Micropore Area Research Articles

Sustainable Production of Activated Carbon from Waste Wood Using Goethite Iron Ore

The growing demand for eco-friendly activated carbon necessitates sustainable production methods. This study investigates the conversion of waste wood into activated carbon using goethite iron ore as an activating agent. A high-temperature rotary furnace was used to activate the carbon at 1373 K. The oxygen released from the iron oxide during the heat treatment reacted with the carbon in the wood, resulting in 49% of activated carbon with BET surface areas between 684 m2/g and 770 m2/g. The activated carbon and char showed type I isotherms with micropore areas between 600 m2/g and 668 m2/g, respectively. Additionally, 92% of the iron in the ore was reduced from ferric to ferrous. The findings demonstrate that goethite iron ore is an effective activating agent for producing wood-based activated carbon while also generating metallic iron as a byproduct. This alternative activation method enhances the sustainability and efficiency of activated carbon production.

Performance of activated carbon derived from tea twigs for carbon dioxide adsorption

Activated carbon from agro-industrial waste, namely tea twigs derived from the processing of Camellia Sinensis branches, using a potassium hydroxide activator for CO2 adsorption has been conducted in this study. Various carbonization temperatures (4000C and 5000C) and heating times of 1 hour and 3 hours were used in this study. The concentration of potassium hydroxide (40% and 60%) and the ratios of activator solutions to carbon precursor made from pyrolysis of tea twigs (2:1 and 4:1) were varied for the chemical activation process. The effectiveness results of the obtained activated carbon were characterized through using Brunauer-Emmett-Teller analyzer and Temperature Programme Desorption-CO2 to determine the surface area and capacity maximum of CO2 adsorption. The optimum condition for the synthesis of activated carbon that produces high surface area was obtained at sample CCS 400/1 A2B1 where biochar carbonized at temperature of 400°C kept for 1 hour with a ratio of activator solution and precursor 4:1 using KOH concentration of 40%. The highest surface area was obtained 1,403 m2 g-1 with pore volume 0.9 m2 g-1 and pore size 1.11 nm and proved the presence of microporous areas in produced activated carbon. The maximum CO2 adsorption capacity obtained in this study was 5.1573 mmol g-1. This result could be related to the higher amount of microporous present in the activated carbon that facilitates the access of CO2 to the active sites at the pores of activated carbon.

Study on adsorption characteristics of biochars and their modified biochars for removal of organic dyes from aqueous solution

Abstract To address organic dye pollution and agricultural waste comprehensive utilization, the biochar (ZB) was prepared using Rosa roxburghii residue as the material for preparation. Three modified biochars (ZBO, ZBS, and ZBH) were created using NaOH, Na2S, and H3PO4 as modifying agents. The morphology, structure, pore size, and elemental composition of biochars were characterized and analyzed by a combination of FTIR, SEM-EDS, and N2 adsorption–desorption techniques. Furthermore, the adsorption performance of the as-prepared biochars was investigated in the adsorption of RhB and MB dye process. The experimental findings showed that adsorption equilibrium for these dyes was achieved in 180 min. Moreover, the dye adsorption on biochars followed a pseudo-second-order kinetic equation. For the biochar (ZB), the Langmuir equation proved to be more appropriate than the Freundlich equation. In contrast, the Freundlich equation was more apt for the modified biochars. More importantly, Pearson's correlation analysis revealed that the adsorption rate and capacity of RhB positively correlated with the specific pore volume, t-plot micropore area, and BET surface area, but a negative one with the pore size. The MB adsorption showed the opposite correlations. This study reveals a novel biochar for adsorbing organic dyes, which provides a strategy for the treatment of Rosa roxburghii residue.

Structural and Ammonia Adsorption Properties of the Gördes Clinoptilolite After HCl Acid Treatment

The effect of activation with HCl on the ammonia adsorption characteristics of natural Gördes clinoptilolite was studied in order to evaluate the usability of this mineral in various environments where ammonia removal is required, such as livestock facilities. Clinoptilolite was treated with HCl solutions (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 M) at 90°C for 4 h. XRD, XRF, FT-IR, TGA, DTA and N2 adsorption techniques were used for structural and thermal characterization of the adsorbents. NH3 adsorption isotherms were measured volumetric analysis at 298 K up to 100 kPa. Acid activation not only caused textural and structural changes such as removal of exchangeable cations but also affected the thermal behavior and gas retention of the clinoptilolite. Nitrogen adsorption results showed that it is possible to improve the specific surface area and micropore area values of clinoptilolite with acid activation up to 1.5 M. In addition, the NH3 adsorption capacities of clinoptilolite samples (4.33-5.01 mmol.g-1) were compared with the ammonia removal data of natural and synthetic zeolites (1.77 - 9.32 mmol.g-1) reported in previous studies.

Regulating the Performance of CO2 Adsorbents Based on the Pyrolysis Mechanism of Self-Sacrificial Templating Agents.

Previous research has proven that the pore shape and nitrogen group content of adsorbents play essential roles in determining their carbon dioxide (CO2) adsorption performance. In this article, a series of nitrogen-doped porous carbon materials were prepared for CO2 adsorption by varying the proportion of carbon nitride, the pyrolysis temperature, and the activation ratio of KOH, using chitosan as the carbon source, carbon nitride (g-C3N4 and g-C3N5) as self-sacrificing templating agents, and KOH as the activator. Among the prepared materials, T6-850-1 has the highest specific surface area (SBET) of 2336 m2/g, and T6-750-1 has the highest microporous area (Smicro) and CO2 adsorption capacity (1 bar, 298 K) of 1969 m2/g and 3.49 mmol/g, respectively. The thermal decomposition temperature and products of carbon nitride templates were characterized and tested by thermogravimetric infrared gas chromatography-mass spectrometry (TG-IR-GC-MS), and the thermal decomposition mechanisms of the two carbon nitride templates were investigated. We found that the thermal stability of the template directly affects the pore structure of the final sample as well as the type and quantity of nitrogen species.

Novel N-doped carbon nanotubes impregnated Mn spheres with polydopamine coating as an efficient polysulfide immobilizer for Li-S batteries

Lithium-sulfur (Li-S) batteries are one of the most promising energy storage and conversion devices due to the high theoretical capacity and cost-effectiveness of sulfur. However, they still suffer from sluggish redox kinetics and the shuttle effect caused by complex polysulfides. In this work, graphitic carbon nitride (g-C3N4) is utilized as a template and further hydrothermally treated with an Mn source and glucose. The pyrolysis of g-C3N4 gives rise to N-doped carbon nanotubes, producing abundant sites for physical confinement and chemical adsorption of polysulfides, while glucose carbonization brings forth amorphous carbon and Mn source produces metal spheres. Afterward, polydopamine (PDA) induces N-doped carbon coating and promotes interface connection as well as electron immigration. This synergistic design possesses a high surface area of micropores and mesopores to aggregate sulfur and accelerate redox kinetics. As a result, the N-doped carbon nanotube with Mn spheres and PDA coating@sulfur (CN/Mn-PDA@S) exhibits a high reversible capacity of 813.5 mAh g−1 at 1 C with a decay rate of 0.064% per cycle and remarkable capacity retention at 2 C with rate performance up to 4 C. Therefore, the novel design of N-doped carbon nanotubes with Mn spheres and PDA coating serves as an efficient polysulfide immobilizer for Li-S batteries.

Integrated formic acid and deep eutectic solvent mediated sustainable synthesis of cellulose nanocrystals from Sterculia foetida shells

The present study reports the green synthesis of cellulose nanocrystals from the shells of Sterculia foetida (SFS) cellulose. Three different methods, alkali, acid and organic acid, were screened for the maximum cellulose extraction. A maximum cellulose yield, 30.6 ± 0.84 w/w, was obtained using 90% formic acid at 110 °C in 120 min. The extracted cellulose was characterized and identified by instrumental analyses. SEM analysis showed skeletal rod-like microfibril structures and similar intra-fibrillar widths. CP/MAS 13C NMR and FTIR spectrum revealed the purity of cellulose and the absence of other components like hemicellulose and lignin. XRD study revealed a cellulose crystallinity index of 88.07%. BET analysis showed a good surface area (3.3213 m2/g) and a micro-pore area of 1.871 m2/g. The cellulose nanocrystals were synthesized from the extracted cellulose using deep eutectic solvents (DES), choline chloride and lactic acid (1:2 ratio). The cellulose nanocrystals (CNC) synthesized from DES-based exhibited zeta potential and particle size of −16.7 mV and 576.3 d.nm. DES-synthesized cellulose nanocrystals were spherical-like shapes, as observed from TEM images. The present results exposed that formic acid is an effective and green catalyst for the extraction of cellulose and DES for the sustainable synthesis of CNC.

Modified H‐BEA Zeolites from Fluorinated Silica Slag Waste by Dry Gel Conversion Method for Shape‐Selective Acylation of 2‐Methoxynaphthalene

AbstractThe high value‐added utilization of the fluorinated silica slag (FSS) waste, an associated by‐product of the anhydrous HF production from the accompanying fluorine resources in phosphate ore, is of great importance, but it remains a challenge. In this work, the Mg modified and unmodified Hβ zeolites from FSS waste were successfully prepared by a green dry gel conversion crystallization method with tetraethylammonium hydroxide (TEAOH) as a structure‐directing agent (SDA). The in situ Mg modified Hβ zeolite (Mg−Hβ) shows much superior catalytic performance to unmodified (Hβ) and post Mg‐modified Hβ (Mg/Hβ) zeolites for acetylation of 2‐methoxynaphthalene (2‐MN) to 6‐acetyl‐2‐methoxynaphthalene (2,6‐AcMN), and the 40.2 % of conversion for 2‐MN with 66.3 % of selectivity for 2,6‐AcMN were achieved, ascribed to the high amount of B acidic sites and the promoted shape‐selective catalysis effect by higher surface area and volume of micropores. This work not only opens a new avenue for the high value‐added utilization of fluorinated silica slag waste, but also generates an efficient solid acid catalyst for the clean production of 2,6‐AcMN through the acetylation of 2‐MN with acetic anhydride.

Physically and chemically modified zeolite templated nitrogenous carbons for enhanced hydrogen adsorption

Carbon materials have great potential for hydrogen adsorption due to their remarkable specific surface area, unique pore size characteristics and ability to functionalize with metal or non-metal. In this work, zeolite templated carbons were physically and chemically modified by varying preparation conditions to study their impact on structure and hydrogen adsorption capacity. The resultant templated carbons showed surface area in the range of 608–1665 m2/g and pore volume between 0.63 to 1.00 cc/g, with 28–48 % microporosity depending on synthesis conditions. The surface area and pore volume increased with increasing carbon deposition temperature from 650 to 750 °C and both decreased at higher carbon deposition temperature of 850 °C. At heat treatment temperature of 900 °C, the surface area and pore volume of templated carbons were observed to be higher. Incorporation of nitrogen heteroatom in carbon matrix during carbon deposition might have facilitated porosity. Use of argon as carrier gas resulted in the highest surface area (1665 m2/g), micropore area (597 m2/g) and pore volume (1.0 cc/g). The same templated carbon showed maximum hydrogen adsorption capacity of 0.20 and 2.81 wt% at 25 and –196 °C, respectively at 15 bar. On addition of platinum to templated carbon, the hydrogen adsorption capacity was significantly improved from 0.20 to 0.28 wt% at 25 °C and from 2.81 to 3.24 wt% at –196 °C. The strong affinity of Pt for hydrogen might have enhanced hydrogen adsorption.

Chitosan pyrolysis in the presence of a ZnCl2/NaCl salts for carbons with electrocatalytic activity in oxygen reduction reaction in alkaline solutions.

The one-step carbonization of low cost and abundant chitosan biopolymer in the presence of salt eutectics ZnCl2/NaCl results in nitrogen-doped carbon nanostructures(8.5 wt.% total nitrogen content). NaCl yields the spacious 3D structure, which allows external oxygen to easily reach the active sites for the oxygen reductionreaction (ORR) distinguished by their high onset potential and the maximum turnover frequency of 0.132 e site⁻1s⁻1. Data show that the presence of NaCl during the synthesis exhibits the formation of pores having large specific volumes and surface(specific surface area of 1217 m2g-1), and holds advantage by their pores characteristics such as their micro-size part, which provides a platform for mass transport distribution in three-dimensional N-doped catalysts for ORR. It holds benefit over sample pre-treated with LiCl in terms of the micropores specific volume and area, seen as their percentage rate, measured in the BET. Therefore, the average concentration of the active site on the surface is larger.

Zero-valent iron on graphite-cellulose biochar catalysts for the Fenton degradation of tetracycline from water

Tetracycline (TC), an antibiotic widely used in the treatment of animal and human diseases and promotion of animal growth. However, its uncontrolled discharge to water sources can also cause the promotion of antibiotic resistant bacteria and genes. In this study, graphite and cellulose were used as raw materials to construct a graphite-biochar (G-BC) by carbothermal reactions. This graphite-biochar was subsequently mixed with ZVI with various mass ratios by ball milling to produce graphite-biochars supported ZVI (ZVI/G-BC) catalysts, further used in the heterogeneous Fenton degradation of tetracycline. The materials were fully characterized by different techniques. The removal of TC by BC, G-BC and ZVI/G-BC was tested under different reaction conditions. The best synthesis conditions were achieved at a heating temperature of 700 °C, a graphite content of 20 %, a ball milling speed of 500 rpm, a ball milling time of 5 h, as well as a G-BC and ZVI mass ratio of 1:3. Graphite improves the conductivity and micropore area of the material, which enhances the removal of TC by ZVI/G-BC catalysts in Fenton-like reactions. TC was first oxidized to intermediate products and then further mineralized to CO2 and H2O. The best TC removal performance was obtained with a catalyst dosage of 1.1 g·L1, a hydrogen peroxide concentration of 140 mM and an initial pH value of 3. The reaction data fitted properly a pseudo first-order kinetic equation. TC removal as high as 91 % was achieved even in the 3rd round of reuse. This study reports a novel ZVI material with high conductivity and good TC removal performance.

Molten salt-assisted microporous biochar derived from poplar sawdust as an efficient cathode matrix for Li-Se battery applications

This study focuses on the employment of molten salts (ZnCl2-KCl-NaCl and K2CO3-Na2CO3-Li2CO3) as alternative activating agents to prepare porous biochars, which serve as efficient cathode matrices for Li-Se battery applications. Poplar sawdust was employed as the biomass feedstock, mixed with molten salts in a 1:5 mass ratio, and then pyrolyzed at a low temperature of 500 ℃ to obtain PB-Cl and PB-Carb, respectively. The obtained porous biochar samples were investigated, and processed for selenium (Se) loading using the melt-diffusion technique, resulting in composites named Se@PB-Cl and Se@PB-Carb, respectively. The composite Se@PB-Cl, with a BET surface area of 787.11 m2 g−1 and a t-plot micropores area of 691.65 m2 g−1, displayed a Se loading of 41.86 % and exhibited enhanced electrochemical performance. At 0.5 C, Se@PB-Cl after 100 cycles delivered a specific capacity of 617.03 mAh g−1. After 500 cycles, at 1 C a specific capacity of 505.9 mAh g−1 was observed. Moreover, the specific capacity of Se@PB-Carb was found to be 339.74 mAh g−1 at 0.5 C after 100 cycles, and 235.97 mAh g−1 at 1 C after 500 cycles. These findings highlight the potential of molten salt-assisted porous biochar obtained from poplar sawdust, as a cost-effective precursor for selenium-based cathodes.

Effects of adding metals to Beta zeolite on ethanol conversion to hydrocarbons

This study investigated the effects of Beta zeolite ion exchange with Fe, Zn, and Co on ethanol conversion to hydrocarbons. Various characterization techniques such as X-ray fluorescence (XRF), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), magic angle rotation nuclear magnetic resonance spectrometry (MAS NMR) of 29Si and 27Al, scanning electron microscopy (SEM), nitrogen physisorption, ammonia temperature-programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR) were employed. Catalytic tests were performed at temperatures from 475 to 550 °C under ambient pressure. The metal addition to Beta zeolite reduced micropore area and volume, decreased the concentration of the extra-framework aluminum, and increased total acid site density and Lewis acid sites, except for Fe. For all catalysts, ethylene was identified as the primary product. However, catalysts containing Zn and Co displayed the formation of propylene and C1 to C3 paraffins. The catalyst with Fe exhibited the highest deactivation and a significant decrease in acidity, attributed to the formation of extra-framework aluminum, resulting in exclusive ethylene production.

The Effect of Diagenetic Modifications on Porosity Development in the Upper Ordovician to Lower Silurian Wufeng and Longmaxi Formations, Southeast Sichuan Basin, China

Diagenesis has been demonstrated to significantly affect porosity development in shale reservoirs, however, the effect of diagenetic modifications on shale pore structures is still unclear. For clarifying this issue, this paper focuses on the Upper Ordovician to Lower Silurian Wufeng and Longmaxi shales, which are the only commercially gas-produced shale plays in China. This study aims to reveal the influence of diagenetic alterations on the WF-LMX shale reservoir quality by integrating total organic carbon (TOC) content, X-ray diffraction (XRD), low-temperature gas (N2) and carbon dioxide (CO2) adsorption experiments, field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDS), and cathodoluminescence (CL) analyses. Three major shale lithofacies were identified, mainly including siliceous, siliceous–argillaceous mixed, and argillaceous shale; the siliceous shale has a relatively high TOC content. The organic pores, intergranular pores, intragranular pores, and fractures are generally developed in the WF-LMX shales. The pore volume (PV) and specific surface area (SSA) of micropores, mesopores, and macropores of siliceous shales are higher than those of mixed shales and argillaceous shales. The TOC content has a strongly positive correlation with PV and SSA for micropores and mesopores. After combustion, the PV and SSA of micropores and mesopores were decreased, whereas the PV and SSA of macropore were significantly increased. In the siliceous shale, organic pore is the dominant pore type due to the fact that a large amount of authigenic microcrystalline quartz aggregates can protect organic pores from compaction. The argillaceous shale has high clay and low TOC content, and the dominant pore type is pores between clay flakes. The siliceous shale has a relatively high TOC content, large PV and SSA, and so are the dessert lithofacies for shale gas exploration.

Study of KOH-activated hydrochar for CO2 adsorption

The use of solid porous materials for CO2 capture is a more environmentally benign approach than conventional wet scrubbing using amine-based solutions. Therefore, in this study, porous carbon materials were prepared using sawdust through hydrothermal carbonization (HTC) to produce hydrochar, followed by KOH activation. The results showed that KOH-activated hydrochar had a specific surface area of 646–1195 m2/g, and a micropore area of 547–1059 m2/g, indicating a microporous structure was developed. The highest CO2 adsorption capacity at tested adsorption temperatures was achieved from activated hydrochar obtained at 750 °C (40 °C: 0.95 mmolCO2/gsample; 75 °C: 0.80 mmolCO2/gsample), which is higher than pristine hydrochar (40 °C: 0.05 mmolCO2/gsample; 75 °C: 0.04 mmolCO2/gsample). Physisorption through pore diffusion and surface coverage and chemisorption involving formation of covalent bonds between adsorbent’s surface functionality and CO2 both contributed to CO2 adsorption. Importantly, the presence of N-containing chemicals, particularly the presence of N-containing functional groups on the surface, played an important role in CO2 adsorption capacity. Based on the current results and relevant literature, the development of ultra-micropore and the introduction of more N-containing functional groups to the surface would be the research focuses to further increase the CO2 adsorption capacity.

Valorization of sponge iron industrial waste into iron-modified zeolite X for ciprofloxacin removal: a multi-parameter optimization study.

Ciprofloxacin (CIP), a commonly used antibiotic, is frequently detected in water bodies and the natural environment. The profound health consequences of CIP have led to growing attention focusing on environmental concerns. Adsorption is highly preferred because of its adaptability and remarkable efficiency in removing CIP. Therefore, the current work focuses on synthesizing an eco-friendly and economical adsorbent for removing CIP. The work aims to remove CIP using zeolite X (ZX), synthesized from dolochar, and subsequently modified ZX into iron-modified zeolite X (FeZX) via ion exchange. The synthesized FeZX had a crystallinity of 82.701%, an average pore size of 5.917 nm, a micropore volume of 0.298 cc/g, a micropore area of 451.807 m2/g, and a total surface area of 478.521 m2/g. The effect of parameters such as initial CIPconcentration, pH, contact period, adsorbent dosage, and iron dosage was analyzed in the batch adsorption studies of CIP using ZX and FeZX. CIP removal of 37.786% was achieved using ZX; hence, the adsorption parameters were optimized to maximize the CIP removal using response surface methodology (RSM), specifically Box-Behnken Design (BBD) using FeZX. Maximum removal of 97.974% was achieved under optimum conditions of 8.06 pH, contact period of 59.422 min, CIP concentration of 17.117 mg/L, and adsorbent dosage of 0.478 g/L. Freundlich isotherm and pseudo-second-order kinetic models werethe most accurate representations of the experimental data. The findings indicatethe significance of using this iron-modified mesoporous zeolite as an adsorbent for efficiently treating CIP wastewater.

Efficient Preparation and Optimization of Activated Carbon Monoliths from Resorcinol-Formaldehyde Resins for CO2 Capture

Activated carbon monoliths with developed porosity, high surface area and excellent adsorption properties were successfully prepared from resorcinol-formaldehyde resins using a physical activation method. The primary objective of this study was to examine the impact of key parameters, namely hexamethylenetetramine content (0.08–0.2 g), pyrolysis heating rate (5–20 °C/min) and activation time (1–7 h), on the final characteristics of the activated carbon in order to identify the optimal operating conditions to achieve the desired properties. All the cured resin samples were pyrolyzed at 900 °C under a nitrogen atmosphere, while the activation process took place in the presence of CO2. The evaluation of the activated carbon materials was based on the CO2 adsorption capacity and BET surface area, micropore area and total pore volume, which were employed as the criteria for selecting the optimal activated carbon. The synthesized porous carbon monoliths exhibited good properties: high BET surface area (900 m2/g), high CO2 adsorption capacity (5.33 mmol/g at 0 °C and 1 bar, 3.8 mmol/g at 25 °C and 1 bar) and good CO2 selectivity for CO2/N2 and CO2/CH4 mixtures. These results were obtained with a pyrolysis heating rate of 5 °C/min and a 3 h activation period.

Greener and Sustainable Production: Production of Industrial Zinc (II) Acetate Solution and Recovery of Some Metals (Zn, Pb, Ag) from Zinc Plant Residue by Ultrasound-Assisted Leaching

Zinc plant residue (ZPR) contains significant amounts of valuable metal (Zn, Pb, Ag, etc.) compounds, as well as various heavy metals and harmful compounds that pollute the environment. Processing such residues allows for the recovery and reuse of valuable metals, which is crucial for sustainable resource management. This study investigated a two-stage leaching process of Zn, Pb, and Ag recovery from ZPR. The first stage of ultrasonic-assisted leaching of ZPR was applied to produce an industrial selective zinc acetate solution. Leaching experiments were carried out with an ultrasonic device in the presence of acetic acid, known as organic acid. Under optimum leaching conditions, the extraction of Zn and Fe metals was obtained as 76.13% and 1.32% Fe, respectively. According to the Brunauer–Emmett–Teller (BET) analysis results on the original sample and ultrasonic leaching residue (ULR), the BET surface area and micropore area increased. However, the mean adsorption pore width decreased. In the second stage, conventional sodium chloride leaching was applied to recover lead and silver from the remaining solid after the first stage. Under the optimum conditions in this stage, 80.12% of Pb and 96.2% of Ag were extracted. The presence of coordination between Zn2+/AcO− (acetate) and Pb2+/Cl− complexes in the leaching solution was revealed by Raman spectroscopy. Finally, according to the characterization analysis of the final leaching residue, it was determined that iron oxides and silicate species accumulated in the solid. In conclusion, a significant reduction in the rate of pollution and toxic metals in ZPR was noticed.Graphical

Targeted Stimulation of Micropores by CS2 Extraction on Molecular of Coal.

The targeted stimulation of micropores based on the transformation of coal's molecular structure is proposed due to the chemical properties and difficult-to-transform properties of micropores. Carbon disulfide (CS2) extraction is used as a targeted stimulation to reveal the internal evolution mechanism of micropore transformation. The variations of microcrystalline structures and micropores of bituminous coal and anthracite extracted by CS2 were analyzed with X-ray diffraction (XRD), low-temperature carbon dioxide (CO2) adsorption, and molecular simulation. The results show that CS2 extraction, with the broken chain effect, swelling effect, and aromatic ring rearrangement effect, can promote micropore generation of bituminous coal by transforming the microcrystalline structure. Furthermore, CS2 extraction on bituminous coal can decrease the average micropore size and increase the micropore volume and area. The aromatic layer fragmentation effect of CS2 extraction on anthracite, compared to the micropore generation effect of the broken chain effect and swelling effect, can enlarge micropores more remarkably, as it induces an enhancement in the average micropore size and a decline in the micropore volume and area. The research is expected to provide a theoretical basis for establishing reservoir stimulation technology based on CS2 extraction.

Feasibility of Microbially Induced Carbonate Precipitation to Enhance the Internal Stability of Loess under Zn-Contaminated Seepage Conditions

Loess is widely distributed in Northwestern China and serves as the preferred engineering construction material for anti-fouling barriers. Heavy metal contamination in soil presents significant challenges to the engineering safety of vulnerable loess structures. Hence, there is an urgent need to investigate the impact of heavy metal ions on their percolation performance. In order to investigate the effectiveness of microbially induced carbonate precipitation (MICP) using Sporosarcina pasturii (CGMCC1.3687) bacteria in reducing internal seepage erosion, a saturated permeability test was conducted on reshaped loess under constant water head saturation conditions. The response of loess to deionized water (DW) and ZnCl2 solution seepages was analyzed by monitoring changes in cation concentration over time, measuring Zeta potential, and using scanning electron microscopy (SEM). The results indicate that the hydrolysis of Zn2+ creates an acidic environment, leading to the dissolution of carbonate minerals in the loess, which enhances its permeability. The adsorption of Zn2+ ions and the resulting diffusion double-layer (DDL) effect reduce the thickness of the diffusion layer and increase the number of free water channels. Additionally, the permeability of loess exposed to ZnCl2 solution seepage significantly increased by 554.5% compared to loess exposed to deionized water (DW) seepage. Following the seepage of ZnCl2 solutions, changes in micropore area ratio were observed, decreasing by 48.80%, while mesopore areas increased by 23.9%. MICP treatment helps reduce erosion and volume shrinkage in contaminated loess. Carbonate precipitation enhances the erosion resistance of contaminated loess by absorbing or coating fine particles and creating bridging connections with coarse particles. These research results offer new perspectives on enhancing the seepage properties of saturated loess in the presence of heavy metal erosion and the geochemical mechanisms involved.