Showing papers on "BET theory published in 2017"

Effective removal of methylene blue from aqueous solutions using magnetic loaded activated carbon as novel adsorbent

Abstract: In this study, magnetic characteristic was added to activated carbon (AC) obtained by ZnCl2 activation of acorn shell. The produced magnetic AC (Fe-AC) was used effectively for the removal of methylene blue (MB) from aqueous solution. The effects of different batch parameters such as adsorbent dosage (0.05–0.2 g/100 mL), initial pH (3–9), temperature (298–318 K), initial dyestuff concentration (50–250 mg/L) and contact time (5–60 min) on the adsorption process were examined. The structural and chemical characterization of the synthesized AC and Fe-AC adsorbents were carried out by using various analytical techniques such as XRD, SEM/EDS, FT-IR and BET analysis techniques. The MB concentration in the solution was determined by UV–VIS spectrophotometer. From the Langmuir isotherm model, the maximum adsorption capacity was found as 330.0 and 357.1 mg/g for AC and Fe-AC adsorbents at 298 K, respectively. The investigations on the effect of the temperature and calculated thermodynamic parameters exposed the endothermic nature of the adsorption process under the studied temperature range. The adsorption/desorption cycling test indicated that the prepared Fe-AC adsorbent had good reusability performance especially up to fourth cycle. Additionally, by considering all results it was concluded that the produced AC and Fe-AC adsorbents as novel adsorbents offer a great promise for the cleaning of MB dyestuff from aqueous solutions because of the advantage of their producibility from a cheap source, high adsorption capacity and fast uptake feasibility.

An Ultrastable and Easily Regenerated Hydrogen-Bonded Organic Molecular Framework with Permanent Porosity

Abstract: A robust hydrogen-bonded organic framework HOF-TCBP (H4TCBP=3,3′,5,5′-tetrakis-(4-carboxyphenyl)-1,1′-biphenyl) has been successfully constructed and structurally characterized. It possesses a permanent 3D porous structure with a 5-fold interpenetrated dia topological network. This activated HOF-TCBP has a high BET surface area of 2066 m2 g−1 and is capable of highly selective adsorption and separation of light hydrocarbons under ambient conditions. It shows excellent thermal stability, as demonstrated by PXRD experiments and N2 adsorption tests. Practical use of HOF-TCBP is facilitated by the ease of its preparation and renewal through rotary evaporation.

Mesoporous zeolite–activated carbon composite from oil palm ash as an effective adsorbent for methylene blue

Abstract: A mesoporous high-surface-area zeolite–activated carbon (Z–AC) composite was prepared by chemically facilitated NaOH activation and hydrothermal treatment with oil palm ash as substrate. The prepared Z–AC composite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, BET surface area and pore structural analysis, and scanning electron microscopy. The adsorption performance of Z–AC for methylene blue (MB) removal was examined using a batch method. The effects of initial dye concentration (25–400 mg/L), temperature (30 °C–50 °C), and pH (3–13) on the adsorption of MB on Z–AC were studied. Pseudo-second-order kinetics was found to describe the adsorption process better than pseudo-first-order kinetics. Freundlich and Langmuir isotherms applied on the adsorption data reveal that data best fitted Freundlich model. The maximum adsorption capacity values of the Z–AC composite for MB were 143.47, 199.6, and 285.71 mg/g at 30, 40, and 50 °C, respectively. These results show that the Z–AC composite could provide basis for more low-cost composites to be used as adsorbents for dye removal.

Fruit peel waste: characterization and its potential uses

Abstract: Globally, India is the leading producer of fruits. Fruits after consumption leave a peel which is a nuisance to the environment as a solid waste. In this article, commonly available large volume-fruit peels (FP) (viz. banana, orange, citrus, lemon and jackfruit) were investigated for surface, physical and chemical characteristics with a view to propose their valorization in detail. Each FP was characterized by proximate and ultimate analysis, porosity, particle density, bulk density, point of zero charge (pH pzc ), surface pH, surface charges, water absorption capacity, BET surface area, scanning electron microscopy, Fourier transform infrared spectroscopy and TGA/derivative of thermogravimetric. The BET surface area of FP is very less, between 0.60 and 1.2 m 2 /g. The pH pzc and surface pH values of orange peel (OP), citrus peel (CP), lemon peel (LP) and jackfruit peels (JFP) are in the range of 3-4. The pH pzc value and surface pH of banana peel (BP) is closer to 7. The order of surface acidity is OP > LP > CP > JFP > BP. From TG curves it is clear that FPs are stable below 150°C. The results will be useful for rational design, when FP is used as a substrate for bioactive compounds, phenolic antioxidants, organic acids, enzymes, biofertilizer, production of energy and as adsorbents.

Nanoporous activated carbon prepared from karanj (Pongamia pinnata) fruit hulls for methylene blue adsorption

Abstract: In this study, karanj ( Pongamia pinnata ) fruit hulls were used as a precursor to prepare low-cost activated carbon with a large surface area through KOH activation. The prepared activated carbon (KFHAC) was characterized through pore structural analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. KFHAC presents a BET surface area of 828.30 m 2 /g, a micropore volume of 0.36 cm 3 /g, and an average pore size of 19.92 A The adsorption performance of KFHAC was evaluated using methylene blue (MB) as the model adsorbate. Adsorption experiments indicated that the pseudo-second-order kinetic and Langmuir adsorption isotherm models can accurately describe the adsorption process. The maximum adsorption capacities ( q m ) of MB were 154.8, 203.4, and 239.4 mg/g at 30 °C, 40 °C, and 50 °C, respectively. This study indicates that karanj fruit hull is a promising precursor for the production of low-cost and efficient activated carbon with a large surface area.

Ultrahigh-surface-area hierarchical porous carbon from chitosan: acetic acid mediated efficient synthesis and its application in superior supercapacitors

Abstract: The development of an effective route to high-performance carbonaceous electrode materials derived from low-cost biomass is critical but remains challenging for supercapacitors. Here we propose a new and cost-effective way to produce chitosan-based hierarchical porous carbons by the union of hydrothermal carbonization and chemical activation. The key to this preparation strategy is the utilization of acetic acid as an additive for hydrothermal carbonization, which not only favors the construction of a conducive environment for accessibility of activator KOH, but also leads to the formation of a rigid semi-carbonized framework substrate for generating an ultrahighly porous structure. Thus, our synthetic approach allows for a lower amount of activation agent and lower heating temperature when compared with normal chemical activation techniques, providing a more efficient way to produce ultrahigh-surface-area carbon materials. The as-prepared hierarchical porous carbon possesses a unique honeycomb-like framework and the highest BET surface area of 3532 m2 g−1 among all the carbon materials derived from chitosan. The combination of the hierarchical pore structure for rapid ion diffusion and the ultrahigh surface area for sufficient electrochemically active sites significantly improves the material's capacitive behaviors. An unusually high capacitance of 455 F g−1, an excellent cycling stability with 99% capacity retention over 20 000 cycles in KOH aqueous electrolyte, and a high energy density of 20.6 W h kg−1 at a power density of 226.8 W kg−1 in 1.8 V Na2SO4 aqueous supercapacitors have been obtained, demonstrating that the chitosan-based hierarchical porous carbons developed here are very attractive for application in supercapacitors.

Synthesis, characterisation and methyl orange adsorption capacity of ferric oxide–biochar nano-composites derived from pulp and paper sludge

Abstract: A Fe2O3–biochar nano-composite (Fe2O3–BC) was prepared from FeCl3-impregnated pulp and paper sludge (PPS) by pyrolysis at 750 °C. The characteristics and methyl orange (MO) adsorption capacity of Fe2O3–BC were compared to that of unactivated biochar (BC). X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the composite material was nano-sized. Fourier transform infrared (FTIR) spectroscopy revealed the presence of hydroxyl and aromatic groups on BC and on Fe2O3–BC, but Brunauer–Emmett–Teller (BET) surface area and Barrett–Joyner–Halenda (BJH) porosity were lower for Fe2O3–BC than BC. Despite the lower BET surface area and porosity of Fe2O3–BC, its MO adsorption capacity was 52.79 % higher than that of BC. The equilibrium adsorption data were best represented by the Freundlich model with a maximum adsorption capacity of 20.53 mg g−1 at pH 8 and 30 min contact time. MO adsorption obeyed pseudo-second-order kinetics for both BC and Fe2O3–BC with R 2 values of 0.996 and 0.999, respectively. Higher MO adsorption capacity for Fe2O3–BC was attributed to the hybrid nature of the nano-composites; adsorption occurred on both biochar matrix and Fe2O3 nanocrystals. Gibbs free energy calculations confirmed the adsorption is energetically favourable and spontaneous with a high preference for adsorption on both adsorbents. The nano-composite can be used for the efficient removal of MO (>97 %) from contaminated wastewater.

Synergistic effect between copper and cerium on the performance of Cux-Ce0.5-x-Zr0.5 (x = 0.1–0.5) oxides catalysts for selective catalytic reduction of NO with ammonia

Abstract: A series of Cux-Ce0.5-x-Zr0.5 oxides catalysts with different Cu/Ce ratio were synthesized by citric acid method. The catalysts were characterized by XRD, BET surface area, H2-TPR, NH3-TPD, NO-TPD, XPS and in-situ DRIFTS. The synergistic effect between copper and cerium on the catalytic performance of Cux-Ce0.5-x-Zr0.5 for selective catalytic reduction of NO with ammonia was investigated. It was found that the Cu0.2-Ce0.3-Zr0.5 catalyst show the excellent SCR activity, N2 selectivity and H2O/SO2 durability in a low temperature range of 150–270 °C even at high gas hourly space velocity of 84,000 h−1. The strong interaction leads to the improvement of the acidity and the increase in the amount of active oxygen species (oxygen vacancy), which are responsible for the higher activity at low temperatures. The SCR reaction process over Cu0.2-Ce0.3-Zr0.5 was also examined using in-situ DRIFTS. The DRIFTS results indicate that abundant ionic NH4+ (Bronsted acid sites), coordinated NH3 on the Lewis acid sites, as well as highly active monodentate nitrate and bridging nitrate species were the key intermediates in the SCR reaction.

Oxygen vacancy-rich mesoporous silica KCC-1 for CO2 methanation

Abstract: Mesoporous silica KCC-1 was successfully synthesized by microemulsion system coupled with microwave-assisted hydrothermal method. Mesoporous silica KCC-1 exhibited spherical morphology surrounded with dendritic fiber with the particle size of 200–400 nm and BET surface area of 773 m2/g. Mesoporous silica KCC-1 has significantly higher number of basicity and oxygen vacancy than those of MCM-41 and SiO2 which directly correlated with the catalytic performance of the catalyst. The activity of mesoporous silica KCC-1 in CO2 methanation is five-fold higher than MCM-41 with the yield of CH4 reached 38.9% at 723 K.

Enhanced adsorption of cationic dyes using sulfonic acid modified activated carbon

Abstract: Activated carbon (MTLAC) and sulfonic acid modified activated carbon (MTLAC-SA) were prepared from a low cost agricultural waste material matured tea leaf (MTL). BET surface area of MTLAC and MTLAC-SA was found to be 1313.4 m2/g and 1169.3 m2/g respectively. Synthesized materials were applied for adsorption of both anionic and cationic dyes. Rhodamine B (RhB), methylene blue (MB), brilliant green (BG), crystal violet (CV) and orange G (OG) were taken as the model dye. After modification, the activated carbon showed enhanced adsorption capacity for adsorption of cationic dyes. The effect of various parameters such as pH, initial dye concentration, adsorbent dose, ionic strength on adsorption process was investigated. A slight increase in adsorption capacity was observed with increase in concentration of existing ion. The equilibrium adsorption data were best described by Langmuir model. The maximum adsorption capacity for RhB and OG using MTLAC-SA (MTLAC) was found to be 757.6 (398.4) mg/g and 105.7 (318.5) mg/g respectively. The adsorption kinetics was best fitted with pseudo second order kinetic model. The thermodynamic study illustrated that the adsorption process is endothermic and spontaneous in nature.

Adsorption of mercury(II) with an Fe3O4 magnetic polypyrrole–graphene oxide nanocomposite

Abstract: To enhance the ability to remove mercury(II) from aqueous media, an Fe3O4 magnetic nanocomposite (PPy–GO) composed of polypyrrole (PPy) and graphene oxide (GO) was synthesized in situ and characterized via scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), zeta potential analysis, vibrating sample magnetometer (VSM) and the Brunauer–Emmett–Teller (BET) method. The performance of the magnetic PPy–GO for adsorbing mercury(II) from water along with the effects of solution pH, adsorbent dosage, coexisting ions, reaction time and temperature were studied in detail. The adsorption kinetics, isotherms and thermodynamics were investigated in detail to gain insights into the adsorption process. The results show that the BET surface area of the magnetic PPy–GO reached 1737.6 m2 g−1. The Langmuir capacity of the magnetic PPy–GO for mercury(II) adsorption was 400.0 mg g−1 at 300 K and pH 7 ± 0.1. After adsorption, the magnetic PPy–GO nanocomposite could be efficiently separated from water via a magnetic field. The adsorption process was endothermic and spontaneous and occurred in accord with the Langmuir and pseudo-second-order models. The overall adsorption of mercury(II) not only involved chemisorption, but was also partially governed by intra-particle diffusion. Data from the preliminary application of magnetic PPy–GO to remove heavy metals from real electroplating effluent indicated a high removal efficiency of over 99% for mercury(II). Finally, a possible adsorption mechanism was discussed. All data showed that the magnetic PPy–GO material is a promising adsorbent to remove mercury(II) from aqueous media.

Enhanced CO2 photocatalytic reduction on alkali-decorated graphitic carbon nitride

Abstract: In this work, visible-light photocatalytic reduction performance of carbon dioxide (CO 2 ) on graphitic carbon nitride (g-C 3 N 4 ) was significantly promoted by the decoration of potassium hydroxide (KOH) on g-C 3 N 4 . More importantly, the role of KOH was thoroughly discussed via various characterizations, control experiments and density functional theory (DFT) calculations. It was found that KOH decoration did not result in any significant difference regards to the morphology, elemental states, BET surface area and light adsorption of g-C 3 N 4 except a drastically enhanced CO 2 adsorption capacity. The promotion effect of KOH on g-C 3 N 4 was mainly contributed by the hydroxide ion (OH − ) functioning as both a hole accepter and a driving force to keep a dynamically stable amount of H 2 CO 3 (probably the major form of CO 2 to be reduced) on the surface of the catalyst. Moreover, the different extents of influence of NaOH and KOH on g-C 3 N 4 were revealed and further explained using computational results. This study supplements current understanding on alkali-promoted photocatalytic processes and provides new insights into the mechanism of CO 2 photocatalytic reduction.

Highly efficient catalytic reductive degradation of various organic dyes by Au/CeO 2 -TiO 2 nano-hybrid

Abstract: Highly improved catalytic reductive degradation of different organic dyes, in the presence of excess NaBH4 over Au/CeO2-TiO2 nano-hybrid as the catalyst is reported in this study. CeO2-TiO2 nanocomposite was prepared by a facile co-precipitation method using ultra-high dilute aqueous solutions. Small amount of Au (only 1 wt%) was loaded onto the nanocomposite material by deposition-precipitation with urea (DPU) method to fabricate the ternary Au/CeO2-TiO2 nano-hybrid. The catalysts were characterized by the representative techniques like XRD, BET surface area, ICP-AES, UV-Vis diffuse reflectance spectroscopy, TEM and XPS. The Au/CeO2-TiO2 nano-hybrid along with NaBH4 exhibited remarkable catalytic activities towards all the probed dyes, namely Methylene Blue, Methyl Orange, Congo Red, Rhodamine B and Malachite Green, with a degradation efficiency of ∼100% in a short reaction time. The degradation reaction followed pseudo-first-order kinetics with respect to the concentration of the dye. Different parameters that affect the rate of the reaction are discussed. A plausible mechanism for methylene blue degradation has also been proposed.