Upgrading recovered carbon black (rCB) from industrial-scale end-of-life tires (ELTs) pyrolysis to activated carbons: Material characterization and CO2 capture abilities.

The current study presents for the first time how recovered carbon black (rCB) obtained directly from the industrial-scale end-of-life tires (ELTs) pyrolysis sector is applied as a precursor for activated carbons (ACs) with application in CO2 capture. The rCB shows better physical characteristics, including density and carbon structure, as well as chemical properties, such as a consistent composition and low impurity concentration, in comparison to the pyrolytic char. Potassium hydroxide and air in combination with heat treatment (500-900 °C) were applied as agents for the conventional chemical and physical activation of the material. The ACs were tested for their potential to capture CO2. Ultimate and proximate analysis, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Raman spectroscopy, thermogravimetric analysis (TGA), and N2/CO2 gas adsorption/desorption isotherms were used as material characterization methods. Analysis revealed that KOH-activated carbon at 900 °C (AC-900K) exhibited the highest surface area and a pore volume that increased 6 and 3 times compared to pristine rCB. Moreover, the AC-900K possessed a well-developed dual porosity, corresponding to the 22% and 78% of micropore and mesopore volume, respectively. At 0 °C and 25 °C, AC-900K also showed a CO2 adsorption capacity equal to 30.90 cm3/g and 20.53 cm3/g at 1 bar, along with stable cyclic regeneration after 10 cycles. The high dependence of CO2 uptake on the micropore volume at width below 0.7-0.8 nm was identified. The selectivity towards CO2 in relation to N2 reached high values of 350.91 (CO2/N2 binary mixture) and 59.70 (15% CO2/85% N2).

Functional Activated Biocarbons Based on Biomass Waste for CO2 Capture and Heavy Metal Sorption.

Inexpensive porous activated biocarbons were prepared from biomass and agriculture waste following the method of thermal and hydrothermal carbonization and activation with superheated water vapor. The activated biocarbons were characterized by nitrogen adsorption-desorption at 77 K, SEM, XRD, Raman spectrometry, FTIR spectroscopy, determination of particle size, and elemental composition by XRF. The specific surface area was in the range of 240-709 m2/g, and the total pore volume was from 0.12 to 0.43 cm3/g. The percentage of microporosity in activated biocarbons was 89-92%. These activated biocarbons have been used for CO2 and heavy metal sorption. Activated biocarbons based on pine cones and birch prepared by thermal carbonization and activation with superheated water vapor had the highest ability to capture CO2 and amounted to 6.43 and 6.00 mmol/g at 273 K, as well as 4.57 and 4.22 mmol/g at 298 K, respectively. The best activated biocarbon was characterized by unchanged stability after 30 adsorption and desorption cycles. It was proved that the adsorption of CO2 depends on narrow micropores (<1 nm). Activated biocarbons have also been analyzed as effective adsorbents for removing Cu2+, Zn2+, Fe2+, Ni2+, Co2+, and Pb2+ ions from aqueous solutions. Activated biocarbons are effective adsorbents for the removal of lead and zinc ions from aqueous solutions.

Sulfur-Doped g-C3N4 Heterojunctions for Efficient Visible Light Degradation of Methylene Blue.

The discharge of synthetic dyes from different industrial sources has become a global issue of concern. Enormous amounts are released into wastewater each year, causing concerns due to the high toxic consequences. Photocatalytic semiconductors appear as a green and sustainable form of remediation. Among them, graphitic carbon nitride (g-C3N4) has been widely studied due to its low cost and ease of fabrication. In this work, the synthesis, characterization, and photocatalytic study over methylene blue of undoped, B/S-doped, and exfoliated heterojunctions of g-C3N4 are presented. The evaluation of the photocatalytic performance showed that exfoliated undoped/S-doped heterojunctions with 25, 50, and 75 mass % of S-doped (g-C3N4) present enhanced activity with an apparent reaction rate constant (kapp) of 1.92 × 10-2 min-1 for the 75% sample. These results are supported by photoluminescence (PL) experiments showing that this heterojunction presents the less probable electron-hole recombination. UV-vis diffuse reflectance and valence band-X-ray photoelectron spectroscopy (VB-XPS) allowed the calculation of the band-gap and the valence band positions, suggesting a band structure diagram describing a type I heterojunction. The photocatalytic activities calculated demonstrate that this property is related to the surface area and porosity of the samples, the semiconductor nature of the g-C3N4 structure, and, in this case, the heterojunction that modifies the band structure. These results are of great importance considering that scarce reports are found concerning exfoliated B/S-doped heterojunctions.

Mechanochemical Degradation of Caffeine and Diclofenac Using Biochar of Fique Bagasse in the Presence of Al: Monitoring by Mass Spectrometry.

Much research has been carried out to remove emerging contaminants using diverse materials. Furthermore, studies related to pollutant degradation have increased over the past decade. Mechanochemical degradation can successfully decompose molecules that are persistent in the environment. In this study, the biochar of fique bagasse with mixtures SiO2, Al, Al2O3, and Al-Al2O3 was treated with a mechanochemical technique using a planetary ball mill to investigate the degradation of caffeine and diclofenac. These tests resulted in the transformation of caffeine and diclofenac due to the use of Al employing mechanochemistry. In fact, through the use of liquid chromatography coupled with mass spectrometry, eight and six subproducts were identified for caffeine and diclofenac, respectively. Additionally, analysis of the molecules proposed for caffeine and diclofenac transformation suggested hydroxylation, demethylation, decarboxylation, oxidation reactions, and cleavage of the C-C and C-N bonds in the pollutants studied. The formation of these transformation products could be possible by reductant oxygen species generated from the molecular oxygen in the presence of aluminum and the energy delivered for ball milling. The results obtained show the potential application in the environmental management of mechanochemical treatment in the elimination of emerging contaminants caffeine and diclofenac.

CO2 adsorption on carbonaceous materials obtained from forestry and urban waste materials: a comparative study.

The increasing emissions of gaseous pollutants of anthropogenic origin, such as carbon dioxide (CO2), which causes global warming, have raised great interest in developing and improving processes that allow their mitigation. Among them, adsorption on porous materials has been proposed as a sustainable alternative. This work presents a study of CO2 equilibrium adsorption at low temperatures (0, 10, and 20 °C) over a wide range of low pressures, on activated carbon derived from Eucalyptus (ES) and Patula pine (PP) forest waste, and carbonaceous material derived from waste tires (WT). The precursors of these materials were previously prepared, and their physicochemical properties were characterized. ES and PP were thermochemically treated with phosphoric acid, and WT was oxidized with nitric acid. Additionally, these materials were used to obtain monoliths using uniaxial compaction techniques and different binding agents, with better results obtained with montmorillonite. A total of six adsorbent solids had their textural and chemical properties characterized and were tested for CO2 adsorption. The highest specific surface area (1405 m2 g-1), and micropore properties were found for activated carbon derived from Eucalyptus whose highest adsorption capacity ranged from 2.27 mmol g-1 (at 0 °C and 100 kPa) to 1.60 mmol g-1 (at 20 °C and 100 kPa). The activated carbon monoliths presented the lowest CO2 adsorption capacities; however, the studied materials showed high potential for CO2 capture and storage applications at high pressures. The isosteric heats of adsorption were also estimated for all the materials and ranged from 16 to 45 kJ mol-1 at very low coverage explained by the energetic heterogeneity and weak repulsive interactions among adsorbed CO2 molecules.

Biodiesel Production Using Palm Oil with a MOF-Lipase B Biocatalyst from Candida Antarctica: A Kinetic and Thermodynamic Study.

This research presents the results of the immobilization of Candida Antarctica Lipase B (CALB) on MOF-199 and ZIF-8 and its use in the production of biodiesel through the transesterification reaction using African Palm Oil (APO). The results show that the highest adsorption capacity, the 26.9 mg·g-1 Lipase, was achieved using ZIF-8 at 45 °C and an initial protein concentration of 1.20 mg·mL-1. The results obtained for the adsorption equilibrium studies allow us to infer that CALB was physically adsorbed on ZIF-8 while chemically adsorbed with MOF-199. It was determined that the adsorption between Lipase and the MOFs under study better fit the Sips isotherm model. The results of the kinetic studies show that adsorption kinetics follow the Elovich model for the two synthesized biocatalysts. This research shows that under the experimental conditions in which the studies were carried out, the adsorption processes are a function of the intraparticle and film diffusion models. According to the results, the prepared biocatalysts showed a high efficiency in the transesterification reaction to produce biodiesel, with methanol as a co-solvent medium. In this work, the catalytic studies for the imidazolate, ZIF-8, presented more catalytic activity when used with CALB. This system presented 95% biodiesel conversion, while the biocatalyst formed by MOF-199 and CALB generated a catalytic conversion percentage of 90%. Although both percentages are high, it should be noted that CALB-MOF-199 presented better reusability, which is due to chemical interactions.

Competitive Adsorption of Caffeine and Diclofenac Sodium onto Biochars Derived from Fique Bagasse: An Immersion Calorimetry Study.

Pharmaceuticals, including caffeine (CFN) and diclofenac sodium (DCF), are a group of emerging pollutants which have the capacity to prompt harmful effects in flora and fauna, even at relatively low concentrations. Additionally, CFN has been determined as one of the most ubiquitous active compounds in the natural environment, whereas DCF is a widely used nonsteroidal anti-inflammatory drug that has been detected in environmental sources around the world. Conversely, the fique is a plant of the Agavaceae family and of the Fucraea genus.Two native species are cultivated in Colombia, Furcraea cabuya and Furcrae macrophylla, in order to extract their fiber, but in this process a lot of waste is produced. In this study, with the fique residues, thermochemical treatments were carried out and 5 biochar samples were obtained, which were calorimetrically characterized and used to investigate their behavior in competitive adsorption of DCF and CFN. The results of the calorimetric studies show that the biochar prepared from fique bagasse have different porous and chemical characteristics, which is related to the different treatments that were used at the time of their preparation. In addition, it was established that the results of the adsorbate-adsorbent interactions determined by calorimetry allow correlation of the adsorption processes of the molecules under study (CFN and DCF). The results show that the NaOH fique biochar (FB850-3Na) presents the highest adsorption capacity in both simple and competitive tests.

Biodiesel Production from Transesterification with Lipase from Pseudomonas cepacia Immobilized on Modified Structured Metal Organic Materials.

This research presents the modification of MOF-199 and ZIF-8 using furfuryl alcohol (FA) as a carbon source to subsequently fix lipase from Pseudomonas cepacia and use these biocatalysts in the transesterification of African palm oil (APO). The need to overcome the disadvantages of free lipases in the biodiesel production process led to the use of metal organic framework (MOF)-type supports because they provide greater thermal stability and separation of the catalytic phase, thus improving the activity and efficiency in relation to the use of free lipase, disadvantages that could not be overcome with the use of other types of catalysts used in transesterification/esterification reactions for the production of biodiesel. The modification of MOFs ZIF-8 and MOF-199 with FA increases the pore volume which allows better immobilization of Pseudomonas cepacia lipase (PCL). The results show that these biocatalysts undergo transesterification with biodiesel yields above 90%. Additionally, studies were carried out on the effect of (1) enzyme loading, 2) enzyme immobilization time, (3) enzyme immobilization temperature, and (4) pH on the % immobilization of the enzyme and the specific activity. The results show that the highest immobilization efficiency for the FA@ZIF-8 support has a value of 91.2% when the load of this support was 3.5 mg/mg and has a specific activity of 142.5 U/g protein. The FA@MOF-199 support presented 80.3% enzyme immobilization and 125% U/g specific activity protein. We established that the specific activity increases in the period from 0.5 to 5.0 h for the systems under investigation. After this time, both the specific activity and the % efficiency of enzyme immobilization decrease. Therefore, 5.0 h (immobilization efficiency of 95 and 85% for FA@MOF-199, respectively) was chosen as the most appropriate time for PCL immobilization. Methods of adding methanol, with three and four steps, were tested, where biodiesel yields greater than 90% were obtained for the biocatalysts synthesized in this work (FA@ZIF-8-PCL and FA@MOF-199-PCL) and above 70% for free PCL, and the maximum yield was reached at a molar ratio between methanol and APO of 4:1 when using the one-step method under the same reaction conditions (as mentioned above). Only the results of FA@ZIF-8-PCL are presented here; however, it should be noted that the results for biocatalyst FA@MOF-199-PCL and lipase-free PCL presented the same behavior. The order of biocatalyst performance was FA@ZIF-8-PCL > FA@MOF-199-PCL > PCL-Free, which demonstrates that the use of FA as a modifier is a novel aspect in the conversion of palm oil into biodiesel components.

Biocatalysts Synthesized with Lipase from Pseudomonas cepacia on Glycol-Modified ZIF-8: Characterization and Utilization in the Synthesis of Green Biodiesel.

This research presents results on the production of biodiesel from the transesterification of acylglycerides present in palm oil, using the biocatalysts ZIF-8-PCL and Gly@ZIF-8-PCL synthesized by immobilization of Pseudomonas Cepacia Lipase as catalytic materials and using pure ZIF-8 and Gly@ZIF-8 (modified ZIF-8) as supports. The Gly@ZIF-8 carbonaceous material was prepared by wet impregnation of ZIF-8 with ethylene glycol as the carbon source, and then thermally modified. The calcination conditions were 900 °C for two hours with a heating rate of 7 °C/min in an inert atmosphere. A textural characterization was performed, and results showed superficial changes of materials at the microporous and mesoporous levels for the Gly@ZIF-8 material. Both the starting materials and biocatalysts were characterized by infrared spectroscopy (FTIR) and Raman spectroscopy. During the transesterification, using the two biocatalysts (ZIF-8-PCL and Gly@ZIF-8-PCL), two supernatant liquids were generated which were characterized by infrared spectroscopy (FTIR), gas chromatography coupled to mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR). The results show that the two routes of synthesis of supports from ZIF-8 will be configured as effective methods for the generation of effective biocatalysts for biodiesel production.

Biogenic Hydroxyapatite Obtained from Bone Wastes Using CO2-Assisted Pyrolysis and Its Interaction with Glyphosate: A Computational and Experimental Study.

In this work, biogenic hydroxyapatite (BHap) obtained from cattle bone waste is proposed as an adsorbent of this dangerous pollutant. Density functional theory (DFT) and calorimetric studies were developed to study the interaction between BHap and glyphosate (GLY). A strong interaction was found in the experiments through the measurement of immersion enthalpy, confirmed by the exothermic chemisorption obtained with DFT calculations. These results suggest that hydroxyapatite is a promising adsorbent material for GLY adsorption in aqueous solutions. In addition, it was determined that the GLY-hydroxyapatite interaction is greater than the water-hydroxyapatite interaction, which favors the GLY adsorption into this material.

Data for the synthesis, characterization, and use of xerogels as adsorbents for the removal of fluoride and bromide in aqueous phase.

Groundwater with high fluoride concentrations has been recognized as one of the serious concerns worldwide. Besides, the fluoride released into the groundwater by slow dissolution of fluoride-containing rocks, various industries also contribute to fluoride pollution [1]. Excess intake of fluoride leads to various health problems such as dental and skeletal fluorosis, cancer, infertility, brain damage, thyroid diseases, etc. [2]. On the other hand, bromide is naturally present in surface and groundwater sources. However, during the chlorination process, bromide can be oxidized to HOBr, which can react with natural organic matter in water to form brominated organic disinfection byproducts, which are very harmful to human health [3]. Among various methods for water treatment, the adsorption process has been widely used and seems to be an efficient and attractive method for the removal of many contaminants in water, such as anions, in terms of cost, simplicity of design, and operation [4], [5]. In the past years, xerogels and carbon xerogels, a new type of adsorbents, which are synthesized by the sol-gel polycondensation of resorcinol and formaldehyde, have gained attention due to their moldable texture and chemical properties [6]. Moreover, melamine addition in resorcinol and formaldehyde xerogels adds basic groups on its surface, favouring Lewis acid-base interactions between xerogels and other components by adsorption [7]. In this data article, the synthesis of three resorcinol-formaldehyde (R/F) xerogels with an increasing amount of melamine (M) was carried out by colloidal polymerization (molar ratios of M/R = 0.5, M/R = 1.0, and M/R = 2.0). Additionally, samples of M/R = 0.5 xerogel were carbonized at 400, 450, and 550 °C under an inert atmosphere to increase their specific area. Organic and carbon xerogels obtained were characterized by FTIR, TGA, SEM, Physisorption of N2, and the pH at the point of zero charge (pHPZC). All organic xerogels were also tested as adsorbents on the removal of fluoride and bromide ions from aqueous phase. The Freundlich, Langmuir, and Radke-Prausnitz isotherm models were applied to interpret the experimental data from adsorption equilibrium. Additionally, the data of the mass of the xerogel needed to remove fluoride and bromide from groundwater and fulfill the maximum concentration levels are also included.

Kinetic Study of Waste Tire Pyrolysis Using Thermogravimetric Analysis.

The influence of particle size (0.3 and 5.0 mm) and heating rate (5, 10, and 20 °C min-1) on the kinetic parameters of pyrolysis of waste tire was studied by thermogravimetric analysis and mathematical modeling. Kinetic parameters were determined using the Friedman model, the Coats-Redfern model, and the ASTM E1641 standard based on Arrhenius linearization. In the Friedman model, the activation energy was between 40 and 117 kJ mol-1 for a particle size of 0.3 mm and between 23 and 119 kJ mol-1 for a particle size of 5.0 mm. In the Coats-Redfern model, the activation energy is in a range of 46 to 87 kJ mol-1 for a particle size of 0.3 mm and in a range of 43 to 124 kJ mol-1 for a particle size of 5.0 mm. Finally, in the ASTM E1641 standard, the activation energy calculated was between 56 and 60 kJ mol-1 for both particle sizes. This study was performed to obtain kinetic parameters from different mathematical methods, examining how the particle size and heating rate influence them.

Enthalpies of Immersion in Caffeine and Glyphosate Aqueous Solutions of SBA-15 and Amino-Functionalized SBA-15.

Mesostructured silica SBA-15 and amino-functionalized silica SBA-15-NH2 were synthesized, and then, characterization, adsorption capacity, and immersion enthalpies in caffeine and glyphosate on SBA-15 and SBA-15-NH2 were evaluated. The enthalpy parameter was determined using a local construction Tian-type heat conduction calorimeter. Calorimetric studies in caffeine solutions exhibit negative enthalpy values; exothermic process characteristics for SBA-15 were between -13.90 and -194.06 J g-1 and those for SBA-15-NH2 were between -7.22 and -60.34 J g-1, and the adsorption capacity of caffeine was better in SBA-15 than that in SBA-15-NH2. In contrast, the enthalpies of immersion in glyphosate solutions were -5.06 to -56.2 J g-1 and the immersion of SBA-15-NH2 in each solution generated enthalpy values of -9.06 to -41.2 J g-1, but the adsorption capacity of glyphosate was better in the amino-functionalized SBA-15. The results show that functionalization of SBA-15 produced differences in physicochemical characteristics of solids, since energy and affinity for the calorimetric liquids are related to the surface properties of solids as well as the chemical nature of the target molecule, immersion enthalpy, was different.

Understanding the solid-liquid equilibria between paracetamol and activated carbon: Thermodynamic approach of the interactions adsorbent-adsorbate using equilibrium, kinetic and calorimetry data.

In this work, we presented the paracetamol-activated carbon interactions and their effect on the adsorption capacity. We evaluated kinetic, equilibrium, and calorimetric data using different solvents (water, HCl 0.1 M, and NaCl 0.1 M) to evaluate the changes in the adsorbent-adsorbate interaction. In addition, the commercial activated carbon (AC) was modified through thermal (ACTT) and chemical (ACNA) methods to change the physicochemical properties of the adsorbents. The relative kinetic constants decrease with the content of basic groups on the activated carbon, indicating a lower influence of diffusion on the adsorption rate when the chemical interactions increase (0.1 ACNA >0.09 AC >0.03 ACTT mmol g-1). The adsorption capacity for AC at acidic pH increases slightly compared to tests carried out in the water. Under this condition, the adsorbed amount of paracetamol was 1.31 mmol g-1. However, the maximum adsorption capacity was achieved on ACTT using water as solvent (1.57 mmol g-1). The paracetamol adsorbed decreases in NaCl (osmotic, ionic strength) on all activated carbons by around 20%. The interaction enthalpy of the paracetamol-activated carbon interaction presents values between - 18.0 and 2.3 J per molecule adsorbed. The Gibbs energy released during the adsorption process is between - 33.1 and - 29.8 kJ mol-1.

Enthalpic and Liquid-Phase Adsorption Study of Toluene-Cyclohexane and Toluene-Hexane Binary Systems on Modified Activated Carbons.

The liquid-phase adsorption of toluene in cyclohexane and hexane solutions on modified activated carbons was evaluated; the energy involved in the interaction between these solutions and the solids was determined by immersion enthalpies of pure solvents and their mixtures, and the contribution of the system constituents was calculated by differential enthalpies. The thermal treatment generated modifications that favored adsorption and interaction with the evaluated solutions, since it increased the textural parameters and the basic character of the samples. Cyclohexane could create greater competition with the adsorption sites compared to hexane, but it favored the increase in adsorption capacities (0.416 to 1.026 mmol g-1) and the interactions with the solid evaluated through the immersion enthalpies. The immersion enthalpies of pure solvents (-16.36 to -112.7 J g-1) and mixtures (-25.65 to -104.34 J g-1) had exothermic behaviors that were decreasing due to the possible displacement of solvent molecules when increasing the solute concentration in the mixtures. The differential enthalpies for toluene were negative (-18.63 to -2.14 J), mainly due to the π-π interaction with the solid, while those of the solvent-solid component tended to be positive values (-4.25 to 55.97 J) due to the displacement of the solvent molecules by those of toluene.

Study of Mercury [Hg(II)] Adsorption from Aqueous Solution on Functionalized Activated Carbon.

Mercury and its compounds are toxic substances, whose uncontrolled presence in the environment represents a danger to ecosystems and the organisms that inhabit in it. For this reason, in this work, we carried out a study of mercury [Hg(II)] adsorption from aqueous solution on functionalized activated carbon. The activated carbons were prepared by chemical activation of a mango seed with solutions of CaCl2 and H2SO4 at different concentrations, later, the carbonaceous materials were functionalized with Na2S, with the aim of increasing the sulfur content in the carbonaceous matrix and its affinity to mercury. The materials were characterized using: proximal analysis, scanning electron microscopy, Boehm titrations, point zero charge (pHPZC), and infrared spectroscopy. Additionally, immersion calorimetries were performed in the mercury solution. The results of textural and chemical characterization show materials with low Brunauer-Emmett-Teller (BET) surface areas between 2 and 33 m2·g-1 and low pore volumes. However, they had a rich surface chemistry of oxygenated groups. The enthalpies of immersion in the mercury solutions are between -31.71 and -77.31 J·g-1, showing a correlation between the magnitude of the enthalpic data and the adsorption capacity of the materials. It was evidenced that the functionalization process produces a decrease in the surface area and pore volume of the activated carbons, and an increase in the sulfur content of the carbonaceous matrix. It was evidenced that the functionalization process generated an increase in the mercury [Hg(II)] adsorption capacity between 21 and 49% compared to those of the nonfunctionalized materials, reaching a maximum adsorption capacity of 85.6 mgHg2+g-1.

Study of CO2 Adsorption on Chemically Modified Activated Carbon With Nitric Acid and Ammonium Aqueous.

The study of CO2 adsorption on adsorbent materials is a current topic of research interest. Although in real operating circumstances, the removal conditions of this gas is carried out at temperatures between 290 and 303 K and 1 Bar of pressure or high pressures, it is useful, as a preliminary approach, to determine CO2 adsorption capacity at 273K and 1 Bar and perform a thermodynamic study of the CO2 adsorption heats on carbonaceous materials prepared by chemical activation from African palm shell with CaCl2 and H3PO4 solutions, later modified with HNO3 and NH4OH, with the aim to establish the influence that these treatments have on the textural and chemical properties of the activated carbons and their relationship with the CO2 adsorption capacity. The carbonaceous materials were characterized by physical adsorption of N2 at 77K, CO2 at 273K, proximate analysis, Boehm titrations and immersion calorimetry in water and benzene. Activated carbons had a BET area between 634 and 865 m2g-1, with a micropore volume between 0.25 and 0.34 cm3g-1. The experimental results indicated that the modification of activated carbon with HNO3 and NH4OH generated a decrease in the surface area and pore volume of the material, as well as an increase in surface groups that favored the adsorption of CO2, which was evidenced by an increase in the adsorption capacity and the heat of adsorption.

Dataset on adsorption of phenol onto activated carbons: Equilibrium, kinetics and mechanism of adsorption.

Two activated carbons (AC) prepared from onion leaves (OL) (Allium fistulosum) and palm kernel shell (PS) (Elaeis guineesis) were used to adsorb phenol from aqueous solution. Adsorption kinetics was studied by Pseudo-first order (PFO) and Pseudo-second order (PSO) models, while equilibrium was modelled using Langmuir, Freundlich, Toth and Redlich Peterson isotherms. Adsorption mechanism was analyzed applying Boyd and intraparticle diffusion models. The parameters of each one of the models were calculated using Minitab17® by non-linear regression. Piecewise linear regression was applied to calculate the parameters of Boyd and intraparticle diffusion models. Phenol adsorption onto activated carbons is describe better by Langmuir isotherm and PSO kinetic model. Maximum adsorption capacity was between 30 and 40 mg.g-1.

Graphene Oxide: Study of Pore Size Distribution and Surface Chemistry Using Immersion Calorimetry.

In this work, the textural parameters of graphene oxide (GO) and graphite (Gr) samples were determined. The non-local density functional theory (NLDFT) and quenched solid density functional theory (QSDFT) kernels were used to evaluate the pore size distribution (PSD) by modeling the pores as slit, cylinder and slit-cylinder. The PSD results were compared with the immersion enthalpies obtained using molecules with different kinetic diameter (between 0.272 nm and 1.50 nm). Determination of immersion enthalpy showed to track PSD for GO and graphite (Gr), which was used as a comparison solid. Additionally, the functional groups of Gr and GO were determined by the Boehm method. Donor number (DN) Gutmann was used as criteria to establish the relationship between the immersion enthalpy and the parameter of the probe molecules. It was found that according to the Gutmann DN the immersion enthalpy presented different values that were a function of the chemical groups of the materials. Finally, the experimental and modeling results were critically discussed.

Adsorption of Pharmaceutical Aromatic Pollutants on Heat-Treated Activated Carbons: Effect of Carbonaceous Structure and the Adsorbent-Adsorbate Interactions.

Drugs are considered emerging pollutants from water sources and are therefore considered to be of high toxicological risk to aquatic fauna. Activated carbon adsorption is one of the methods approved by the Word Health Organization to remove pharmaceutical compounds from water in treatment plants due to its cost and easy implementation. This study presents the modification of a commercial activated carbon by heat treatment at 1073, 1173, and 1273 K. The impact of the physicochemical changes of the adsorbent on the adsorption capacity of salicylic acid and methylparaben, compounds derived from phenol, was studied. Finally, the adsorbate-adsorbent interactions are evaluated through immersion calorimetry. It is observed that at 1173 K, activated carbon increases its surface area by 29%. At higher temperatures, the surface area drops to 21%. In the activated carbon subjected to heat treatment at 1173 K, it increases the adsorption capacity of salicylic acid and methylparaben by 24 and 34%, respectively, compared to activated carbons subjected to higher temperatures. The interaction enthalpies (adsorbate-adsorbent interaction) have values between -12 and 5 J g-1.