Palm Stone Research Articles

Sulphonated date palm (Phoenix dactylifera) stone via microwave‑assisted H2SO4 activation: optimisation with desirability function for methylene blue adsorption

ABSTRACT In this work, a sulphonated date palm (Phoenix dactylifera) stone (SDPS) was produced as a cost-effective and renewable adsorbent for the removal of a cationic dye called methylene blue (MB). The production process involved the use of microwave irradiation combined with H2SO4 activation under the condition of 600 W microwave radiation for 15 min. The physicochemical characteristics of SDPS were evaluated using various analytical techniques, including XRD, BET, FTIR, pHpzc, and SEM. The Box-Behnken design (BBD) was employed to optimise key adsorption variables, including A: SDPS dosage (0.02–0.1 g/100 mL), B: pH (4–10), and C: contact time (5–25) min. According to the BBD model, the most effective removal of MB (98.4%) occurred with a dosage of 0.06 g/100 mL of SDPS, a pH of 10, and a contact time of 25 min. The rate of adsorption of the MB dye followed a pseudo second order (PSO) model, whereas the equilibrium adsorption was described by the Langmuir and Temkin models. The maximum adsorption capacity (q max ) of SDPS for MB dye was found to be 122.3 mg/g at 25°C. Several contributions to the MB dye adsorption process include electrostatic interactions, H-bonding, pore filling, and π-π stacking onto the SDPS adsorbent surface.

Efficient and low-cost mesoporous magnetic carbon composites derived from date palm stones for environmental remediation of hexavalent chromium

This study was performed to achieve two important scientifically challenging goals, environmental remediation of toxic heavy metals and utilization of agricultural lignocellulosic wastes. In this work, a series of mesoporous magnetic carbon (MMC) adsorbents were synthesized by carbothermic reduction at different temperatures employing date palm (Phoenix dactylifera L.) stones as the carbon source. The synthesized adsorbents were characterized by different technquies and the results confirmed the presence of zero-valent iron (ZVI) nanoparticles and other iron oxides as products of the carbothermal reduction. The nature of phases present, crystallite size and the surface properties were found to be dependent on the calcination temperature. The adsorbent MMC700 exhibited the smallest (ZVI) crystallite size 36 nm and the largest SBET 341 m2/g. All adsorbents showed mesoporous structure with mesopore average diameter lower than 6 nm. The performance was evaluated in the removal process of toxic Cr(VI) in an aqueous medium, and the optimum conditions of the process were reported. The removal process was dependant of solution pH where best results was achieved at pH = 2. Complete removal of chromium was achieved in less than 5 min by MMC700. The results were better fitted with pseudo-second-order kinetics and followed the Freundlich model isotherm. The maximum adsorption capacity was found to be 265.25 mg/g for MMC700, suggesting its application as an efficient, low-cost, and easily separable adsorbent for the toxic Cr(VI) removal process. The prepared adsorbents exhibited superior performance in the removal process compared to other agricultural wastes or biomass - derived adsorbents reported in literature.

Remediation of 2,4,6-trichlorophenol from aqueous solution by raw and chemical modified date palm stone biomass: Kinetics and isotherms studies

Raw and citric acid chemically treated date palm stone agro-waste biomass (RDSB and CA-MDSB) powders were used to remove an important class of emerging industrial pollutants, i.e., 2,4,6-trichlorophenol (2,4,6-TCP) from aqueous solutions towards sustainable waste utilization to develop cost-effective technology for treating wastewater. The biomass characterization was performed by using different analytical techniques such as CHN elemental analysis, particle size, BET, FTIR, and SEM-EDX, TGA analysis. The FTIR spectral analysis revealed that the main chemical groups (N–C, O=C, H-O, H-C, and O–C) were involved in trapping 2,4,6-TCP. The highest adsorption was achieved with a contact time of 150 and 120 min, an initial concentration of 50-200 mg/L, and a biosorbent dosage ranging from 0.1 to 1.0 g/L RDSB and CA-MDSB, respectively. The experimental kinetic data of the adsorption process for both adsorbents (RDSB and CA-MDSB) fitted very well with the pseudo-second-order kinetic model and Langmuir equilibrium data. The 2,4,6-TCP maximum monolayer adsorption capacities were 53.7, and 123.8 mg/g for RDSB and CA-MDSB, respectively. The present research confirms that the date palm stone biomass could be used as an effective and low-cost biosorbent for the remediation of 2,4,6-TCP from an aqueous environment.

Production of activated carbon from date palm stones by hydrothermal carbonization and microwave assisted KOH/NaOH mixture activation for dye adsorption

Date palm stones are regarded as possible alternatives to activated carbon (AC) precursors with high potential for various environmental applications. In this research study, date palm stones derived activated carbon (DPSAC) was used as adsorbent for removing toxic remazol brilliant blue R (RBBR). The synthesis of DPSAC involved a chemical treatment using KOH and NaOH (1:1). Characterization of DPSAC revealed that it exhibited a BET surface area of 715.30 m2/g, Langmuir surface area of 1061.93 m2/g, total pore volume of 0.39 cm3/g, and average pore diameter of 2.15 nm. Adsorption uptake of RBBR increased (from 24.54 to 248.54 mg/g), whereas the removal percentage decreased (from 98.16 to 82.85%) when the initial RBBR concentration increased (from 25 to 300 mg/L). The adsorption process performed best under acidic conditions (pH 3), with an RBBR uptake of 98.33 mg/g. Because of the high R2 values (0.9906 and 0.9779) and low average errors (6.24 and 13.95%), this adsorption process followed the Freundlich isotherm and pseudo-first-order (PFO) models, respectively. The Langmuir adsorption capacity (Qm) was 319.63 mg/g. Thermodynamic parameters were − 11.34 kJ/mol for ∆H° (exothermic in nature), 0.05 kJ/mol K for ∆S° (increasing randomness level at solid–liquid interface), − 27.37 kJ/mol for ∆G° (spontaneous), and 6.84 kJ/mol for Ea (controlled by physisorption).

Heating rate and ZSM-5 catalyst effects on date palm (Phœnix dactylifera L.) stones pyrolysis: Thermogravimetric analysis, production and characterization of syngases and bio-oils

In the present investigation, Date palm stones (DPS) were pyrolyzed under Nitrogen atmosphere in a laboratory scale fixed-bed reactor. Pyrolysis experiments were carried out at different heating rates (5 and 10 °C/min), both in absence and presence of ZSM-5 catalyst (20 wt%). The effects of heating rate and ZSM-5 catalyst on DPS thermal behavior, pyrolysis products yields, syngases and bio-oils proprieties were investigated. TGA results showed that adding ZSM-5 revealed no significant impact on DPS thermal behavior. However, increasing the heating rate was followed by an increase in degradation peaks temperatures and maximum mass-loss rates (in absolute terms). These same effects were found when proceeding in presence of ZSM-5. Micro-GC results showed that the heating rate rise led to a thermal shift of pyrolytic gases (CO2, CO, C2H6, CH4 and H2) release towards higher temperatures. However, the ZSM-5 addition had accelerated their release and enhanced their quality by essentially reducing CO2 contents by about 13%, for both heating rates. The produced syngases from DPS pyrolysis have proven good biofuels proprieties thanks to their important proportions of CH4 (17.19–21.74%) and H2 (12.54–18.51%). DPS pyrolysis at a heating rate of 5 °C/min and in presence of ZSM-5 (20 wt%) can be defined as the optimum operational conditions that lead to maximum production of bio-oil (43.48%) with better quality. Under these conditions, DPS bio-oil presented the highest Carbon (73.58%) and Hydrogen (10.63%) contents and the lowest Oxygen (14.89%) and Nitrogen (0.9%) contents. Moreover, it had the highest HHV of 34.37 MJ/kg and the lowest viscosity of 8.54 mPa s, comparing to other bio-oils produced at 10 °C/min with and without ZSM-5 and to the bio-oil produced at 5 °C/min without ZSM-5. GC-MS analysis revealed that Dodecanoic acid and Oleic acid were the predominant components in DPS bio-oil with the respective percentages of 17.83 and 16.49%. This experimental investigation proved the potential use of date palm stones as renewable feedstocks for bio-oil production by pyrolysis. Furthermore, the low pyrolysis gradient (5 °C/min) and the use of ZSM-5 catalyst have shown interesting results in enhancing the bio-oil quantity and quality.

Potentials of mono- and multi-metal ion removal from water with cotton stalks and date palm stone residuals

In this work, cotton stalks(Gossypium barbadense) and date palm stones (Phoenix dactylifera) have been used as biosorbents to remove cadmium; Cd(II), lead; Pb(II), and zinc; Zn(II) from mono- and multi-solutions. Each biosorbent was characterized using SEM-EDX, and FT-IR. The findings showed that pH, dose, contact time, metal concentration, and particle size affect the treatment process. The adsorption pattern was Pb(II) > Cd(II) > Zn(II) for both biosorbents. The adsorption performance of cotton stalks was higher than that of date palm stones. The fitted maximum uptake capacities; qm of cotton stalks were higher than those of date palm stones. The maximum adsorption at optimum conditions of Pb(II), Cd(II), and Zn(II) with cotton stalks were 98%, 92.1%, and 78.9%, respectively, within 30 min. While the maximum adsorption of Pb(II), Cd(II), and Zn(II) with date palm stones were 94.6%, 76%, and 68.6%, respectively. Results confirmed the antagonistic effect of heavy metal removal at optimum conditions. Biosorbents could remove ~ 100% of the metal ions from real wastewater samples. Regeneration investigation revealed a successful reusability of both biosorbents for four cycles.

Photocatalytic removal of nitrate from water using activated carbon-loaded with bimetallic Pd-Ag nanoparticles under natural solar radiation

The increase of nitrate contamination of surface and groundwater has raised a concern, because of its impact on both environment and human health. In this study, photocatalysis for nitrate treatment in water was conducted using activated carbon prepared from date palm stone decorated with single and bimetals nanoparticles using solar radiation. The prepared catalyst was characterized by XPS, SEM, EDX, TGA, and surface area analyzer instruments. The photocatalytic effect of the prepared catalyst was studied using nitrate solution and acid scavengers with different concentrations. Significant photocatalytic activity was observed for activated carbon when modified with Pd–Ag. The obtained results showed that the conversion of nitrate takes place mainly through nitrogen gas (N2) rather than nitrite (NO2–) or ammonium (NH4+). Formic acid as a hole scavenger with 0.05 M shows the maximum conversion for nitrate. The prepared photocatalyst shows stability for five cycles of nitrate ion reduction. Moreover, the results showed that the prepared catalyst could be applied for the removal of nitrate from groundwater and river water samples.

Neural network for modeling the capture of lead and cadmium ions from wastewater using date palm stones

The current theoretical and experimental study was to thoroughly examine the capability of date stones for scavenging cadmium and lead ions from simulated wastewater. Three layers-artificial neural network (ANN) with 115 batch tests proved that the best conditions achieved the highest sorption efficiency (>63% for Cd(II) and > 91% for Pb(II)) where time 1 h, pH 5–6, dosage 5 g/100 mL, speed 100 rpm and temperature 25 °C. A satisfactory matching between the measurements and the ANN outputs was recognized with coefficient of determination greater than 99%. The ANN has also revealed throughout the sensitivity analysis that the initial pH and contact time with importance of 25 and 39% for cadmium and lead ions respectively were considered to be the most influential parameters in the removal process. Among Langmuir, Freundlich, and ANN models, the latter one was well fitted the sorption data. This model was substituted in solute transport equation to describe the spatial and temporal distribution of metal ions through the packed column. From the breakthrough curves, the well agreement between the theoretical and measurements (Willmott’s index almost greater less than 0.97), the date stones sorbent have had greater tendency to sorb lead ions than that of cadmium ones.

An Archaeological Investigation of Laloi East Molluscs Site at Kpone, Ghana

Abstract This article is a report of an archaeological investigation of the Laloi East Molluscs Site at Kpone, Greater Accra Region, Ghana. Although radiometric dates for this shell midden are currently unavailable, we believe that Laloi East dates to the Later Stone Age. If so, this site would be one of only two LSA sites in Ghana found and excavated along the coast rather than in the forested interior. This article examines shellfish exploitation and other major subsistence strategies of the population that settled the site in the past. The principal cultural materials recovered from the excavations comprised large quantities of molluscs’ remains belonging to a variety of species, other faunal remains, pottery, palm kernel nuts, charcoal, stone slabs, and lithic tools. The combined evidence indicates that molluscs’ exploitation was the principal subsistence strategy of the settlers, undertaken alongside hunting, trapping, herding and the gathering of edible botanical resources such as palm fruits.

Utilization of date palm stones for bio-oil and char production using flash and fast pyrolysis

Flash and fast pyrolysis of date palm stones (Phoenix dactylifera L.) was carried out in two different well-swept fixed-bed reactors under a nitrogen atmosphere and the effect of pyrolysis temperature (400–700 °C) and retention time on the product yields and compositions was investigated. The results show that fast or flash pyrolysis of date palm stones yields more bio-oil than char or non-condensable gases, especially at moderate temperatures. A maximum bio-oil yield was obtained at a pyrolysis temperature of 500 °C as 40.4% and 38.3% via the flash and fast pyrolysis methods, respectively. The functional groups, morphology, surface areas, and the C, H, N, and O and ash, moisture, volatile matter, and fixed carbon content of the chars were examined using Fourier transform infrared spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, ultimate analysis devices, and proximate analysis, respectively. Chars with a maximum surface area were used for the adsorption of dyes from aqueous solutions and the adsorption capacity and the kinetics of the chars were determined. Bio-oil composition was investigated using gas chromatography/mass spectrometry and the content of C, H, N, and O was determined by ultimate analysis. The results show that the saturation adsorption capacities of char from flash pyrolysis are 100 and 70.9 mg/g for Methylene Blue and Acid Red 111, and that these values from fast pyrolysis are 105.2 and 97.1 mg/g for Methylene Blue and Acid Red 111, respectively. The bio-oils contain higher levels of oxygen than the chars. The heating values vary from 27.5 to 31.3 MJ/kg and from 24.9 to 28.2 MJ/kg for bio-oils and chars, respectively. In addition, the bio-oil products from the pyrolysis of date palm stones are predominantly fatty acids. The results indicate that the bio-oil products obtained by the pyrolysis of date palm stone may be used as fuel or for the production of chemicals, and the solid products used as fuel or adsorbents.

A Date Palm Stone Ileal Perforation Discovered During Treatment of a Strangulated Umbilical Hernia

Ingestion of foreign bodies is a frequent reason for consultation or admission to the emergency room. It is frequently accidental and involves children whose peak age varies between 9 months and three years. Reported cases of intestinal perforation by stone are rare. Herein we report one case of ileal perforation with a date palm stone discovered during the treatment of an emergency strangulated umbilical hernia in a 2-year-old patient. Clinically, there was a painful, irreducible, non-expansive umbilical swelling with coughing and vomiting. The other hernial orifices were free. Temperature was 36°C, respiratory rate 98 movements per minute, pulse rate 23 beats per minute. Biologically, hemoglobin was 11.4 G/dl, white blood cells were 9 giga/l. The diagnosis of strangulated umbilical hernia was retained. Intraoperatively, we found a small loop incarcerated in the umbilical ring and perforated in two places by a date palm stone. We proceeded with extraction of the stone, resection with both holes, followed by terminal ileo-ileal anastomosis. The postoperative course was simple and no complications were noted after a 2-year follow-up.

A Novel Coated of Mg/Fe Layered Double Hydroxide on Date Palm Stones

Mg/Fe layered double hydroxide coated low cost activated carbon (AC-Mg/Fe) was synthesized to be as a novel material by a co-precipitation method. The using of Scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction Analysis (XRD) and Specific surface area of materials by Brunauer–Emmett–Teller analysis (BET) were employed for characterize the synthesized coated adsorbent. The XRD and SEM displayed that the particles on the surface of low cost activated carbon are regular and good-defined, and the structure of LDHs is typical lamellar. The crystallite size of the coated adsorbent according to the XRD analysis was to be 96.7 nm. The contents of the Fe and Mg after modification increase noticeably according to the EDS analysis. From BET analysis, it was an increasing in the specific surface area of the adsorbent from 22.57 m2/g (before synthesize) to 81.77 cm/g (after synthesize). This analysis resulted in successfully coated Mg/Fe layered double hydroxide (Mg/Fe-LDH) on activated carbon for preparing of a high capacity adsorbent and magnetic sorbent for easy separation by magnetic field.

Organic residues and biochar to immobilize potentially toxic elements in soil from a gold mine in the Amazon

Waste from gold mining (Au) is a threat to the ecosystem and human health because it contains high levels of potentially toxic elements (PTEs). Organic waste and biochar can be used to recover contaminated soils from mining areas because they have the potential to immobilize PTEs and improve soil fertility, enabling revegetation. The objective of this study was to investigate the efficiency with which organic residues and biochar immobilize PTEs in a multicontaminated soil of a small-scale Au mine in the state of Pará. The soil from a gold mining area was mixed with different proportions (v/v) of coffee ground residues (Bcoffee), Brazil nut tegument residues (BN), açai palm stone residues (A), and Brazil nuts biochar residues to determine which treatment is best for immobilizing PTEs. The treatments with the addition of BN and A resulted in low pH and high contents of organic matter (OM) and phosphor (P) The BN increased the available levels of Ba and reduced the available levels of Ni. The addition of coffee ground residues and biochar increased the uptake of Ba, Pb, and Ni in lettuce plants compared to treatments with BN and A. Plants grown with A showed higher dry matter yield and lower absorption and translocation of PTEs. Thus, the addition of BN and A residues in PTE phytostabilization programs in PTE-multicontaminated soils is a potential possibility.

Date (Phoenix dactylifera L.) palm stones as a potential new feedstock for liquid bio-fuels production

In the present investigation, Date (Phoenix dactylifera L.) stones were utilized in the production of different types of biodiesel in addition to bio-oil. The oil was extracted from the date stones with a yield of 10.50wt% and is used in the production of fatty acid methyl, ethyl and mixed methyl/ethyl esters via KOH- catalyzed transesterification process with methanol, ethanol and mixed methanol and ethanol, respectively. Properties of the obtained biodiesels, such as the density, kinematic viscosity, flash point, acid value, cloud and pour points, total and free glycerin contents and the refractive index were evaluated and found comparable to those of ASTM D 6751 biodiesel. The FTIR spectroscopy confirmed conversion of date stone oil to biodiesel. The date stones were also tested as new non-edible feedstock for bio-oil production by pyrolysis process in a semi batch reactor. The influence of the pyrolysis temperature, pyrolysis time and precursor particles size on the bio- oil yield was investigated. Maximum bio- oil yield (52.67%±1.50) was obtained at 500°C pyrolysis temperature with a pyrolysis time of 60min and feed particle size of 0.25mm. The ultimate analysis, FTIR spectroscopy and adsorption column chromatography were determined to characterize the chemical composition of the obtained bio- oil. Furthermore, several important fuel properties, like the density, kinematic viscosity, flash point, pour point and the acidity index of date stones bio- oil were also determined following ASTM standard test methods and found comparable to those documented for other bio- oils in literature. The chemical composition of the bio- oil produced through pyrolysis of date stones showed the potential of date stones as an important source of alternative fuel and chemicals as well.

Preparation and calorimetry characterization of nitrogen-enriched activated carbons and their application in the removal of carbon dioxide

This paper reports the preparation and characterization of granular carbon materials those were prepared using chemical activation of African palm stone with ZnCl 2 and then chemically modified in order to increase the nitrogen content. Functionalization processes with activated carbons, modify their textural and chemical characteristics, this fact was observed using N 2 adsorption at 77 K, Boehm titration, infrared Spectroscopy using immersion calorimeter in liquids with different chemical nature (H 2 O, C 6 H 6 , NaOH and HCl). The results show that the solids obtained have BET surface area and pore volume up to 1200 m 2 /g and 0.44 cm 3 /g, respectively. Immersion enthalpies of samples are between -9.87 and 141.9 J/g. The results show that with the process of functionalization employed in this work, increasing in the nitrogen content and the modification of the adsorbents surface is achieved. Finally, we found that with this activation and modification procedure, the activated carbons produced have a CO 2 adsorption capacity until 174 mg CO 2 /g.

Photocatalytic activity of transition metal ions-loaded activated carbon: Degradation of crystal violet dye under solar radiation

In this work, activated carbon (AC) was prepared from date palm stone by chemical activation method. Its properties were investigated, the surface of the AC was found to be acidic (pHpzc of 3.95), Brunauer-Emmet-Teller (BET) surface area of 12.7m2/g, with meso and microporous structures. The prepared AC was loaded with Zn(II), Cd(II), Cu(II), and Pb(II) metal ions by adsorption and ion exchange. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) were used to elucidate the morphology, composition, and bonding of loaded metal ions to the functional group on carbon surface. The prepared AC and its loaded metal ions showed significant catalytic activity for the degradation of crystal violet (CV) under solar radiation. The highest photocatalytic degradation rate was obtained using Zn(II)-loaded AC with 80% mineralization in 40h. The Zn(II)-loaded AC was used for many cycles of photocatalytic degradation of CV without loss in its catalytic efficiency. The highest degradation rate was obtained at pH 6.5. The degradation rate was found to be inversely proportional to the CV concentration and mesh size of the catalyst. The degradation of the CV was found to take place via ̇OH attack.

The extent of change in the physicochemical characteristics and pollutants sequestration of date palm stones after microemulsion modification

The extent of change in the physicochemical characteristics and pollutants sequestration of date palm stones after microemulsion modification

Chemical Analysis of Different Parts of Date Palm (Phoenix dactylifera L.) Using Ultimate, Proximate and Thermo-Gravimetric Techniques for Energy Production

The objective of the study was to analyze chemical structure of date palm (Phoenix dactylifera L.) by employing ultimate, proximate and thermo-gravimetric techniques. Samples from different anatomical parts of date palm, namely trunk, frond base, frond midrib, leaflets, coir, fruit stem, date stone, and fruit empty bunches were considered for the experiments. Based on the findings in this work palm leaflet samples gave the highest amount of extractives content (32.9%), followed by date palm stone specimens with 31.5%. Cellulose content values of 32.8% and 47.5% were obtained for date palm stone and palm coir samples, respectively. Overall the hemicellulose contents of all samples were relatively similar to those of typical wood or non-wood lignocellulosic materials with the two exceptions of palm coir and palm leaflets. Both palm coir and palm leaflet specimens had 12.6% and 16.1% hemicellulose content. Volatile matter values of 74.3% and 87.5% were determined for leaflets and fruit empty bunch samples. The ash content of the samples ranged from 1.4% for date stone to 15.2% for palm leaflet samples. The thermal decomposition was completed below a temperature of 500 °C with an exception of those samples taken from palm leaflets. Taken together the data indicate that date palm stone and palm coir revealed could be more viable for renewable energy production than the other specimens considered in this work.

Characterisation of granular activated carbon prepared by activation with CaCl2 by means of gas adsorption and immersion calorimetry

The textural characteristics of granular activated carbons obtained by chemical activation of African palm stone with CaCl2 were established with nitrogen adsorption at 77 K, carbon dioxide adsorption at 273 K, and immersion calorimetry in benzene. A comparison was made between the fit of N2 adsorption experimental data with the calculated isotherms using two models: non-local density functional theory and quenched solid density functional theory. The calorimetric technique allowed measurement of the immersion enthalpies in benzene and subsequent calculation of the accessible areas of the carbons. A correlation was established between the enthalpic parameters and it was found that immersion enthalpy in benzene increased with the increasing surface area and pore volume of the carbons. Also the samples were characterized chemically using Boehm titrations.

Accessible area and hydrophobicity of activated carbons obtained from the enthalpy characterization

Were determined the immersion enthalpy in benzene and water for 24 carbonaceous materials, granular activated carbon and activated carbon monoliths prepared from African palm stone by chemical activation with H3PO4, ZnCl2 and CaCl2 solutions. The immersion enthalpies in benzene and water were exothermic, in accordance with a surface process that takes place between the solid and liquid. Benzene enthalpies for this set of solids were −20.26 and −181.1 J g−1 and water enthalpies were between −7.42 and −67.01 J g−1. The textural and chemical surface properties of the activated carbons were related to the immersion enthalpies. Since the evaluation of the porous structure was made with non-polar liquids with which the solid does not have a specific interaction, immersion enthalpy was proportional to the surface area accessible to liquid molecules, which was calculated from the enthalpic determinations based on the assumption of the existence of a direct relationship between the immersion enthalpy and the total area of the solid accessible to liquid molecules. The hydrophobic factor was calculated by dividing the immersion enthalpy in benzene and the immersion enthalpy in water; this is related to the acidity, basicity and hydrophobicity of the activated carbons.