Home Physical Sciences Influence of Chemical Osmosis on Solute Transport and Fluid Velocity in Clay Soils
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Influence of Chemical Osmosis on Solute Transport and Fluid Velocity in Clay Soils

  • Zhihong Zhang , Gailei Tian EMAIL logo and Lin Han
Published/Copyright: April 7, 2020

Abstract

Solute transport through the clay liner is a significant process in many waste landfills or unmanaged landfills. At present, researchers mainly focus on the test study about semi-membrane property of clay material, however, the influence of chemical osmosis caused by membrane effect on solute transport and fluid velocity is insufficient. In this investigation, based on the classical advection-diffusion equation, a one-dimensional solute transport model for low-permeable clay material has been proposed, in which the coupled fluid velocity related with hydraulic gradient and concentration gradient is introduced, and the semi-membrane effect is embodied in the diffusion mechanism. The influence of chemical osmosis on fluid velocity and solute transport has been analyzed using COMSOL Multiphysics software. The simulated results show that chemical osmosis has a significant retarded action on fluid velocity and pollutant transport. The proposed model can effectively reveal the change in process of coupled fluid velocity under dual gradient and solute transport, which can provide a theoretical guidance for similar fluid movement in engineering.

1 Introduction

It is well known that clay materials can exhibit semipermeable membrane behavior, which has been proven by large amount of indoor and on-site experiments [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11] Technical researchers typically pay more attention to the influence of clay membrane behavior on practical engineering, i.e. solid waste landfill, geothermal exploitation, nuclear waste disposal, intrusion of saltwater, and so on. When different concentrated chemicals exist on both sides of clay soils, due to the permeable membrane behavior of clay, it only allows the passage of water molecules while preventing chemicals under the concentration gradient to dislocate. The water molecules in low concentration solution will move to the high concentration solution to maintain bilateral concentration balance. The process of water flow due to concentration gradient is called chemical osmosis. The osmotic efficiency coefficient ɷ is usually used to demonstrate the ideal condition of clay as a semi-membrane material.

The concept of the osmotic efficiency coefficient was first proposed by Staverman [12], which was defined by the ratio of osmosis pressure measured value and the theoretically calculated value, under constant temperature. , This concept has since been used to explain the osmotic mechanism in engineering practices. The investigation of Garavito [3] and Cruchaudet [4] showed that the osmotic efficiency coefficient decreases with the increase of solution concentration. Shackelford’s research group [8, 9, 10] conducted research on the measurement of the osmotic efficiency coefficient, the influence factors such as solution ions, solution concentration, clay mineral types and other factors. In addition, Zuo and Wu et al. [13, 14, 15, 16] conducted some indoor experiments with clay materials to study the osmotic efficiency coefficient in different areas in China. Some researchers focussed on the influence of the osmotic efficiency coefficient on contaminant transport [17, 18, 19, 20]. Their results indicated that chemical movement was hindered when ω value increased. Baechler [21] performed numerical simulations on the chemical migration with viewing ω value as the function of solute concentration. The simulated results showed that the relationship between ω value and solute concentration had a significant influence on solute transport. Liu et al. [22] proposed a coupling dynamic model of solute transport, considering the effect of membrane behavior and cation exchange, the results indicated that the chemiosmosis in geo-synthetic clay liner (GCL) could effectively delay the solute transport velocity. It is noteworthy that in the process of solute transport, the retardation effect due to chemiosmosis increases with the decrease of the solute concentration. Sun et al. [16] proposed that chemical osmosis was the key factor affecting the pore water movement and it even exceed hydraulic head. Thus chemical osmosis is of significance to control the concentration distribution with time and space of contaminant and it will change the breakthrough flux of solute. However, the influence mechanism of chemical osmosis to pore water flow has not been analyzed by researchers. Most importantly, there is less quality evaluation of results and discussion about the intrinsic mechanism of the chemical osmosis effect on contaminant transport process.

The aim of the study is to propose a 1D contaminant transport model for low permeability clay media based on the classical convection-diffusion equation. The combined driving action of hydraulic gradient and concentration gradient is taken into consideration, and the coupled fluid velocity caused by the hydraulic gradient and the concentration gradient is introduced. Furthermore, the diffusion mechanism incorporates the semi-membrane effect of clay material. The COMSOL Multiphysics software is used to conduct a numerical simulation to investigate the chemical osmosis on pore fluid flow and solute transport. The numerical results can afford a theoretical support for multi-physics fields coupled process.

2 Modified solute transport model

The classical 1D convection-diffusion model of solute transport can be described by the following equation,

(1)Rdct=Jv+D2cz2

where R d is the retardation factor of clay to chemicals. It can be expressed as Rd=1+Kdρsnunder linear pattern of adsorption, where Kd is the adsorption coefficient; ρs is the density of solid; c is the contaminant concentration; Jv is the solute flux due to convection; D is the effective diffusion coefficient of chemicals.

When the semi-permeability membrane of clay media is taken into account, the solute flux due to convection can be given by the following,

(2)Jv=1ωvfc

where vf is the true velocity of pore fluid across the clay. The relationship between true velocity and average velocity is given as the following,

(3)vf=vn

where n is the porosity and v is the average velocity or Darcy velocity. If the hydraulic gradient and chemical concentration gradient exist simultaneously, the flow of pore fluid will be driven by dual gradient.

(4)v=khih+kcic

where k h is the hydraulic coefficient; i h is the fluid hydraulic gradient; k c is the chemical hydraulic coefficient and i c is the chemical concentration gradient. The chemical hydraulic coefficient and chemical concentration gradient can be written as

(5)kc=ωkh
(6)ic=1γwπz

where γ w is the unit weight of pore water and π is the osmotic pressure.

For the contaminant with anionic and cationic valency 1:1, the osmotic pressure can be approximately expressed by Vander Hoff formula when the concentration value of contaminant is less than 1 M/L.

(7)π=RTc

where R is the universal gas constant and T is the absolute temperature.

Because the pore channels of clay are different in shape, the diffusion coefficient of contaminant is generally less than that in free water. In general, the effective diffusion coefficient of contaminant in soil can be written as [8]

(8)D=τ1ωD0
(9)τ=nm

where τ is the tortuosity factor [23]; D0 is the diffusion coefficient of contaminant in free water and m is the empirical coefficient.

Table 1

Model parameter.

ParameterD0 (m2/s)Kd (L/kg)R (J/mol/K)T (K)ρs (kg/m3)γw (N/m3)kh (cm/s)nω
Value5.0×10-90.81428.31429826001.0×1041.0×10-70.50.05
  1. Note: Kd value is from [26].

Substituting Eqs.(2)-(9) into Eq.(1) yields,

(10)1+Kdρsnct=.1ωkhnih+ωkhnRTγwMczc+nm1ωD02cz2

where M is the molar mass of contaminants.

Eq.(10) is the convection-diffusion equation of 1D contaminant transport considering chemical osmosis effect under the combined action of a hydraulic gradient and concentration gradient.

3 Numerical simulation

3.1 Transport system of solute in clay liner

Figure 1 shows a schematic representation of clay liner. It can be seen that the leachate produced by the waste decomposition will leak into the clay soils, and further break through the clay liner into the ground water, which will result in a potential danger of ground water contamination.

Figure 1 A schematic of clay liner.
Figure 1

A schematic of clay liner.

3.2 Solution conditions and model parameters

The model simulations were carried out using COMSOL Multiphysics software. The research object is the clay liner with depth 1m. Sodium chloride (NaCl) solution is taken as the contaminated source with constant concentration.

The Cauchy boundary condition is occupied in the numerical simulation as follows:

Initial conditions: c(z,0) = 0, (0 < z <1m)

Boundary conditions: c ( 0,t ) = c0 , ( z = 0,t ≥ 0 ) ;

λcz+μc=0,(z=1m,t0)

where λ and μ are the Cauchy condition parameters. In this study, μ/λ=0.1m-1 [24], λ=17.37m [25].

3.3 Simulation results

In order to study the influence of chemical osmosis on contaminant transport, the proposed convection-diffusion equation is solved by COMSOL Multiphysics software. The results include two cases (considering chemical osmosis and ignoring chemical osmosis), in which the convection-diffusion equation ignoring chemical osmosis is as following:

(12)1+Kdρsnct=1ωkhnihc+nm1ωD02cz2

3.3.1 Influence of chemical osmosis on solute transport and fluid velocity

The NaCl concentration at the upper boundary of clay liner is 0.04 mol/L, the hydraulic gradient is 3 [27]. The concentration distributions results of NaCl with depth considering chemical osmosis and ignoring chemical osmosis are shown in Figure 2. It can be seen that at the same transport time and any soil depth, the contaminant concentration considering chemical osmosis is obviously smaller than that ignoring chemical osmosis, which shows that the chemical osmosis has a significant retardation effect on contaminant transport. The main reason is that the NaCl concentration in the pore fluid of soil is less than that of the external concentration of the soil. The concentration difference inside and outside clay will cause semi-permeable membrane effect, thus the pore water will flow from a low concentration to high concentration area under the driving force of a concentration gradient. It is noteworthy that the water movement under the concentration gradient is opposite to that of water movement under the hydraulic gradient, which can delay the contaminant migration.

Figure 2 Distribution of solute concentration with depth.
Figure 2

Distribution of solute concentration with depth.

The evolution of NaCl concentration with time on the bottom boundary of the clay liner has been shown in Figure 3. It can be seen that the accumulated concentration values, considering chemical osmosis effect, are less than those ignoring chemical osmosis effect at any time. Furthermore, the concentration difference caused by considering chemical osmosis versus ignoring chemical osmosis increases with the time elapsed. For example, the concentration difference reaches 0.006 mol/L when transport time reaches 20 years, which is 16% of input NaCl concentration. According to the quality standard for ground water of People’s Republic of China, the drinking water standard III for chloride is 0.25 g/L. The breakthrough time of NaCl ignoring chemical osmosis is 10.18 years, however, it reaches 12.24 years when considering chemical osmosis. The results show that the breakthrough time considering chemical osmosis reduces by 20% under the same simulated condition.

Figure 3 Distribution of solute concentration with time at the bottom boundary.
Figure 3

Distribution of solute concentration with time at the bottom boundary.

The distributions of pore fluid velocity with soil depth at different transport time are shown in Figure 4.

Figure 4 Distribution of pore fluid velocity with depth.
Figure 4

Distribution of pore fluid velocity with depth.

It can be seen from Figure 4 that chemical osmosis has a significant effect on seepage velocity. Over time, due to weaker chemical osmosis, the effect of the reduction gradually decreases with the decrease of concentration difference between internal and external clay soil. When the chemical osmosis effect is not considered, the pore fluid movement is only caused by the hydraulic gradient, thereby the velocities are determined and controlled by hydraulic conductivity and head difference. The hydraulic conductivity coefficient kh is constant when soil structure is stable. Then the seepage velocity will keep constant under the fixed hydraulic gradient. The calculated seepage velocity reaches 9.5 cm/year as illustrated in Figure 4 (green line). It is noteworthy that the seepage velocities change under the chemical osmosis effect. At the early stage (i.e. 1 year) the seepage velocity at 0.1 m soil depth is negative (shown with black line), which indicates the chemical osmosis at the upper soil is more intense. The main reason is that most of the contaminant ions have not entered into the soil layer at the early stage, the concentration difference between internal and external of the upper soil reaches the extreme state, which means that the difference reaches the maximum value. Therefore, the chemical osmosis effect induced by the concentration gradient is strongest. According to the membrane effect, the water will flow from low concentration to high concentration, and the water velocity from internal to external soil is even more than the water velocity flowing into the internal soil caused by head difference, so the overall apparent velocity appears negative. As the time goes on, the contaminant ions enter the soil continuously, which leads to concentration difference; the internal and external concentration of soil gradually decreases. At the macroscopic scale, the downward flow velocity induced by hydraulic gradient becomes the dominate factor, thereby the overall velocity values are positive. It can be seen that at different simulated migration times (1 year, 5 years, 10 years and 20 years), the total velocity is less than that obtained when ignoring chemical osmosis. The results show that the inhibitory effect of the concentration gradient on velocity is still present in soil, and the influence weakens gradually as the time elapses. In addition, the inhibitory action of chemical osmosis on total flow velocity gradually decreases with the increase of soil depth, which means the values of chemical osmosis velocity induced by concentration difference of internal and external soil layer decrease gradually.

3.3.2 Influence of contaminant concentration on solute transport and fluid velocity

The concentration difference is a necessary condition for the chemical osmotic flow. The contaminant concentration values of the upper boundary of the soil layer will directly affect the contaminant concentration difference between internal and external soil layer, and further affect the exertion of the chemical osmosis effect. In order to quantitatively evaluate the influence of the initial input concentration of contaminant on fluid velocity and contaminant migration, 4 cases with different solute concentrations (0.01 mol/L, 0.02 mol/L, 0.03 mol/L and 0.04 mol/L) at the upper boundary of soil were studied. Since the initial contaminant concentration was different, the ordinate was chosen to be dimensionless in order to obtain the consistent simulation results. It can be seen in Figure 5 that the cumulative values of contaminant concentration show a decreasing trend with the increase of initial concentration of contaminant. The higher the contaminant concentration, the larger the concentration difference between inside and outside of the soil. Thereby the stronger the chemical osmosis effect induced by contaminant concentration, the more obvious the reverse inhibition action on velocity. In the end the strong inhibition action to contaminant transport causes the downward flux of contaminant to decrease (shown in Figure 6). Figure 6 shows that the seepage velocities of pore fluid are positive when initial concentration is less than 0.03 mol/L, which indicates that the seepage direction of pore fluid is consistent with the contaminant migration, and the promoting action of hydraulic gradient on contaminant migration is greater than that of slowing down of chemical osmosis on contaminant migration.

Figure 5 Distribution of pollutant concentration with time at the lower boundary.
Figure 5

Distribution of pollutant concentration with time at the lower boundary.

Figure 6 Distribution of pore water velocity with depth (1 year).
Figure 6

Distribution of pore water velocity with depth (1 year).

In this investigation, the breakthrough condition of contaminant is c/c0×100% =10% according to the judgement standard put forward by Zhang et al [24]. The calculated breakthrough times of contaminant with 4 kinds of concentration are shown in Table 2. The results show that the time for contaminant to break through clay liner increases with the increase of initial concentration of contaminant. When the contaminant concentrations at the upper boundary reach 0.02 mol/L, 0.03 mol/L and 0.04 mol/L, the elongation ratio of breakthrough time reaches 4%, 9% and 15%, respectively, individually compared with the upper boundary concentration 0.01 mol/L.

Table 2

Breakthrough time of pollutant under different initial pollutant concentration.

c0 (mol/L)0.010.020.030.04
Breakthrough time (year)10.4110.8511.3811.97

4 Conclusions

Based on the classical convection-diffusion equation, the 1D contaminant transport model for low-permeability clay medium has been proposed. The chemical osmosis mechanism due to the semi-permeable membrane of clay, linear adsorption pattern, and the coupled fluid velocity under the combining driving action of hydraulic and concentration gradient, are considered. A series of numerical simulations have been carried out using COMSOL Multiphysics software. The results suggest that:

  1. Compared with pore fluid velocity induced by the hydraulic gradient, the chemical osmosis effect has obvious reverse inhibition action on fluid velocity.

  2. The direction of fluid velocity produced by chemical osmosis is opposite to that produced by water head, which plays an inhibited action on solute transport and causes the prolongation of the breakthrough time.

  3. The higher the upper boundary contaminant concentration, the stronger the chemical osmosis effect and the lower the contaminant migration velocity.

Acknowledgements

This work was supported by Key Program of Beijing Natural Science Foundation of China (No.8171001). Financial support is gratefully acknowledged.

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

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Received: 2019-03-01
Accepted: 2019-12-19
Published Online: 2020-04-07

© 2020 Zhihong Zhang, Gailei Tian, Lin Han, published by De Gruyter

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

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  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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