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Abstract : Separation and Recovery of SiC Particles Discharged from Silicon Wafer Production Process
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Abstract: In the slicing process of silicon wafer from silicon single crystal, it has been the general way to cut silicon by wire saws with the lubricant mixture of silicon carbide, as SiC, particles and wrapping oil. After slicing the silicon single crystal, the waste liquor containing SiC and silicon powders is discharged from the process. The particle sizes of SiC and Si are about 10μm and 1μm, respectively and the weight ratio is about 9:1. The particles discharged from slicing waste liquor become the mixture of SiC and SiO2, when the waste liquor is burned after treating the lubricant oil by a filter press. In terms of the minimization of wastes and environment, it is preferable to separate and recover the valuable SiC from SiO2. In order to solve the problem mentioned above, flotation method can be applied to accomplish the separation of SiC from SiO2. The cationic surfactants of dodecyl-tri-methyl-ammonium chloride (abbreviated as DTMAC hereafter) and tri-methyl-octyl-ammonium chloride (abbreviated as TMOAC hereafter) were used in this study. The adsorption amount of surfactants on SiC and SiO2 particles was measured. The flotation behaviors of SiC and SiO2 were investigated by changing pH, gas flow rate and flotation time in the presence of DTMAC. The purity and yield of SiC were also discussed in the flotation process comprising of roughing, cleaning and scavenging steps. A series of flotation process for SiC gave the purity and yield of 99.7% and 96.7%, respectively. Keywords: Flotation, SiC, SiO2, silicon wafer slicing waste, TMOAC, DTMAC.Download Full Article |
Abstract : Application of Polyacrylamide for Methylene Blue Removal from Aqueous Solutions
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Abstract: In this study the removal of methylene blue (MB) dye from aqueous solutions by polyacrylamide (PAA) as a potential adsorbent was reported. PAA was characterized using SEM and FTIR measurements. Batch adsorption experiments were performed as a function of the solution pH, contact time, solute concentration and temperature. Evaluation of the obtained data with isotherm studies indicated that the adsorption process was matched well with the Langmuir model. The maximum capacity of adsorbent for MB was 111.1 mg g−1. Kinetic studies were carried out on various kinetic models and the pseudo-second order kinetic model was fitted very well with experimental data. Moreover, the thermodynamic parameters indicated that the adsorption reaction was endothermic and spontaneous process. Keywords: Polyacrylamide,Removal,Methylene blue, Isotherm, Kinetic.Download Full Article |
Abstract : Production and Characterization of Bio-Chars and Bio-Oils Formed by Pyrolysis of Persian Hogweed (Heracleum persicum Desf.) in A Fixed-Bed Reactor
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Abstract: Pyrolysis of Persian Hogweed(Heracleum persicum Desf.) stalks were performed in a fixed-bed tubular reactor with (K2CO3, ZnCl2) and without catalyst at three different temperatures (400, 500 and 600 oC) with a constant heating rate of 50 oC/min. and with a constant sweeping gas (N2) flow rate of 100 cm3/min. The amounts of bio-char, bio-oil and gas produced were calculated and the compositions of the obtained bio-oils were characterized by GC-MS. The effects of pyrolysis parameters such as temperature and catalyst on the product yields were investigated. According to the results, both temperature and catalyst had significant effects on the conversion of Heracleum persicum Desf.into bio-chars, bio-oils and gaseous products. The highest bio-oil yield of 41.42% by weight including aqeous phase was achieved with 10% potassium carbonate catalyst at 500 oC. 71 different compounds were identified by GC-MS in the bio-oils obtained at 500 oC. Keywords: Energy, Biomass, Pyrolysis, Bio-oil, Persian Hogweed, Heracleum persicum Desf.Download Full Article |
Abstract : Ab Initio and Density Functional Predictions of Solvation Free Energies of Cyclic Polyethers (CH2CH2O)n (n=2,6) in Aqueous and Tetrachloromethane Solutions
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Abstract: Solvation free energies ∆Gsoltot of cyclic polyethers (CH2CH2O)n (n=2,6) in aqueous and tetrachloromethane solutions have been calculated at HF, MP2 and B3LYP/6-311G (d,p) levels of theory using CPCM, IEFPCM and SMD implicit solvation models. It has been found that ∆Gsoltot are negative for both solvents, they increase linearly with system sizes and they are more important in water solution. The electrostatic contributions to the solvation free energies ∆Gsolele are also more important in water because of their polar nature. In water, CPCM and IEFPCM models give a close values, which are slightly different from SMD values. In tetrachloromethane solvent CPCM model seems overestimate ∆Gsolele. For both solvents the non-electrostatic contributions to the solvation free energies ∆Gsoln-ele provided by SMD are remarkably different to those given by CPCM and IEFPCM models Keywords: Continuum model, Solvation free energy, Cyclic polyether, Water, Tetrachloromethane.Download Full Article |
