نشریه شیمی و مهندسی شیمی ایران
سال سی و دوم شماره 3 (پیاپی 69، پاییز 1392)

Occurrence of iron deficiency in different age groups in population of Iran shows the importance of food fortification by iron and Folic Acid (FA). Cereals especially wheat are the most suitable tool for fortification aims due to their majority in Iranian diet. On the other hand, determination of material concentration after fortification is necessary to inhibit overdose. Folic acid measurement in complex matrix of bread (particulary in very low concentration of ppm or mg/L) needs to set up of special analytical method for extraction from flour and bread also preconcentration of FA. In this research, measurement of FA content in fortified bread samples by HPLC system was conducted. Optimization of separation conditions in HPLC system for identification of folic acid was conducted by change of several reagent concentration (%v/v) to obtain optimum retention time of FA peak. To preconcentration of FA (from ppb to ppm level), three preparation methods including solid phase extraction, extraction with magnetic nano-particle and Hollow Fiber Liquid Phase Microextraction (HF-LPME) (two and three phase modes) were evaluated. Based on obtained results two phase HF-LPME was selected. Optimization of separation by HF-LMPE with various solvents (n-octanol, n-hexanol, dodecan, isobutyl methyl ketone and benzyl alcohol) containing 10% w/v Aliquate 336 showed that octanol causes the maximum extraction efficiency. In this research effects of pH and time on efficiency of extraction were evaluated. Results show that pH=8 increases extraction efficiency. Also, by increasing time up to 45 min extraction efficiency was increased and then by further increase of time was decreased due to solvent loosing. Enrichment factor on the base of calibration curve slope with and without pre-condensation was calculated and 69 obtained. Extraction efficiency was calculated by enrichment factor and 3.5% was obtained. Spike method was used for confirmation of data accuracy. Also, FA preconcentration and separation was done in one hour. Samples (after texture degradation, extraction, separation and condensation) were injected to HPLC for concentration determination. Content of folic acid in bread samples was in the range of 0.3-1.0 mg/g with average of 5.9 mg/g bread, while the added ep�" in
p� �5� in one hour. Samples (after texture degradation, extraction, separation and condensation) were injected to HPLC for concentration determination. Content of folic acid in bread samples was in the range of 0.3-1.0 mg/g with average of 5.9 mg/g bread, while the added concentration of folic acid to wheat flour was 1.5 mg/g. This difference is due to long time after bread preparation or temperature and time of cooking phase. Spike method confirmed the accuracy of data by error less than 10%. Resulted approaches from this research were evaluation of fortification efficiency, as well as set up of an accurate analytical method for extraction, preconcentration and determination of folic acid content in the range of mg/g in bread matrix for the first time in I.R. Iran.

Carboxymethyl cellulose is a polysaccharide which forms strong and clear films. Montmorillonite and cellulose nanowhiskers are two types of nanoparticles with sheet and rod geometric shapes, respectively. Montmorillonite is nonrenewable and non biodegradable and cellulose nanowhiskers are renewable and biodegradable filler. Cellulose nanowhiskers are not produced commercially and in this research we prepared them from cotton linter. Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) indicated that the prepared nonowhiskers suspernsion having an average length of 240 nm and diameter of 13 nm respectively. In this study, carboxymethyl cellulose (CMC)-Polyvinyl alcohol (PVA) nanocomposite films, containing 3-10% nanoparticles (W/W CMC), were prepared by casting method and their physical properties were compared. In comparison to control film, 28.21% reduction in Water Vapor Permeability (WVP) was observed in the films containing 10% Wt cellulose nonowhiskers and samples with 7% cellulose nanowhiskers, whowed the lowest surface hydrophilicity (contact angle = 59.28°). On the other hand, nanocomposite containing 10% montmorillonite exhibited 29.06% reduction in WVP compared to the control film samples with 10% montmorillonite, shwed the lowest surface hydrophilicity (contact angle = 65.09°). Significant difference in WVP value and contact angle of two types of nanocomposit only observed at 3 and 10% content of nanoparticles, respectively, by Duncan test (Pg) of the resulted nanocomposite films. The glass transition ddisappeared gradually and no glass transition was observed in the thermograms of the films containing higher amount of nanoparticles. Adding of nanoparticles caused to decrease in melting point of the both type of films.

In this work, water absorption behaviour of biodegradable low density polyethylene-thermoplastic starch (LDPE-TPS) blends is investigated. Thermoplastic starch was prepared by melt mixing starch and glycerol (35 wt.%) using an internal mixer at 140 °C and rotor speed of 60rpm for 8 minutes. LDPE/TPS blends containing various amounts of starch (10-40 wt.%) were prepared with (3 wt.%) and without PE-g-MA using single screw extruder. Water absorption test was carried out at room temperature and using related standard methods. The results indicate that with increase in TPS content and also increasing the immersion time, water absorption increase unit the constant value is obtained. After 21 days of the immersion time, 10.5% and 16.3% increase in water absorption were obtained for uncompatibilized and compatibilized blends containing 40 wt.% TPS, respectively. The results also show that after immersion tests, the tensile properties such as ultimate tensile strength and Young's modulus decrease.

Heat pipe and Two-Phase Closed Thermosyphon (TPCT) are devices for heat transmission. It consists of an evacuated close tube filled with a certain amount of working fluid or nanofluid. Nanofluids being suspensions of nano-sized solid particles in a base fluid are considered as new mediums for heat transfer in thermal devices. The present study is an experimental investigation which examines the effects of CuO-Acetone nanofluids with different solid weight fraction on the thermal performance of a two-phase closed thermosyphon. Experimental results show that in most cases the thermal efficiency decreased except at 1 %wt concentration. Also in comparison to pure acetone. Thermal resistance of TPCT dectreased in 0.5 and 1 %wt concentrations. In addition, the impact of two filling ratios at 1 %wt concentration was studied.

Separation is usually one of the costly stages in chemical and petrochemical industries. Pressure Swing Adsorption (PSA) is an important unit for gas separation and purification. In order to develop the PSA technology, a pilot plant including four beds each with 1 meter length and 3.5 centimeter diameter was designed and built in Tarbiat Modares University. This pilot includes vaccum pump, control systems and analysis systems to study the operational conditions of beds carefully. In order to test this pilot plant, separation of CO2 /N2 mixture using Zeolite 13X type and carbon molecular sieve was studied. In this study an 8 stage cycle including: repressurization with feed, adsorption, equalization to depressurization, blow down, purge in medium pressure, equalization to pressurization, evacuation and preloading was used. The test have been done in pressure range of 2.7 to 4.7 bar, cycle time of 400 to 640 seconds and 3 product flow rate (1, 2, 3 L/min). The effects of pressure, cycle time and product flow rate were studies, using 560 seconds for a cycle time at 3.7 bar, the maximum purity of 97.6% was obtained.

In this research, the capability of PEG / salt aqueous biphasicsystems were investigated for the extraction of zinc without addition of any extractant. For this purpose, chloride ion as an inorganic extractant used to extract zinc from synthetic zinc solution. The effect of several experimental parameters such as concentration of chloride, PEG, Na2SO4, and pH of salt-rich phase for extraction of zinc(II) were studied. Finally, the existing chloride ion in PEG / sodium sulphatesalt solution, under optimum conditions of pH=1.5, concentration of chloride ion=1 mol/L, PEG1500=50%, (weight percent in solution) sodium sulphate=15%, initial weight of zinc=3.4 mg, the extent of 80% of zinc was extracted and transferred from salt-rich phase into the PEG phase.

In the present study, phenol removal from aqueous solutions using stabilized emulsion liquid membrane by polymer has been studied. For this purpose, the initial emulsion liquid membrane was stabilized by addition of a proper polymeric solution and then it was dispersed in an external phase containing phenol. In addition to the stability of the membrance, the effect of various parameters such as temperature, stirring speed, internal phase concentrarion, the ratio of the phases and pH of the external phase, which affects on the stability of the globules, were studied. The most stable membrane was obtained by addition of 3 wt.% of PIB to the primary emulsion at 30 °C and 210 rpm. The stability time was increased from 10 to 35 minutes that was very stuitable for this extraction. The results showed that the extraction efficiency is increased by increase in the ratio of the phases (Row), internal reagent concentration and acidity of the external phase. Under such condition, more than 94% of the initial phenol from a 100 ppm feed solution was extracted within 35 minutes.

The enhanced oil recovery from oil wet carbonate rocks using wettability alteration mechanism by surface active compounds was investigated. The imbibition tests were done by two typical anionic and cationic surfactants, sodium dodecyl sulfate and hexadecyltrimethylammonium bromide, respectively. The experiments were carried out at one of the Iranian oil reservoir condition. The efficiency of oil recovery by anionic surfactant was approximately equal to brine imbibition at reservoir condition. The results showed that the cationic surfactants have the high potential for enhanced oil recovery by spontaneous imbibition.

The significance of obtaining representative samples in optimizing reservoir management is clearly obvious for petroleum experts. Always, representative samples is tried to collect in preliminary time of production by standard methods. In the basis of valid theories, sampling operation must be done before reduction of bulk reservoir pressure below initial dew point pressure for retrograde gas reservoirs. Because representative samples can be collected just in this limited time. However Equilibrium Contact Mixing (ECM) method claims to obtain original in-situ fluid composition from non-representative samples without time limitation, so it contravenes valid theories. Huge differences between governed standards of sampling that are in the basis of valid theories and the ECM method make us to test ECM in two aspects and compare it to the recombination method. Case studies of Iranian gas condensate reservoirs and synthetic models in the basis of real PVT data are our aspects. For simulating ECM method, detailed characterization of Equation Of State (EOS) in a dynamic process is used for the first time. Also synthetic models are constructed by compositional simulator and sampling is performed in depleted conditions. Then ECM and recombination methods are performed on obtained samples. In conclusion, we find that ECM in a current form is not performable in all gas condensate systems and it needs a modification. Therefore, we propose modified ECM method as an accurate and performable method in every condition. Also, we conclude that accuracy of modified ECM method is reduced by increasing the richness of reservoir fluid. In addition, ECM is investigated in two retrograde gas fields from center and south of Iran as case studies. Therefore accuracy of ECM is checked and endorsed in the basis of rock and fluid properties of Iranian reservoirs. In conclusion, current standards and theories of sampling are contravened by ECM and modified ECM methods. By comparing results of ECM, modified ECM and recombination methods, it is understood that the modified ECM and ECM methods are more accurate than recombination. Hence useless but accurate ECM and modified ECM techniques must be replaced to not accurate but utilized recombination.

Biodegradable polymer of polyhydroxybutyrate (PHB) is an intracellular inclusion that accumulated by certain microorganism under unfavorable growth condition as a carbon and energy reserve. Properties of PHB are similar to polypropylene, and it has been attracted by some different industries. The main problem in achieving the commercial production of this substance is its high final cost. One of the most significant ways to reduce the cost of this valuable biopolymer is the application of high-productivity processes and low-priced raw materials as a substrate. Solid State Fermentation (SSF) is a useful system for production of secondary metabolites using some of the agricultural residues as substrates. This study aims at utilizing the SSF process and microorganism of Wautersia eutropha and investigating the mixture of corn bran and grem as the low-priced substrates in PHB production. Two effective factors including, the composition percentage of substrate and temperature in the production of PHB and enriching the substrate by molasses for the purpose of increasing the productivity of this metabolite in Erlen scale have been evaluated. The maximum PHB production and related productivity at 28 °C and substrate containing 50% corn germ were obtained 3.255 g/kg and 0.045 g/kg/h, respectively.