Current Issue : October - December Volume : 2013 Issue Number : 4 Articles : 7 Articles
Biosorption and desorption of chromiumand lead on shoots biomass of Schoenoplectus californicuswere investigated by performing\r\nbatch sorption tests in different conditions of pH, biosorbent dose, and initial concentration in simple and binary solutions.\r\nLangmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models were employed to describe sorption equilibrium.\r\nFilters and biomass were characterized before and after treatments by environmental scanning electron microscopy and X-ray\r\nenergy-dispersive spectrometry.The optimal conditions for biosorption were found to be pH 5 for both metals. The contact time\r\nto reach pseudoequilibrium changed as a function of pH and the metal studied.The highest optimisation of biosorbent dose was\r\n5 g L-1 at pH7 and 15 g L-1 at pH 5 for both metals. The most effective extracting agents for lead and chromium proved to be HNO3\r\nand NaOH, respectively. The recovery of lead was greater than of chromium because the Cr(III) sorption mechanisms involve a\r\nstronger binding energy than the mechanisms for Pb(II), such as in intern sphere complexes. Both metals accounted for a high %\r\nremoval (>90%) under the best sorption conditions. The use of Schoenoplectus californicus proved to be an efficient and economical\r\nalternative for the treatment of effluents contaminated with lead and chromium....
The applicability of ionic liquid-methanol cosolvent system to both extract bio-oil and simultaneously pretreat the carbohydrate\r\nfraction of jatropha and safflower biomass for enzymatic hydrolysis to fermentable sugars is presented. Although pretreatment with\r\neither the cosolvent or pure ionic liquid yielded comparable hydrolysis kinetics and fermentable sugar yields on safflower whole\r\nseeds, the addition of alcohol to the ionic liquid was necessary to optimally recover both bio-oil and fermentable sugars.The ionic\r\nliquid [C2mim][Ac] was far more effective than [C2mim][MeSO4] with optimum processing conditions occurring at a cosolvent\r\nconcentration of 70ââ?¬â??30 wt% of [C2mim][Ac] to methanol and a processing temperature of 120Ã?°C. Under these conditions, the\r\nmajority of the bio-oil was extracted and 25.4 wt% (safflower) and 14.3 wt% (jatropha) of the whole seed biomass were recovered\r\nas fermentable sugars. The recovery of fermentable sugars from the carbohydrate fraction was as high as 74% and 78% for jatropha\r\nand safflower seeds, respectively, when using [C2mim][Ac] cosolvent. A preliminary theoretical analysis of two potential oil seed\r\nprocessing pathways using the cosolvent system suggested that the corecovery of bio-oil, fermentable sugars, and a protein rich\r\nmeal can recover a majority of the energy contained in the original biomassââ?¬â?a result that improves upon the traditional approach\r\nof solely extracting bio-oil....
For heterogeneous catalytic reactions, the empirical power lawmodel is a valuable tool that explains variation in the kinetic behavior\r\nwith changes in operating conditions, and therefore aids in the development of an appropriate and robust kinetic model. In the\r\npresentwork, experiments are performed on 1.0 wt% Pt/Al2O3 catalyst over awide range of experimental conditions and parametric\r\nsensitivity of the power law model to the kinetics of the dehydrogenation of methylcyclohexane is studied. Power law parameters\r\nsuch as order of the reaction, activation energy, and kinetic rate constants are found dependent upon the operating conditions.\r\nWith H2 in the feed, both apparent order of the reaction and apparent activation energy generally increase with an increase in\r\npressure. The results suggest a kinetic model, which involves nonlinear dependence of rate on the partial pressure of hydrogen and\r\nadsorption kinetics of toluene or some intermediate....
Catalytic gasification of bamboo in a laboratory-scale, fluidized bed reactor was investigated. Experiments were performed to\r\ndetermine the effects of reactor temperature (400, 500, and 600�°C), gasifying medium (air and air/steam), and catalyst to biomass\r\nratio (0 : 1, 1 : 1, and 1.5 : 1) on product gas composition,H2/COratio, carbon conversion efficiency, heating value, and tar conversion.\r\nFromthe results obtained, it was shown that at 400�°C with air/steamgasification, maximum hydrogen content of 16.5% v/v, carbon\r\nconversion efficiency of 98.5%, and tar conversion of 80% were obtained. The presence of catalyst was found to promote the tar\r\nreforming reaction and resulted in improvement of heating value, carbon conversion efficiency, and gas yield due to increases in\r\nH2, CO, and CH4. The presence of steamand dolomite had an effect on the increasing of tar conversion...
Supercritical adsorption coupled with the high adsorption capacity of silica aerogel allows the preparation of a new kind of delivery\r\nsystems of poor water soluble drugs. In order to overcome drawbacks of conventional techniques where the use of liquid solvents\r\ncan cause the fracture of aerogel porous structure, in this work a new adsorption process of drugs from a supercritical mixture is\r\nproposed. Adsorption takes place from a fluid solution of the drug in supercritical CO2 and ethanol as cosolvent. A fixed bed\r\nadsorption plant has been developed to allow fast mixing of fluid phase and effective contact in the adsorption column. The\r\nuse of ethanol as cosolvent allows to overcome the limitation of supercritical adsorption due to low solubility of many drugs in\r\nsupercritical CO2. Adsorption isotherms were measured for one-model substance, nimesulide, at 40�°C, and breakthrough curve\r\nwas experimentally obtained.The drug loading of the drug into silica aerogel was up to 9 wt%.Thedrug composite was characterized\r\nusing scanning electron microscopy, and release kinetics of the adsorbed drug were also evaluated by in vitro dissolution tests. The\r\ndissolution of nimesulide fromloaded aerogel ismuch faster than dissolution of crystalline nimesulide. Around 80% of nimesulide\r\ndissolves from the aerogel within 6 minutes, whereas dissolving 80% of the crystalline drug takes about 90 min....
The present analysis is concerned with the criteria for the onset of flow reversal of the fully developed mixed convection in a\r\nvertical channel under the effect of the chemical reaction. The governing equations and the critical values of the buoyancy force are\r\nsolved and calculated numerically via MAPLE. Parameter zones for the occurrence of reversed flow are presented. The exothermic\r\nchemical reaction is found to enhance the flow reversal and made flow reversal possible for symmetrical walls temperature....
An effective oxidative system consisting of hydrogen peroxide, formic acid, and sulfuric acid followed by an extractive stage were\r\nimplemented to remove dibenzothiophene in the simulated fuel oil. The results revealed such a great performance in the case\r\nof H2O2 in the presence of formic and sulfuric acids that led to the removal of sulfur compounds. Sulfuric acid was employed\r\nto increase the acidity of media as well as catalytic activity together with formic acid. The oxidation reaction was followed by a\r\nliquid-liquid extraction stage using acetonitrile as a polar solvent to remove produced sulfones from the model fuel. The impact of\r\noperating parameters including the molar ratio of formic acid to sulfur (nF/nS), hydrogen peroxide to sulfur (nO/nS), and the time\r\nof reaction was investigated using Box-Behnken experimental design for oxidation of themodel fuel. A significant quadraticmodel\r\nwas introduced for the sulfur removal as a function of effective parameters by the statistic analysis....
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