Display omitted
•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 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.
Display omitted
•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.
Display omitted
•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.
Display omitted
•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.
Display omitted
•Spherical carbon was obtained from hydrothermal treatment (HT) of sucrose.•HT in conjunction with subsequent KOH activation produced activated carbon (AC).•AC has a BET surface area ...of 1534m2g−1 and 82.6% of micropores.•The Methylene Blue maximum monolayer adsorption capacity on AC was 704.2mgg−1.
This work reports the synthesis of activated carbon (AC) obtained by KOH chemical activation of spherical carbon (SC) produced from hydrothermal treatment (HT) of sucrose. Scanning electron microscopy was used to characterize the morphology and the sphere sizes of SC, which showed average diameter of 2.86μm. SC showed low values of BET surface area (SBET) and total volume of pores (VT), whereas AC presented characteristics of microporous materials with SBET and VT of 1534m2g−1 and 0.765cm3g−1, respectively. FT-IR analysis and Boehm method indicated that the AC surface has essentially acid functional groups, which was confirmed by pHPZC values of 3.0. The adsorption equilibrium data of Methylene Blue (MB) onto AC were best fitted to the Redlich–Peterson model. The maximum adsorption capacity monolayer was of 704.2mgg−1, which showed to be high compared to other ACs reported in the literature. The kinetic data showed better fit to the pseudo-first-order model at low MB concentration, and with the increasing of concentration, to the pseudo-second-order and Elovich models. Thermodynamic parameters indicated that MB–AC adsorption process is spontaneous and endothermic.
The present paper reports the application of augmented simplex-centroid mixture design to obtain a high BET surface area activated carbon using as reactants KOH, K2CO3 and K2C2O4. The optimum mixture ...composition was 2.51 g of KOH, 0.49 g of K2CO3 and absence of K2C2O4, generating an optimized AC (ACop) with SBET value equals to 1984 m2 g−1. The results herein obtained show that low amounts of K2CO3 can catalyze the pore development in the presence of KOH, increasing the surface area. Furthermore, the fractal dimensions of ACop are greater than 2.72, indicating the material has a complex pore structure with irregularities self-similar upon variations of resolution, as seen by SEM images. The TPD curves showed that the ACop has different oxygenated molecular fragments, which agrees with the pHPZC value (5.05). The ACop was applied in the adsorption of rhodamine B (RhB) and metformin (Met) in both binary and monocomponent systems. The simultaneous adsorption at 30 °C reveals that the adsorption capacity of RhB is 630.94 mg g−1, while for Met the value is 103.83 mg g−1.
Display omitted
•A simplex-centroid mixture design was applied in the production of activated carbon (AC).•The optimized AC showed specific surface area of 1984 m2 g−1.•The monocomponent and binary adsorptions showed differences in rhodamine B and metformin adsorption.•The proposed binary adsorption mechanism was confirmed by DFT-based quantum chemical descriptors.
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.
► 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.
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.
Display omitted
•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.
PDF
