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Molecular dynamics simulation of sI methane hydrate under compression and tension

  • Qiang Wang , Qizhong Tang and Sen Tian EMAIL logo
Published/Copyright: February 20, 2020

Abstract

Molecular dynamics (MD) analysis of methane hydrate is important for the application of methane hydrate technology. This study investigated the microstructure changes of sI methane hydrate and the laws of stress–strain evolution under the condition of compression and tension by using MD simulation. This study further explored the mechanical property and stability of sI methane hydrate under different stress states. Results showed that tensile and compressive failures produced an obvious size effect under a certain condition. At low temperature and high pressure, most of the clathrate hydrate maintained a stable structure in the tensile fracture process, during which only a small amount of unstable methane broke the structure, thereby, presenting a free-motion state. The methane hydrate cracked when the system reached the maximum stress in the loading process, in which the maximum compressive stress is larger than the tensile stress under the same experimental condition. This study provides a basis for understanding the microscopic stress characteristics of methane hydrate.

1 Introduction

Methane hydrate [1, 2] (hereinafter referred as “hydrate”) is a kind of ice-like clathrate crystalline, which is widely distributed in continental margin, continental slope and permafrost zone. Hydrate is regarded as a promising alternative energy source and has gradually attracted the attention of scholars. The study of hydrate has a potential application in the fields of energy source development [3, 4, 5], gas storage and separation [6, 7, 8] and desalination of sea water [9, 10, 11]. Geological hazards and environmental problems caused by gas exploration are simultaneously discussed [12, 13]. Hydrate is formed by methane gas (guest molecule) and water (host molecule) under high pressure and low temperature. When small gas molecules exist, the water molecules bind to each other via hydrogen bond interactions; thereby forming a cage-shaped structure with different shapes and sizes with the gas molecule wrapped in it. Gas and water molecules interact with one another through the van der Waals force, which reduces the energy of the entire structure and achieves a stable state [14, 15]. If the polyhedron cage-shaped hydrate lattice formed by the water molecule is not occupied by the guest molecule, then the empty hydrate lattice can be regarded as a special kind of ice, but it is unstable and prone to collapse. The filling of a guest molecule is helpful to the stability of the hydrate lattice, and the hydrate will be more stable when many guest molecules are filled.

Currently, various experimental measurements are performed to explore the mechanical characteristics of hydrate. However, experimental hydrate samples often have defects (e.g. porous, vacancy and polycrystalline) [16, 17, 18] or contain impurities, such as sand sediments and silicas, which result in errors. Also, keeping the hydrate at a certain temperature and pressure through experiment equipment is difficult. Therefore, the mechanisms of hydrate deformation, defect formation and crack propagation still lack systematic in depth research results, especially for the mechanical properties of pure hydrate from a microcosmic perspective. The micro-mechanisms of the mechanical properties of hydrate is a basic task in natural gas exploration and production. However, studies that have been carried out on it are limited. The properties of materials would vary with different sizes at micro/nanoscale. Thus, in this study, we investigate the size effect by molecular dynamics (MD). The normalized stretching force also affect the size relevant properties at nanoscale because the definition of force (pressure) have the parameter of length.

sI methane hydrate is a common type of hydrate, which is a unit cell of body-centred cubic (bcc) structure that contains 46 water molecules [19, 20, 21]. In this study, MD simulation is used to perform compression and tension of sI methane hydrate in different scales based on the experimental data. MD simulation is a useful method in investigating the micro-mechanisms of materials [22, 23, 24, 25, 26]. This method has been successfully applied in the study of the thermal and interfacial properties of hydrate [27, 28]. Ning et al. [29, 30] investigated the compressibility of CH4/CO2 hydrate mixtures and mechanical instability of mono/poly-crystalline hydrate, recently, and revealed the mechanical behaviour of hydrate at the molecular level. This study is intended to investigate the changes in the microstructure of pure sI methane hydrate and the laws of stress–strain evolution under the condition of compression and tension by MD simulation. Thus, the mechanical characteristics and the microstructure evolution mechanism of sI methane hydrate under different stress conditions are explored to provide theoretical guidance for the practical exploitation of hydrate.

2 Model and Computational Method

2.1 Simulation Model

Hydrate is the compound in which the hydrogen-bonded cages formed by water molecules hold the methane molecules. So far, the lattice structures of hydrate have three types, including sI (cubic) [31], sII face-centred cubic [32] and sH (hexagonal) [33] lattice structures. The sI hydrate was employed to carry out the compression and tension tests and build the simulation model in this study. Its unit cell is composed of 8 guest molecules (methane molecules) and 46 host molecules (water molecules) arranged in the cubic box of 12×12×12 Å3. Combined MD simulation with compression and tension tests, 2×2×4, 2×2×6, 2×2×8, 2×2×10, 2×2×12, 2×2×17 and 2×2×22 unit cells (X×Y×Z axis) of sI hydrate were constructed to investigate their dynamic characteristics under various compression and tension.

The methane molecules fully occupied the cage structures. Thus, the coordinates of the atoms of the sI hydrate unit cell were determined by X-ray experiments [34]. The MD simulations were performed using large-scale atomic/molecular massively parallel simulator software [35, 36, 37]. The Lennard-Jones (LJ) potential and the TIP4P model [38, 39] were adopted as the force field for methane and water because of its computational simplicity, respectively. Although TIP4P and SPCE models were widely used in describing water interactions, the LJ potential was usually adopted as the force field for methane. The 12-6 LJ potential equation [40, 41] is expressed as

(1)Uij(rij)=4εij[(σijrij)12(σijrij)6],

where U is the potential energy; rij is the distance between two interplay particles i and j; and ε and σ are the energy and length scales for the interaction, respectively. The equation of the TIP4P model [42, 43] is shown as

(2)Uij=Ushort+UCoulombic=4εij[(σijrij)12(σijrij)6]+qiqj4πε0rij,

Where q is the partial charge, and ε0 is the dielectric constant. Figure 1 shows the molecular geometry of the TIP4P model for water. Table 1 shows the force field parameters for methane and water.

Figure 1 Molecular geometry of TIP4P model for water.
Figure 1

Molecular geometry of TIP4P model for water.

Table 1

Force field parameters for methane and water.

Atomσ (Å)Ε (kJ/mol)q (e)
O3.15360.648
H0.52
M−1.04
CH43.73271.2465

The O-H bond length is rOH=0.9572 Å, the H-O-H angle is θH-O-H=104.52° and the O-M length is rOM=0.15 Å. The cross interactions amongst different types of particles were described by the Lorentz-Berthelot compositing rules [44], and the electrostatic interactions of the systems were calculated by using the Ewald sum method [45].

2.2 Computational Parameters

Initially, the simulation systems based on energy minimization were established, with the whole equilibrated at 200 K in NVT ensemble for 1,000,000 steps. Notably, in all of the simulations of the present study, periodic boundary conditions were applied in the X, Y and Z axes. Then, the time-step was set as 0.2 fs, and the temperature was controlled by Nose-Hoover algorithm. Next, the systems were equilibrated at 200 K and 10 MPa in NPT ensemble for 1,000,000 steps to produce the test samples, such as the 2×2×4 hydrate system shown in Figure 2, for compressing and stretching. Afterwards, the samples were used for the tension test to verify the simulation.

Figure 2 Simulation model for 2×2×4 unit cells of sI methane hydrate.
Figure 2

Simulation model for 2×2×4 unit cells of sI methane hydrate.

The stretching test was loading in the Z axis because the stress–strain relationships of sI hydrate were almost same in the X, Y and Z axes [30]. More specifically, the stretching test changed the Z dimension of the simulation box at a constant engineering strain rate of 1×107/s at 200 K and 10 MPa. The tests lasted from 2,000,000 to 4,000,000 steps for different samples to break the hydrate. Meanwhile, the compression tests were performed using the original samples with the same constant engineering strain rate of 1×107/s at 200 K and 10 MPa, which lasted 2,000,000 to 4,000,000 steps for different samples.

Ethical approval: The conducted research is not related to either human or animal use.

3 Results and Discussions

3.1 Strain-stress curves during stretching

Herein, the simulation systems are denoted as Systems 4, 6, 8, 10, 12, 17 and 22 for 2×2×4, 2×2×6, 2×2×8, 2×2×10, 2×2×12, 2×2×17 and 2×2×22 unit cells of sI methane hydrate, respectively. The stretching of the tension test is homogenous and isotropic based on the study of Wu et al. [30]. The stretching stress causes the cracks in the hydrate. Herein, e.g. 2×2×8 unit cells are shown in Figure 3, in which the strain of hydrate in the Z axis before the stretching is 0. As the stress was gradually loaded, the hydrate strained in the Z direction. When the strain reached 0.19, a clear microcrack (hydrate hydrogen bond rupture) at nanoscale appeared in the hydrate system. Then, the crack expanded rapidly to the entire hydrate when the strain was 0.22. Some methane molecules were released in free movement state due to the hydrogen bond rupture of the hydrate cage structure. In addition, under the stable state of low temperature and high pressure, no phenomenon of complete decomposition of hydrate was observed. Most hydrate cage structures remained stable.

Figure 3 Snapshots of 2×2×8 unit cells during stretching.
Figure 3

Snapshots of 2×2×8 unit cells during stretching.

The stress of the test region in the Z axis is the main stress because the hydrate deforms along the Z axis, as presented in Figure 4. Stress increased with strain, which was similar to elastic deformation. Then, the hydrate reached its maximum stress and cracked rapidly. This maximum value was less than that in the experiments [13], but close to that in the simulation results presented by Ning et al. [29, 30]. Stress is calculated on the basis of the pressure tensor of the atoms in the Z direction. However, it did not correspond with practice that the hydrate system still had residual stress in the Z direction when the hydrate broke. Therefore, the stress of the strain-stress curves in Figure 4 (a) is zero when the length of the cracks exceeded 2 Å, considering the interactions of hydrogen bonds.

Figure 4 Strain–stress curves (a) in Z axis during stretching, and the maximum stress of different systems (b) in Z axis during stretching.
Figure 4

Strain–stress curves (a) in Z axis during stretching, and the maximum stress of different systems (b) in Z axis during stretching.

The hydrates synthesised by the process of experiments contained impurities; whereas the sI hydrate studied here was pure. Further, the maximum stress decreased with an increase in the size of hydrate in the Z axis from 4 to 10 cells (Figure 4 (b)). This finding indicates that the hydrate follows the size effect when the system size is under 10 cells. However, the maximum stress fluctuated when the size was over 10 cells. The maximum tensile stress of the hydrate was in the Z direction, and the cells at a size of 4, 6, 8 and 10 decreased, thereby demonstrating the existence of a size effect. When the hydrate size exceeded 10 cells, the maximum stress value was smaller than that before. Compared with the cells at a size of 4, 6, 8 and 10, no regularity, but value fluctuation, were found.

3.2 Strain–stress curves during compressing

The strain–stress curves in the Z axis during compressing are presented in Figure 5. Similar to the stretching process, the compressive stress increased with strain and reached its maximum with strain larger than that of the maximum stress during the stretching process and the maximum tensile stress in the corresponding hydrate system. The explanation is given as follows. The hydrate crystal is composed of a hydrogen bond network of water molecules, in which the hydrogen bond is attributed to the physical intermolecular interactions. Therefore, the physical intermolecular interactions are weaker than the intramolecular interactions, and thus the hydrogen bond is easy to break when stretching. However, when the hydrogen bond is compressing, the microstructure will be adjusted at a certain angle to increase the strain. The microstructure of hydrate will change to fit the compression. Compressive stress is large when the distance between particles is small.

Figure 5 Strain–stress curves (a) in Z axis during compressing, and the maximum stress of different systems (b) in Z axis during compressing.
Figure 5

Strain–stress curves (a) in Z axis during compressing, and the maximum stress of different systems (b) in Z axis during compressing.

The structure of the hydrates was destroyed after reaching the maximum compressive stress, and stress decreased sharply and, finally, reached stability when the compression system continued to be compressed. This phenomenon was attributed to the periodic boundary conditions in the MD simulation in this research. After the hydrate was destroyed under pressure, the destroyed particle structure was still compressing until the system could not be compressed any more. In addition, the maximum stress of the hydrate under compression varied with the system size, which was similar to that of the tension. A certain size effect in the 4, 6, 8, 10-cell system was observed, and no regularity was found when the size exceeded 10 cells (Figure 5 (b)).

4 Conclusions

The stress characteristics of hydrate particles are vital in the investigation of the microscopic properties of hydrate particles. In terms of the mechanisms of hydrate deformation, defect formation and crack propagation are still inconclusive, especially for the pure hydrate from the perspective of mechanical properties microscopically. Moreover, the micro-mechanisms of hydrate’s mechanical properties are scarce. In this study, the mechanical properties of hydrates are investigated by MD simulation, which was built by the classic sI methane hydrate. The compression of sI methane hydrate with different sizes and the relationship of stress–strain between the stretching and compressing process were discussed.

In the stretching and compressing process, similar to elastic deformation, stress increased with strain. Then, the hydrate reached its maximum stress and cracked rapidly. In the case of tensile fracture under low temperature and high pressure in a pure hydrate system, the cage-shaped structure of most hydrates was stabilized. Only a small amount of methane broke through and detached from the cage-shaped structure, which exists in a free-motion state. In the case of compressive fracture of this system, after the hydrate was destroyed under pressure, the destroyed particle structure was still compressing until the system could not be compressed any more. Under the 10-cell size (simulation condition), the tensile and compressive failures of the hydrate showed large correlation with the system size. In other words, obvious size effect was observed under certain conditions. When the hydrate size exceeded 10 cells, the maximum stress was smaller than before. Compared with the cells with the size of 4, 6, 8 and 10, no regularity, but value fluctuation, were found. The compressive stress reached its maximum, which was larger than that of tensile stress in the corresponding hydrate system. Furthermore, the strain value of the maximum compressive stress was also larger than that of the maximum tensile stress.

This study aims to investigate the change in microstructure of sI methane hydrate and the law of stress–strain evolution under the condition of stress and tensile tests at low temperature and high pressure. It not only expounded the mechanical characteristic mechanism of sI methane hydrate under a pressured state, but also microscopically obtained the law of stability of natural gas hydrate structure initially. Hopefully, a deepened study of micro-stress mechanism of hydrate particles would provide theoretical guidance and lay a basis for the efficient exploitation of natural gas hydrate in practical projects.

Acknowledgement

The authors would like to acknowledge the colleagues from the State Key Laboratory of Coal Mine Disaster Dynamics and Control for their perspectives and suggestions related to experimental study and data analyses.

This research is supported by the National Natural Science Foundation of China (Grant No. 51904040 and 51874055), Chongqing Research Program of Basic Research and Frontier Technology (cstc2018jcyjAX0522), Doctoral Foundation of Southwest University of Science and Technology (Grant No. 17zx7161 and 17LZXT05), the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT_17R112), and Innovation Support Program for Chongqing Overseas Returnees (Grant No. cx2018071).

  1. Conflict of interest: Authors declare no conflict of interest.

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Received: 2018-10-05
Accepted: 2019-12-05
Published Online: 2020-02-20

© 2020 Qiang Wang et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  37. Comparative studies of two vegetal extracts from Stokesia laevis and Geranium pratense: polyphenol profile, cytotoxic effect and antiproliferative activity
  38. Fragmentation pattern of certain isatin–indole antiproliferative conjugates with application to identify their in vitro metabolic profiles in rat liver microsomes by liquid chromatography tandem mass spectrometry
  39. Investigation of polyphenol profile, antioxidant activity and hepatoprotective potential of Aconogonon alpinum (All.) Schur roots
  40. Lead discovery of a guanidinyl tryptophan derivative on amyloid cascade inhibition
  41. Physicochemical evaluation of the fruit pulp of Opuntia spp growing in the Mediterranean area under hard climate conditions
  42. Electronic structural properties of amino/hydroxyl functionalized imidazolium-based bromide ionic liquids
  43. New Schiff bases of 2-(quinolin-8-yloxy)acetohydrazide and their Cu(ii), and Zn(ii) metal complexes: their in vitro antimicrobial potentials and in silico physicochemical and pharmacokinetics properties
  44. Treatment of adhesions after Achilles tendon injury using focused ultrasound with targeted bFGF plasmid-loaded cationic microbubbles
  45. Synthesis of orotic acid derivatives and their effects on stem cell proliferation
  46. Chirality of β2-agonists. An overview of pharmacological activity, stereoselective analysis, and synthesis
  47. Fe3O4@urea/HITh-SO3H as an efficient and reusable catalyst for the solvent-free synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives
  48. Adsorption kinetic characteristics of molybdenum in yellow-brown soil in response to pH and phosphate
  49. Enhancement of thermal properties of bio-based microcapsules intended for textile applications
  50. Exploring the effect of khat (Catha edulis) chewing on the pharmacokinetics of the antiplatelet drug clopidogrel in rats using the newly developed LC-MS/MS technique
  51. A green strategy for obtaining anthraquinones from Rheum tanguticum by subcritical water
  52. Cadmium (Cd) chloride affects the nutrient uptake and Cd-resistant bacterium reduces the adsorption of Cd in muskmelon plants
  53. Removal of H2S by vermicompost biofilter and analysis on bacterial community
  54. Structural cytotoxicity relationship of 2-phenoxy(thiomethyl)pyridotriazolopyrimidines: Quantum chemical calculations and statistical analysis
  55. A self-breaking supramolecular plugging system as lost circulation material in oilfield
  56. Synthesis, characterization, and pharmacological evaluation of thiourea derivatives
  57. Application of drug–metal ion interaction principle in conductometric determination of imatinib, sorafenib, gefitinib and bosutinib
  58. Synthesis and characterization of a novel chitosan-grafted-polyorthoethylaniline biocomposite and utilization for dye removal from water
  59. Optimisation of urine sample preparation for shotgun proteomics
  60. DFT investigations on arylsulphonyl pyrazole derivatives as potential ligands of selected kinases
  61. Treatment of Parkinson’s disease using focused ultrasound with GDNF retrovirus-loaded microbubbles to open the blood–brain barrier
  62. New derivatives of a natural nordentatin
  63. Fluorescence biomarkers of malignant melanoma detectable in urine
  64. Study of the remediation effects of passivation materials on Pb-contaminated soil
  65. Saliva proteomic analysis reveals possible biomarkers of renal cell carcinoma
  66. Withania frutescens: Chemical characterization, analgesic, anti-inflammatory, and healing activities
  67. Design, synthesis and pharmacological profile of (−)-verbenone hydrazones
  68. Synthesis of magnesium carbonate hydrate from natural talc
  69. Stability-indicating HPLC-DAD assay for simultaneous quantification of hydrocortisone 21 acetate, dexamethasone, and fluocinolone acetonide in cosmetics
  70. A novel lactose biosensor based on electrochemically synthesized 3,4-ethylenedioxythiophene/thiophene (EDOT/Th) copolymer
  71. Citrullus colocynthis (L.) Schrad: Chemical characterization, scavenging and cytotoxic activities
  72. Development and validation of a high performance liquid chromatography/diode array detection method for estrogen determination: Application to residual analysis in meat products
  73. PCSK9 concentrations in different stages of subclinical atherosclerosis and their relationship with inflammation
  74. Development of trace analysis for alkyl methanesulfonates in the delgocitinib drug substance using GC-FID and liquid–liquid extraction with ionic liquid
  75. Electrochemical evaluation of the antioxidant capacity of natural compounds on glassy carbon electrode modified with guanine-, polythionine-, and nitrogen-doped graphene
  76. A Dy(iii)–organic framework as a fluorescent probe for highly selective detection of picric acid and treatment activity on human lung cancer cells
  77. A Zn(ii)–organic cage with semirigid ligand for solvent-free cyanosilylation and inhibitory effect on ovarian cancer cell migration and invasion ability via regulating mi-RNA16 expression
  78. Polyphenol content and antioxidant activities of Prunus padus L. and Prunus serotina L. leaves: Electrochemical and spectrophotometric approach and their antimicrobial properties
  79. The combined use of GC, PDSC and FT-IR techniques to characterize fat extracted from commercial complete dry pet food for adult cats
  80. MALDI-TOF MS profiling in the discovery and identification of salivary proteomic patterns of temporomandibular joint disorders
  81. Concentrations of dioxins, furans and dioxin-like PCBs in natural animal feed additives
  82. Structure and some physicochemical and functional properties of water treated under ammonia with low-temperature low-pressure glow plasma of low frequency
  83. Mesoscale nanoparticles encapsulated with emodin for targeting antifibrosis in animal models
  84. Amine-functionalized magnetic activated carbon as an adsorbent for preconcentration and determination of acidic drugs in environmental water samples using HPLC-DAD
  85. Antioxidant activity as a response to cadmium pollution in three durum wheat genotypes differing in salt-tolerance
  86. A promising naphthoquinone [8-hydroxy-2-(2-thienylcarbonyl)naphtho[2,3-b]thiophene-4,9-dione] exerts anti-colorectal cancer activity through ferroptosis and inhibition of MAPK signaling pathway based on RNA sequencing
  87. Synthesis and efficacy of herbicidal ionic liquids with chlorsulfuron as the anion
  88. Effect of isovalent substitution on the crystal structure and properties of two-slab indates BaLa2−xSmxIn2O7
  89. Synthesis, spectral and thermo-kinetics explorations of Schiff-base derived metal complexes
  90. An improved reduction method for phase stability testing in the single-phase region
  91. Comparative analysis of chemical composition of some commercially important fishes with an emphasis on various Malaysian diets
  92. Development of a solventless stir bar sorptive extraction/thermal desorption large volume injection capillary gas chromatographic-mass spectrometric method for ultra-trace determination of pyrethroids pesticides in river and tap water samples
  93. A turbidity sensor development based on NL-PI observers: Experimental application to the control of a Sinaloa’s River Spirulina maxima cultivation
  94. Deep desulfurization of sintering flue gas in iron and steel works based on low-temperature oxidation
  95. Investigations of metallic elements and phenolics in Chinese medicinal plants
  96. Influence of site-classification approach on geochemical background values
  97. Effects of ageing on the surface characteristics and Cu(ii) adsorption behaviour of rice husk biochar in soil
  98. Adsorption and sugarcane-bagasse-derived activated carbon-based mitigation of 1-[2-(2-chloroethoxy)phenyl]sulfonyl-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl) urea-contaminated soils
  99. Antimicrobial and antifungal activities of bifunctional cooper(ii) complexes with non-steroidal anti-inflammatory drugs, flufenamic, mefenamic and tolfenamic acids and 1,10-phenanthroline
  100. Application of selenium and silicon to alleviate short-term drought stress in French marigold (Tagetes patula L.) as a model plant species
  101. Screening and analysis of xanthine oxidase inhibitors in jute leaves and their protective effects against hydrogen peroxide-induced oxidative stress in cells
  102. Synthesis and physicochemical studies of a series of mixed-ligand transition metal complexes and their molecular docking investigations against Coronavirus main protease
  103. A study of in vitro metabolism and cytotoxicity of mephedrone and methoxetamine in human and pig liver models using GC/MS and LC/MS analyses
  104. A new phenyl alkyl ester and a new combretin triterpene derivative from Combretum fragrans F. Hoffm (Combretaceae) and antiproliferative activity
  105. Erratum
  106. Erratum to: A one-step incubation ELISA kit for rapid determination of dibutyl phthalate in water, beverage and liquor
  107. Review Articles
  108. Sinoporphyrin sodium, a novel sensitizer for photodynamic and sonodynamic therapy
  109. Natural products isolated from Casimiroa
  110. Plant description, phytochemical constituents and bioactivities of Syzygium genus: A review
  111. Evaluation of elastomeric heat shielding materials as insulators for solid propellant rocket motors: A short review
  112. Special Issue on Applied Biochemistry and Biotechnology 2019
  113. An overview of Monascus fermentation processes for monacolin K production
  114. Study on online soft sensor method of total sugar content in chlorotetracycline fermentation tank
  115. Studies on the Anti-Gouty Arthritis and Anti-hyperuricemia Properties of Astilbin in Animal Models
  116. Effects of organic fertilizer on water use, photosynthetic characteristics, and fruit quality of pear jujube in northern Shaanxi
  117. Characteristics of the root exudate release system of typical plants in plateau lakeside wetland under phosphorus stress conditions
  118. Characterization of soil water by the means of hydrogen and oxygen isotope ratio at dry-wet season under different soil layers in the dry-hot valley of Jinsha River
  119. Composition and diurnal variation of floral scent emission in Rosa rugosa Thunb. and Tulipa gesneriana L.
  120. Preparation of a novel ginkgolide B niosomal composite drug
  121. The degradation, biodegradability and toxicity evaluation of sulfamethazine antibiotics by gamma radiation
  122. Special issue on Monitoring, Risk Assessment and Sustainable Management for the Exposure to Environmental Toxins
  123. Insight into the cadmium and zinc binding potential of humic acids derived from composts by EEM spectra combined with PARAFAC analysis
  124. Source apportionment of soil contamination based on multivariate receptor and robust geostatistics in a typical rural–urban area, Wuhan city, middle China
  125. Special Issue on 13th JCC 2018
  126. The Role of H2C2O4 and Na2CO3 as Precipitating Agents on The Physichochemical Properties and Photocatalytic Activity of Bismuth Oxide
  127. Preparation of magnetite-silica–cetyltrimethylammonium for phenol removal based on adsolubilization
  128. Topical Issue on Agriculture
  129. Size-dependent growth kinetics of struvite crystals in wastewater with calcium ions
  130. The effect of silica-calcite sedimentary rock contained in the chicken broiler diet on the overall quality of chicken muscles
  131. Physicochemical properties of selected herbicidal products containing nicosulfuron as an active ingredient
  132. Lycopene in tomatoes and tomato products
  133. Fluorescence in the assessment of the share of a key component in the mixing of feed
  134. Sulfur application alleviates chromium stress in maize and wheat
  135. Effectiveness of removal of sulphur compounds from the air after 3 years of biofiltration with a mixture of compost soil, peat, coconut fibre and oak bark
  136. Special Issue on the 4th Green Chemistry 2018
  137. Study and fire test of banana fibre reinforced composites with flame retardance properties
  138. Special Issue on the International conference CosCI 2018
  139. Disintegration, In vitro Dissolution, and Drug Release Kinetics Profiles of k-Carrageenan-based Nutraceutical Hard-shell Capsules Containing Salicylamide
  140. Synthesis of amorphous aluminosilicate from impure Indonesian kaolin
  141. Special Issue on the International Conf on Science, Applied Science, Teaching and Education 2019
  142. Functionalization of Congo red dye as a light harvester on solar cell
  143. The effect of nitrite food preservatives added to se’i meat on the expression of wild-type p53 protein
  144. Biocompatibility and osteoconductivity of scaffold porous composite collagen–hydroxyapatite based coral for bone regeneration
  145. Special Issue on the Joint Science Congress of Materials and Polymers (ISCMP 2019)
  146. Effect of natural boron mineral use on the essential oil ratio and components of Musk Sage (Salvia sclarea L.)
  147. A theoretical and experimental study of the adsorptive removal of hexavalent chromium ions using graphene oxide as an adsorbent
  148. A study on the bacterial adhesion of Streptococcus mutans in various dental ceramics: In vitro study
  149. Corrosion study of copper in aqueous sulfuric acid solution in the presence of (2E,5E)-2,5-dibenzylidenecyclopentanone and (2E,5E)-bis[(4-dimethylamino)benzylidene]cyclopentanone: Experimental and theoretical study
  150. Special Issue on Chemistry Today for Tomorrow 2019
  151. Diabetes mellitus type 2: Exploratory data analysis based on clinical reading
  152. Multivariate analysis for the classification of copper–lead and copper–zinc glasses
  153. Special Issue on Advances in Chemistry and Polymers
  154. The spatial and temporal distribution of cationic and anionic radicals in early embryo implantation
  155. Special Issue on 3rd IC3PE 2020
  156. Magnetic iron oxide/clay nanocomposites for adsorption and catalytic oxidation in water treatment applications
  157. Special Issue on IC3PE 2018/2019 Conference
  158. Exergy analysis of conventional and hydrothermal liquefaction–esterification processes of microalgae for biodiesel production
  159. Advancing biodiesel production from microalgae Spirulina sp. by a simultaneous extraction–transesterification process using palm oil as a co-solvent of methanol
  160. Topical Issue on Applications of Mathematics in Chemistry
  161. Omega and the related counting polynomials of some chemical structures
  162. M-polynomial and topological indices of zigzag edge coronoid fused by starphene
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