Preparation and characterization of activated carbon from cotton stalks in a two-stage process

Activated carbons are prepared from cotton stalks by chemical activation with ZnCl₂, H₂SO₄ and physical activation using CO₂ and steam-CO₂ mixture for temperatures of 750, 850 and 900 °C. The effects of activation temperature and duration time, impregnation concentration of agent, impregnation times, and physical activating agent are examined. These materials are characterized by adsorption/desorption of N₂ to determine the BET areas, thermogravimetric analysis (TG, DTA), FTIR and scanning electron microscopy (SEM). ZnCl₂ under CO₂ atmosphere was found more effective than H₂SO₄ as a chemical reagent under identical conditions in terms of porosity development. The maximum BET surface area is found to be 2053 m²/g for active carbons produced with ZnCl₂ activation under CO₂ atmosphere.     

CO2 adsorption studies on hydroxy metal carbonates M(CO3)x(OH)y (M = Zn, Zn-Mg, Mg, Mg-Cu, Cu, Ni, and Pb) at high pressures up to 175 bar

Carbon dioxide (CO(2)) adsorption capacities of several hydroxy metal carbonates have been studied using the state-of-the-art Rubotherm sorption apparatus to obtain adsorption and desorption isotherms of these compounds up to 175 bar. The carbonate compounds were prepared by simply reacting a carbonate (CO(3)(2-)) solution with solutions of Zn(2+), Zn(2+)/Mg(2+), Mg(2+), Cu(2+)/Mg(2+), Cu(2+), Pb(2+), and Ni(2+) metal ions, resulting in hydroxyzincite, hydromagnesite, mcguinnessite, malachite, nullaginite, and hydrocerussite, respectively. Mineral compositions are calculated by using a combination of powder XRD, TGA, FTIR, and ICP-OES analysis. Adsorption capacities of hydroxy nickel carbonate compound observed from Rubotherm magnetic suspension sorption apparatus has shown highest performance among the other components that were investigated in this work (1.72 mmol CO(2)/g adsorbent at 175 bar and 316 K).     

Customer rebates and retailer incentives in the presence of competition and price discrimination

Promotions are important tools for matching supply and demand in many industries. In the United States automotive industry, promotions are frequently offered, which may be given directly to customers (rebates) or given to dealers (incentives) to stimulate demand. We analyze the performance of customer rebate and retailer incentive promotions under competition. We study a setting with two manufacturers making simultaneous pricing and promotion decisions, and with two price-discriminating retailers as Stackelberg followers making simultaneous order quantity decisions. In the benchmark case with no promotions, we characterize the equilibria in closed form. We find that retailer incentives can be used by manufacturers to simultaneously improve each of their profits but can potentially lead to lower retailer profits. When manufacturers use customer rebates, we show that a manufacturer is able to decrease the profit of her competitor while increasing her own profit, although she is also at risk for her competitor to use rebates in a similar fashion. Unlike the monopoly case where the manufacturers are always better off with retailer incentives, customer rebates can be more profitable under some cases in the presence of competition. Using numerical examples we generate insights on the manufacturers’ preference of promotions in different market settings.     

EPR study of free radical in gamma-irradiated bis(cyclopentadienyl)zirconium dichloride single crystal

Bis(cyclopentadienyl)zirconium dichloride (BCZD; zirconocene dichloride) single crystals were exposed to ⁶⁰Co-γ irradiation at room temperature. The irradiated single crystals were investigated between 125 and 470?K by electron paramagnetic resonance spectroscopy. The spectra of the crystals were found to be temperature independent. The paramagnetic center was attributed to the cyclopentadienyl radical. The g values of the radiation damage center observed in BCZD single crystal and the hyperfine structure constants of the free electron with nearby protons were obtained.     

On the measurements of particles by imaging methods: Theoretical and Experimental Aspects

Imaging techniques in particle sizing have always been important. Nevertheless, owing to the progress in CCD cameras, these techniques have found new potential which strongly depends on the capability to describe the image formation. Based on a combination of the generalized Lorenz-Mie theory and the diffraction theory, the image characteristics are described, taking into account the beam size, particle location, direction of observation and collecting optics characteristics. In the case of forward detection, a finite coherence is introduced and the results are compared with those obtained by a convolution approach, with the point spread function assumed to be Gaussian. Then some experimental results are displayed which underline the improvement achieved in particle size measurement.     

Synthesis of monodisperse iron oxide nanocrystals by thermal decomposition of iron carboxylate salts

Iron oxide (Fe(3)O(4), magnetite) nanocrystals of 6 to 30 nm with narrow size distributions (sigma = 5-10%) were prepared by the pyrolysis of iron carboxylate salts.     

Beneficiation of borax by reverse flotation in boron saturated brine

Flotation is one of the plausible methods for recovering borax fines discharged as fine waste to the tailings dam in the Kirka borax processing plant. A literature review dealing with the flotation behavior of boron minerals reveals that clay minerals in the boron ores coat boron minerals and thus deteriorate the quality of boron concentrates produced by direct flotation. The main objective of this study is therefore to recover borax fines from the tailings of the concentrator by reverse flotation. A three-level-factor experimental design was used to determine the main and interaction effects of variables selected on the metallurgical performance of reverse flotation. An analysis of variance for experimental results indicates that interaction effects of the variables for concentrate quality and recovery of B2O3 is nonsignificant and the most important variable for grade of concentrate and recovery is the collector dosage. It is shown that a concentrate assaying 11.25% B2O3 with 89.90% B2O3 recovery could be produced by means of single-stage (rougher) reverse flotation. Additionally, in order to produce a sufficient-quality concentrate, a multistage reverse flotation scheme involving rougher, scavenger, and two cleaners was devised. A final concentrate containing 23.47% B2O3 with 81.78% B2O3 recovery was obtained from these tests. The reverse flotation method can be thus considered as an important option for the beneficiation of borax fines.     

Thermodynamic-based environmental and enviroeconomic assessments of a turboprop engine used for freight aircrafts under different flight phases

Journal of Thermal Analysis and Calorimetry - In this study, the kerosene fueled turboprop engine of a freight aircraft is investigated along with exergy dynamic, sustainability,...     

Energy,exergy and environmental assessments of biodiesel and diesel fuels for an internal combustion engine using silicon carbide particulate filter

Journal of Thermal Analysis and Calorimetry - The affiliation of the fourth author was published incorrectly.