Nanoporous rice husk derived carbon for gas storage and high performance electrochemical energy storage

We report on the gas storage behaviour and electrochemical charge storage properties of high surface area activated nanoporous carbon obtained from rice husk through low temperature chemical activation approach. Rice husk derived porous carbon (RHDPC) exhibits varying porous characteristics upon activation at different temperatures and we observed high gas uptake and efficient energy storage properties for nanoporous carbon materials activated even at a moderate activation temperature of 500 °C. Various experimental techniques including Fourier transform-infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy and pore size analyser are employed to characterise the samples. Detailed studies on gas adsorption behaviour of CO₂, H₂ and CH₄ on RHDPCs have been performed at different temperatures using a volumetric gas analyser. High adsorption capacities of ~9.4 mmol g^?1 (298 K, 20 bar), 1.8 wt% (77 K, 10 bar) and ~5 mmol g^?1 (298 K, 40 bar) were obtained respectively for CO₂, H₂ and CH₄, superior to many other carbon based physical adsorbents reported so far. In addition, these nanoporous carbon materials exhibit good electrochemical performance as supercapacitor electrodes and a maximum specific capacitance of 112 F g^?1 has been obtained using aqueous 1 M Na₂SO₄ as electrolyte. Our studies thus demonstrate that nanoporous carbon with high porosity and surface area, obtained through an efficient approach, can act as effective materials for gas storage and electrochemical energy storage applications.     

Supporting of Potassium Copper Hexacyanoferrate on Porous Activated Carbon Substrate for Cesium Separation

Abstract

Activated carbon (AC) was chosen for carrying potassium copper hexacyanoferrate (KCuCF) to prepare a new Cs-selective material. The adsorbent was prepared by repetitious batch precipitation reaction of Cu²⁺ with [Fe(CN)₆]^4?. Characterization analyses identified the backbone formula of the activated carbon-supported KCuCF with K₂Cu[Fe(CN)₆], and shown the successful loading of KCuCF microcrystals on the porous carbon substrate with a loading percentage of 12.5 wt%, and with BET specific surface area and a total pore volume of 527.8 m²/g and 0.38 cm³/g for AC and 160.8 m²/g and 0.16 cm³/g for KCuCF-loaded activated carbon (KCuCF-AC), respectively. The optimal Cs adsorption capacity of about 0.46 mmol·g^?1 was observed between the HNO₃ concentration of 0.5–1.5 M, and the capacity even reached to 0.38 mmol·g^?1 in the presence of a large amount of competing cations. The results indicate that activated carbon has no significant effect on the selectivity of the as-synthesized composite.     

Fixed‐Bed Removal of Free and Complexed Ni from Synthetic and Industrial Aqueous Solutions

Abstract

This paper evaluates the application of several biosorbents for Ni removal from aqueous solutions in the absence and in the presence of EDTA. Fixed bed experiments were performed (Ni influent concentration, 2 mg dm^?3; EDTA doses, 0, 5, and 10 mg dm^?3; pH=7) to study the process feasibility as refining after conventional physicochemical treatment. In absence of EDTA, uptake capacity followed the order peat > Posidonia oceanica > chitosan > chitin ? Scharlau AC. Maximum uptakes of 8.95 mg g^?1 and 5.10 mg g^?1 were found for peat and Posidonia oceanica, respectively. In the presence of EDTA, removal capacity decreased for all biosorbents; Ni was detected in the effluent from the beginning of the operation, indicating low ability to retain Ni EDTA‐complexes. Activated carbon presented the ability to remove complexed Ni. Peat exhibited the best performance for the treatment of an industrial spill from a metal‐finishing facility, with effluent Ni concentration lower than 0.2 mg dm^?3 for more than two weeks of treatment (3500 pore volumes of treated wastewater).     

Equilibrium modeling,kinetic and thermodynamic studies on the adsorption of Cr(VI) using activated carbon derived from matured tea leaves

A new porous carbon with high surface area of 1,313.41 m² g^?1 with pore volume 1.359 cm³ g^?1 has been synthesized from matured tea leaves by chemical activation method using phosphoric acid. The carbon was found to be highly efficient for removal of Cr(VI) from aqueous solution. The effects of various parameters such as contact time, initial metal ion concentration, pH, temperature and amount of adsorbent on the extent of adsorption were studied. Langmuir, Freundlich and Temkin adsorption models were used to interpret the experimental data. The adsorption data were best fitted with Langmuir isotherm model. The adsorption capacity of Cr(VI) onto the activated carbon calculated from Langmuir isotherm was found to be 30.8 mg g^?1 at pH 4.8 and temperature 303 K. The adsorption capacity increases from 25.36 to 32.04 mg g^?1 with an increase in temperature from 303 to 323 K at initial Cr(VI) concentration of 60 mg L^?1. The adsorption process followed a pseudo second order kinetic model. Thermodynamic parameters ΔH⁰ (28.6 KJ mol^?1), ΔG⁰ at three different temperatures [(?0.145, ?1.09, ?2.04) KJ mol^?1] and ΔS⁰ (94.87 J mol^?1 K^?1) were calculated. These values confirm the adsorption process to be endothermic and spontaneous in nature.     

Effects of polydimethylsiloxane coating of Ni-MOF-74 on CH<Subscript>4</Subscript> storage

Ni-MOF-74 was prepared by microwave heating and coated with polydimethylsiloxane (PDMS) via vapor deposition. Both the pristine and the PDMS-coated Ni-MOF-74 samples were exposed to moisture in air (relative humidity of 75%) for different periods of time, and their methane storage capacities under 35 bar conditions were measured. The pristine sample had a Brunauer-Emmett-Teller (S_BET) surface area of 1,050 m²·g^?1, with a CH₄ uptake capacity of 113.8 mg·g^?1 at 300 K and 35 bar. After exposure to moisture for seven days, the BET surface area and CH₄ uptake capacity declined drastically, whereas the PDMS-coated sample maintained its original BET surface area (1,018 m²·g^?1) and CH₄ uptake capacity (107.7 mg·g^?1). After exposure to moisture in air for 30 days, however, even the PDMS-coated sample lost almost 60% of its CH₄ storage capacity. All the methane storage capacity data were linearly correlated with the BET surface areas of the Ni-MOF 74 samples.     

Methylene Blue Adsorption on Natural and Modified Clays

Toxic methylene blue dye is removed from water by accumulating it on the surface of clay minerals. Clay adsorbents are obtained from kaolinite, montmorillonite, and their acid activated forms. The adsorption experiments are carried out in a batch process in environments of different pH, initial dye concentration, amount of clay, interaction time, and temperature. Adsorption of dye is best described by second order kinetics. In the temperature range of 303 to 333 K, the Langmuir monolayer capacity for three kaolinite species increased from 45.5 to 56.5 mg g^?1, 45.9 to 57.8 mg g^?1, 46.3 to 58.8 mg g^?1, and for three montmorillonites species from 163.9 to 181.8 mg g^?1, 166.7 to 188.8 mg g^?1, and 172.4 to 192.3 mg g^?1. The interaction is an endothermic process driven by entropy increase and spontaneous adsorptive accumulation is ensured by favorable Gibbs energy decrease. It is found that acid activation enhances the adsorption capacity of kaolinite and montmorillonite.     

Adsorption of Cu(II) from Aqueous Solution by Porous Mn3[Co(CN)6]2 · nH2O Nanospheres

Prussian blue analogue of porous Mn₃[Co(CN)₆]₂ · nH₂O nanospheres with a large surface area were prepared by simple mixing K₃[Co(CN)₆]₂ and manganous nitrate solution at room temperature. The morphology and structure of the prepared products were characterized by XRD, FE-SEM, TEM, and BET. The results indicated that the product was composed of nanospheres with the diameter of ～250 nm, which was of porous structure with the pore diameter in the 2.5–4 nm range. The adsorption behavior of Cu(II) ions from aqueous solution onto porous nanospheres was investigated as a function of parameters, such as the equilibrium time, the pH, the initial concentration, and the temperature. A maximum adsorption capacity of 140.85 mg g^?1 of Cu(II) was achieved. Due to the simple synthetic method and its high adsorption capacity, the porous nanospheres had the potential to be utilized as an effective adsorbent for Cu(II) removal.     

Application of mesoporous magnetic nanosorbent developed from macadamia nut shell residues for the removal of recalcitrant melanoidin and its fractions

ABSTRACT

A novel mesoporous magnetic nanosorbent developed from macadamia nut shell residues was applied as an adsorbent for the removal of dissolved organic carbon (DOC) associated with melanoidin and its fractions in a batch system. The most favored molecular fraction of the melanoidin for adsorption onto the nanosorbent was 1–5 kDa with adsorption capacity of 10.26 mg DOC g^?1 achieving 68.4% removal efficiency. The sorption behaviors were all well fitted to a pseudo-second-order kinetic model and Langmuir isotherm. Optimum operating conditions needed for the maximum uptake of 14.7 mg DOC g^?1 were found to be pH of 6.3, temperature of 41.7°C at the dosage of the magnetic nanosorbent of 877.7 ppm.     

Preparation and molten salt-assisted KOH activation of porous carbon nanofibers for use as supercapacitor electrodes

Carbon nanofiber paper was prepared by electrospinning from thermosetting phenolic resin, followed by activation via KOH-containing molten salt at high temperature. By adding a small dosage of KOH in the molten salt the porous volume and specific surface area could be greatly improved. The obtained porous carbon nanofibers had a specific surface area of 1007 m² g^?1, total pore volume of 0.363 cm³ g^?1, micropore volume of 0.247 cm³ g^?1. The electrochemical measurements in 6 M KOH aqueous solution showed that the porous carbon nanofibers possessed high specific capacitance and considerable rate performance. The maximal specific capacitance of 288 F g^?1 was achieved at 0.2 A g^?1 and the specific capacitance could still remain 204 F g^??1 at 20 A g^?1 with the retention of 71%. In the molten salt system, the reaction between activating agent and carbon could be more efficient, hence, such molten salt-assisted activation method was considered as a general activation method for the high-specific-surface-areaed carbons.     

Selective sorption of diethyl phthalate on pH-responsive,molecularly imprinted polymeric adsorbents

ABSTRACT

A novel synthetic route for preparation of pH-responsive molecularly imprinted adsorbents for separation of diethyl phthalate (DEP) is proposed. Polymers were synthesized using acrylic acid (AAc) and methyl methacrylate (MMA) crosslinked using ethylene glycol dimethacrylate (EGDMA) or divinylbenzene (DVB). The carried out tests revealed the pH-driven recognition of synthesized sorbents toward DEP. It was found that sorbents derived from mixture of 30% AAc:MMA (1:1) and 70 wt.% of DVB in the presence of 7 wt.% of template were the best. The DEP sorption took the highest value (85 mg g^?1) at pH = 5, while desorption with extent of 92% was the most efficient at pH = 8.     

One-pot generation of mesoporous carbon supported nanocrystalline H3PW12O40 heteropoly acid with high performance in microwave esterification of acetic acid and isoamyl alcohol

Ordered mesoporous carbon-supported H₃PW₁₂O₄₀ heteropoly acid materials (HPW/OMCs) have been rationally synthesized for the first time. The method is based on the evaporation-induced triconstituent co-assembly effect using the sol–gel process, wherein soluble resol polymer is used as an organic precursor, and triblock copolymer F127 is used as a template. The ordered mesoporous carbon-supported H₃PW₁₂O₄₀ heteropoly acid materials were analyzed and characterized by X-ray diffraction, N₂ adsorption and desorption (BET), and transmission electron microscope. The mesoporous carbon-supported H₃PW₁₂O₄₀ materials possess an ordered mesostructure, narrow pore size distributions (around 2.8–3.6 nm), high pore volumes (up to 0.49 cm³ g^?1), high specific BET surface areas (up to 590 m² g^?1), tailorable HPW content (up to 30 wt%), and well dispersion of HPW particles. Moreover, the resultant mesoporous ordered mesoporous carbon-supported H₃PW₁₂O₄₀ materials exhibit high catalytic activity in microwave esterification of acetic acid and isoamyl alcohol. The obtained 20 % HPW/OMC catalyst exhibits high catalytic performance with 96.7 % of isoamyl acetate yield at temperature of 120 °C, alcohol/acid molar ratio of 2, catalyst amount of 0.2 g, microwave irradiation power of 800 W, and reaction time of 18 min. It was believed that the concentration of H₃PW₁₂O₄₀ have a crucial effect on the HPW/OMCs’ porosity, mesostructure and catalytic performance.     

Improved electrochemical performances of sulfur-microporous carbon composite electrode for Li/S battery

A sulfur-microporous (S-MIP) carbon composite was prepared for use as a cathode for rechargeable Li/S batteries. Two sulfur-embedded methods, S-impregnation (IS) and S-liquefied pore filling (LS), were applied for the preparation of the S-MIP carbon composites. The pristine elemental S of the polycrystalline α-S₈ undergoes a structural change to an amorphous-S (a-S) structure in the S-MIP carbon composite created by the IS method. During sulfur loading of 40–50 wt %, the S-MIP carbon composite created by the IS method showed a BET SSA value of around 500 m² g^?1 and a pore volume of 0.2 cm³ g^?1. However, after the LS process was applied to the S-MIP carbon composite, at 160 °C and 10 h, the a-S structure in the S-MIP carbon composite became recrystalline α-S₈. Little remained of the porosity in the S-MIP carbon composite prepared by the LS method due to the large portion of the S crystalline phase. The best discharge capacity was obtained with an S-MIP carbon composite created by the IS method, with the result of 680 mA h g^?1 after 50 cycles at 0.1 °C, i.e., ~47 % higher than that by the LS method.     

New Multi‐Dentate Ion‐Selective AXAD‐16‐MOPPA Polymer for the Preconcentration and Sequential Separation of U(VI), Th(IV) from Rare Earth Matrix

Abstract

A new class of multi‐dentate ligand anchored polymeric resin has been synthesized by grafting Amberlite XAD‐16 with [2‐(1‐Methyl‐3‐oxo‐2‐phenyl‐2, 3‐dihydro‐1H‐pyrazol‐4‐ylcarbamoyl)‐ethyl]‐phosphinic acid (AXAD‐16‐MOPPA). The modification steps involved during the grafting process are characterized by FT‐IR spectroscopy, ³¹P and ¹³C‐CPMAS (cross‐polarized magic angle spin) NMR spectroscopy, CHNPS elemental analysis and thermogravimetric analysis. The influence of various physio‐chemical parameters on the quantitative extraction of metal ions by the resin phase are studied and optimized by both static and dynamic methods. The developed grafted polymer shows greater selectivity for actinide ions like U(VI) and Th(IV) when compared to the lanthanides with greater distribution ratio values in highly acidic matrices. However, the lanthanides compete for the active sites in near neutral conditions. But the sorbed actinide ions and lanthanide elements can be separated by the sequential elution methodology. Moreover, the polymer exhibits faster metal ion phase exchange kinetics, where with a high sample flow rate of 25 mL min^?1 quantitative analyte sorption is achievable during the extraction chromatographic column operation for all the analytes. It also offers good ion‐selectivity and greater preconcentration factor values of 400 for U(VI) and 333 for Th(IV) in 4M HNO₃ conditions. The resin shows very high sorption capacity values of 1.45 mmol g^?1 for U(VI), 1.39 mmol g^?1 for Th(IV), and 1.31 mmol g^?1 for La(III) at near neutral conditions. Finally, the developed grafted resin has been successfully applied in extracting Th(IV) from matrix monazite sand which comprises large rare earth matrix, U(VI) from seawater and also U(VI) and Th(IV) from simulated nuclear spent fuel mixtures. The analytical data obtained from triplicate measurements are within 3.5% rsd, reflecting the reproducibility and reliability of the developed method.     

Catalytic Hydrogenation of Aqueous Phase Nitrate Over Fe/C Catalysts

Catalytic hydrogenation of nitrate in water has been carried out over Fe/C catalysts at ambient temperature using batch and continuous reactors. In batch reaction nitrate reduction activity of 2.9 mmol g _metal ^?1  min^?1 with nearly 100% selectivity towards nitrogen was obtained. Column study shows nitrate reduction below 5 ppm for an initial concentration of 100 ppm. Break through capacity, to reach concentration of 45 mg L^?1, is more than 530 bed volumes. The catalysts were characterized using XRD, SEM–EDAX and XPS. With high selectivity and activity the catalytic system in present study could be a potential option for nitrate removal from water.     

A simple route to prepare pomegranate‐like polystyrene‐based microspheres with high porosity

Pomegranate‐like polystyrene‐based microspheres with high porosity were successfully prepared via a simple route involving two steps. The first step was the preparation of polystyrene‐based microspheres with multi‐cores and a non‐porous shell via suspension polymerization of divinylbenzene and vinylbenzyl chloride. Nitrogen sorption failed to characterize the pore structure of the microspheres because of the non‐porous shell, but the results of Hg intrusion indicated that the pore volume of the microspheres was 0.36 cm³ g^?1. The second step was post crosslinking of the microspheres derived from the first step. Extensive porosity was generated in the shell and the pomegranate‐like structure of the microspheres remained almost unchanged. The results showed that the pore volumes of the final products derived from N₂ sorption and Hg intrusion were 0.54 cm³ g^?1 and 0.66 cm³ g^?1, respectively. Overall, this provides a simple and feasible route to biomimetic preparation of pomegranate‐like polystyrene‐based microspheres with high porosity. Copyright © 2011 Society of Chemical Industry     

Hydrothermal synthesis of mesoporous TiO<Subscript>2</Subscript> nanotubes and their adsorption affinity toward Basic Violet 2

Hydrothermal method was used to synthesize TiO₂ nanotubes (TNTs), which are considered as a novel adsorbent with high surface area and adsorption capacity. Different methods including X-ray diffraction (XRD), transmission electron microscope (TEM) and Brunauer–Emmett–Teller (BET) analysis were used to investigate and identify synthesized TNTs. The adsorption capacity of TNTs was investigated with regard to removing Basic Violet 2 (BV2) as a model organic pollutant from aqueous solution. The mean outer, inner diameter and thickness of the TNTs were found to be approximately 9, 4 and 2.5 nm, respectively. BET–BJH method was used for measuring specific surface area and pore volume of the TNTs which turned out to be 200.38 m² g^?1 and 0.44 cm³ g^?1, respectively. The results of the study indicated synthesized TNTs may be considered as efficient and effective adsorbent for removing BV2 (75.63%) from aqueous solution. The impact of the operational variables, i.e. initial BV2 concentration (2–20 mg L^?1), dosage of adsorbent (0.01–0.6 g), and pH (2–8) in relation to the adsorption capacity of BV2 onto TNTs were investigated. The experimental results of the study were meticulously taken into consideration for discussing and analyzing the adsorption isotherms and kinetics. It was found that the collected experimental data regarding the kinetic and isotherm examinations were compatible and well-matched with the pseudo-first order kinetic model and Langmuir isotherm model (R ²?=?0.9634).     

Adsorption of rhodium by modified mesoporous cellulose/silica sorbents: equilibrium,kinetic, and thermodynamic studies

A cellulose/silica hybrid was fabricated through the simultaneous deposition of silica and cellulose from their blends. The product was treated with ethylenediamine then carbon disulfide to functionalize amine and thio moieties to the hybrid surface to obtain R-N and R-NS, respectively. The new sorbents obtained were characterized by FT-IR, SEM, and BET. The data obtained indicated the functionalization of amine and thio moieties to the hybrid surface and the formation of thermally stable mesoporous particles with surface area of 319 and 63.5 m² for R-N and R-NS, respectively. Batch and column studies were carried out to verify the behavior of the two sorbents towards Rh(III) ions from their chloride solutions. The batch studies showed maximum uptake capacity values of 51 and 60 mg g^?1, where column studies showed 76.5 and 90 mg g^?1 for R-N, R-NS, respectively. The data obtained were interpreted to get the equilibrium, isotherm, kinetics, and thermodynamics adsorption parameters. The adsorption process is favorable and dominated by entropic changes, follow the pseudo-second order kinetics, and fitted well with Langmuir and Dubinin–Radushkevitch adsorption isotherms. The data obtained from batch and column studies indicates the applicability of the obtained cellulose/silica composites in retrieval of Rh(III) ions at higher efficiency.     

The efficient removal of dyes over magnetic Ni embedded on mesoporous graphitic carbon material

Magnetically separable Ni embedded on graphitic mesoporous carbon (NMC) material was fabricated through a facile “sol–gel” route using glucose, nickle nitrate, poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) (P123) and tetraethyl orthosilicate as carbon source, catalyst and magnetic precursor, soft template and porogen. The obtained NMC material exhibited highly graphitic degree with high surface area of 790 m² g^?1, large pore size at 3.9 nm and pore volume of 0.69 cm³ g^?1. The saturation magnetization was enhanced to 6.82 emu g^?1 because of aggregation of magnetic Ni particles to clusters. NMC material showed excellent removal to Rhodamine B and the adsorption capacity reached to 168.1 mg g^?1 within 120 min. NMC material could be easily separated by an external magnet and reused after ethanol extraction.     

Synthesis of High Surface Area MgAl2O4 Nanopowder as Adsorbent for Leather Dye Removal

Abstract

MgAl₂O₄ nanopowder has been prepared by alkoxides hydrolysis with further calcination at temperature of 700°C. The adsorption of a leather dye, Direct Black 38, onto this material was investigated. The sample was characterized by X-ray-diffraction (XRD), N₂ adsorption–desorption isotherm and Fourier transform infrared spectroscopy. The results showed that sample present a pure phase, and the average nanocrystal size of 8 nm, the BET surface area is about 206.5 m² · g^?1 and total pore volume is about 1.44 cm³ · g^?1. Adsorption kinetics data were modeled by film and pore diffusion model. The experimental isotherm was described by the Langmuir model. MgAl₂O₄ nanopowder presented a great removal efficiency of leather dye by adsorption process, with a maximum adsorption capacity of 833 mg of dye per gram of adsorbent.     

Carbon dioxide capture under postcombustion conditions using amine-functionalized SBA-15: Kinetics and multicyclic performance

ABSTRACT

In this work, ordered mesoporous SBA-15 was synthesized and functionalized by polyethyleneimine (PEI). The morphological properties were characterized by N₂ adsorption/desorption, field–emission scanning electron microscopy (FE-SEM), high–resolution transmission electron microscopy (HR-TEM) and Fourier transform infrared (FTIR) spectroscopy methods. The carbon dioxide (CO₂) uptake on the sorbents, kinetics of CO₂ adsorption/desorption and long-term multicycle stability of PEI-impregnated sorbent were measured. An optimal amine loading of 50 wt.% showed a CO₂ adsorption capacity ~3.09 mmol g^?1 using 10% pre-humidified CO₂ at 75°C. The presence of moisture in flue gas showed a promoting effect in CO₂ sorption capacity. The temperature swing adsorption/desorption cycles showed excellent multicycle stability over 60 cycles during 65 h of operations under humid CO₂.