Articles in Press
   2010
   2009
   2008
   2007
   2006
   2005
 
Volume 12, Issue 1
Electrical and Computer Engineering
Volume 12, Issue 2
Civil and Mechanical Engineering
Volume 12, Issue 4
Civil and Mechanical Engineering
Volume 12, Issue 3
Chemistry and Chemical Engineering
   2004
   2003
   2002
   2001
   2000
   1999
   1998
   1997
   1996
   1995
   1994
Volume 12, Issue 3, 2005
Chemistry and Chemical Engineering


Anaerobic Degradation of Molasses Stillage in a Pilot UASB Reactor
 
        A. Torkian (PhD.)
  • S.J. Hashemian [PhD.]
  • M. Hakimjavadi [PhD.]
  • E. Azimi [PhD.]

Preview   Download PDF
 

The feasibility of a mesophilic anaerobic treatment of an alcohol distillery wastewater (beet molasses stillage) was studied in a 1300 l Upflow Anaerobic Sludge Blanket (UASB) reactor for a period of 180 days. The system was seeded with 600 L of mesophilic anaerobic sludge harvested from the bottom of a dairy anaerobic lagoon. Nutrients were added to acidified effluent and after adjusting the pH in an equalization tank, the system was fed with a diluted effluent containing COD in the range of 1000-11000 mg/L at 30\degree C. Initially, the system had an OLR of 1 kg COD m^-3 d^-1 and upflow velocity was maintained at 0.6 m/h (HRT=6 h) throughout the study. A gradual increase in OLR, through increased feed concentration, resulted in an excessive sludge washout necessitating the addition of calcium carbonate to act as a nuclei for granule formation. After 20 days of operation and at an OLR of 5.3 kg COD m^-3 d^-1, signs of granule formation were abserved, as indicated by increased VSS at the bottom of the reactor and reduced effluent VSS. At this point, the loading to the system was increased in four stages up to 16 kg COD m^-3 d^-1 (COD removal efficiency of 95%) to evaluate the optimum operational conditions of the system. During this period, the VSS/SS ratio remained constant at 0.83 and the SLR varied from 0.14 to 0.81 kg COD kg^-1 VSS d^-1. The performance of the system, based on unit reactor volume and unit microbial mass, was 10 kg SCOD m^-3 d^-1 and 0.25 kg SCOD kg^-1 VSS d^-1, respectively.


Disturbance Rejection Problem in the Control of Wastewater Treatment Systems
 
        F. Ghavipanjeh (PhD.)

Preview   Download PDF
 

Wastewater treatment systems are unreliable in terms of their performance. Many parameters could affect their efficiency in which load disturbances are the major cause of large perturbations in the system and the consequent deterioration in the effluent quality. It is known that the variation of the influent flow rate is more important than variations of the various components of the influent. In this paper, the effect of influent flow variation on the system has been modeled and added to the control system structure, in order to alleviate the performance problem. The control system is based on PIP/TDC methodology, which has been published in numerous papers since 1987 and also described briefly here. This kind of control system could bring some advantages to wastewater treatment systems, compared to other more well-known control systems. All experiments have been applied to an activated sludge simulation benchmark and the results show an improvement in the control performance.


Study of Some Micronutrients in Selected Medicinal Plants
 
        N. Fatima (PhD.)
  • Z.T. Maqsood [PhD.]
  • B. Khan [PhD.]

Preview   Download PDF
 

Momordica charantia, Eugenia Jambolanum, Allium Sativum and Trigonella foenum graecum are commonly used vegetables and seeds. For several decades, these food materials have been successfully applied to some aspects of primary health care [1-3], especially as anti-hyperglycemic agents. Gymnema sylvestre and Adiantum Capillus Veneris are also some of a few very commonly used anti-diabetic plant products. These medicinal plants are extensively studied, but, in terms of organic constituents, however, their metal contents may play important roles. These species were selected to investigate their metals content, specifically, those which have a significant role in carbohydrate metabolism. Chromium, iron, manganese and zinc were investigated for this study. The level of the various metals was generally low and within statutory limits. Trigonella foenum-graecum was found to be the most suitable of all.


Effects of Graphite Content on the Oxidation Resistance of MgO-C Refractory Bricks
 
        M.A. Faghihi-Sani (PhD.)
  • B. Hashemi [PhD.]
  • Z.A. Nemati [PhD.]

Preview   Download PDF
 

The effects of graphite content on the density and oxidation behavior of MgO-C refractory samples were studied. The samples were formulated with various amounts of graphite and their oxidation behavior was investigated (in an isothermal condition)

    using a Thermo Gravimetric system (TG), in air and at temperatures ranging from 900\degree C to 1450\degree C. The preliminary results showed that the porosity and density of tempered samples were decreased when the graphite content was increased. However, after heating the samples at higher temperatures, the decreasing rate of porosity was lowered. At the beginning of the oxidation process, the rate of weight loss was high, but was gradually decreased when the thickness of the decarburized layer increased. The overall results indicated that although the higher graphite content increased the weight loss, it reduced the thickness of the oxidized layer.


Application of the Pitzer and the MSA-Based Models in Predicting the Activity and the Osmotic Coefficients of Aqueous Electrolyte Solutions
 
        C. Ghotbi (PhD.)
  • G. Azimi [PhD.]
  • V. Taghikhani [PhD.]

Preview   Download PDF
 

The GV-MSA, the BMCSL-MSA and the Pitzer models were used to correlate the individual, the mean ionic activity coefficients and the osmotic coefficients of symmetric and asymmetric electrolyte solutions. In order to compare the results obtained from the GV-MSA with those obtained from the Pitzer and the BMCSL-MSA models, the same experimental data and the same minimization procedure were used and the new sets of parameters for the BMCSL-MSA and the Pitzer models were also reported. The values for the osmotic coefficients of electrolyte solutions were calculated directly using the values of the mean ionic activity coefficients obtained from the models studied in this work. The results for the individual and the mean ionic activity coefficients, as well as the osmotic coefficients up to saturation concentration obtained from the GV-MSA model, compared with those of the BMCSL-MSA, the Pitzer and the Khoshkbarchi-Vera models.


Triphase Catalytic Reactions Using Clay Intercalates
 
        N. Shabestary (PhD.)
  • S. Khazaeli [PhD.]
  • N. Long [PhD.]

Preview   Download PDF
 

A naturally occurring clay mineral, hectorite, was used as the support for quaternary ammonium cations. The intercalation of the cations by the clay has the advantage of separation of the catalyst from the product by a simple filtration technique. Several quaternary ammonium cation clay intercalates have been used to investigate the effects of alkyl chain length, size and shape of these catalysts in converting n-butyl bromide to n-butyl chloride. It appears that the hectorite intercalates have a great tendency for emulsification in the presence of organic solvent (toluene) and water. In fact, the emulsification being facilitated by the clay intercalates helps to bring the nucleophile from the aqueous phase into contact with the substrate, which is contained in the organic phase. The rate of the reaction was measured for the biphase reaction (no supporting clay) and for the triphase catalytic system (with supporting clay) for comparison. Relatively large differences in reactivity have been observed between the catalysts chosen in this research. The results have indicated that quaternary ammonium with certain carbon numbers has higher catalytic activity.


Immobilization of Penicillin G Acylase on Non-Porous Ultrafine Silica Particles
 
        A. Kheirolomoom (PhD.)
  • H. Fazelinia [PhD.]

Preview   Download PDF
 

In this paper, immobilization of penicillin G acylase onto non-porous ultrafine silica particles has been studied. The amount of penicillin G acylase immobilized was increased by increasing the free enzyme concentration and, at 0.45 mg/ml concentration of the free enzyme, 80% of the enzyme was immobilized. The optimum pH for immobilization was found to be 7.0, close to the pI of the enzyme. Although immobilization of the enzyme on ultrafine silica particles with and without glutaraldehyde showed almost the same activities, the enzyme immobilized with glutaraldehyde retained its initial activity much longer during 40 cycle-repeated batches with a half life of 163.2 h.


Estimating Volatile Organic Compound Emissions from Wastewater Circulating Aeration Tanks
 
        S. Yaghmaei (PhD.)
  • A. Rashidkhani [PhD.]

Preview   Download PDF
 

The need for the control of Volatile Organic Compounds (VOCs) has led engineers to modify wastewater aeration tank systems. In this research, air recirculation has been investigated as a possible VOC control strategy for these systems. A steady-state mathematical model of VOC emission rates has been developed from the fundamentals of VOC convection, volatilization and biodegradation. This model has been used to study the effect of aeration recirculation in enhancing the biodegradation of VOCs in the system, using dichloromethane as a typical VOC. A feasibility study considering plants of various sizes is needed to compare the costs and benefits of air recirculation to other VOC control strategies.


Production of Low Ester (LM) Pectin by De-esterification of High Ester (HM) Apple Pectin
 
        I. Alemzadeh (PhD.)
  • A.A. Saifkordi [PhD.]
  • D. Kahforooshan [PhD.]
  • P. Nahid [PhD.]

Preview   Download PDF
 

In this paper, LM pectin production from commercial apple pectin by using acid, alkali and ammonia methods in the presence of ethanol was studied. Also, the effect of different parameters such as, temperature, time, acid, alkali and ammonia treatment in LM pectin production were evaluated. In all the experiments, low temperature showed a better influence from a recovery, purity and low de-polymerization viewpoint. Optimum conditions in the acid method reached at pH=2, t=17 hrs and T=30\degree C, in the alkaline method reached at pH=11, t=3 hrs and T=5\degree C and in the ammonia method reached at 2 N ammonia and T=5\degree C, were determined.


Comparative Study of Thermodynamic Parameters of Vanadium (IV) and (V) Acetohydroxamate Complexes
 
        N. Fatima (PhD.)
  • K. Ali [PhD.]
  • Z.T. Maqsood [PhD.]

Preview   Download PDF
 

Acetohydroxamic acid, CH_3CONHOH, forms highly stable complexes with vanadium (V) and vanadium (IV) in 1:1, 1:2 and 1:3 mole ratios. The stability of these complexes can be determined in terms of thermodynamic parameters

    \Delta G,\Delta H and \Delta S. The preliminary data, obtained through pH titration at various temperatures, was processed and analyzed by the computer program BEST for the refinement of graphically calculated log \beta values. Graphs of \ln\beta versus 1/T, gave a straight line, with a slope -\Delta H/R and intercept \Delta S/R. Enthalpy and free energy changes for V(V) complexes were found in the order of ML>ML_2>ML_3 with a negative sign. Whereas entropy change was found to be in the same order but positive, for vanadium (IV) acetohydroxamic acid complexes, the order of \Delta G, \Delta H and \Delta S was ML>ML_3>ML_2. The \Delta S is most positive for a 1:1 complex, while \Delta G and \Delta H are more negative for the same.


Removal and Recovery of Cu^+2, Cr^+3 and Ni^+2 by Using Dried Biomass of Sargassum Algae in a Batch System
 
        B. Barkhordar (PhD.)
  • M. Ghiasseddin [PhD.]

Preview   Download PDF
 

Algae are a group of living organisms that play an important role in heavy metal removal from polluted wastes. Their usage is rather economical, especially if the waste is not heavily polluted. Since the use of live algae creates some problems, products of their dried mass were used in this study. The sargassum species was collected from the Persian Gulf, dried, cut in pieces and then used as the biomass. The adsorption process, with influencing factors such as initial concentrations, retention time, pH and temperature, were considered. In dilute wastewater (less than 25 mg/l), this method can reduce the concentration of remaining heavy metals after 10 min retention time at a suitable level, for discharging into the environment. pH and temperature did not have an effect on the results. Absorption equations for the metals in question have been developed and the economical evaluation was compared using statistical methods. To recover metals and regenerate the biomass, EDTA and HCl were examined. It was found that using EDTA (4 mM) and HCl (pH=2) after 90 min had an efficiency of about %85 and %75 and EDTA is more efficient than HCl. It should also be mentioned that recovery has cost benefit if the metal of interest is noble and valuable. After 5 consequent cycles of adsorption and recovery using HCl and EDTA, the biomass lessened by 30% and 16%, respectively. The remaining heavy metal in the algae is increased gradually until we have 90% reduction in recovery using HCl and 65% using EDTA, because the active cell wall group of algae is damaged by HCl. During the first cycle, most of the metals were recovered. The primary and annual recovery costs were about 90 and 350 times more than the value of recovered heavy metal.


In-Situ Digestion of Serum Samples in Graphite Furnace Prior to Determination by ETAAS
 
        N.M. Najafi (PhD.)
  • A. Massumi [PhD.]
  • M. Shafaghizadeh [PhD.]

Preview   Download PDF
 

An accurate in-situ digestion method was developed for this approach to separate the traces of Pb, Mn and Zn from their concomitant in serum samples, prior to determination by ETAAS. Pd was used as a modifier to stabilize the analyte from decomposition at 900-1000 (\degree C). Stabilization was much more effective if the mixture modifier and digested sample were first pre-pyrolyzed