فهرست مطالب سپیده سلطانیان

Sulfate is one of the major ions in natural waters and wastewaters. The presence of sulfite is important in terms of that is converted into sulfate and sulfide in environment. Because of the high solubility and stability of these ions and consequently their health problems, removal of them from aqueous solutions is a sophisticated issue. This study was conducted aiming to evaluating the impact of electro coagulation process in the removal of highly concentrated sulfate and sulfite ions from aqueous.
This experimental study was carried out on laboratory scale using a glass tank with the volume of 500 ml and 2 aluminum electrodes. Then, the synthesized samples containing concentrations of 500 and 1,000 and 1,500 ppm sulfate and sulfite were transferred to a reservoir and the removal of ions in the retention time intervals of ,30, 60 and 90 min and voltages of 10, 20 and 30 volts were examined.
The most sulfite removal rate was 80 percent and voltage 30 and retention time of 90 minutes with concentration of 1000 mg/l. And the most sulfate removal rate was 72 percent and voltage10 and retention time of 90 min with concentration of 1500 mg/l.
The results show that the electrocoagulation technology can also be used in high concentrations by adjusting the suitable retention time, initial concentration and voltage.

Azo groups of dyes used widely for coloring yarn. Methylene blue is one of this group's dyes therefore with benzene rings in its structure caused the toxicity and its persistence in the environment. So that the its deficiency of proper treatment can cause the irreparable damage to the environment. One of the ways to removal these dyes from natural sources are absorbed by the absorbent. So the aim of this study is Kinetic and isotherm study of methylene blue adsorption by powdered pumice from the aquatic environment. Adsorption process was investigated in vitro at neutral pH, a constant concentration of dye and adsorbent dosage. The residual concentration of the dye solution through adsorption was measured at a wavelength nm 665 by using a spectrophotometer (Cary 50 manufacturers of Perkin Elmer). In order to understand how to adsorption, obtained data were fitted with Langmuir, Freundlich, Temkin, Harikens-jura and Dubinin-Radushkevich isotherms and Pseudo –first –order, Pesedo – second – order, Intraparticle diffusion and Elovich Kinetics. Results showed that in the between of five isotherm models, the adsorption process is most obeyed of Harikens-jura isotherm (R2=0.9914). Also the adsorption process has appropriate obeyed of both Langmuir and Freundlich isotherms (R2=0.9633 and R2=0.9365) and it is means that the adsorption process occurs in a mono- layer and multi-layer. The low of mean free energy (E= 0.323 KJ/mol) in Dubinin-Radushkevich showed that the physical absorption process is dominant adsorption. Also adsorption process is obeyed of pseudo – second – order model. According to the results, can say Methylene blue adsorption multi -layer is most occurs than mono- layer and the pumice is the effectiveness adsorbent for removal methylene blue dye (RL=0.2).

Nitrite and nitrate are preservatives that have been used in meat products (sausages) and include carcinogenic effects. The aim of this study was determining the mount of nitrite and nitrate in different types of meat products marketed in Kermanshah. The method of study is descriptive – cross-sectional. 100 samples were taken from meat products factories (19 factories) randomly. Nitrite and nitrate level was determined by spectrophotometric method. The mean differences were analyzed using ANOVA and T. Test methods. Level of nitrite and nitrate in different types of meat products were between 96 – 168 ppm respectively and 167 – 763 ppm respectively. Level of nitrite and nitrate in 76% and 70% samples were up to 100 ppm and 500 ppm. The difference between the means of nitrite and nitrate level in sausages with different meat content was not significant. The differences between the means of nitrite and nitrate level in different factories were significant (P<0.05). High level of nitrite and nitrate in meat products is worrying. Consequently observation the standards and measures these food additives in sausages are essential.