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The contamination of water bodies by synthetic organic compounds coupled with climate change and the growing demand for water supply calls for new approaches to water management and treatment. To tackle the decontamination issue, the activation of peroxymonosulfate (PMS) using copper magnetic ferrite (CuMF) nanoparticles prepared under distinct synthesis conditions was assessed to oxidize imidacloprid (IMD) insecticide. After optimization of some operational variables, such as CuMF load (62.5-250 mg L-1), PMS concentration (250-1000 µM), and solution pH (3-10), IMD was completely oxidized in 2 h without interferences from leached metal ions. Such performance was also achieved when using tap water but was inhibited by a simulated municipal wastewater due to scavenging effects promoted by inorganic and organic species. Although there was evidence of the presence of sulfate radicals and singlet oxygen oxidizing species, only four intermediate compounds were detected by liquid chromatography coupled to mass spectrometry analysis, mainly due to hydroxyl addition reactions. Concerning the changes in surface properties of CuMF after use, no morphological or structural changes were observed except a small increase in the charge transfer resistance. Based on the changes of terminal surface groups, PMS activation occurred on Fe sites.

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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.

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The objective of this research was to produce an activated carbon (AC) from exhausted coffee grounds (ECG) and chemically activate it with natural lye from eucalyptus ash to subsequently evaluate the fluoride adsorption process in an aqueous medium. The thermal analysis of ECG was determined as well as solubilized extraction, alkalinity and calcium content of eucalyptus ashes. AC was characterized by elemental analysis, scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), analysis of textural properties, pH and point of zero charge (PZC). The AC presented macroporosity and XRD confirmed the amorphous characteristic of cellulose-containing materials. Carboxylic acid functional group was identified in the AC surface, which can contribute to the adsorption of fluoride. The specific surface area of ECG and AC were 189.01 and 21.74 m2/g. The adsorption kinetics of fluoride revealed that equilibrium is reached around 800 min and the data followed the pseudo-second order model. The Freundlich model fitted the experimental data with the best quality and Freundlich's constant n allowed inferring that the adsorption is favorable and the isotherm appears to be L-type, with an initial downward curvature, which suggests less availability of active sites when increasing the adsorbent concentration.

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The increase in burning, deforestation, and the exorbitant use of fossil fuels have contributed to the increase in carbon dioxide emissions; this gas is responsible for the intensification of the greenhouse effect and radical climate changes. In this way, it becomes necessary to find alternatives to reduce its emission. Porous carbon materials synthesized from lignocellulosic waste can be employed in technologies for capture and utilization of CO2 due to the advantages such as selectivity, low-cost synthesis, high surface area and pore volume, and thermal and chemical stability. Considering the availability of Brazil nut biomass residues in the Amazon region, this article proposes to synthesize activated carbon from the lignocellulosic residue using physical and chemical activation methods for CO2 capture. The analysis of N2 adsorption-desorption isotherms proves the predominance of a microporous structure when using the two synthesis methods described here. In physical activation, the surface area was 912 m2/g, while, in chemical activation, it was 1421 to 2730 m2/g. The sample treated via the chemical method (BS6-K1) showed better performance in CO2 adsorption, with adsorption results of 3.8 and 6 mmol/g of CO2 at 25 ℃ and 0 °C, respectively, at 101 kPa. CO2 adsorption capacity is due to the high volume of ultramicropores. It is believed that the microporous carbon material synthesized from Brazil nut residues is an alternative precursor for carbon materials used as CO2 capture.

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This paper presents the results obtained from the chemical activation of bacterial nanocellulose (BCN) using fique juice as a culture medium. BNC activation (BNCA) was carried out with H3PO4 and KOH at activation temperatures between 500 °C to 800 °C. The materials obtained were characterized morphologically, physicochemically, superficially, and electrochemically, using scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), the physisorption of gases N2 and CO2 at 77 K and 273 K, respectively, cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy (EIS). The samples activated with H3PO4 presented specific surface areas (SBET) around 780 m2 g-1, while those activated with KOH values presented specific surface areas between 680 and 893 m2 g-1. The XPS analysis showed that the PXPS percentage on the surface after H3PO4 activation was 11 wt%. The energy storage capacitance values ranged between 97.5 F g-1 and 220 F g-1 by EIS in 1 M H2SO4. The samples with the best electrochemical performance were activated with KOH at 700 °C and 800 °C, mainly due to the high SBET available and the accessibility of the microporosity. The capacitance of BNCAs was mainly improved by electrostatic effects due to the SBET rather than that of pseudocapacitive ones due to the presence of phosphorus heteroatoms.

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In this work, carbon dots were created from activated and non-activated pyrolytic carbon black obtained from waste tires, which were then chemically oxidized with HNO3. The effects caused to the carbon dot properties were analyzed in detail through characterization techniques such as ion chromatography; UV-visible, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy; ζ potential; transmission electron microscopy (TEM); and spectrofluorometry. The presence of functional groups on the surface of all carbon dots was revealed by UV-visible, FTIR, XPS, and Raman spectra. The higher oxidation degrees of carbon dots from activated precursors compared to those from nonactivated precursors resulted in differences in photoluminescence (PL) properties such as bathochromic shift, lower intensity, and excitation-dependent behavior. The results demonstrate that the use of an activating agent in the recovery of pyrolytic carbon black resulted in carbon dots with different PL properties. In addition, a dialysis methodology is proposed to overcome purification obstacles, finding that 360 h were required to obtain pure carbon dots synthesized by a chemical oxidation method.

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Bark residues of the forest species Cedrela fissilis were physically and chemically modified with zinc chloride (ZnCl2) as an activating agent. The two modified materials were analyzed as adsorbents in removing atrazine and 2,4-D herbicides from effluents. Firstly, the precursor material and the modified ones were characterized by different techniques to identify the structural changes that occurred in the surfaces. Through TGA, it was observed that both modified materials have thermal stability close to each other and are highly superior to the precursor. X-ray diffractions proved that the amorphous structure was not altered, the three materials being highly heterogeneous and irregular. The micrographs showed that the treatments brought new spaces and cavities on the surface, especially for the material carbonized with ZnCl2. The pHPZC of the modified materials was close to 7.5. The physically modified material had a surface area of 47.31 m2 g-1 and pore volume of 0.0095 cm3 g-1, whereas the carbonized material had a surface area of 98.12 m2 g-1 and pore volume of 0.0099 cm3 g-1. Initial tests indicated that none of the adsorbents were efficient in removing 2,4-D. However, they showed good potential for removing atrazine. The Koble-Corrigan isothermal model best fits the experimental data, with a maximum capacity of 3.44 mg g-1 and 2.70 mg g-1 for physically modified and with ZnCl2, respectively. The kinetic studies showed that the system tends to enter into equilibrium after 120 min, presenting good statistical indicators to the linear driving force model (LDF). The surface diffusion coefficients were 2.18×10-9 and 2.37×10-9 cm2 s-1 for atrazine adsorption on the physically and chemically modified materials. These results showed that the application of residues from the processing of cedar bark is promising. However, new future studies must be carried out to improve the porous development of the material and obtain greater adsorption capacities.

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Physical adsorption on activated carbons has shown to be a very attractive methodology for CO2 separation from flue gas streams and biogas. In this context, the goal of this work was to prepare granular activated carbons intended for CO2 adsorption from an abundant and low-cost biomass residue (coconut shell) by using practical and cost-effective procedures. By the first time, parameters involved in chemical activation with dehydrating agents (H3PO4 or ZnCl2) and/or physical activation with CO2 were systematically screened in depth in order to obtain materials with improved performance for CO2 adsorption on a volume basis. Compared with the commonly used mass basis, the data expressed on a volume basis are very important for industrial applications because they permit to estimate the efficiency of a fixed bed adsorption column. The work permitted to prepare granular activated carbons with a blend of relatively high gravimetric CO2 uptake and bulk density, so that high volumetric CO2 uptakes were attained. The highest values were 2.67 and 1.17 mmol/cm3 for CO2 pressures of 1.0 and 0.15 bar, respectively. It is remarkable that the obtained results were similar to those reported by other authors for carbons chemically activated with KOH, the activation methodology that has been widely claimed as the one that produce ACs with the best performances for CO2 adsorption, but which involves severe restrictions. Therefore, the present work can be considered a very important step in paving the way toward making CO2 adsorption an each time more interesting technology to reduce the emissions of anthropogenic greenhouse gases.

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Pyrolysis is a feasible solution for environmental problems related to the inadequate disposal of waste tires, as it leads to the recovery of pyrolytic products such as carbon black, liquid fuels and gases. The characteristics of pyrolytic carbon black can be enhanced through chemical activation in order to produce the required properties for its application. In the search to make the waste tire pyrolysis process profitable, new applications of the pyrolytic solid products have been explored, such as for the fabrication of energy-storage devices and precursor in the synthesis of nanomaterials. In this study, waste tires powder was chemically activated using acid (H2SO4) and/or alkali (KOH) to recover pyrolytic carbon black with different characteristics. H2SO4 removed surface impurities more thoroughly, improving the carbon black's surface area, while KOH increased its oxygen content, which improved the carbon black's stability in water suspension. Pyrolytic carbon black was fully characterized by elemental analysis, inductively coupled plasma-optical emission spectrometry (ICP-OES), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), N2 adsorption/desorption, scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), dynamic light scattering (DLS), and ζ potential measurement. In addition, the pyrolytic carbon black was used to explore its feasibility as a precursor for the synthesis of carbon dots; synthesized carbon dots were analyzed preliminarily by SEM and with a fluorescence microplate reader, revealing differences in their morphology and fluorescence intensity. The results presented in this study demonstrate the effect of the activating agent on pyrolytic carbon black from waste tires and provide evidence of the feasibility of using waste tires for the synthesis of nanomaterials such as carbon dots.

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Activated carbons (ACs) from Pinus canariensis cones were developed by KOH chemical activation. The effect of the impregnation KOH/carbonized cones ratio (IR = 1, 2, or 3) and temperature (873, 973, 1073 K) on main chemical, textural, and morphological characteristics of the resulting ACs was systematically examined. CO2 adsorption capacity from gaseous streams was evaluated by gravimetric adsorption tests, and the analysis of breakthrough curves was determined in a packed-bed column at 303 K and atmospheric pressure. Comparison of CO2 adsorption capacities of the ACs at 273 K and 303 K at equilibrium showed that those samples developed at 973 K with IR = 3 (BET surface area ~ 1900 m2 g-1) attained the highest values (6.4 mmol g-1 and 1.9 mmol g-1, respectively), even though the ACs obtained at 1073 K with the same IR exhibited the largest surface area (2200 m2 g-1). Thermodynamic parameters evaluated from CO2 adsorption isotherms determined in the range 273-333 K for the former sample pointed to a physisorption, spontaneous, and exothermic process; isosteric heat of adsorption was also estimated for the range of surface coverage of the equilibrium isotherms. The kinetics of CO2 adsorption onto all the ACs was successfully described by the linear driving force model. The breakthrough curves were properly represented by the Thomas' model, the longest breakthrough time and highest adsorption capacity being also attained for the bed packed with the ACs developed at 973 K with IR = 3. Higher CO2 adsorption capacities of the ACs were directly related to the presence of narrow micropores (< 0.9 nm) induced by the stronger activation conditions. However, an excessively severe combination of the IR and activation temperature exerted a negative influence on CO2 adsorption onto the ACs, likely due to micropores widening.

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The aim of this research is to prepare various carbonaceous materials with different textural, structural and chemical characteristics, using mango seed a rarely used residue for the preparation of activated carbons, as the precursor material. The mango seed was analyzed by TGA and SEM also methodological data about the preparation of activated carbons are provided. Four activated carbons were prepared using sulfuric acid (H2SO4) and calcium chloride (CaCl2) as activating agents and were characterized by means of TGA, SEM/EDX, Boehm Titration, isotherm determination of N2 adsorption-desorption at -196 °C and immersion calorimetry. Four carbons were obtained with superficial areas BET between 6 and 33 m2 g-1 and different chemical characteristics associated with the changes in the concentration of the activating agents. The activated carbons that were prepared with the highest activating agent concentrations, obtained better results in the amount of oxygenated surface groups, the total acidity and the amount of fixed carbon. The enthalpy of immersion in water was between 7 and 16 J g-1.

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The adsorption characteristics of C.I. basic blue 26 (BB26) from aqueous solutions onto H3PO4-activated carbons (ACs) produced from açai stones (Euterpe oleracea Martius) and Brazil nut shells (Bertholletia excelsa H. B. K) were investigated in a batch system. The ACs were characterized by XRD, FT-IR, N2 adsorption at 77 K, mercury porosimetry, and acidity/basicity analysis. The pseudo-first-order, pseudo-second-order kinetic models and intraparticle diffusion model were used for the kinetic interpretations. The adsorption processes follow the pseudo-second-order kinetic model. The Boyd plots revealed that the adsorption processes were mainly controlled by film diffusion. Equilibrium data were analyzed by the Langmuir and Freundlich models, at different temperatures. The equilibrium data were best represented by the Langmuir isotherm. The adsorption processes were found to be favorable, exothermic, and spontaneous. The açai stones and Brazil nut shells-based ACs were shown to be effective adsorbents for removal of BB26 from aqueous solutions.

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In this work, we report the synthesis and purification of polyvinyl alcohol-polyaniline (PVA⁻PANI) copolymers at different aniline concentrations, and their molecular (¹H-NMR and FTIR), thermal (TGA/DTG/DSC), optical (UV⁻Vis-NIR), and microstructural (XRD and SEM) properties before and after activation with glutaraldehyde (GA) in order to obtain an active membrane. The PVA⁻PANI copolymers were synthesized by chemical oxidation of aniline using ammonium persulfate (APS) in an acidified (HCl) polyvinyl alcohol matrix. The obtained copolymers were purified by dialysis and the precipitation⁻redispersion method in order to eliminate undesired products and compare changes due to purification. PVA⁻PANI products were analyzed as gels, colloidal dispersions, and thin films. ¹H-NMR confirmed the molecular structure of PVA⁻PANI as the proposed skeletal formula, and FTIR of the obtained purified gels showed the characteristic functional groups of PVA gels with PANI nanoparticles. After exposing the material to a GA solution, the presence of the FTIR absorption bands at 1595 cm-1, 1650 cm-1, and 1717 cm-1 confirmed the activation of the material. FTIR and UV⁻Vis-NIR characterization showed an increase of the benzenoid section of PANI with GA exposure, which can be interpreted as a reduction of the polymer with the time of activation and concentration of the solution.

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This work reports for the first time the use of chemically activated biochar as electrode modifier for nickel determination. The biochar activation was performed by refluxing with HNO3, which promoted a higher nickel preconcentration compared to unmodified and modified biochar precursor electrodes. Morphological and structural characterization revealed the increase of surface acid groups, surface area and porosity of biochar after activation. Nickel determination was investigated adopting an alternative voltammetric methodology based on monitoring the Ni(II)/Ni(III) redox couple. In the proposed method, it was not necessary to use a complexing agent and the biochar itself was responsible for the analyte preconcentration. A linear response for Ni(II) concentration range from 1.0 to 30 µmol L-1 and a limit of detection of 0.25 µmol L-1 were obtained. The method was successfully applied for Ni(II) determination in spiked samples of bioethanol fuel and discharge water, with recoveries values between 103 and 109%.

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Resumen En el presente estudio se muestra la producción de carbón activado a partir de la biomasa residual generada en la producción de palma de aceite, fibra (F) y cáscara (C). Se realizó activación química con ZnCl2 y se evalúo la capacidad de remoción de azul de metileno (AM) para diferentes concentraciones (50, 100 y 150 mg/L). Los resultados mostraron un buen desarrollo de poro por dicho método de activación, con áreas superficiales de 835,3 m2/g para la fibra activada (FA) y 575,1 m2/g para la cáscara activada (CA). Se encontró un buen ajuste de los datos experimentales al modelo cinético de pseudo segundo orden y a las isotermas de Langmuir y Freundlich con capacidades máximas de adsorción de 763,4 y 724,6 mg/g para FA y CA, respectivamente.

Abstract The production of activated carbon from residual biomass generated in the production of oil palm, fiber (F) and shell (C) was studied. The chemical activation was done using ZnCl2 and the adsorption capacity of methylene blue (AM) at different concentrations (50, 100, and 150 mg/L) was evaluated. Results showed a good development of pore with surface areas of 835.3 m2/g for activated fiber (FA) and 575.1 m2/g for activated shell (CA). A good fit of the experimental data with the pseudo second order kinetic model and with Langmuir and Freundlich isotherms models was found. In addition, maximum adsorption capacities of 763.4 and 724.6 mg/g for FA and CA were found, respectively.

Resumo No presente estudo e mostrada a produção de carvão ativado a partir da biomassa residual gerada na produção de fibra de palmeira de óleo (F) e casca (C). A ativação química foi realizada com ZnCl2, foi avaliada a capacidade de remoção do azul de metileno (AM) para diferentes concentrações (de 50, 100 e 150 mg/L). Os resultados mostraram um bom desenvolvimento do poro pelo método de ativação estudado para com áreas de superfície de 835,3 m2/g para a fibras activada (FA) e 575,1 m2/g para a casca activada (CA). Foi encontrado um bom ajuste dos dados experimentais ao modelo da cinética de pseudo segunda ordem e a isotermas de Langmuir e Freundlich com capacidades máximas de adsorção de 763,44 e 724,6 mg/g para a FA e CA, respectivamente.

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Activated carbon honeycomb-monoliths with different textural properties were prepared by chemical activation of African palm shells with H(3)PO(4), ZnCl(2) and CaCl(2) aqueous solutions of various concentrations. The adsorbents obtained were characterized by N(2) adsorption at 77 K, and their carbon dioxide adsorption capacities were measured at 273 K and 1 Bar in volumetric adsorption equipment. The experimental adsorption isotherms were fitted to Langmuir and Tóth models, and a better fit was observed to Tóth equation with a correlation coefficient of 0.999. The maximum experimental values for adsorption capacity at the highest pressure (2.627-5.756 mmol·g(-1)) are between the calculated data in the two models.

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Se preparan carbones activados por activación química de residuos de llantas con soluciones acuosas de diferente concentración de dos activantes químicos (H3PO4 y KOH) y por activación física con CO2. Los carbones activados caracterizados por determinación de isotermas de adsorción de N2 a 77 K, que muestran la forma típica de estructuras mesoporosas, que permiten calcular el área superficial específica para los carbones activados obtenidos que presentaron valores entre 25,4 y 157,3 m²g-1. Las entalpías de inmersión de los carbones activados en benceno y agua se encuentran entre 3,12 y 27,6 Jg-1 y 9,81 y 30,6 Jg-1, respectivamente, y muestran el tipo de interacciones superficiales que pueden tener los sólidos porosos obtenidos con diferentes adsorbatos. Se encontró un comportamiento lineal directamente proporcional para la relación entre el volumen de microporo y el área superficial, y una relación de segundo orden entre el área superficial y la entalpía de inmersión en benceno. De acuerdo con las condiciones de preparación se obtienen sólidos porosos adecuados para la adsorción de compuestos en fase líquida dado su mayor volumen de mesoporos.

Activated carbons are prepared by chemical activation from waste tire with aqueous solutions at different concentrations of two activating agents-H3PO4 and KOH--and by physical activation with CO2. The activated carbons are characterized by the determination of adsorption isotherms N2 at 77 K, which show the form typical of structures mesoporous and allow calculating the surface specific area, for the activated carbons obtained that presented values between 25,4 and 157,3 m²g-1. The immersion enthalpies of the activated carbons in benzene and water present values that are between 3,12 and 27,6 Jg-1 and 9,81 and 30,6 Jg-1, respectively, and show the surface interactions type that can have the porous solids obtained with different adsorbates. A directly linear proportional behavior for the relation between the micropore volume and the surface area, and a relation of the second order between the surface area and the immersion enthalpy in benzene were found. In agreement with the conditions of preparation, the solid porous obtained are adapted for the adsorption of compounds in liquid phase because of its major mesoporous volume.

Se preparam carvões ativados por activação química de resíduos de llantas com soluções acuosas de diferente concentração de duas activantes químicos (H3PO4 e KOH), e por activação física com CO2. Os carvões ativados se caracterizam por determinação de isotermas de adsorção de N2 a 77 K, que mostram a forma característica de estruturas mesoporosas, permitem calcular o área superficial específica para os carvões ativados obtidos que apresentaram valores entre 25,4 e 157,3 m²g-1. As entalpías de imersão dos carvões ativados em benzeno e água, encontram-se entre 3,12 e 27,6 Jg-1 e 9,81 e 30,6 Jg-1, respectivamente e mostram o tipo de interações superficiais que podem ter os sólidos porosos obtidos com diferentes adsorbatos. Encontrou-se um comportamento linear diretamente proporcional para a relação entre o volume de microporo e o área superficial e uma relação de segundo ordem entre o área superficial e a entalpía imersão em benzeno; de acordo ás condições de preparação se obtêm sólidos porosos adequados para a adsorção de compostos em fase líquida dado seu maior volume de mesoporos.