO­2 using a dynamic flow adsorption instrument is described. Fractal dimension is an additional technique to characterize surface morphology. Surface fractal dimension, a quantitative measurement of surface ruggedness, can be determined by adsorbing a homologous series of adsorbates onto an adsorbent sample of mesoporous TiO­2. Titania wet gel prepared by hydrolysis of Ti-alkoxide was immersed in the flow of supercritical CO2 at 60 °C and the solvent was extracted.  Mesoporous TiO­2 consists of anatase nano-particles, about 5nm in diameter, have been obtained. After calcination at 600 °C, the average pore size of the extracted gel, about 20nm in diameter, and the pore volume, about 0.35cm3g-1, and the specific surface area, about 58 m2g-1. Using the N2 adsorption isotherm, the surface fractal dimension, DS, has been estimated according to the Frenkel-Halsey-Hill (FHH) theory. The N2 adsorption isotherm for the as-extracted aerogel indicates the mesoporous structure. Two linear regions are found for the FHH plot of the as-extracted aerogel. The estimated surface fractal dimensions are about 2.49 and 2.68. Both of the DS  values indicate rather complex surface morphology. The TEM observation shows that there are amorphous and crystalline particles. Two values of DS may be attributed to these two kinds of particles. The two regions are in near length scales, and the smaller DS, DS =2.49, for the smaller region. This result indicates that there are two kinds of particles, probably amorphous and anatase particles as shown by the TEM observation.     Keywords: surface fractal dimensions, CO2 supercritically extraction, sol-gel, aerogel, titania

Multi-Angle Investigation of the Fractal Characteristics of Nanoscale Pores in the Lower Cambrian Niutitang Shale and Their Implications for CH4 Adsorption

2021 ◽  
Vol 21 (1) ◽  
pp. 156-167
Author(s):  
Yang Wang ◽  
Caifang Wu ◽  
Yong Qin ◽  
Shimin Liu ◽  
Rui Zhang
Keyword(s):  
Fractal Dimension ◽  
Clay Minerals ◽  
Lower Cambrian ◽  
Fractal Dimensions ◽  
Methane Adsorption ◽  
Bet Surface Area ◽  
Commercial Development ◽  
Pore Structures ◽  
Nanoscale Pore ◽  
Pore Types

Shale gas has received widespread interest due to its successful commercial development in China. Pore structures in shale can directly control its gas storage and migration properties. In this study, field emission scanning electron microscopy (FE-SEM), low-pressure N2/CO2 adsorption and highpressure methane adsorption were used to investigate the nanoscale pore structures of the Lower Cambrian Niutitang Formation in the southeastern Upper Yangtze platform. The fractal parameters of the pore structures were also calculated using the Frenkel–Halsey–Hill (FHH) model. The relationships between the fractal dimensions and TOC content, mineral composition and pore structure parameters were also discussed. The results show that organic matter and clay minerals are primary factors affecting the nanoscale pore development. Slit-shaped pores and ink-bottle-shaped pores are the predominant pore types in the Niutitang shale. The Brunauer-Emmett-Teller (BET) surface areas vary from 4.91 m2/g to 34.33 m2/g, and the pore volumes range from 0.689 m3/100 g to 2.964 m3/100 g. Two fractal dimensions (D1 and D2) of the Niutitang shale were obtained using the FHH model, with D1 ranging from 2.605 to 2.684, and D2 ranging from 2.681 to 2.865. D1 adequately characterizes the surface roughness of the pore structures, while D2 represents the complexity of the pore types. Inter-particle (InterP) pores commonly have greater shape complexities than OM pores and intra-particle (IntraP) pores, based on analyses using Image-Pro Plus software. In addition, the TOC content and clay minerals have great effects on the fractal dimension D1. Meanwhile, the fractal dimension D1 increases with increasing BET surface area, but there is no definite relationship between the fractal dimensions and pore volumes. Both the fractal dimensions D1 and D2 are negatively correlated with pore sizes. Further investigation indicates that the fractal dimension D1 exhibits a strong positive relationship with the methane adsorption capacity indicating that Niutitang shales with greater values of the fractal dimension D1 have higher methane adsorption capacities.

Study and Elucidation of Fractal Dimension in Anionic and Cationic Clays: Relationship between Fractal Dimensions to the Amount Adsorbed and Pore Size

2018 ◽  
Vol 30 ◽  
pp. 25-42
Author(s):  
Salah Bahah ◽  
Saci Nacef ◽  
Derradji Chebli ◽  
Brahim Djellouli ◽  
Abdallah Bouguettoucha
Keyword(s):  
Fractal Dimension ◽  
Zeta Potential ◽  
Fractal Dimensions ◽  
Molar Ratio ◽  
Relative Pressure ◽  
Hill Model ◽  
Heterogeneous Distribution ◽  
Anionic Clays ◽  
Surface Fractal ◽  
Bet Analysis

In order to search the correlation between textural properties and geometrical heterogeneity in clays, as characterized by the surface fractal dimension, we used, three different cationic clays; namely Kaolin of Hamam Dbagh, Montmorillonite (Mt) of Maghnia and a sample prepared from Sodium Montmorillonte (Na-Mt)) and three different synthetic anionic clays, ZnAlCO3, MgAlCO3at a molar ratio equal to three (R=3), and NiAlCO3with different molar ratios (R=2, R=3 and R= 4). This DSparameter was evaluated from nitrogen (N2) analysis gas. the fractal Frenkel-Halsey-Hill (FHH) (DS) models was used to estimate the surface fractal dimensions at two ranges of relative pressure, the first between 0.08 and 0.22, which were found Ds to be 2.59, 2.53 and 2.68 from Kaolin, Montmorillonite and Sodium Montmorillonte clays respectively and 2.33, 2.61, 2.53, 2.56 and 2.56 for ZnAlCO3and MgAlCO3, NiAlCO3(2, 3 and 4) respectively, and other at medium relative pressure, which there was an excellent linear adjustment for F-H-H equation within the range between 0.37 and 0.82, which were found Ds to be 2.77, 2.64 and 2.82 for Kaolinite, Montmorillonite and Sodium Montmorillonte clays respectively, and 2.68, 2.64, 2.40, 2.60, 2.47 for ZnAlCO3, MgAlCO3, NiAlCO3(2, 3 and 4) respectively. SEM Characterization confirmed the heterogeneous distribution of the particles and the BET analysis confirmed the fractal nature of the surface of these materials. The zeta potential of the sample which is most used as an indicator of dispersion stability, show a proportionality between increases of zeta potential with increase of dimension fractal (DS), for the same type of clays ( (NiAlCO3) with (R=2, 3 and 4) and Mt, Na-Mt). Key words: Anionic clays; Cationic clays; Fractal dimension; geometrical heterogeneity; Frenkel-Halsey-Hill model.

scholarly journals Full‐Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE‐SEM, Gas Adsorption and Mercury Intrusion Porosimetry

Minerals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 543 ◽  
Author(s):  
Wang ◽  
Jiang ◽  
Jiang ◽  
Chang ◽  
Zhu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Fractal Dimension ◽  
Pore Structure ◽  
Clay Minerals ◽  
Sichuan Basin ◽  
Mercury Intrusion Porosimetry ◽  
Fractal Dimensions ◽  
Full Scale ◽  
Mercury Intrusion ◽  
Longmaxi Shale

Pore structure determines the gas occurrence and storage properties of gas shale and is a vital element for reservoir evaluation and shale gas resources assessment. Field emission scanning electron microscopy (FE‐SEM), high‐pressure mercury intrusion porosimetry (HMIP), and low‐pressure N2/CO2 adsorption were used to qualitatively and quantitatively characterize full‐scale pore structure of Longmaxi (LM) shale from the southern Sichuan Basin. Fractal dimension and its controlling factors were also discussed in our study. Longmaxi shale mainly developed organic matter (OM) pores, interparticle pores, intraparticle pores, and microfracture, of which the OM pores dominated the pore system. The pore diameters are mainly distributed in the ranges of 0.4–0.7 nm, 2–20 nm and 40–200 μm. Micro‐, meso‐ and macropores contribute 24%, 57% and 19% of the total pore volume (PV), respectively, and 64.5%, 34.6%, and 0.9% of the total specific surface area (SSA). Organic matter and clay minerals have a positive contribution to pore development. While high brittle mineral content can inhibit shale pore development. The fractal dimensions D1 and D2 which represents the roughness of the shale surface and irregularity of the space structure, respectively, are calculated based on N2 desorption data. The value of D1 is in the range of 2.6480–2.7334 (average of 2.6857), D2 is in the range of 2.8924–2.9439 (average of 2.9229), which indicates that Longmaxi shales have a rather irregular pore morphology as well as complex pore structure. Both PV and SSA positively correlated with fractal dimensions D1 and D2. The fractal dimension D1 decreases with increasing average pore diameter, while D2 is on the contrary. These results suggest that the small pores have a higher roughness surface, while the larger pores have a more complex spatial structure. The fractal dimensions of shale are jointly controlled by OM, clays and brittle minerals. The TOC content is the key factor which has a positive correlation with the fractal dimension. Clay minerals have a negative influence on fractal dimension D1, and positive influence D2, while brittle minerals show an opposite effect compared with clay minerals.

scholarly journals Nanopore Structure and Fractal Characteristics of Lacustrine Shale: Implications for Shale Gas Storage and Production Potential

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 390 ◽  
Author(s):  
Lei Chen ◽  
Zhenxue Jiang ◽  
Shu Jiang ◽  
Keyu Liu ◽  
Wei Yang ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Surface Area ◽  
Clay Minerals ◽  
Shale Gas ◽  
Negative Relationship ◽  
Quartz Content ◽  
Average Pore ◽  
Positive Correlation ◽  
Fractal Characteristics ◽  
Lacustrine Shale

In order to better understand nanopore structure and fractal characteristics of lacustrine shale, nine shale samples from the Da’anzhai Member of Lower Jurassic Ziliujing Formation in the Sichuan Basin, southwestern (SW) China were investigated by total organic carbon (TOC) analysis, X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FE-SEM), and low-pressure N2 adsorption. Two fractal dimensions D1 and D2 (at the relative pressure of 0–0.5 and 0.5–1, respectively) were calculated from N2 adsorption isotherms using the Frenkel–Halsey–Hill (FHH) equation. The pore structure of the Lower Jurassic lacustrine shale was characterized, and the fractal characteristics and their controlling factors were investigated. Then the effect of fractal dimensions on shale gas storage and production potential was discussed. The results indicate that: (1) Pore types in shale are mainly organic-matter (OM) and interparticle (interP) pores, along with a small amount of intraparticle (intraP) pores, and that not all grains of OM have the same porosity. The Brunauer–Emmett–Teller (BET) surface areas of shale samples range from 4.10 to 8.38 m2/g, the density-functional-theory (DFT) pore volumes range from 0.0076 to 0.0128 cm3/g, and average pore diameters range from 5.56 to 10.48 nm. (2) The BET surface area shows a positive correlation with clay minerals content and quartz content, but no obvious relationship with TOC content. The DFT pore volume shows a positive correlation with TOC content and clay minerals content, but a negative relationship with quartz content. In addition, the average pore diameter shows a positive correlation with TOC content and a negative relationship with quartz content, but no obvious relationship with clay minerals content. (3) Fractal dimension D1 is mainly closely associated with the specific surface area of shale, suggesting that D1 may represent the pore surface fractal dimension. Whereas fractal dimension D2 is sensitive to multiple parameters including the specific surface area, pore volume, and average pore diameter, suggesting that D2 may represent the pore structure fractal dimension. (4) Shale with a large fractal dimension D1 and a moderate fractal dimension D2 has a strong capacity to store both adsorbed gas and free gas, and it also facilitates the exploitation and production of shale gas.

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