Narrow Results

To obtain a better understanding of detonation properties of ammonium nitrate (AN) and activated carbon (AC) mixtures, steel tube tests with several diameters were carried out for various compositions of powdered AN and AC mixtures and the influence of the charge diameter on the detonation velocity was investigated. The results showed that the detonation velocity increased with the increase of the charge diameter. The experimentally observed values were far below the theoretically predicted values made by the thermodynamic CHEETAH code and they showed so-called non-ideal detonation. The extrapolated detonation velocity of stoichiometric composition to the infinite diameter showed a good agreement with the theoretical value.

Dog conch shell powder (DCSP) and coconut shell powder (CSP) are used as the calcium carbonate source (energizer) and carbon source, respectively, in the pack carburizing of SCM 420 low carbon steel. The surface hardness of the carburized specimens is investigated for various CSP:DCSP ratios and carburizing temperatures. It is found that a significant improvement in the hardness level is obtained for a DCSP concentration of 40% and a carburizing temperature of 950${}^{\circ }$C. It is additionally shown that while DCSP can be used as an energizer in the carburizing process, it cannot be used as an activated carbon source. Finally, it is shown that the surface hardness of the carburized specimens can be significantly improved through a further quenching operation in water. Overall, the results presented in this study confirm the potential for utilizing natural resources such as DCSP and CSP for the pack carburizing of low-to-medium carbon steels.

The well-defined poly(hydroxyethyl acrylate) (PHEA) brushes were grafted from the surfaces of the activated carbon (AC) powder with the controlled/"living" radical polymerization technique. First, surface functional groups of the AC powder were homogenized to hydroxyl groups by oxidizing with nitric acid and then reducing with lithium tetrahydroaluminate (LiAlH₄) at first. Second, the surface hydroxyl groups were treated with bromoacetylbromide, and the bromoacetyl groups were introduced. And in the third step, the bromoacetyl activated carbon (BrA-AC) powder were used as macro-initiators for the surface-initiated atom transfer radical polymerization (SI-ATRP) of hydroxyethyl acrylate (HEA) in the presence of 1,10-phenanthroline and Cu(I)Br as catalyst in a water system. The graft parameters calculated from the elemental analyses (EA) results, conversion of monemer (C%) and percentage of grafting (PG%) were 5.74% and 28.7%, respectively, after polymerizing for 5 h. The graft polymerizations exhibited the characteristics of a controlled/"living" polymerization, and no homopolymer was found in the proposed polymerizing process. The preparation procedure of the poly(hydroxyethyl acrylate) grafted activated carbon (PHEA-AC) powder was also investigated by X-ray photoelectron spectroscopy (XPS). The PHEA-AC powder is expected to be used as selective adsorbents because of their abundant homogenized surface hydroxyl groups.

The hyperbranched aliphatic polyester grafted activated carbon (HAPE-AC), was successfully prepared by the simple "one-pot" method. The surface functional groups of commercial activated carbon particles were homogenized to hydroxyl groups by being oxidized with nitric acid and then reduced with lithium tetrahydroaluminate (LiAlH₄) at first. Secondly, the surface hydroxyl groups were used as the active sites for the solution polycondensation of the AB₂ monomer, 2, 2-bis(hydroxymethyl)propionic acid (bis-MPA), with the catalysis of p-toluenesulfonic acid (p-TSA). The homogenization of the surface groups of the activated carbon particles and the graft polymerization of the hyperbranched aliphatic polyester were investigated by X-ray photoelectron spectroscopy (XPS) technique. The products were also characterized with Fourier transform infrared (FT-IR) and scanning electron microscope (SEM). The competitive adsorption properties of the products toward the heavy metal ions (Cu(II), Hg(II), Zn(II), and Cd(II)) also proved the translations of the surface groups.

In order to analyze the adsorption capacities of different solid substrates, we present a multi-step method to separately study the isotherm at different pressure ranges (steps). The method is based on simple gas isotherm measurements (nitrogen, methane, carbon dioxide, argon, and oxygen) and is tested to describe the adsorption process and characterize a graphitized surface (GCB) and two different granular activated carbons (GAC). The GCB isotherms are described as a sum of Fowler-Guggenheim-Langmuir shifted curves; isotherm behaviors are quite similar at different temperatures, but change below a certain threshold. In GAC the first steps show the same adsorption characteristics at low pressures (Dubinin's description), but this behavior changes at higher pressure regimes, which allows one to elucidate how heterogeneous the surfaces are or how strong the interactions between adsorbed molecules are for this marginal adsorption to occur. We tested different approaches (from BET multilayer to Aranovich) and found quite different features. We finally conclude that if the description of the adsorption on complex substrates, such as those presented here, is carried using only one model, e. g. Dubinin in case of GACs, the resulting characteristics of the adsorbent would be very biased.

A series of activated carbon (AC) supported Au nanocatalysts with different loadings of Au were prepared by using the homogeneous deposition–precipitation (HDP) method. The samples were characterised with myriad techniques such as X-ray diffraction (XRD), CO-chemisorption, N₂ adsorption–desorption measurements, transmission electron microscopy (TEM), inductively coupled plasma-optical emission spectrometer (ICP-OES) and X-ray photoelectron spectroscopy (XPS) to understand the structural and textural properties in detail. The catalysts were tested for the vapour phase oxidation of glycerol to glyceric acid under base-free medium in an aerobic condition at normal atmospheric pressure. The Au/AC nanocatalysts with smaller size Au particles ($<6$nm) showed higher glycerol conversion and selectivity for glyceric acid, and also a longer catalyst life. While the larger Au particles ($>10$nm) showed less activity and selectivity. Among all the nanocatalysts tested, the 1.0wt.% Au/AC sample having smaller particle size of Au showed the best catalytic performance in terms of glycerol conversion and glyceric acid selectivity. These results suggest that the oxidation activities of Au/AC nanocatalysts are strongly influenced by the size of Au nanoparticle, nature of the support material and through a metal-support interaction.

Five different physically motivated analytic isotherm models are fit to experimental $(P,V)$ data from seven different sources reporting studies of the adsorption of CO₂ by activated carbon. The model behavior upon parameter optimization suggests that multi-layer adsorption does not play a dominant role in CO₂ uptake by activated carbon. Only by explicitly modeling two distinct types of binding sites in the first adsorption layer does the model fully capture the nuances of the data. The values of the best-fit parameters provide good support for a widely used structural model of activated carbon: that it may be represented by nanoscopic flakes of hexagonally bonded carbon, the edges of which are terminated by functional groups. This conclusion is confirmed by comparison of the fitting parameter values to published results of first-principles calculations of the interaction of CO₂ with systems having chemical features representative of this structural model.

Dimethyl disulfide (DMDS) is an important fine chemical that can be prepared by the refined Merox process of oxidation of sodium methyl mercaptide (SMM) in the presence of a catalyst. In this paper, a novel activated carbon (AC) supported cobalt(II) tetraaminophthalocyanine (AC-CoTAPc) catalyst was prepared by the chemical grafting method. EA, UV-vis, FT-IR, BET and XPS were used to characterize the structure of the new catalyst. The effects of reaction time, catalyst dosage, reaction temperature and oxygen pressure on SMM conversion per pass (CPP${}_{SMM})$, yield (Yield${}_{DMDS})$ and purity of DMDS product (Purity${}_{DMDS})$ were investigated to evaluate the catalytic performance of new AC-CoTAPc catalyst. The results show that free CoTAPc is easily dissolved in this DMDS product, which needs extra post treatment and cannot be reused. The supported catalyst AC-CoTAPc can easily solve these problems and can be properly reused four times to get Yield${}_{DMDS}$ and CPP${}_{SMM}$ higher than 70% and 90%. Under optimum conditions, the Yield${}_{DMDS}$ andCPP${}_{SMM}$ of the AC-CoTAPc catalyst could be as high as 87.4% and 98.1%, with a purityof DMDS product of above 99.9%. AC-CoTAPc exhibits better catalytic and reuse performance than the commercial AC-supported sulphonated cobalt(II) phthalocyanine (AC-CoPcS) catalyst and shows broad industrial application prospects.

Micro-porous activated carbons (ACs) with a narrow pore size distribution of 0.4–0.6nm and high specific surface areas (1160–1315m²$\cdot$ g${}^{-1})$ are prepared from environment-friendly, low-grade potassium humate (HA-K, carbon resource) and mild activating agent potassium acetate (CH₃COOK). Microstructure characterizations indicate that the introduction of activating agent CH₃COOK is a key step to achieve high specific surface area and carbonization degree. These ACs contain small amount of oxygen and nitrogen, and show obvious pseudo-capacitance besides double layer capacitance. As a result, the optimized ACs achieve high specific capacitances of 311F$\cdot$g${}^{-1}$ and 317F$\cdot$g${}^{-1}$ at 0.1A$\cdot$g${}^{-1}$ in 2M KOH and 1M H₂SO₄ aqueous electrolytes, respectively. This sample also shows a good charge-discharge cycling stability within 10 000 cycles.

Carbon nanotubes (CNTs) were doped by ammonium borate as the sources of nitrogen and boron. Under the protection of Ar gas, boron-nitrogen doped CNTs were prepared through nitriding and boronization at high temperature. It is a conductive additive. Then, the obtained CNTs were mixed with activated carbon (AC), SP, sodium dodecyl sulfate (SDS), and cellulose fiber to prepare electrodes. With all the materials, a symmetric electric double-layer supercapacitor (EDLC) was assembled. Next, the materials and electrodes were also characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The factors, chemical connections, and specific surface area of the CNTs were analyzed by X-ray energy spectrum analysis (EDS), X-ray photoelectron spectroscopy (XPS), as well as a specific surface area and porosimetry analyzer (BET). In addition, the electrochemical performances of electric double-layer capacitors were tested with the help of cyclic voltammetry, constant-current charging and discharging, and so on. From the results, we can make a conclusion, that is, both B and N atoms were added into the CNTs and formed bonds successfully with carbon atoms mutually. Besides, the specific surface area is about 1.5 times than that of the CNT. When the charge/discharge current density reaches 50mA/g, we can find that the mass specific capacitance of the capacitor can run up to 32.19F/g. Also, we observe that the maximum power density is close to 220W/kg (700mA/g), and the energy density can arrive 9.31Wh/kg (50mA/g). Based on the impedance test, the electrodes are characterized with low impedance. After 2000 cycles, the boron-nitrogen doped double-layer capacitors maintain a capacitance retention ratio of above 95%. Its power density can still achieve 220W/kg when the energy density keeps at 3.46Wh/kg. In other words, the electrochemical performance functions of the electric double-layer capacitors are enhanced while the CNTs serve as the electrodes.

MIL-101(Cr)/AC was synthesized by in situ incorporation of activated carbon powder via hydrothermal method. The water stability, n-hexane adsorption and regeneration of the MIL-101(Cr)/AC were experimentally measured. The results showed that the MIL-101(Cr)/AC exhibited the larger surface area (3319.3m²/g) than that of MIL-101(Cr) and AC, respectively. The addition of activated carbon was beneficial to improve the yield of MIL-101(Cr)/AC. The pore structure parameter and XRD of the MIL-101(Cr)/AC changed little after in water for 24h. Furthermore, the adsorption capacity of MIL-101(Cr)/AC for n-hexane was 786mg/g, which increased to 23.0% and 27.7% compared with MIL-101(Cr) and AC, respectively. Kinetic fitting of data indicated that the pseudo-first order model can more accurately describe the adsorption process of n-hexane on MIL-101(Cr)/AC and the intraparticle diffusion was not the sole rate-controlling step. Besides, the regeneration efficiency of MIL-101(Cr)/AC was over 92% after 10 consecutive n-hexane adsorption/desorption cycles.

Malachite green (MG) pollution has a negative impact on human health. At present, the method of removing it is inconvenient to operate and the cost is high, which has aroused widespread concern. In this study, MgO functionalized magnetic activated carbon (MgO-mAC) prepared by the sol–gel method was used to remove MG in water. The physical and chemical properties of MgO-mAC were tested by SEM, TEM, FTIR, XRD, BET and VSM. The effects of adsorbent dosage, solution pH, contact time, initial MG concentration and temperature on adsorption were studied by batch experiments. The adsorption kinetics data is well described by a pseudo-second-order model. The equilibrium data fits the Langmuir isotherm well. When the pH is 8 and the contact time is 360min, the maximum adsorption capacity of MG is 3809mg$\cdot$g${}^{-1}$. In thermodynamic studies, $\Delta {\mathrm{\text{G}}}^{\circ }<0$, $\Delta {\mathrm{\text{H}}}^{\circ }>0$, $\Delta \mathrm{\text{S}}>0$, MG adsorption is an endothermic and spontaneous adsorption process. The current synthesis method is simple in operation and cheap in raw materials, which can greatly reduce the cost of synthesis. Hence, the MgO-mAC material will be an effective adsorbent for removing MG from aqueous solutions.

For the treatment of dye wastewater, it is of great significance to develop new adsorbents with high adsorption capacity and good separation effect. In this study, the Fe-Co magnetic activated carbon material (CN-Fe-Co-AC) was first prepared by high-temperature calcination. CN-Fe-Co-AC is physically characterized by various methods. CN-Fe-Co-AC can efficiently and quickly remove the organic dyes methylene blue (MB) and acid blue 80 (AB80). The adsorption of MB and acid blue based on CN-Fe-Co-AC adsorbent is mainly through the specific surface area and the functional groups on the surface. During this recovery process, the adsorption activity of CN-Fe-Co-AC for MB and AB80 decreased slightly. Kinetic data can be described using a Pseudo-second-order model and the data for adsorption equilibrium can be described using the Langmuir isotherm. The theoretical adsorption capacities of MB and AB80 are 104.82mg/g and 26.94mg/g, respectively. After repeated use of five times, the removal rate of MB exceeded 96%, and the removal rate of AB80 exceeded 75%. The excellent adsorption performance and recyclability of CN-Fe-Co-AC indicate that this material has certain potential application value.

Three activated carbon materials with different pore characteristics were prepared. The relationship between the electrochemical performances and the pore characteristics of the obtained carbons as electrode material for supercapacitors was elucidated. The results show that three carbon materials have almost equal specific-surface-area capacitance of 0.12 F ⋅ m^-2. The energy density depends largely on the carbon surface area whereas the power density depends not only on the surface area, but also on the pore size and pore size distribution. The carbon sample with a BET surface area of 2000 m² ⋅ g^-1 and multimodal peak pore systems consisting of micropores at 1.5 nm and mesopores at about 3.8 nm exhibits excellent power density of 1662 W kg^-1.

Petroleum coke (PC) was expanded by using KMnO₄ as oxidant and HClO₄ as intercalator so as to decrease the amount of KOH needed for the successive activation. Activated carbon (AC) was prepared by activation of the expanded PC (EPC) at KOH/coke mass ratio of 3:1 (denoted as EAC-3). As a comparison, AC was also made by activation of PC at KOH/coke mass ratio of 3:1, 4:1 and 5:1 (denoted as AC-3, AC-4 and AC-5). Influence of expanding modification on the structure and performance of PC and AC was investigated. The results revealed that the expanding treatment increased the interplanar distance of PC microcrystalline from 0.344 to 0.362 nm and decreased the microcrystalline thickness from 2.34 to 1.57 nm. The specific surface area of EAC-3 and AC-5 was 3461 and 3291 m²⋅g^-1, respectively. The average pore size of EAC-3 was 2.19 nm, which is 0.11 nm larger than that of AC-5. At a scan rate of 0.5 mV⋅s^-1, EAC-3 and AC-5 achieved a specific gravimetric capacitance of 486 and 429 F⋅g^-1, respectively. Supercapacitor based on EAC-3 possessed lower resistance and better power performance.

In present study, the electrochemical performance of eco-friendly and cost-effective titanium oxide (TiO₂)-based and zinc oxide-based nanocomposite electrodes were studied in neutral aqueous Na₂SO₃ electrolyte, respectively. The electrochemical properties of these composite electrodes were studied using cyclic voltammetry (CV), galvanostatic charge–discharge (CD) and electrochemical impedance spectroscopy (EIS). The experimental results reveal that these two nanocomposite electrodes achieve the highest specific capacitance at fairly low oxide loading onto activated carbon (AC) electrodes, respectively. Considerable enhancement of the electrochemical properties of TiO₂/AC and ZnO/AC nanocomposite electrodes is achieved via synergistic effects contributed from the nanostructured metal oxides and the high surface area mesoporous AC. Cations and anions from metal oxides and aqueous electrolyte such as Ti⁴⁺, Zn²⁺, Na⁺ and can occupy some pores within the high-surface-area AC electrodes, forming the electric double layer at the electrode–electrolyte interface. Additionally, both TiO₂ and ZnO nanoparticles can provide favourable surface adsorption sites for anions which subsequently facilitate the faradaic processes for pseudocapacitive effect. These two systems provide the low cost material electrodes and the low environmental impact electrolyte which offer the increased charge storage without compromising charge storage kinetics.

In the current work, activated carbon monoliths have been prepared by application of different phenolic hydrocarbons namely catechol and resorcinol as carbon precursors. For synthesis of carbon monolith, the precursors have been mixed with Genapol PF-10 as template and then polymerized in the presence of lysine as catalyst. Then the polymerized monolith carbonized in inert atmosphere at 700°C and activated by water steam at 550°C. It was found that resorcinol polymerization is easier than catechol and occurred at 90°C while for polymerization of catechol elevated temperature of 120°C at hydrothermal condition is necessary. The prepared activated carbon samples have been characterized by various analysis methods including scanning electron microscopy (SEM), surface area measurement, and transmission electron microscopy (TEM). The adsorptions of three different aromatic hydrocarbons by the prepared activated carbon samples have also been investigated by high performance liquid chromatography (HPLC) and UV–Vis spectroscopy. It was found that carbon monolith prepared by catechol as carbon precursor has higher adsorpability and strength in comparison with the other sample. The higher performance of carbon monolith prepared by catechol can be associated with its higher active sites in comparison with resorcinol.

A novel low cost Na${}^{+}$/Li${}^{+}$ hybrid electrolyte was proposed for hybrid supercapacitor. By partly substituting Lithium salt with Sodium salt, the Li${}^{+}$/Na${}^{+}$ hybrid electrolyte exhibits synergic advantages of both Li${}^{+}$ and Na${}^{+}$ electrolytes. Our findings could also be applied to other hybrid power sources.

In this study, composite $\gamma$-MnO₂/activated carbon (AC) was prepared by chemical deposition method, and then it was assembled into electrode and electrochemical capacitor. Effects of reaction temperature and MnO₂ content were studied. Materials were characterized by X-ray diffraction, scanning electron microscope and electrochemical test. MnO₂ prepared at 30${}^{\circ }$C was amorphous, and it displayed the high specific capacitance as nearly four times as MnO₂ at 80${}^{\circ }$C. Due to MnO₂ particles which would block carbon pores when its content was too high, the composite containing 30% of MnO₂ exhibited the largest specific capacitance of 278.3F/g at 0.2A/g in K₂SO₄ electrolyte. The equivalent series resistance and charge transfer resistance of material were only 1.35$\mathrm{\Omega }$ and 1.41$\mathrm{\Omega }$, respectively. After 1000 cycles, the capacitance retention was still 91.6%. It indicated that chemical deposition was a facile, low cost and effective method to prepare MnO₂/AC with good electrochemical performances.

Electrode materials with high performance and low cost are demanding in supercapacitor applications. Novel V₂O₃ nanofoam@activated carbon composites have been prepared simply and cost-efficiently. Due to the mesoporous structure and high specific surface of V₂O₃ nanofoam and the good electric conductivity of activated carbon, the obtained composites exhibit an obviously improved specific capacitance as high as 185F/g, which overpasses bulk V₂O₃ (119F/g) and activated carbon (113F/g). The rate capability of V₂O₃ nanofoam@activated carbon composites has also been improved, owing to the increased electron transport accelerated by the activated carbon and the fast electrolyte ion intercalation/deintercalation facilitated by mesopores of V₂O₃ nanofoam. The composites retain 56% of initial specific capacitance when the current density increases from 0.05A/g to 1.0A/g. Therefore, the obtained V₂O₃ nanofoam@activated carbon composites are low-cost electrode materials with obviously improved electrochemical performance, which are idea for supercapacitor application.