Showing papers on "BET theory published in 2016"
TL;DR: In this paper, the synthesis of activated carbon (AC) obtained by KOH chemical activation of spherical carbon (SC) produced from hydrothermal treatment (HT) of sucrose was reported.
416 citations
TL;DR: In this paper, a low cost adsorbent (RH) was applied for Rhodamine B (RhB) uptake from aqueous solution, and the results showed that RH is about 1143 times more economical when compared with commercial activated carbon.
393 citations
TL;DR: In this article, 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 were evaluated.
318 citations
TL;DR: SEM, XRD, XPS and FT-IR analysis suggested that the multi-adsorption mechanisms including precipitation, ligand exchange and complexation interactions can be evidenced during the phosphate adsorption process by La-composites in La-BC.
293 citations
TL;DR: In this paper, the effects of activation temperature and impregnation ratio on the surface area, total pore volume, micropore volume and pore size distribution of activated carbons were examined.
Abstract: Activated carbons were prepared from Fox nutshell by chemical activation with H 3 PO 4 in N 2 atmosphere and their characteristics were studied. The effects of activation temperature and impregnation ratio were examined. N 2 adsorption isotherms characterized the surface area, total pore volume, micropore volume and pore size distribution of activated carbons. Activated carbon was produced at 700 °C with a 1.5 impregnation ratio and one hour of activation time has found 2636 m 2 /g and 1.53 cm 3 /g of highest BET surface area and total pore volume, respectively. The result of Fourier-infrared spectroscopy analysis of the prepared activated carbon confirmed that the carbon has abundant functional groups on the surface. Field emission scanning electron micrographs of the prepared activated carbon showed that a porous structure formed during activation.
253 citations
TL;DR: In this article, a facile ultra-rapid solution method was developed to fabricate ZnO nanosheets with tunable BET surface area and rich oxygen-vacancy defects.
Abstract: A facile ultra-rapid solution method was developed to fabricate ZnO nanosheets with tunable BET surface area and rich oxygen-vacancy defects. The addition of 1 mol L−1 Na2SO4 led to an increase of BET surface area of ZnO nanosheets from 6.7 to 34.5 m2/g, through an electrostatic-controlled growth and self-assembly mechanism. Detailed analysis based on Raman scattering, room-temperature photoluminescence, X-ray photoelectron spectroscopy and electron spin resonance revealed that the as-prepared ZnO nanosheets were rich in oxygen-vacancies. Increased BET surface area led to a further increase of surface oxygen-vacancy concentration. The rich oxygen-vacancies promoted the visible-light absorption of the ZnO nanosheets, leading to high photocurrent responses and photocatalytic activities towards the degradation of rhodamine B (apparent rate constants, k = 0.0179 min−1) under visible-light illumination (λ > 420 nm), about 13 and 11 times higher, respectively than that of ZnO nanoparticles with few oxygen defects. In addition, the high-surface-area ZnO nanosheets could be effectively hybridized with Ag3PO4 nanoparticles, resulting in a further enhancement of the visible-light photocatalytic performance (k = 0.0421 min−1). This increase in performance was attributed to the increased visible-light absorption as well as the energy level matching, the latter leading to efficient charge transfer between oxygen-vacancy-rich ZnO nanosheet and Ag3PO4, suggesting a synergistic effect of surface oxygen vacancies and Ag3PO4 coupling.
217 citations
TL;DR: In this paper, the chitosan/TiO 2 composite nanofibrous adsorbents were developed by two techniques including TiO 2 nanoparticles coated chitosa-nibers (coating method) and electrospinning of chitosi-nigram solutions (entrapped method) for the removal of Pb (II) and Cu(II) ions in a batch system.
Abstract: The chitosan/TiO 2 composite nanofibrous adsorbents were developed by two techniques including TiO 2 nanoparticles coated chitosan nanofibers (coating method) and electrospinning of chitosan/TiO 2 solutions (entrapped method). The potential of prepared nanofibers was investigated for the removal of Pb (II) and Cu (II) ions in a batch system. The nanofibers were characterized by SEM, FTIR and BET analysis. Kinetic and equilibrium studies showed that the experimental data of Pb (II) and Cu (II) ions were best described by pseudo-first-order and Redlich–Peterson isotherm models using the both chitosan/TiO 2 nanofibers. The maximum adsorption capacities of Cu (II) and Pb (II) ions using entrapped and coating methods were found to be 710.3, 579.1 and 526.5, 475.5 mg/g at equilibrium time of 30 min and 45 ° C, respectively. The reusability studies indicated that the chitosan/TiO 2 nanofibers prepared by entrapped method could be reused frequently without significant loss in adsorption performance after five adsorption/desorption cycles. Whereas, lower than 60% of total adsorption in first cycle took place for metal ions sorption using nanofibers prepared by coating method. The sorption studies of metal ions in a binary system revealed that the selectivity of metal sorption using chitosan/TiO 2 nanofibrous adsorbent was in order of Cu (II) > Pb (II).
196 citations
TL;DR: In this article, a facile approach was used as an efficient adsorbent for removing fluoride from Ce-Fe bimetal oxides with hierarchical pore structure, and the results showed that the maximum adsorption capacity was as high as 60.97% with a wide range of pH from 2.9 to 10.1.
193 citations
TL;DR: In this paper, the use of activated carbons after pyrolysis of waste potato peels for the removal of cobalt ions from synthetic wastewaters (composed of various Co(II) concentrations in distilled water which adjusted previously at different pH values) without any coexisting ions was investigated.
185 citations
TL;DR: Analysis of simulation snapshots elucidated the contributions of "pore-filling" and "monolayer-formation" to the nitrogen adsorption loadings in different MOF pores, revealing the origin of inaccuracies in BET-calculated monolayer loadings, which largely explain discrepancies between BET areas and NASAs.
Abstract: Metal–organic frameworks (MOFs) can exhibit exceptionally high surface areas, which are experimentally estimated by applying the BET theory to measured nitrogen isotherms. The Brunauer, Emmett, and Teller (BET)-estimated nitrogen monolayer loading is thus converted to a “BET area,” but the meaning of MOF BET areas remains under debate. Recent emphasis has been placed on the usage of four so-called “BET consistency criteria.” Using these criteria and simulated nitrogen isotherms for perfect crystals, we calculated BET areas for graphene and 25 MOFs having different pore-size distributions. BET areas were compared with their corresponding geometrically calculated, nitrogen-accessible surface areas (NASAs). Analysis of simulation snapshots elucidated the contributions of “pore-filling” and “monolayer-formation” to the nitrogen adsorption loadings in different MOF pores, revealing the origin of inaccuracies in BET-calculated monolayer loadings, which largely explain discrepancies between BET areas and NASAs. ...
184 citations
TL;DR: In this article, a comparative study of a series of doped ceria catalysts towards environmental applications like CO and soot oxidation catalysis is presented. And the physicochemical properties of the doped Ceria materials have been comparatively analyzed to correlate the influence of dopants with their improved behaviour in both the oxidation reactions.
Abstract: This article represents a comparative study of a series of doped ceria catalysts towards environmental applications like CO and soot oxidation catalysis. Transition and rare earth metals of varying size and reducibility property have been selected namely, zirconium (Zr), hafnium (Hf), iron (Fe), manganese (Mn), praseodymium (Pr), and lanthanum (La) as dopants. A facile coprecipitation approach has been used to incorporate the dopants into ceria lattice.The formation of homogeneous solid solutions and their respective physicochemical properties have been confirmed by employing XRD analysis, BET surface area measurements, TEM, Raman, UV-DRS, XPS, and TPR techniques. All the doped CeO2 samples exhibited smaller crystallite size, larger BET surface area, and higher amounts of oxygen vacancies than that of pure CeO2. CO oxidation has been performed in the presence of oxygen under atmospheric pressure, and 300–850 K temperature range in a fixed bed microreactor. Soot oxidation was carried out in presence of air using a thermo gravimetric analyzer within a much wider temperature window of 300–1273 K. The physicochemical properties of the doped ceria materials have been comparatively analyzed to correlate the influence of dopants with their improved behaviour in both the oxidation reactions. Vital role of ‘lattice oxygen’ in CO oxidation and ‘active oxygen species’ in soot oxidation on the catalyst surface has been considered, assuming that Mars and van Krevelen mechanism and active oxygen mechanism play the key role in CO and soot oxidation, respectively. The O 1s XP spectra confirmed that Mn doped ceria (denoted as CM) exhibited most loosely bound lattice oxygen and highest concentration of surface adsorbed oxygen species compared to other materials. Accordingly, a superior CO and soot oxidation activity have been observed for manganese doped ceria. Significant lowering of T50 (390 K and 669 K for CO and soot oxidation respectively) temperature have been observed in both the oxidation reactions; which is primarily attributed to the considerable lowering of lattice oxygen binding energy and higher concentration of surface adsorbed oxygen species.
TL;DR: In this paper, a mesoporous sulfur-modified iron oxide (MS-Fe) was prepared as a heterogeneous H2O2 catalyst for degradation of BPA, and the time evolution of degradation followed pseudo-first-order kinetics.
Abstract: A mesoporous sulfur-modified iron oxide (MS-Fe) was prepared as a heterogeneous H2O2 catalyst for degradation of BPA. The physico-chemical properties of MS-Fe and bare M-Fe were characterized by BET surface area measurement, SEM, XRD, FTIR and XPS. Both M-Fe and MS-Fe composites appeared as cubic microparticles with abundant pores and cracks as well as large surface area. As depicted by XRD, EDX and XPS, M-Fe is mainly consisted of hematite while MS-Fe is a kind of S-doped iron oxide with about 5–6% of sulfur element in terms of atomic ratio. In contrast to the poor catalytic activity of bare M-Fe, the MS-Fe composites showed greatly improved efficiencies for H2O2 activation for BPA degradation. The high catalytic activity of this new Fenton-like catalyst can be obtained at different initial pH in range of 3.0–9.0. The time evolution of degradation of BPA followed pseudo-first-order kinetics, and the first-order rate constants showed a linear relationship with parameters of initial pH, catalyst dosage and concentration of BPA. However, the H2O2 dosage showed a dual effect on BPA degradation because excessive H2O2 addition lead to scavenging of hydroxyl radicals (OH). The investigation of working mechanisms of MS-Fe suggested a synergistic effect of homogeneous and heterogeneous degradation reaction, wherein a strong acidic environment, abundant surface-bonded hydroxyl group and electron-mediating effect of sulfur all contributed to fast activation of H2O2. Overall, this new material overcomes the limitation of narrow working pH range and shows a fast oxidation of BPA with a low H2O2 and catalyst dosage, would have a good potential for environmental application.
TL;DR: Water treatment residuals (WTRs), generated as a byproduct during the deironing and demanganization process of infiltration water, were characterized and examined as arsenate and arsenite sorbent as discussed by the authors.
TL;DR: In this article, a solvent-free mechanochemical method is proposed to synthesize composites (Cu-BTC@GO) of Cu-BTC and graphite oxide within 30 min. The resulting composites were characterized by N 2 adsorption, PXRD, SEM, FT-IR and TG.
TL;DR: In this paper, a double cleaning process was used to convert waste rubber tires into activated carbon by pyrolysis, activation and chemical treatment with 4M HNO 3 for 3h at 90°C for the enhancement of surface functionalities.
TL;DR: In this article, the effects of Mn2+-doping on the structural, optical and photocatalytic properties of ZnO particles were investigated and it was shown that Mn2−doping shifts the optical absorption to the visible region, increases the specific surface area of the photocatalyst and reduces the recombination of electronhole pairs.
TL;DR: In this paper, the authors reported the adsorption of Cr (VI) from aqueous solutions on activated carbon prepared from mango kernel, a seasonal waste from mango fruits, pulverized in a micro-pulverizing mill.
TL;DR: In this article, hard carbons (HC) prepared by cellulose pyrolysis were investigated with varying pyrolysisation temperature from 700°C to 1600°C, and different tests in Na//HC cells with NaPF6 ethylene carbonate/dimethyl carbonate (EC/DMC).
TL;DR: In this article, the performance of bare and Pd-loaded SnO 2 thick film sensors were measured under UV-light irradiation, using a UV-LED of 365nm wavelength and light intensities ranging from 0 to 137mW cm −2 at room temperature (30 °C).
Abstract: NO 2 gas sensing performance of bare and Pd-loaded SnO 2 thick film sensors were measured under UV-light irradiation, using a UV-LED of 365 nm wavelength and light intensities ranging from 0 to 137 mW cm −2 at room temperature (30 °C). Template free conventional and microwave-assisted hydrothermal methods were applied to synthesize SnO 2 powder with different specific surface areas and morphologies (rod-shape and nanoparticle). Two different Pd-loaded SnO 2 (0.03 and 0.1 wt%) powders were also prepared by a simple wet-impregnation method. XRD, FE-SEM/SEM, XPS, BET surface area and BJH pore size distribution measured with N 2 adsorption isotherms were utilized to characterize structural and morphological characteristics of all the samples. The results clearly confirmed that the presence of a low amount of Pd could effectively enhance the response value to 5 ppm NO 2 gas and shorten the recovery time under the UV-light irradiation so that the sensor loaded with 0.1 wt% Pd (0.1Pd_MH1_400 sensor) showed the largest improvement in response value (almost 11 times) and recovery time (around 27 s) compared with the bare SnO 2 sensor (MH1_400) at an UV-light intensity of 79 mW cm −2 . This enhancement is most likely due to the role of Pd in facilitating the sensing reactions via producing additional NO 2 adsorption sites on the SnO 2 surface. Moreover, in the present study, the SnO 2 sensor which was fabricated from as-synthesized, i.e. uncalcined, powder (MH1) showed the highest response (over 3000) compared with other sensors under an UV-light intensity of 7 mW cm −2 with a recovery time of about 48 s. The drastic decrease in the resistance in air of this sensor under the UV-light irradiation may be a possible reason for the highest response value. It was also revealed that high NO 2 response could be achieved only at the optimum conditions of both the number of the NO 2 adsorption sites (optimum specific surface area) and the electron density in the bulk under the UV-light irradiation.
TL;DR: A robust nanostructured porous NiFe-based oxygen evolution catalyst made by selective alloy corrosion is reported on, which exhibits a catalytic activity towards water oxidation of 500 mA/cm2 at 360 mV overpotential and is stable for over eleven days.
Abstract: A major challenge in the field of water electrolysis is the scarcity of oxygen-evolving catalysts that are inexpensive, highly corrosion-resistant, suitable for large-scale applications and able to oxidize water at high current densities and low overpotentials. Most unsupported, non-precious metals oxygen-evolution catalysts require at least ∼350 mV overpotential to oxidize water with a current density of 10 mA cm−2 in 1 M alkaline solution. Here we report on a robust nanostructured porous NiFe-based oxygen evolution catalyst made by selective alloy corrosion. In 1 M KOH, our material exhibits a catalytic activity towards water oxidation of 500 mA cm−2 at 360 mV overpotential and is stable for over eleven days. This exceptional performance is attributed to three factors. First, the small size of the ligaments and pores in our mesoporous catalyst (∼10 nm) results in a high BET surface area (43 m2 g−1) and therefore a high density of oxygen-evolution catalytic sites per unit mass. Second, the open porosity facilitates effective mass transfer at the catalyst/electrolyte interface. Third and finally, the high bulk electrical conductivity of the mesoporous catalyst allows for effective current flow through the electrocatalyst, making it possible to use thick films with a high density of active sites and ∼3 × 104 cm2 of catalytic area per cm2 of electrode area. Our mesoporous catalyst is thus attractive for alkaline electrolyzers where water-based solutions are decomposed into hydrogen and oxygen as the only products, driven either conventionally or by photovoltaics.
TL;DR: In this paper, a hyper-crosslinked β-cyclodextrin porous polymer (BnCD-HCPP) was designed and synthesized facilely by β-cycle-decodextrin benzylation and subsequent crosslinking via a Friedel-Crafts alkylation route.
Abstract: A hyper-crosslinked β-cyclodextrin porous polymer (BnCD-HCPP) was designed and synthesized facilely by β-cyclodextrin benzylation and subsequent crosslinking via a Friedel–Crafts alkylation route. The BnCD-HCPP shows an extremely high BET surface area, large pore volume, and high thermal stability, making it a highly efficient adsorbent for removal of aromatic pollutants from water. The adsorption efficiency in terms of distribution coefficient, defined as the ratio of adsorption capacity to equilibrium adsorbate concentration, ranged from 103 to 106 mL g−1 within a concentration of 0–100 ppm, one order of magnitude higher than that of other β-cyclodextrin-based adsorbents reported previously. The molar percentage of adsorbate to β-cyclodextrin exceeded 300%, suggesting that the adsorption occurred not only in the cyclodextrin cavities via a 1 : 1 complexation, but also in the nanopores of the BnCD-HCPP created during the hyper-crosslinking. The BnCD-HCPP can be further functionalized by incorporation of gold nanoparticles for catalytic transformation of adsorbed phenolic compounds such as 4-nitrophenol to 4-aminophenol.
TL;DR: In this article, a hybrid graphene oxide based inverse spinel nickel ferrite (GONF) nano-composite material and subsequent utilization in heavy metal removal from aqueous solution is described.
TL;DR: In this article, the deactivation and regeneration of arsenic is studied on novel CeO2-WO3/TiO2 for selective catalytic reduction (SCR) of NOx with NH3.
Abstract: Deactivation and regeneration of arsenic are studied on novel CeO2–WO3/TiO2 for selective catalytic reduction (SCR) of NOx with NH3. It is found that the activity and N2 selectivity of poisoned catalyst are inhibited immensely at the entire temperature range. The fresh, poisoned and regenerated catalysts are characterized using XRD, BET, XPS, H2-TPR, NH3-TPD, NO + O2-TPD, in situ Raman and in situ DRIFTS. The characterization results indicate that the poisoning of arsenic decrease BET surface area, surface Ce3+ concentration and the amount of Lewis acid sites and adsorbed NOx species but increase the reducibility and number of chemisorbed oxygen species. According to the in situ DRIFTS investigations, the adsorption of surface-adsorbed NH3 and NOx species is suppressed at low temperature, while the reactivity between surface-adsorbed NH3 and NO is prohibited at high temperature. A novel H2 reduction regeneration not only effectively removes arsenic from the poisoned catalysts, but promotes surface Ce3+/Ce4+ ratio and form new NOx adsorptive sites. However, it also affects the chemical properties of catalyst such as crystalline Ce2(WO4)3 forming, surface active oxygen species raise and loss of Bronsted acid sites.
TL;DR: In this article, the authors used a combination of physical steam activation and chemical activation to produce activated carbon from palm kernel shell (PKS) and coconut shell (CS) for CO2 adsorption from simulated flue gas.
TL;DR: In this article, the use of biobased chitosan-polybenzoxazine (CTS-PBZ) as a precursor for high CO2 adsorbing carbon aerogels (CAs) was reported.
Abstract: The present study reports for the first time the use of biobased chitosan-polybenzoxazine (CTS-PBZ) as a precursor for high CO2 adsorbing carbon aerogels (CAs). Montmorillonite (MMT) is used to reinforce the CTS-PBZ aerogel. MMT-CTS-PBZ nanocomposite aerogels are synthesized using the freeze-drying technique and then cross-linked via ring-opening polymerization of benzoxazine followed by carbonization at 800 °C. Polybenzoxazine improves the structural stability for removing CO2 from the environment even at a high pressure. The properties of polymeric and nanocomposite aerogels have been evaluated using X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The microstructure of the CAs is characterized by N2 adsorption–desorption measurements. The CAs exhibit mesoporous materials with pore sizes in the range of 2–7 nm and high BET surface area. The total pore volume of CAs is as large as 0.296 cm3 g–1, and the maximum BET surface area is 710 m2 g–1. Breakthrough curves of CO2 ads...
TL;DR: In this paper, the effects of various process parameters: temperature, pressure, solution flow rate and initial solution concentration, on the product yields, morphology, size, size distribution, surface area and textural properties of the particles were investigated by FESEM, HRTEM analyses and BET analyzers, and their formation mechanisms were deduced by the solubility behavior of lignin with liquid CO2 and DMF in the operating system.
TL;DR: A tunnel-type α-MnO2 with a nanorod morphology was prepared via a simple solvent-free synthesis method for use in aqueous zinc-ion battery (ZIB) as mentioned in this paper.
TL;DR: The results suggest that montmorillonite K10 and its acid treated forms would be suitable for removing Crystal violet from aqueous solution.
15 Sep 2016
TL;DR: Copper(II) oxide nanoparticles were synthesized at low temperature using cold finger assisted magnetron sputtering technique and were applied as adsorbent for the rapid removal of noxious Cr(VI) ions from the solvent phase and were in good agreement with the pseudo second order kinetic behaviour.
Abstract: Copper(II) oxide nanoparticles were synthesized at low temperature using cold finger assisted magnetron sputtering technique and were applied as adsorbent for the rapid removal of noxious Cr(VI) ions from the solvent phase. The average size of CuO nanoparticles from TEM analysis was found to be 8 nm in addition to this the BET surface area (84.327 m2/g) was found to be significantly high in comparison to the previously CuO nanoparticles synthesized via green route. The synthesized CuO nanoparticles is crystalline in nature and exhibits monoclinic phase, which was confirmed using various analytical techniques such as SAED, XRD and Raman analysis. The impact of influential parameters including pH, adsorbent dose, contact time, stirring speed, initial Cr(VI) ions concentration, and temperature were optimized using batch adsorption method in order to obtain maximum removal of Cr(VI) ions. From the thermodynamic parameters, the positive value of enthalpy (ΔH) and negative value of Gibbs free energy (ΔG) indicate the endothermic and spontaneous nature of Cr(VI) ions adsorption, respectively. The adsorption kinetics data was well fitted and found to be in good agreement with the pseudo second order kinetic behaviour.
TL;DR: In this article, two nickel-aluminum hydrotalcite (HTLC) samples were synthesized by coprecipitation method at different pH values and investigated as catalysts for the hydrogenation of carbon dioxide.
Abstract: Two nickel–aluminum hydrotalcite samples (HTLCs) were prepared by a coprecipitation method at different pH values and investigated as catalysts for the hydrogenation of carbon dioxide. The newly synthesized samples have been compared with a reference alumina supported nickel-based commercial catalyst, with equal nickel content. The as-prepared and commercial samples were characterized by BET analysis, atomic adsorption spectroscopy (AAS), X-ray diffraction (XRD), and temperature-programmed techniques (H2-TPR and CO-TPD). Catalytic activity of the analyzed samples was investigated toward hydrogenation of CO2 at atmospheric pressure by varying reaction temperature between 250 and 400 °C. The maximum CO2-to-CH4 conversion value achieved by hydrotalcyte was ≈86% at 300 °C. The superior performance of HTLCs has been put in relationship with the major catalysts reducibility nature and with the higher metal surface area and metal dispersion. The stability of the HTLCs was investigated through long-term tests, re...