Inverse gas chromatographic characterization of halloysi-te-carbon composites as adsorbents for skin disinfectants from water solutions

: The influence of physicochemical parameters of halloysite-carbon composites on the adsorption of skin disinfectants was investigated. The dispersive surface free energy and acid-base properties of halloysite-carbon composites were determined using inverse gas chromatography. The free adsorption energy was higher for all halloysite-carbon composites compared to the unmodified halloysite, which acted as a less electron-donating adsorbent. In contrast, the composite obtained using halloysite nanotubes (HNT) and ground microcrystalline cellulose as the carbon precursor exhibited the highest free adsorption energy and the Kb/Ka ratio. These results suggest that the free adsorption energy can be an additional factor influencing the adsorption process. We demonstrated that the composite with the highest free adsorption energy is effective for removing triclosan,


Introduction
Inverse gas chromatography (IGC) is often used for characterizing surface properties of adsorbents, including surface energy heterogeneity, adsorption heat, specific adsorption interactions , free surface energy, and acid-base properties (Shi B et al. 2011).The surface energy of solid adsorbents consists of dispersive and specific components, with the dispersive surface free energy significantly affecting surface properties (Shi B et al. 2011).The Dorris-Gray method (Dorris G.M., Gray D.G. 1980) and the Schultz method (Schultz J. et al. 1987) are commonly used to calculate surface dispersive free energy.Numerous studies have used IGC to characterize the surface properties of silica, alumina, polymers, paper fillers, wood, minerals, carbon fibers, single-wall and multi-wall carbon nanotubes, carbon blacks and graphite, and activated carbons (Gholami F. et  Chlorophenols are used in the production of biocides, cosmetics, plant protection products, and disinfectants.Although the use of triclosan in cosmetics or pharmaceuticals that come into contact with the skin is prohibited, its concentrations in surface waters can reach up to 2,300 ng/L (Bilal, M. et al (2020).Triclosan, chloroxylenol, and chlorophene have toxic effects on organisms and are commonly found in both surface and underground waters.Since these waters serve as a source of drinking water for humans, monitoring their occurrence and effectively removing these compounds from the aquatic environment is a crucial and ongoing research challenge (Gogoi, A. et al. 2018).
In our previous works, we presented the synthesis of halloysite-carbon adsorbents using sucrose as the carbon precursor and demonstrated their use for removing ketoprofen, naproxen, and diclofenac from water.(Szczepanik B. et al. 2019, Szczepanik B. et al. 2020).In another study, we explored two methods for preparing halloysite-carbon composites with cellulose as the carbon precursor.These composites were characterized using the SEM/EDS analysis, low-temperature nitrogen adsorption/desorption methods, and infrared spectrometry (FT-IR).We evaluated their adsorption properties for removing triclosan, chloroxylenol and chlorophene from water (Frydel L. et al. 2023).While the adsorption properties of the halloysite-carbon adsorbents were described by their specific surface area and carbon content, this information alone may be insufficient to fully explain their adsorption behavior.
In this study, we characterized halloysite-carbon composites using IGC and investigated how the obtained physicochemical parameters influence the adsorption of triclosan, chloroxylenol, and chlorophene by these materials.Understanding the impact of these parameters on the adsorption process can help explain the adsorption abilities of halloysite-carbon composites.

Theoretical background
Inverse gas chromatography (IGC) is a fast and precise technique that modifies conventional gas chromatography.The main goal of IGC is to study the interaction between the adsorbent and the adsorbate by introducing test substances with known properties into a column containing the tested adsorbent.The retention times and peak profiles of these substances provide information on the physicochemical parameters of the adsorbent (Ocak H. et al. 2008, Voelkel A. et al. 2015, Słomkiewicz P. M. 2019).The most important factors influencing the adsorption process include temperature, pressure, and the flow rate of the carrier gas.
Surface energy includes dispersion interactions, van der Waals forces, and polar interactions, such as acid-base interactions, hydrogen bonds, and π-π interactions (Szczepanik B. et al. 2020).Two main types of interactions occur between the adsorbent and the test substances: London dispersion forces (temporary dipole-induced dipole interactions) and specific intermolecular interactions (resulting from the interactions between polar functional groups).These interactions are characterized using adsorption free energy (ΔG a ) and surface free energy (γ s ).
The adsorption free energy is the sum of the dispersive (ΔG ad ) and the specific (ΔG asp ) adsorption free energy, while the surface free energy is the sum of the dispersive (γ sd ) and the specific (γ ssp ) surface free energy (Voelkel A. et al. 2015.).In the Schultz method, the adsorption free energy is calculated only on the basis of the dispersion part: Inverse gas chromatography (IGC) is a fast and precise technique that modifies ventional gas chromatography.The main goal of IGC is to study the interaction between adsorbent and the adsorbate by introducing test substances with known properties into a umn containing the tested adsorbent.The retention times and peak profiles of these stances provide information on the physicochemical parameters of the adsorbent (Ocak H. al. 2008, Voelkel A. et al. 2015, Słomkiewicz P. M. 2019).The most important factors luencing the adsorption process include temperature, pressure, and the flow rate of the rier gas.
Surface energy includes dispersion interactions, van der Waals forces, and polar eractions, such as acid-base interactions, hydrogen bonds, and π-π interactions (Szczepanik et al. 2020).Two main types of interactions occur between the adsorbent and the test stances: London dispersion forces (temporary dipole-induced dipole interactions) and cific intermolecular interactions (resulting from the interactions between polar functional ups).These interactions are characterized using adsorption free energy (ΔG a ) and surface e energy (γ s ).
The adsorption free energy is the sum of the dispersive (ΔG ad ) and the specific (ΔG asp ) orption free energy, while the surface free energy is the sum of the dispersive (γ sd ) and the cific (γ ssp ) surface free energy (Voelkel A. et al. 2015.). the Schultz method, the adsorption free energy is calculated only on the basis of dispersion part: (1) ere: R is the gas constant (J/(mol K)), T is the column temperature (K), V' N,n is the rected retention volume of n-alkane (cm 3 ), C is a constant.
Free adsorption energy of the methylene group is also taken into account in order describe the interactions between the adsorbent and the adsorbate: (2) ere: is the free energy of adsorption of the methylene group (J/mol), N A is the ogadro's number, is the cross-sectional area of the methylene group (m 2 ), is the persion component of surface free energy (mJ/m 2 ), and is the dispersion energy of the ted molecule (mJ/m 2 ). ( where: R is the gas constant (J/(mol K)), T is the column temperature (K), V' N,n is the corrected retention volume of n-alkane (cm 3 ), C is a constant.Free adsorption energy of the methylene group ΔG CH 2 is also taken into account in order to describe the interactions between the adsorbent and the adsorbate: Inverse gas chromatography (IGC) is a fast and precise technique that modifies ventional gas chromatography.The main goal of IGC is to study the interaction between adsorbent and the adsorbate by introducing test substances with known properties into a umn containing the tested adsorbent.The retention times and peak profiles of these stances provide information on the physicochemical parameters of the adsorbent (Ocak H. al. 2008, Voelkel A. et al. 2015, Słomkiewicz P. M. 2019).The most important factors luencing the adsorption process include temperature, pressure, and the flow rate of the rier gas.
Surface energy includes dispersion interactions, van der Waals forces, and polar ractions, such as acid-base interactions, hydrogen bonds, and π-π interactions (Szczepanik et al. 2020).Two main types of interactions occur between the adsorbent and the test stances: London dispersion forces (temporary dipole-induced dipole interactions) and cific intermolecular interactions (resulting from the interactions between polar functional ups).These interactions are characterized using adsorption free energy (ΔG a ) and surface energy (γ s ).
The adsorption free energy is the sum of the dispersive (ΔG ad ) and the specific (ΔG asp ) orption free energy, while the surface free energy is the sum of the dispersive (γ sd ) and the cific (γ ssp ) surface free energy (Voelkel A. et al. 2015.). the Schultz method, the adsorption free energy is calculated only on the basis of dispersion part: (1) ere: R is the gas constant (J/(mol K)), T is the column temperature (K), V' N,n is the rected retention volume of n-alkane (cm 3 ), C is a constant.
Free adsorption energy of the methylene group is also taken into account in order escribe the interactions between the adsorbent and the adsorbate: (2) ere: is the free energy of adsorption of the methylene group (J/mol), N A is the ogadro's number, is the cross-sectional area of the methylene group (m 2 ), is the persion component of surface free energy (mJ/m 2 ), and is the dispersion energy of the ted molecule (mJ/m 2 ). (2) where: -ΔG CH 2 is the free energy of adsorption of the methylene group (J/mol), N A is the Avogadro's number, a CH 2 is the crosssectional area of the methylene group (m 2 ), γ s d is the dispersion component of surface free energy (mJ/m 2 ), and γ l d is the dispersion energy of the tested molecule (mJ/m 2 ).
The cross-sectional area of the methylene group a CH 2 can be calculated from the following equation: The cross-sectional area of the methylene group can be calculated from the follow equation: where: M is the molar mass (g) and Ρ is the pressure at the exit of the column (Pa).
The value of can be calculated from the linear form of the following equation: The dependency graph of RT•ln = f is a straight line.The sur free energy value is determined based on the slope coefficient of the line.The ver distance on the axis from the n-alkane line to the point corresponding to the polar subst represents the specific adsorption energy component (ΔG asp ).The Schultz method allow determining both the dispersive component of surface free energy and the spe adsorption free energy component ΔG asp .
The acetone acetonitrile, ethyl acetate, dichloromethane were purchased from Aldrich.
All reagents were of analytical grade.

The characterization of materials by IGC method
Chromatographic tests were performed using the IGC SEA -Inverse Gas Chromatogra & Surface Energy Analyzer, equipped with a flame ionization detector supplied hydrogen at 40 cm 3 /min.and air at 250 cm 3 /min.Helium was used as the carrier gas , w constant flow rate of 20 cm 3 /min through the column.Retention measurements w performed at 140°C, with the detector and dispenser temperatures set at 180°C.G columns, 30 cm in length and 3 mm in internal diameter, were used for the chromatogra measurements.Each adsorbent was isolated on both sides with approximately 2 cm of g wool .Unmodified halloysite nanotubes (HNT) were used as a comparative material fo carbon-halloysite composites.The mass of the adsorbents ranged from 18 to 45 mg.
substances were divided into two groups: non-polar substances (hexane, heptane, oc where: M is the molar mass (g) and Ρ is the pressure at the exit of the column (Pa).
The value of γ s d can be calculated from the linear form of the following equation: The cross-sectional area of the methylene group can be calculated from the foll equation: where: M is the molar mass (g) and Ρ is the pressure at the exit of the column (Pa).
The value of can be calculated from the linear form of the following equation: The dependency graph of RT•ln = f is a straight line.The s free energy value is determined based on the slope coefficient of the line.The v distance on the axis from the n-alkane line to the point corresponding to the polar sub represents the specific adsorption energy component (ΔG asp ).The Schultz method allo determining both the dispersive component of surface free energy and the s adsorption free energy component ΔG asp .

Materials and Reagents
The hexane, heptane, octane, nonane were all purchased from P.O.Ch.(Gliwice, Poland The acetone acetonitrile, ethyl acetate, dichloromethane were purchased from Aldrich.
All reagents were of analytical grade.

The characterization of materials by IGC method
Chromatographic tests were performed using the IGC SEA -Inverse Gas Chromatog & Surface Energy Analyzer, equipped with a flame ionization detector supplied hydrogen at 40 cm 3 /min.and air at 250 cm 3 /min.Helium was used as the carrier gas , constant flow rate of 20 cm 3 /min through the column.Retention measurements performed at 140°C, with the detector and dispenser temperatures set at 180°C.columns, 30 cm in length and 3 mm in internal diameter, were used for the chromatog measurements.Each adsorbent was isolated on both sides with approximately 2 cm o wool .Unmodified halloysite nanotubes (HNT) were used as a comparative material carbon-halloysite composites.The mass of the adsorbents ranged from 18 to 45 mg substances were divided into two groups: non-polar substances (hexane, heptane, o The dependency graph of RT•ln The cross-sectional area of the methylene group can be calculated from th equation: where: M is the molar mass (g) and Ρ is the pressure at the exit of the column (Pa).
The value of can be calculated from the linear form of the following equatio The dependency graph of RT•ln = f is a straight line.T free energy value is determined based on the slope coefficient of the line.T distance on the axis from the n-alkane line to the point corresponding to the pola represents the specific adsorption energy component (ΔGasp).The Schultz method determining both the dispersive component of surface free energy and t adsorption free energy component ΔGasp.

Materials and Reagents
The hexane, heptane, octane, nonane were all purchased from P.O.Ch.(Gliwice, Po The acetone acetonitrile, ethyl acetate, dichloromethane were purchased from Aldri All reagents were of analytical grade.

The characterization of materials by IGC method
Chromatographic tests were performed using the IGC SEA -Inverse Gas Chrom & Surface Energy Analyzer, equipped with a flame ionization detector sup hydrogen at 40 cm 3 /min.and air at 250 cm 3 /min.Helium was used as the carrier g constant flow rate of 20 cm 3 /min through the column.Retention measurem performed at 140°C, with the detector and dispenser temperatures set at 18 columns, 30 cm in length and 3 mm in internal diameter, were used for the chrom measurements.Each adsorbent was isolated on both sides with approximately 2 c wool .Unmodified halloysite nanotubes (HNT) were used as a comparative mate carbon-halloysite composites.The mass of the adsorbents ranged from 18 to 4 substances were divided into two groups: non-polar substances (hexane, hepta is a straight line.The surface free energy value is determined based on the slope coefficient of the line.The vertical distance on the axis from the n-alkane line to the point corresponding to the polar substance represents the specific adsorption energy component (ΔG asp ).The Schultz method allows for determining both the dispersive component of surface free energy γ s d and the specific adsorption free energy component ΔG asp .

Materials and Reagents
The hexane, heptane, octane, nonane were all purchased from P.O.Ch.(Gliwice, Poland).The acetone acetonitrile, ethyl acetate, dichloromethane were purchased from Aldrich.All reagents were of analytical grade.

The characterization of materials by IGC method
Chromatographic tests were performed using the IGC SEA -Inverse Gas Chromatography & Surface Energy Analyzer, equipped with a flame ionization detector supplied with hydrogen at 40 cm 3 /min.and air at 250 cm 3 /min.Helium was used as the carrier gas , with a constant flow rate of 20 cm 3 /min through the column.Retention measurements were performed at 140°C, with the detector and dispenser temperatures set at 180°C.Glass columns, 30 cm in length and 3 mm in internal diameter, were used for the chromatographic measurements.Each adsorbent was isolated on both sides with approximately 2 cm of glass wool .Unmodified halloysite nanotubes (HNT) were used as a comparative material for the carbon-halloysite composites.The mass of the adsorbents ranged from 18 to 45 mg.Test substances were divided into two groups: non-polar substances (hexane, heptane, octane, nonane) and polar substances (acetone, acetonitrile, ethyl acetate, dichloromethane).Methane served as the calibration substance.The test substances were introduced using an autosampler onto the column with the adsorbent, with adsorbent  surface coverage values ranging from 0.0063 to 0.7 mmol/g.Adsorption parameters of the adsorbents were determined using the Cirrus Plus operational program.Among the polar solvents, acetone and ethyl acetate are amphoteric substances, acetonitrile is a basic substance, and dichloromethane is an acidic substance (Table 1) (Gutmann, V 1978, Riddle F.L., Fowkes F.M. 1990).

Adsorption measurements
The details of the batch adsorption measurements are described in Frydel L. et al. (2023).For the adsorption experiments, we used halloysite from the Dunino mine (H), halloysite nanotubes (HNT), and halloysite-carbon composites prepared by two methods.The first method involved dissolving microcrystalline cellulose in a solution of zinc chloride(II) dissolved in hydrochloric acid before adding it to the halloysite.The second method involved milling halloysite and microcrystalline cellulose, with temperatures set at 500 and 800 o C for both methods.The samples were labelled as follows: HZn5 (referred to as H-Zn 500 in Frydel . et al. 2023,), Hm5 (referred to as H-m 500 in Frydel . et al. 2023), HZn8 (in Ref . Frydel L. et al. 2023 H-m 800), HNTZn5 (in Ref .Frydel L. et al. 2023), HNTm5 (referred to as HNT-m 500 in Frydel et al. 2023), HNTZn8 (referred to as HNT-Zn 800 in Frydel et al. 2023), and HNTm8 (referred to as HNT-m 800 in Frydel et al. 2023).
The removal efficiency of adsorbates from the solution (%R) was calculated based on the equation ( 5): and polar substances (acetone, acetonitrile, ethyl acetate, dichloromethane).Methane s the calibration substance.The test substances were introduced using an autosampler column with the adsorbent, with adsorbent surface coverage values ranging from to 0.7 mmol/g.Adsorption parameters of the adsorbents were determined using the lus operational program.ng the polar solvents, acetone and ethyl acetate are amphoteric substances, rile is a basic substance, and dichloromethane is an acidic substance (Table 1) n, V 1978, Riddle F.L., Fowkes F.M. 1990).ion measurements details of the batch adsorption measurements are described in Frydel L. et al. (2023).
adsorption experiments, we used halloysite from the Dunino mine (H), halloysite es (HNT), and halloysite-carbon composites prepared by two methods.The first involved dissolving microcrystalline cellulose in a solution of zinc chloride(II) d in hydrochloric acid before adding it to the halloysite.The second method involved halloysite and microcrystalline cellulose, with temperatures set at 500 and 800 o C for thods.The samples were labelled as follows: HZn5 (referred to as H-Zn 500 in et al. 2023,), Hm5 (referred to as H-m 500 in Frydel . et al. 2023), HZn8 (in Ref . . et al. 2023H-m 800), HNTZn5 (in Ref . Frydel L. et al. 2023) (Frydel L. et al. 2023).The carbon content in halloysitecomposites ranges from 14.12% for HNTm5 to 32.26% (% wt.) for HNTZn8, g the order: HNTm5 < Hm5 < HZn5 < HNTm8 < Hm8 < HZn8 < HNTZn5 < 8.The HNTZn5 and HNTZn8 samples contain the highest carbon amounts (30.00 and (5) where: C 0 and C e are the initial and equilibrium concentrations of the solution (mg/dm 3 ), respectively.

Characteristics of adsorbents by inverse gas chromatography
Tables 2-4 present the values of adsorption free energy (ΔG a ) determined by the Schultz method, the specific free energy of adsorption (ΔG asp ), and the acid-base constants for all tested adsorbents.The values of free adsorption energy for the tested adsorbents are summarized in Table 2.The highest free adsorption energy (ΔG a ) is observed for the following adsorbents: HNTm8, Hm8 and HNTZn8, suggesting that these materials exhibit the best adsorption properties.Adsorptionfree energy values above 100 mJ/m 2 indicate very high activity (Voelkel A. et al. 2015).
The specific free adsorption energy (ΔG asp ) and the ratio of carbon content to oxygen content (C/O) are influenced by the presence and concentration of surface functional groups.As shown in Table 3 The values are greater than 1 for all of the tested materials, indica all adsorbents are basic (they are electron donors) and have more basi sites.These adsorbents will interact more strongly with acidic s halloysite-carbon composites, the most basic (electron-donating) m HZn5, and HNTm8.This is confirmed by the ratio and the high component of the free adsorption energy (ΔG a sp ) for basic aceton (electron-acceptor) material is HNTZn8, as evidenced by the lowes highest ΔG a sp value for acidic dichloromethane in the case of this concentration of acidic (electron-acceptor) functional groups on th results in a low value of the ratio and a high ΔG a sp value for a Conversely, the high concentration of basic (electron-donating) fun surface of Hm8 and HNTm8 results in high ratios and ΔG a sp value (see Table 5) The values of the dispersive surface free energy for the obt compared with those obtained for carbon materials (see Table 6).T ratios for the tested adsorbents are summarized in Table 4.
The values are greater than 1 for all of the tested materials, indicating that the surfaces of all adsorbents are basic (they are electron donors) and have more basic sites and fewer acidic sites.These adsorbents will interact more strongly with acidic substances.Among the halloysite-carbon composites, the most basic (electron-donating) materials include Hm8, HZn5, and HNTm8.This is confirmed by the Tables 2-4 present the values of adsorption free energy (ΔG a ) determined by the Schult method, the specific free energy of adsorption (ΔG asp ), and the acid-base constants for a tested adsorbents.
The values of free adsorption energy for the tested adsorbents are summarized in Table 2 The highest free adsorption energy (ΔG a ) is observed for the following adsorbents: HNTm8 Hm8 and HNTZn8, suggesting that these materials exhibit the best adsorption properties Adsorption-free energy values above 100 mJ/m 2 indicate very high activity (Voelkel A. et a 2015).
The specific free adsorption energy (ΔG asp ) and the ratio of carbon content to oxyge content (C/O) are influenced by the presence and concentration of surface functional groups As shown in Table 3, ΔG a sp values increase together with a higher C/O ratio.The HNTm8 an HNTZn8 composites exhibit both a high C/O ratio and high ΔG a sp values.The HNTm8 an HNTZn8 adsorbents have the highest specific free energy of adsorption as determined by th Schultz method.The ratios for the tested adsorbents are summarized in Table 4.
The values are greater than 1 for all of the tested materials, indicating that the surfaces o all adsorbents are basic (they are electron donors) and have more basic sites and fewer acidi sites.These adsorbents will interact more strongly with acidic substances.Among th halloysite-carbon composites, the most basic (electron-donating) materials include Hm8 HZn5, and HNTm8.This is confirmed by the ratio and the high values of the specifi component of the free adsorption energy (ΔG a sp ) for basic acetonitrile.The most acidi (electron-acceptor) material is HNTZn8, as evidenced by the lowest the ratio and th highest ΔG a sp value for acidic dichloromethane in the case of this adsorbent.The highes concentration of acidic (electron-acceptor) functional groups on the surface of HNTZn results in a low value of the ratio and a high ΔG a sp value for acidic dichloromethane Conversely, the high concentration of basic (electron-donating) functional groups on th surface of Hm8 and HNTm8 results in high ratios and ΔG a sp values for basic acetonitrile (see Table 5) The values of the dispersive surface free energy for the obtained adsorbents wer compared with those obtained for carbon materials (see Table 6).The HNTm8 adsorben ratio and the high values of the specific component of the free adsorption energy (ΔG a sp ) for basic acetonitrile.The most acidic (electron-acceptor) material is HNTZn8, as evidenced by the lowest the HNTZn5 and HNTZn8 composites.

Characteristics of adsorbents by inverse gas chromatography
Tables 2-4 present the values of adsorption free energy (ΔG a ) det method, the specific free energy of adsorption (ΔG asp ), and the aci tested adsorbents.
The values of free adsorption energy for the tested adsorbents are The highest free adsorption energy (ΔG a ) is observed for the followi Hm8 and HNTZn8, suggesting that these materials exhibit the be Adsorption-free energy values above 100 mJ/m 2 indicate very high a 2015).
The specific free adsorption energy (ΔG asp ) and the ratio of ca content (C/O) are influenced by the presence and concentration of su As shown in (see Table 5) The values of the dispersive surface free energy for the ob compared with those obtained for carbon materials (see Table 6).
ratio and the highest ΔG a sp value for acidic dichloromethane in the case of this adsorbent.The highest concentration of acidic (electron-acceptor) functional groups on the surface of HNTZn8 results in a low value of the 32.26%, respectively).In addition, the largest specific surface areas are observed fo HNTZn5 and HNTZn8 composites.

Characteristics of adsorbents by inverse gas chromatography
Tables 2-4 present the values of adsorption free energy (ΔG a ) determined by the Sc method, the specific free energy of adsorption (ΔG asp ), and the acid-base constants fo tested adsorbents.
The values of free adsorption energy for the tested adsorbents are summarized in Tab The highest free adsorption energy (ΔG a ) is observed for the following adsorbents: HN Hm8 and HNTZn8, suggesting that these materials exhibit the best adsorption prope Adsorption-free energy values above 100 mJ/m 2 indicate very high activity (Voelkel A. 2015).
The specific free adsorption energy (ΔG asp ) and the ratio of carbon content to ox content (C/O) are influenced by the presence and concentration of surface functional gro As shown in Table 3, ΔG a sp values increase together with a higher C/O ratio.The HNTm8 HNTZn8 composites exhibit both a high C/O ratio and high ΔG a sp values.The HNTm8 HNTZn8 adsorbents have the highest specific free energy of adsorption as determined b Schultz method.The ratios for the tested adsorbents are summarized in Table 4.
The values are greater than 1 for all of the tested materials, indicating that the surfac all adsorbents are basic (they are electron donors) and have more basic sites and fewer a sites.These adsorbents will interact more strongly with acidic substances.Among halloysite-carbon composites, the most basic (electron-donating) materials include H HZn5, and HNTm8.This is confirmed by the ratio and the high values of the spe component of the free adsorption energy (ΔG a sp ) for basic acetonitrile.The most a (electron-acceptor) material is HNTZn8, as evidenced by the lowest the ratio and highest ΔG a sp value for acidic dichloromethane in the case of this adsorbent.The hi concentration of acidic (electron-acceptor) functional groups on the surface of HNT results in a low value of the ratio and a high ΔG a sp value for acidic dichloromet Conversely, the high concentration of basic (electron-donating) functional groups on surface of Hm8 and HNTm8 results in high ratios and ΔG a sp values for basic aceton (see Table 5) The values of the dispersive surface free energy for the obtained adsorbents compared with those obtained for carbon materials (see Table 6).The HNTm8 adso ratio and a high ΔG a sp value for acidic dichloromethane.Conversely, the high concentration of basic (electron-donating) functional groups on the surface of Hm8 and HNTm8 results in high 32.26%,respectively).In addition, the largest specific surface area HNTZn5 and HNTZn8 composites.

Characteristics of adsorbents by inverse gas chromatography
Tables 2-4 present the values of adsorption free energy (ΔG a ) dete method, the specific free energy of adsorption (ΔG asp ), and the acid tested adsorbents.
The values of free adsorption energy for the tested adsorbents are s The highest free adsorption energy (ΔG a ) is observed for the followin (see Table 5) The values of the dispersive surface free energy for the obta compared with those obtained for carbon materials (see Table 6).T ratios and ΔG a sp values for basic acetonitrile.(see Table 5) The values of the dispersive surface free energy for the obtained adsorbents were compared with those obtained for carbon materials (see Table 6).The HNTm8 adsorbent exhibits higher values of the specific component of surface free energy than the carbon materials, with the exception of spherical activated carbon.

Adsorption experiments in batch system
This paper also discusses the influence of the adsorbent type on the adsorption of triclosan, chloroxylenol and chlorophene from water.The removal efficiencies of these adsorbates for the adsorbents used are collected in Table 7.The detailed data on the adsorption process are presented in Frydel L. et al. (2023).
, HNTm5 (referred to -m 500 in Frydel et al. 2023), HNTZn8 (referred to as HNT-Zn 800 in Frydel et al. nd HNTm8 (referred to as HNT-m 800 in Frydel et al. 2023).removal efficiency of adsorbates from the solution (%R) was calculated based on the (C e are the initial and equilibrium concentrations of the solution (mg/dm 3 ers of the porous structure and carbon content for HNT, H-carbon and HNT-carbon ites are presented in Table 2 Hm8 and HNTZn8, suggesting that these materials exhibit the best Adsorption-free energy values above 100 mJ/m 2 indicate very high ac 2015).The specific free adsorption energy (ΔG asp ) and the ratio of car content (C/O) are influenced by the presence and concentration of sur As shown in Table 3, ΔG a sp values increase together with a higher C/O HNTZn8 composites exhibit both a high C/O ratio and high ΔG a sp va HNTZn8 adsorbents have the highest specific free energy of adsorptio Schultz method.The ratios for the tested adsorbents are summarized The values are greater than 1 for all of the tested materials, indicat all adsorbents are basic (they are electron donors) and have more basic sites.These adsorbents will interact more strongly with acidic su halloysite-carbon composites, the most basic (electron-donating) m HZn5, and HNTm8.This is confirmed by the ratio and the high component of the free adsorption energy (ΔG a sp ) for basic acetoni (electron-acceptor) material is HNTZn8, as evidenced by the lowes highest ΔG a sp value for acidic dichloromethane in the case of this concentration of acidic (electron-acceptor) functional groups on th results in a low value of the ratio and a high ΔG a sp value for a Conversely, the high concentration of basic (electron-donating) fun surface of Hm8 and HNTm8 results in high ratios and ΔG a sp value

Table 1 .
Properties of the polar solvents used (AN -acceptor number, DN -donor number).

Table 4 .
Specific component of adsorption free energy ΔG a sp(kJ/mol) for adsorbents.

Table 2 .
Parameters of the porous structure and carbon content obtained for HNT, H-carbon and HNT-carbon composites[14].

Table 3 .
Dispersive surface free energy of adsorbents determined by the Schultz method.

Table 6 .
Dispersive surface free energy of HNT and obtained halloysite-carbon composites.
, ΔG a sp values increase together with a higher C/O ratio.The HNTm8 and HNTZn8 composites exhibit both a high C/O ratio and high ΔG a sp values.The HNTm8 and HNTZn8 adsorbents have the highest specific free energy of adsorption as determined by the Schultz method.The 2015).The specific free adsorption energy (ΔG asp ) and the ratio of car content (C/O) are influenced by the presence and concentration of sur As shown in Table 3, ΔG a sp values increase together with a higher C/O HNTZn8 composites exhibit both a high C/O ratio and high ΔG a sp va HNTZn8 adsorbents have the highest specific free energy of adsorptio Schultz method.The ratios for the tested adsorbents are summarized