Enhancement of methanogenic activity by micronutrient control: Micronutrient availability in relation to sulfur transport.

The main purpose of this research was to clarify the influence of the addition of iron (Fe) alone (0-100 mg/L) or 50 mg/L of Fe with 2 mg/L each of cobalt (Co), copper (Cu) and nickel (Ni) on the methanogenic activity of a mesophilic two-stage UASB system treating ethanol wastewater at a fixed chemical oxygen demand (COD) loading rate of 16 kg/m3/day under a continuous mode of operation and steady state condition. The addition of Fe provided the dual benefits of a reduction in both the dissolved sulfide and the hydrogen sulfide (H2S) content in produced gas, resulting in marginally improved hydrogen (H2) and methane (CH4) productivities. When the Fe dosage was increased beyond the optimum value of 50 mg/L, the process performance drastically declined, as a consequence of the high total volatile fatty acid (VFA) concentrations that inhibited both the acidogens and methanogens predominantly present in the 1st and 2nd reactors, respectively. The chemical precipitation of iron sulfide was responsible for the reduction of produced H2S in both the aqueous and gaseous phases as well as the minimization of added amounts of all other micronutrients to fulfil the sufficiency of all micronutrients for anaerobic digestion (AD). The addition of 2 mg/L each of Co, Cu and Ni together with 50 mg/L Fe resulted in the greatest enhancement in process performance, as indicated by the improved CH4 yield (mL/g COD applied) to about 42.3%, compared to that without micronutrient supplement.

Influence of Rigid-Elastic Artery Wall of Carotid and Coronary Stenosis on Hemodynamics.

Cardiovascular system abnormalities can result in serious health complications. By using the fluid-structure interaction (FSI) procedure, a comprehensive realistic approach can be employed to accurately investigate blood flow coupled with arterial wall response. The hemodynamics was investigated in both the coronary and carotid arteries based on the arterial wall response. The hemodynamics was estimated based on the numerical simulation of a comprehensive three-dimensional non-Newtonian blood flow model in elastic and rigid arteries. For stenotic right coronary artery (RCA), it was found that the maximum value of wall shear stress (WSS) for the FSI case is higher than the rigid wall. On the other hand, for the stenotic carotid artery (CA), it was found that the maximum value of WSS for the FSI case is lower than the rigid wall. Moreover, at the peak systole of the cardiac cycle (0.38 s), the maximum percentage of arterial wall deformation was found to be 1.9%. On the other hand, for the stenotic carotid artery, the maximum percentage of arterial wall deformation was found to be 0.46%. A comparison between FSI results and those obtained by rigid wall arteries is carried out. Findings indicate slight differences in results for large-diameter arteries such as the carotid artery. Accordingly, the rigid wall assumption is plausible in flow modeling for relatively large diameters such as the carotid artery. Additionally, the FSI approach is essential in flow modeling in small diameters.

Preparation of Metal Nitride Particles Using Arc Discharge in Liquid Nitrogen.

A simple process to synthesize metal nitride particles was proposed using submerged arc discharge plasma in liquid nitrogen. Gibbs standard free energy was considered for the selection of the nitride-forming materials. In this study, titanium (Ti) and aluminum (Al) electrodes were used as raw materials for nitride particle preparation. Liquid nitrogen acted as a dielectric medium as well as a nitridation source in this process. A copper electrode was also used as a non-reactive material for comparison with the reactive Ti and Al electrodes. As the operating conditions of the experiments, the arc discharge current was varied from 5 A (low-power mode) to 30 A (high-power mode). The formation of titanium nitride (TiN) and aluminum nitride (AlN) was confirmed in the particles prepared in all experimental conditions by X-ray powder diffraction (XRD). The observation using a field emission scanning electron microscope (FE-SEM) and a field emission transmission electron microscope (FE-TEM) indicated that the synthesized TiN particles showed a cubic morphology, whereas AlN particles containing unreacted Al showed a spherical morphology. The experiments using different metal electrode configurations showed that the anode generated most of the particles in this process. Based on the obtained results, a particle formation mechanism was proposed.

Preparation of a Pd/Al2O3 Catalyst with Microwave-Induced Plasma Jet Irradiation under Atmospheric Pressure.

Microwave-induced plasma under atmospheric pressure is an effective technique for catalyst preparation. A Pd/Al2O3 catalyst was prepared using a fixed bed with microwave plasma irradiation. The activity of the catalyst was compared with that of catalysts made using the plasma spouted bed and the conventional furnace. From the results of X-ray powder diffraction (XRD) spectra and transmission electron microscopy (TEM) images, plasma treatment induced a rapid reduction process (PdO→Pd). Moreover, the plasma treatment derived the growth of a different facet from Pd (111) to Pd (100). A different kind of phase transition behavior was observed with plasma-treated alumina. H2 chemisorption analysis confirmed that the plasma treatment had a positive effect on the dispersion of Pd metal on the support. These improvements to the properties of the catalyst resulted in excellent performance in hydrogenation of acetylene.

Preparation of Catalyst with Microwave Induced Plasma Jet Combined with Spouted Bed.

Plasma technologies have been widely used for various catalyst preparation in recent years. The plasma combined with a spouted bed reactor can provide homogeneous particle treatment and make gas temperature high enough to treat particles. In this work, a combination of microwave induced plasma and spouted bed was proposed and applied for the catalyst preparation. As a model catalyst, Pd/Al2O3 was prepared by the plasma spouted bed with various operating conditions and the selective hydrogenation of acetylene to ethylene was chosen to evaluate their catalytic activity. Catalyst characterizations were carried out by SEM, XRD, TEM, and H2 chemisorption to elucidate the effects of the plasma spouted bed. Despite the short treatment time, Pd/Al2O3 was successfully produced using the plasma spouted bed. For comparison, the conventional heating process with an electric furnace was used to prepare Pd/Al2O3. For the plasma spouted bed treatment, it had contrary effect from the conventional method. The average diameter of Pd nanoparticles of PS-4 was smaller than that of CM-500 despite high temperature condition in the plasma spouted bed. It is suggested that Pd/Al2O3 catalyst prepared by the plasma spouted bed showed different catalytic reaction behavior with the conventional method.