The present work reports the preparation of activated carbon fibers (ACFs) from pineapple plant leaves, and its application on caffeine (CFN) removal from aqueous solution. The preparation procedure ...was carried out using the H3PO4 as activating agent and slow pyrolysis under N2 atmosphere. The characterization of materials was performed from the N2 adsorption and desorption isotherms, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, Boehm titration and pHpzc method. ACFs showed high BET surface area value (SBET = 1031m2 g−1), well-developed mesoporous structure (mesopore volume of 1.27cm³ g−1) and pores with average diameter (DM) of 5.87nm. Additionally, ACFs showed features of fibrous material with predominance of acid groups on its surface. Adsorption studies indicated that the pseudo-second order kinetic and Langmuir isotherm models were that best fitted to the experimental data. The monolayer adsorption capacity was found to be 155.50mgg−1. thermodynamic studies revealed that adsorption process is spontaneous, exothermic and occurs preferably via physisorption. The pineapple leaves are an efficient precursor for preparation of ACFs, which were successful applied as adsorbent material for removal of caffeine from the aqueous solutions.
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•Pineapple plant leaves were used as raw material for preparation of activated carbon fibers (ACFs).•ACFs were prepared under slow pyrolysis using H3PO4, as activating agent.•ACFs showed high BET surface area (1031m2 g−1) and mesoporous development.•Adsorption studies of Caffeine (CFN) removal using ACFs were investigated.•ACFs showed monolayer maximum adsorption capacity of 155.50mgg−1 at 25°C for CFN.
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•KOH-super activated carbon (SAC) was first produced from Jatoba’s barks.•SAC was successfully applied in the paracetamol (PCT) adsorption.•The regenerated SAC (RSAC) was obtained ...after several thermal regeneration cycles.•SAC and RSAC showed SBET values of 2794 m² g−1 and 889 m² g−1, respectively.•A PCT adsorption mechanism was proposed based on the molecular orbital theory.
A super activated carbon (SAC) was produced by KOH-activation of a biomass waste for paracetamol (PCT) adsorption from aqueous solution and for adsorption-thermal regeneration cycles. The SAC and the regenerated SAC after five adsorption-regeneration cycles (RSAC-5th) were fully characterized by several techniques. The N2 physisorption showed that the SBET values of the SAC and RSAC-5th are remarkably different, being 2794 m² g−1 and 889 m² g−1, respectively. The XPS analysis demonstrated that the SAC surface is composed by oxygen containing-groups, whilst the RSAC-5th also presents nitrogen ones, provenient from the PCT molecules. The adsorption studies revealed that the maximum adsorption capacity (Qm) for the SAC (356.22 mg g−1) is higher than that for RSAC-5th (113.69 mg g−1). Also, the results demonstrated that the PCT adsorption is governed by both physisorption and chemisorption and the ab initio calculations showed the chemisorption mainly occurs in carboxylic groups.
► Use of NaOH as activating agent in the coconut activated carbon production. ► NaOH promotes the microporosity development of the char. ► Microporous characteristics of the activated carbon allow ...that it adsorbs high amount of methylene blue (916.26
mg
g
−1).
Activated carbons (ACs) of coconut shell produced by NaOH activation at impregnation ratios of NaOH:char (w/w) equal to 1:1 (AC-1), 2:1 (AC-2) and 3:1 (AC-3) were prepared. The properties of these carbons, including BET surface area, pore volume, pore size distribution, and pore diameter, were characterized from N
2 adsorption isotherms. It was found that the ACs are essentially microporous and that the BET surface area was in order of 783 m
2
g
−1 for AC-1, 1842 m
2
g
−1 for AC-2, and 2825 m
2
g
−1 for AC-3. Scanning electron microscopy images showed a high pore development while Boehm method and Fourier-transform infrared spectroscopy spectra indicated the presence of acid functional groups which was confirmed by pH drift method. The adsorption equilibrium and kinetics of methylene blue (MB) onto AC-3 were carried out. Experimental data were fitted to the four isotherm models (Langmuir, Freundlich, Toth and Redlich–Peterson), and was found that Langmuir model presented the best fit, showing maximum monolayer adsorption capacity of 916
mg
g
−1. The kinetic studies showed that experimental data follow pseudo-second-order model. The mechanism of the adsorption process was described from the intraparticle diffusion model. The AC-3 has a high surface area and showed to be an efficient adsorbent for removal of MB from aqueous solutions.
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•NaOH-activated carbon was produced from guava seeds (AC–GS).•AC–GS exhibited microporous feature (85%) and SBET of 2573.6m2g−1.•Kinetic, isotherm and thermodynamic studies for ...amoxicillin removal were evaluated.•AC–GS presented maximum monolayer adsorption capacity of 570.48mgg−1 at 25°C.
We report the preparation and characterization of NaOH-activated carbon of high surface area produced from guava seeds (AC–GS) and its application for amoxicillin (AMX) adsorption. The AC–GS was fully characterized from the N2 adsorption and desorption isotherms, scanning electron microscopy (SEM), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), Boehm titration and pHPZC. Additionally, the kinetics, equilibrium and thermodynamic parameters on the adsorption of AMX onto AC–GS were evaluated. The AC–GS showed BET surface area of 2573.6m2g−1 and microporous features (85%), presenting average pore diameter of 1.96nm, which are suitable for AMX adsorption. The experimental adsorption data were modelled using several kinetic (pseudo-first order, pseudo-second order and Elovich) and isotherm (Freundlich, Langmuir, Redlich–Peterson and Dubinin–Radushkevich) models, which suggested that the adsorption of AMX onto AC–GS occurs predominantly by chemisorption showing a maximum monolayer adsorption capacity of 570.48mgg−1 (pH=4.0; T=25°C), which stands out compared to various adsorbents found in literature. Additionally, the thermodynamic parameters revealed the spontaneity of AMX adsorption (ΔG°=−1.915kJmol−1 at 298K) and its endothermic characteristic (ΔH°=21.33kJmol−1), evidencing the high-efficiency of AC–GS for AMX adsorption and its great potential for organic pollutants removal.
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•A NaOH-activated carbon was prepared from macadamia nut shells.•The ACM showed BET surface area of 1524m2g−1 and microporous feature (78.2%).•Kinetic and equilibrium studies were ...applied for tetracycline removal.•The ACM presented maximum monolayer adsorption capacity of 455.83mgg−1.
A NaOH-activated carbon was prepared from macadamia nut shell using the impregnation ratio of 3:1 (NaOH:char) (wt:wt). The obtained material (ACM) was characterized by several techniques and methodologies such as, N2 adsorption–desorption isotherms, SEM, FT-IR, Boehm titration, and pHpzc. The results demonstrated that the ACM is composed mainly of micropores (78.2%), presenting BET surface area of 1524m2g−1. Through the SEM and FT-IR analysis it could be observed that significant changes occurred on the material surface after the activation procedure. According to Boehm titration, the ACM has on its surface a majority of basic groups which is in agreement with the obtained pHpzc value of 8.74. The ACM was applied for tetracycline (TC) removal in order to assess its potential as an adsorbent. Thus, adsorption studies were carried out and several kinetic and isotherm models were employed. The isotherm model which best fitted to experimental data was Temkin, while the best fitted kinetic model was Elovich. ACM showed maximum monolayer adsorption capacity (Qm) of 455.33mgg−1. The intraparticle diffusion and film diffusion mechanisms were studied by the equations of Weber & Morris and Boyd, respectively. According to the results, the limiting step of the adsorption of TC onto ACM is influenced by intraparticle diffusion and by film diffusion.
The adsorption of methylene blue (MB) onto activated carbon produced from flamboyant pods (
Delonix regia) and obtained under optimized conditions (AC
op) was carried out in this work. The ...experimental equilibrium data were analyzed using the isotherms of Langmuir, Freundlich, Jovanovic, Harkins–Jura, Tempkin, Redlich–Peterson, Toth, Radke–Prausnitz, Sips, Vieth–Sladek, and Brouers–Sotolongo. The adsorption kinetics of pseudo-first order, pseudo-second order, and Avrami were used for the kinetic studies. For the Toth isotherm, the value of maximum adsorption capacity (
Q
m
=
889.58
mg
g
−1) was close to the experimental value (
Q
m
=
890
mg
g
−1), and the correlation coefficient (
R
2) was 0.9836. The experimental data fitted very well to Avrami kinetic model. The Fourier-transform infrared spectroscopy spectra and the scanning electron microscopy images showed the presence of MB adsorbed onto AC
op. Several possible mechanisms of interaction that can occur in the MB–AC
op system are discussed. AC
op is a fast and effective adsorbent for removing MB from aqueous solutions.
Denim fabric waste was used as a carbon precursor, and chemically activated with phosphoric acid in the ratio of 1:1 (v:m) under a slow pyrolysis process to obtain activated carbon fibers (ACFs). The ...chemical and physical properties of the ACFs were investigated from the thermogravimetric analysis (TGA), N2 porosimetry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman and Fourier transform infrared spectroscopy (FTIR), Boehm titration method, and point of zero charge (pHPZC). The obtained ACFs showed high yield (53%), BET surface area of 1582 m2 g−1, mesoporous features (average pore diameter of 3.60 nm), and surface acidic properties (pHPZC value of 2.13 and 1.13 mmol g−1 of acidic groups). The ACFs were applied in the removal of textile dye, Remazol Brilliant Blue R (RBBR), from aqueous solution. The adsorption isotherm and kinetic studies showed that adsorption of RBBR on the ACFs were better described by the pseudo-second order kinetic model and the Freundlich equilibrium model. The maximum adsorption capacity of the ACFS for RBBR was determined to be 292 mg g−1, which is higher than other adsorbent materials reported in the literature. The adsorption thermodynamic parameters indicated that adsorption process is spontaneous and exothermic.
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•ACFs were synthesized from denim waste and H3PO4 with slow pyrolysis.•ACFs showed SBET value of 1582 m2 g−1 and mesoporosity features.•BJH method showed a narrow pore distribution and average diameter of 3.6 nm.•Adsorption studies for removal of RBBR from solutions were successfully performed.•ACFs showed a maximum adsorption capacity of 292 mg g−1 at 25 °C for RBBR.
•Activated carbon was prepared from a new material, buriti shells.•A microporous activated carbon (75.10% of micropores) was obtained.•The adsorption dynamics was evaluated by several isotherm and ...kinetic models.•Monolayer adsorption capacity for methylene blue is 274.62mgg−1.
The present study reports the preparation of an activated carbon produced from buriti shells (ACb) using ZnCl2 as activating agent and its ability to remove methylene blue dye (MB) from aqueous solutions. The obtained ACb was characterized by N2 adsorption–desorption isotherms, SEM and FT-IR. The results show that ACb presents microporous features with BET surface area (SBET) of 843m2g−1 and functional groups common in carbonaceous materials. Adsorption studies were carried out and experimental data were fitted to three isotherm models (Langmuir, Freundlich, and Redlich–Peterson) and four kinetic models (pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion). The isotherm model which best fitted to experimental data was Redlich–Peterson. However, the g parameter of this model indicated that the adsorption of MB onto ACb occurs according to the mechanism proposed by Langmuir, which showed maximum monolayer adsorption capacity of 274.62mgg−1. Kinetic studies demonstrated that the Elovich model is suitable to describe the experimental data. Moreover, it was found that the intraparticle diffusion is the limiting step of adsorption process.
The development of advanced carbon nanomaterials that can efficiently extract pollutants from solutions is of great interest for environmental remediation and human safety. Herein we report the ...synthesis of magnetic activated carbons via simultaneous activation and magnetization processes using carbonized biomass waste from coconut shells (Cb’s) and FeCl3·6H2O as precursor. We also show the ability of the materials to efficiently extract toxic organic dyes from solutions and their ease of separation and recovery from the solutions using a simple bar magnet. Textural characterization shows that the materials are microporous. Further analyses of the deconvoluted XPS spectra and X-ray diffraction patterns reveal that the materials possess magnetite, maghemite and hematite. SEM and TEM images show that an increase in the ratio of FeCl3·6H2O:Cb leads to an increase in the material’s magnetic properties. The point of zero charge (pHpzc) indicates that the materials have acidic characteristics. Adsorption kinetic studies carried out onto MAC1 indicates that the Elovich model can satisfactorily describe the experimental data at low initial concentrations and the pseudo-second order model can best fit the data at higher initial concentrations. Moreover, adsorption equilibrium studies reveal that the Langmuir model adequately allows the determination of the materials’ adsorption capacity. Our adsorption and equilibrium fit of the data include nonlinear models and are thus more informative compared with those in other recent, related works, in which only linear fits have been presented. Extensive mechanistic studies for the adsorption processes are also included in the work.