نشریه شیمی و مهندسی شیمی ایران
سال سی و سوم شماره 2 (پیاپی 72، تابستان 1393)

The use of sulfur widely recommended in the construction industry due to its low price and having specific characteristics such as adhesion and anti-corrosion properties. However, medication of chemical and mechanical characteristics of sulfur by reaction with modifiers and mixing with mineral powders is necessary. In this research, modified sulfur was prepared by reaction of molten sulfur with olefinic additive. Then it was mixed with various amounts of silica, mica and talc fillers to make composite samples. These samples were then tested for tensile, flexural and compressive strength. The test results show that the maximum flexural and compressive strength of the composite samples obtained with 10% talc and highest tensile strength obtained with samples containing 12% mica. Furthermore, addition of silica powder caused a significant increase in the viscosity of the modified sulfur.

In this research, the microwave energy was used to modify the physicochemical properties of ilmenite surface for improvement of ilmenite floatability. The XPS analysis showed that microwave irradiation oxidizes the Fe2+ ions to Fe3+ ones; and the relative content of Fe3+ on the surface of ilmenite increases from 48.5% to 66%. This oxidation process decreases the ilmenite zeta potential; as its PZC (Point of Zero Charge) was changed from pH=5.4 to pH=3.0. The increase of Fe3+ ions increases the chemisorption of oleate ions on the surface of ilmenite; and results in the formation of more insoluble ferric iron oleate. The maximum adsorption of oleate ions occurs at a pH range of 6-7. After microwave irradiation the measured contact angle of ilmenite increases from 91 to 96 degrees. After oleate adsorption, the surface zeta potential of non-irradiated and irradiated ilmenite is obtained -66.3 mV and -78.1 mV, respectively. Thus, the changes in the physicochemical properties of ilmenite occurred by microwave irradiation improves the hydrophobicity and floatability of ilmenite in a wide pH range.

New drug delivery systems are considered as a destructive technology in diagnosis and treatment of disease. Metal Organic Frameworks (MOFs), as a relatively new crystalline nano porous material family have demonstrated promising horizon in drug delivery field due to their unique properties, such as high pore volume, and regular porosity, and the presence of tunable organic linkers within the framework which allow modulation of the pore sizes. This study investigates the potential of an anionic structure belongs to this family in absorption and delivery of a cationic antiarrhythmic drug, Procainamide hydrochloride. Procainamide hydrochloride has a short half-life in vivo and must be dosed every 3-4 hours. Therefore, it is an ideal candidate for controlled release administration. For this initial study, an anionic metal-organic framework formulated as {Zn3(Benzenedicarboxilate)4Dimethylammomium2.8Dimethylformamide} was chosen. This structure has a thermal stability (decomposition point is above 300◦C), and regular porosity. Cationic drug was introduced in to the pores through a cationic exchange process with dimethyl ammonium cations. Maximum loading (7.36%) was achieved after one week. Steady drug release was observed after 24 hours; and more than 70% drug release was obtained after 72 hours.

Transdermal drug delivery systems are considered in recent years as a promising alternative to oral delivery and hypodermic injections.The present work reports on the development of water-in-oil (w/o) emulsions for the transdermal administration of desmopressin acetate. Microemulsion components included: Tween80 and Span80 (surfactants), 1-decanol (co-surfactant), and isopropyl myristate (oil phase). The effects of formulation components, hydrophilic-lipophilic balance (HLB,7-9), ratio of surfactants and co-surfactant mixture to oil phase (Smix/oil,5:5-7:3) and ratio of surfactants to co-surfactant (S/Cs, 2:1- 5:1) on skin flux was evaluated using Design-Expert software 7.0.0. It was concluded that skin flux was increased when S/Cs and Smix/oil were decreased and by increasing HLB skin flux enhanced. The following optimized formulation was obtained by the software: HLB = 8, S/Cs = 3, and Smix/oil = 5.46. Stability and skin permeation of optimized formulation was measured. Based on the results of this research, by reducing the viscosity and increasing the system polarity, drug skin flux of microemulsion increases. Studies of skin permeation show that transdermal drug delivery of large-molecule drugs because of small dimensions and ingredients that act as skin enhancers are possible.

The superabsorbent was obtained from acrylic monomers and cross linker. Ultrasound was irradiated from a probe and bath system. The present work investigated the parameters of solvent, ionic strength, pH, acoustic power and pulse. The results show that increasing glycerol in the solution changes the viscosity of the reaction for the better and increases the reaction rate. Another major finding was that increasing ultrasonic power and pulse hastens the reaction. This is due to more cavitations and production of more radicals. These findings provide a better understanding of hydrogel synthesis and enable us to control the pertinent parameters.To study the swelling behavior of obtained hydrogels, the related experiments were performed in different pH. Results showed that ultrasonic acrylic hydrogel are sensitive to pH. Therefore, these hydro gels are capable for fast drug absorption and release according to the high porous structure and swelling control by these parameters.

In this paper, the structural parameters and electronic charge distributionof TaB2 compound have been calculated and investigated in hexagonal phase with p6/mmm space group. The calculations have been performed with ultra-soft pseudo-potential in the frame work of Density Functional Theory (DFT) by using the plane waves (pw) method that implemented in Quantum Espresso package. In this method, the Generalized Gradient Approximation has been used for exchange-correlation energy. With respect to high quantity of bulk modulus and low quantity of the volume and linear compressibility it's being understood that this compound has a very hard structure. The figure of electronic density distribution indicates a covalent bond between Ta and B atoms also between two neighbor B atoms. The obtained results from this research have good accord with experimental results and other works.

In this paper, a new mixing rule for predicting the surface tension of liquid mixtures is presented. The resulting equation is provided by a combination of Gibbs- Vollmer relation and NRTL activity coefficient model. The proposed model accurately predicts the surface tension of aqueous and non-aqueous solutions in a wide range of concentration. In order to evaluate the ability of this model, several surface tension of binary liquid systems were measured tensiometer (Kruss K20 Easy Dyne). The experimental data available in the literature also were used to prove the accuracy of the model. The results showed that the proposed model can predict accurately the experimental data in a wide range of concentration. Data of non-aqueous solutions were predicted with high precision as absolute average error of less than 1% was achieved for most of these systems. For aqueous systems with a high degree of non-ideality the deviation from experimental data is higher than other systems (up to 10%). This error occurred because the molecules with strong hydrogen bonds that can form a complex non-ideal mixture, even the use of accurate activity coefficient model could not eliminate completely the error. However, the model predictions are satisfactory and acceptable.

In the present study, a bubbling fluidized bed was constructed. Three kinds of rotating distributors with hexagonal, blade, and swirling configurations of holes have been studied. The analysis of the experimental data showed that rotational speed and input air velocity are the key parameters that influence the fluidization quality and its minimum velocity. Through the comparison of different configurations of rotating distributors in bubbling fluidized bed, it was observed that the blade configuration of holes has the best operation in terms of fluidization quality.

In this research the contamination and concentration of various elements were studied by measuring chemical and biological parameters such as chloride and bicarbonate, BOD5, COD, pH, EC, TDS and metals (Cr, Cd, Pb, Zn, Fe, and Mn) in the leachate samples and also moisture, chloride, potassium, bicarbonate and pH in the various depth of landfill soil samples.The value of BOD5/COD was 0.35, this result shows that this site is old landfill and leachate is biodegradable. Due to composition of organic compounds of leachate in soil and production of organic acids and carbon dioxide, pH of soil initially reduces and liquid limit increases but plastic limit will not change much. As a result plastic range increases but in the depth of the soil more increase occurred.

Hot Filter Cake (HFC) is one of the valuable residues in cathodic zinc producer factory inIran that isobtained in cobaltremoval formzincoreleachingstage.HFChas15-25% zinc, 0.5-1.5% Co, 3-8% Mn and some minor other elements. This cake is secondary source of these elements. In this investigation sodium hydroxide was used as selective leaching of zinc from HFC. At high sodium hydroxide concentration zinc ion dissolved as complex.Effective parameters such as sodium hydroxide concentration, temperature, solid liquid ratio, agitation rate and particle size were studied on zinc recovery. Results showed that sodium hydroxide concentration and temperature has significant effect but particle size has minor effect of zinc recovery. Final results maximum zinc recovery obtained 95.66 percent in two stage leaching at temperature 95 0C, sodium hydroxide concentration 8 M, solid liquid ratio 1:10, agitation rate 850 rpm and particle size 38-75 micron.