Iranian Journal of Chemistry and Chemical Engineering
Year:2013 | Volume:32 | Issue:2 (66)|Papers Count:14

Two multivariate calibration methods are compared for the simultaneous chromatographic determination and separation of Sulfamethoxazole (SMX) and Phthalazine (PHZ) by High Performance Liquid Chromatography (HPLC). Multivariate calibration techniques such as Classical Least Squares (CLS) and Inverse Least Squares (ILS) were introduced into HPLC to determine the quantification by using UV detector at 235, 250, 260 and 270 nm. Sixteen binary mixtures of SMX and PHZ as calibration set and eight binary mixtures as prediction set were used. Results show that, Relative Errors of Prediction (REP) of CLS and ILS for SMX and PHZ were 0.17%, 0.63% and 0.15%, 0.56%, respectively.

A viscosity model, based on Eyring’s absolute rate theory combined with a cubic PR equation of state and Wong-Sandler mixing rule, has been proposed in order to correlate viscosities of aqueous solutions of alkanolamine mixtures at atmospheric pressure and different temperatures. In the proposed method, the energy and size parameters in studied Equation of State (EoS) have been obtained using the Wong – Sandler (WS) mixing rule combined with the NRTL and Wilson Gibbs equations. The NRTL and Wilson parameters for aqueous solutions of alkanolamine mixtures have been correlated using measured viscosity data at atmospheric pressure and different temperatures. The overall average deviation between the experimental and calculated viscosities of studied aqueous solutions of alkanolamine mixtures using Wilson model is 0.92%.

Binary Logistic Regression (BLR) has been developed as non-linear models to establish quantitative structure- activity relationships (QSAR) between structural descriptors and biochemical activity of carbonic anhydrase inhibitors. Using a training set consisted of 21 compounds with known ki values, the model was trained and tested to solve two-class problems as active or inactive on the basis of the predicted value for IC50. Many quantitative descriptors were generated to express the physicochemical properties of 21 compounds with optimized structures. After filtration of these descriptors, 39 of descriptors for carbonic anhydrase (CA, EC 4.2.1.1) isozyme IX (CAIX) and 45 for isozymeXII (CAXII) remained and were selected for QSAR study. Logistic regression was then used to non-linearly select the most important descriptors and to develop a model for prediction of IC50. To evaluate the performance of the established models, Jjackknife and self consistency tests were performed during implementation of the two model-building methods. The applied indices including accuracy, sensitivity, and specificity were 85%, 82% and 100% for CAIX and also 71%, 68% and 80% for CAXII respectively. The primary advantage of such an approach is the reduction of redundant variables and the consequent improvement in the efficiency of modeling.

Potentiometric investigation on {H2O+NaNO3+PEG1500} mixtures were made at T=308.15K, using electrochemical cells with two ion-selective electrodes, (Na+ glass) as the cation ion-selective electrode against (NO3- solvent-polymer PVC) as the anion ion-selective electrode. The mean ionic activity coefficients of NaNO3 were measured at different concentrations of NaNO3 and PEG. Maximum concentration of electrolyte and PEG were 1 mol/kg and 0.12 mol/kg, respectively. The experimental data was modeled by utilizing the modified Pitzer equation and the activity coefficient ratio of PEG was evaluated by using Maxwell’s cross differential relation.

The interaction of brilliant green with herring sperm DNA was investigated in detail by spectrometric methods in g-cyclodextrin systems. On the condition of physiological pH, brilliant green prefers to form the 1:1 inclusion complex with g-cyclodextrin. All the evidences indicated that the binding modes between g-cyclodextrin-brilliant green and DNA were grooving binding and partial non-classical intercalative binding. The binding ratio of the inclusion complex with DNA is 6:1. The calculated thermodynamic parameters suggested that the binding of the inclusion complex to DNA was driven mainly by entropy.

In concentration of hydrogen peroxide, first, the solution should be quite pure, and then, it concentrate with methods such as vacuum distillation and cooling crystallization, because impurities in the hydrogen peroxide solution in high concentrations are causing decomposition of this substance; that is very dangerous. The purpose of this article is separation of chromium and magnesium cations from 35wt% commercial hydrogen peroxide solution by ion exchange method with strong acid cation resin Amberlite IR-120 H+ with styrene divinylbenzene copolymer network and sulfunic acid functional group. In separation of chromium and magnesium, we used batch system and tank equipped with mixer. Effect of the amount of resin and contact time on the separation of cation is investigated. The metal ion concentration in the original solution and the metal ions left unsorbed were determined by Inductively coupled plasma spectrometry (Varian Vista ICP–AES) technique. In determining the effect of the amount of resin and contact time on separation of cation, amount of chromium and magnesium in hydrogen peroxide solution was 0.1 mg/mL, 0.3 mg/mL and 0.5 mg/mL. Experimental results obtained from the separation of chromium and magnesium compared with Freundlich, Langmuir and Jovanovic adsorption isothermal models. Results show that these models only in a certain range of concentration, are consistent with experimental results.

The adsorption and desorption properties of SQD-85 resin for Cu (II) had been investigated. A series of experiments were conducted in a batch system to assess the effect of the system variables, i.e. initial pH, contact time and temperature. The results show that the optimal pH for the adsorption was 5.99 in the HAc-NaAc system, and the maximum adsorption capacity was estimated to 324 mg/g at 298 K. The apparent activation energy Ea and adsorption rate constant k298K values were 6.19 kJ/mol and 9.73×10-5 s-1, respectively. The isotherms of adsorption data fitted well to Langmuir model. Thermodynamic parameters (DG, DS, DH) suggested that Cu (II) adsorption by SQD-85 resin was endothermic and spontaneous in nature. Thomas model was applied to determine the characteristic parameters of column useful for process design. Desorption studies revealed that Cu (II) ion could be eluted with 1.0 mol/L HCl solution., which indicated that Cu (II) in aqueous solution could be removed and recovered by SQD-85 resin efficiently. Adsorption mechanism was also proposed for the adsorption of Cu (II) onto SQD-85 resin using FT-IR spectrometry technique.

In this study a sample of bentonite obtained from Semnan mines, was modified by a surfactant to prepare an organoclay with high surface area. BET analysis showed that the modification increased its surface significantly. The prepared sorbent was used for removal of dyes and other organic pollutants from a waste water obtained from Ekbatan textile company. Adsorption was studied in various times to obtain the saturation time. PH variation has significant effect on adsorption and led to variation of adsorbed pollutant. At pH=4.5 the pollutant concentration became minimum which showed the pH is optimum pH for adsorption. Increasing the sorbent to waste solution ratio up to 1.2 g/L also increased the sorption. Adsorption isotherm was investigated for fitting with Langmuir isotherm and it has good fitness.

Mercaptans are commonly present in petroleum products. Their foul odor and highly corrosive nature make them the most undesirable sulfur compounds so they should be removed because of environmental issues. Merox process is used for oxidation of mercaptans to disulfide using air in the presence of alkaline solution and Merox catalyst. In this paper, due to lack of information about the kinetic of mercaptan oxidation, the kinetic of conversion of ethyl mercaptan in gasoline and kerosene is studied in order to be able to model and simulate this process. The experiments were carried out in a semi-batch bubble column reactor and it was proved that increasing the temperature, improves the rate of the reaction. The obtained results were analyzed and a correlation for the rate of reaction is suggested. The suggested equation is first-order with respect to mercaptan concentration.

Bubble column reactors are used in a wide variety of applications such as multiphase bioreactors, catalytic slurry reactors, and absorption processes. The superficial gas velocity-gas holdup relationship and transition point are two important parameters for characterizing the hydrodynamics of a bubble column reactor. In this study, systematic investigation of a nitrogen - water - glass beads bubble column was conducted using the Taguchi experimental design method. The L16 (45) orthogonal array was selected for experiments design. Results showed that the order of importance of parameters is as follows: bed porosity, the ratio of height to diameter, and superficial gas velocity. A novel mathematical model was developed using the experimental data and based on 4th order polynomial. This model was successfully used to obtain the transition point with a high accuracy. The results of the mathematical method were in close agreement with those of the drift flux method. For liquid level of H=12D and slurry content of 13 vol%, transition velocity of 2.98 cm/s was calculated using the presented method, while a velocity of 3.14 cm/s was obtained from the drift flux method.

This work concerns the peristaltic flow of a Williamson fluid model in an inclined asymmetric channel under combined effects of heat and mass transfer. The governing nonlinear partial differential equations are simplified under the lubrication approach and then solved analytically and numerically. The analytical results are computed with the help of regular perturbation and the numerical results are found by using shooting method.

In this research, the effect of bubble surface area flux, Sb, and particle size on flotation rate constant, k, of pyrite (FeS2) particles was studied using bubble-particle interactions. The bubble-particle collision, attachment and detachment efficiencies were calculated under different flow regimes. The k increased with increase in the collision efficiency and decrease in the detachment efficiency. Also the bubble-particle collection efficiency increased with increase in the Sb. Thus difficulty in the floating of fine particles was attributed to low efficiency of the bubble-particle collision efficiency while difficulty in the floating of coarse particles was due to high efficiency of bubble-particle detachment. Maximum collision, attachment and detachment efficiencies were obtained as 81.57%, 50.60% and 51.89%, respectively.

Efflux time measurements are carried out for gravity draining of a liquid from a large cylindrical tank (where the flow is essentially laminar) through single exit pipe in the absence and presence of Cetyl Pyridinium Chloride (CPC) surfactant solutions. The variables considered are initial height of liquid in the tank, dia. of tank, length of the exit pipe and concentration of surfactant. The dia. of exit pipe in all the cases however remained constant. Drag reduction is expressed as the difference in efflux time in the absence and presence of surfactant solutions. Maximum drag reduction at optimum surfactnat concentration is reported. It is observed that during draining, Froude number remains constant.

In this study, decolorization of the diazo dye, Reactive Black 5 (RB5) in a Coprinus cinereus peroxidase-catalyzed reaction has been investigated. A bisubstate kinetic model for the reaction rate based on the Ping-Pong mechanism was assumed for the enzymatic decolorization. Experiments were conducted at different RB5 and hydrogen peroxide concentrations in a batch manner to estimate the intrinsic kinetic parameters. These parameters were used for the modeling of decolorization in a continuous reactor that was compared with experimental results. An acceptable agreement was observed between the model and experimental data.