•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.
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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.
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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.
The present work reports the development and application of bismuth-film electrode (BiFE), obtained by in situ method on the pencil-lead graphite surface, for simultaneous Cd(II) and Pb(II) ...determination at trace levels, as alternative to replace the mercury-film electrodes. Experimental factors, deposition time (td), deposition potential (Ed), and Bi(III) concentration (CBi), were investigated by applying a 23 factorial design using 0.10 mol/L acetate buffer solution (pH 4.5) as supporting electrolyte. The analysis conditions of the differential pulse technique were td = 250 s, Ed = -1.40 V, and CBi = 250 mg L−1. The validation of the method employing BiFE was accomplished by determination of merit figures. The detection limits were of 11.0 μg L−1 for Cd(II) and 11.5 μg L−1 for Pb(II), confirming that proposed method is attractive and suitable for heavy metals determination. Additionally, the BiFE developed was successfully applied for the Cd(II) and Pb(II) determination in wastewater sample of battery industry.
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•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.
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•Mesoporous activated carbon was produced from industrial laundry sewage sludge (AC).•Surface area of AC decreased with increase of activation temperature.•Kinetic, isotherm and ...thermodynamic studies for Remazol Brilliant Blue R removal were evaluated.•AC showed maximum monolayer adsorption capacity of 33.5mgg−1 at 25°C.•Spent activated carbon (ACsp) was submitted to thermal regeneration cycles.
Mesoporous activated carbon (AC) was prepared from sewage sludge of industrial laundry by slow pyrolysis followed of physical activation with CO2 and applied to remove reactive dye Remazol Brillant Blue R (RBBR) from aqueous solutions. The effect of activation temperature was investigated. The materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and N2 adsorption-desorption isotherms. The ACs prepared at activation temperatures of 750°C (AC750), 800°C (AC800) and 850°C (AC850) exhibited BET surface areas (SBET) of 159m2g−1, 156m2g−1 and 65m2g−1, respectively, and mesoporous features with average pore diameters ranging from 4.56 to 5.88nm. The SEM images indicated the formation of cavities on the surfaces of ACs with increasing temperature. The XRD patterns showed the presence of minerals in ACs and sewage sludge such as quartz, muscovite, dolomite and calcite. Inorganic and organic contents were evidenced by TGA, and surface groups by FT-IR. The values of pHPZC indicated basic characteristics for AC750, and acidic for AC800 and AC850. The AC750 was applied in the RBBR adsorption from aqueous solution. Adsorption kinetics and adsorption equilibrium showed that the pseudo-second order and Freundlich models were best fitted to experimental data. The Langmuir monolayer maximum adsorption capacity was 33.47mgg−1. The thermodynamic parameters indicated the adsorption is a spontaneous process and favored at higher temperatures (endothermic reaction). The thermal regeneration of spent AC750 showed it can be reused on adsorption processes.
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•Photocatalysis was applied for treatment of textile effluent using the catalysts: TiO2, ZnO and Nb2O5.•UV irradiation was applied.•Solution pH, catalyst concentration and ...photocatalytic activity were investigated.•After photodegradation, the effluent toxicity decreased in for up to 3 times.•Nb2O5 becomes a promising alternative to replace the commercial TiO2 P25.
In this work, photocatalysis was employed in the treatment of textile effluent from industrial laundry jeans using the catalysts TiO2 P25 (commercial), TiO2, ZnO and Nb2O5, under artificial UV irradiation. The parameters investigated were: pH of the solution and catalyst concentration. The photocatalytic activity was evaluated by means of kinetic efficiency (rate constant and half life time), thermodynamic (absorbance reduction at 228, 254, 284, 310, 350, 500 and 660nm), COD reduction, mineralization in terms of the formation of inorganic ions (NH4+, NO3−, NO2−, SO42− and Cl−) and toxicity reduction (bioassays using Artemia salina). The photocatalytic degradation of textile effluent at pH 3.0 and catalyst concentration of 0.250gL−1 showed the best results, being found 95.91%; 87.35%; 86.95% and 59.18% of absorbance reduction at 660nm (λmax) after 300min of artificial irradiation with TiO2 P25, Nb2O5, TiO2 and ZnO, respectively. TiO2 and Nb2O5 were responsible for the reduction of approximately 70 and 66% of COD and the photocatalytic activity of TiO2 was very close to TiO2 P25. In this sense, Nb2O5 becomes a promising alternative to replace the commercial TiO2 P25. Bioassays with Artemia salina confirmed the efficacy of the treatment, indicating that after photodegradation there was an expressive decrease in effluent toxicity for up to 3 times.
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.
A new efficient photocatalyst consisting of TiO2-activated carbon composite (TiO2/AC) was synthesized by sol-gel process and applied to decomposition of tetracycline (TC). Its properties and ...catalytic activity were evaluated in comparison with bare TiO2 and P25, based on several characterization techniques and TC photodegradation kinetic studies. The results showed TiO2/AC has better structural and electronic features for photocatalysis; SBET of 129m2g–1, exclusively anatase phase, crystal size of 8.53nm and band gap energy of 3.04eV. The catalytic activity of the material was evaluated based on photodegradation kinetic studies of TC from aqueous solution (with initial concentration=50mgL−1 and catalyst dosage=1.0gL−1). Non-linear kinetic model of pseudo-first order were fitted to the resulting experimental data. The apparent first-order rate constant (kapp=42.9×10–3min–1) and half-life time (t1/2=16.1min) determined for TiO2/AC were better than those for P25 and bare TiO2. TC degradation by-products were investigated by HPLC-MS, showing TC was completely degraded after 75min, producing fragments with m/z smaller than 150.
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