Sharif Digital Repository

Xanthan is a water-soluble anionic polysaccharide that is produced by anaerobic fermentation using the bacterium Xanthomonas campstris. Xanthan is used in various industries, including food industry and oil industry because of its appropriate rheological properties. For this reason, various studies have been done on the production and recovery of xanthan. In this study conditions for recovery of xanthan gum were investigated and optimized by response surface methodology. Initially xanthan production under optimal conditions that determined in previous studies i.e. YM broth at 30 ⁰C without pH control was performed. After production, the gum separation was investigated using food solvents... 

Biological removal of sulfur compounds from petroleum is one of the major attractions of environmental technologies in the oil industry. Inefficient sulfur removal in refining processes causes sulfur oxides (SOx) production after combustion, which has adverse effects on the environment.Today the most common way to remove sulfur from crude oil is Hydrodesulfurization which has poor performance in removing some heterocyclic compounds such as thiophenes. Increase the amount of sulfur in the remaining oil reserves and the other hand, more stringent environmental regulations, has led researchers to development and invent new methods for desulfurization. Biological desulfurization is one of these... 

In this research, Response Surface Methodology was applied to study the effects of Na-Montmorillonite and glycerol on some functional properties of corn starch films. Films were prepared by casting method according to central composite design. No antimicrobial activities were observed against Escherichia coli and Staphylococcus aureus. The minimum of hydrophilicity and the maximum of tensile strength were obtained by maximization of clay and minimization of plasticizer in the considered range, which resulted in minimum transparency. Biodegradation of corn starch/glycerol/Na-MMT nanocomposites by soil burial according to ASTM D6400 and enzymatic degradation tests were carried out for up to 6... 

Vitamin C is an essential for the survival of human, animals and plants. Human and most animals can not produce vitamin C in their bodies, thus the need to produce vitamin C as a supplement is necessary. Nowadays, for the industrial production of vitamin C, two Chinese and Rychstyn methods are used, the first method is a two-step method which is accomplished biological and the second method is done chemically. In Chinese method, first step, which is the most important step is production of L-sorbose from D-sorbitol by Gluconobacter oxydans bacteria .Thus, in this study it was attempted to optimize the production of L-sorbose to be used in industrial production of L-ascorbic acid. In... 

To investigate the metallic cation (Ni and Pb) removal performance of the rice barn-obtained biochar which was modified by nitric acid and titanium nanoparticles (TiO2) adsorption tests were conducted in continuous and non-continuous systems. First section addressed the characterization of the synthesized sorbents using field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy dispersive X ray spectroscopy (EDX) and sorption-desorption porosity analysis (BET). In the second section, the effect of different parameters such as pH, initial concentration of the metallic ions, temperature, time, sorbent content, ionic... 

Photocatalytic degradation is one of the developing modern and effective methods for decontamination of hazardous pollutants of chemical industrial wastewater. In spite of great developments in this field of research and its various advantages, finding a process with high efficiency and optimization of the operating parameters are still required to be investigated. In this study, the photocatalytic degradation of 2-Nitrophenol under natural sunlight irradiation using industrial photocatalysts such as TiO2 (Hombikat), ZnO, WO3 and TiO2 (P25) was investigated. The photocatalysts were characterized by the XRD, BET, SEM and DRS tests and the effects of significant operating parameters (the... 

Roller compacted concrete is a dry concrete with zero slump which is constructed in layers. Roller compacted concrete dams are generally weak in interlayers. The bonding strength and permeability of the interlayer affect the performance of the dam’s structure and its safety. In this study, the mechanical characteristics and the permeability of the interface layer of RCC are investigated by considering three key parameters, including water-to-cement ratio (w/c) of concrete, w/c ratio of bedding mortar and time interval between pouring each layer. More than 300 RCC specimens are prepared. To evaluate the properties of the interface between the mortar and the first layer surface, various tests... 

Biodiesel as an alternative fuel for fossil diesel has many benefits such as reducing regulated air pollutants emissions, reducing greenhouse gases emissions, being renewable, biodegradable and non-toxic. In this study, used frying oil was used as a low cost feedstock for biodiesel production by alkali-catalyzed transesterification. The used frying oil was originally a mixture of various oils obtained from vegetables that are native to Iran. The design of experiments was performed using a 5-level-5-factor central composite design coupled with response surface methodology in order to study the effect of factors on the yield of biodiesel and optimizing the reaction conditions. The factors... 

In this study three type of nanofiltration membranes were prepared from PVC for water softening; (i) asymmetric PVC nanofiltration membrane, and two different thin film composite (TFC) membranes: (ii) polyamide (PA)/PVC composite membrane (iii) poly vinyl alcohol (PVA)/PVC composite membrane. Asymmetric nanofiltration membranes were prepared by phase inversion. The effect of PVC concentration, solvent (THF) and additive (PVP) on morphology and performance were studied by scanning electron microscopy (SEM) and measuring pure water flux and salt rejection. Increasing PVC concentration decreased pure water flux and increased salt rejection. Adding tetrahydrofuran(THF) decreased the pure water... 

Nowadays, due to depletion of fossil fuels and the emission of green house gases, biodiesel has attracted lots of attention as a renewable, non-toxic, and biodegradable fuel. Biodiesel can be produced from different resources such as vegetable oil, animal fat and algae oil. In this study, waste frying oil was used as a raw material that can reduce the probable hazardous effects of its disposal and produce a clean fuel at the same. Biofuel was produced through an enzymatic method using the whole cell of Rizopu oryzae (a filamentous fungus) in both immobilized and free forms. In order to find the optimum conditions for biodiesel production, four variables including temperature, methanol to oil... 

In this thesis, photocatalytic oxidation as a potential method for the treatment of organic environmental contaminants is deeply investigated. While the photocatalytic degradation of various organic compounds under UV light irradiation has been widely investigated, visible-light-induced photocatalytic degradation of low-levels of the pollutants such as Dibenzothiophene (DBT) and 2-Nitrophenol (2-NP) are occasionally reported. In the present work, Lanthanide / Polyethylene glycol -modified TiO2 (La/PEG/TiO2) and Fe,Cu,S/TiO2 have been successfully synthesized by a sol–gel method. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission... 

Sulfur compounds are very undesirable and result in Corrosion in metal equipment, air pollutions and poisoning of refinery Catalysts such as reforming Catalyst. Therefore, application of Hydrodesulfurization (HDS) process in order to decrease the amount of sulfur in petroleum cuts has a great importance. HDS process is the most usual and efficientmethod for sulfur removal. In this method sulfur compounds at vigorous operating conditions such as high temperature and pressure in the presence of catalyst react with hydrogen and produce hydrogen disulfide and hydrocarbon. Sulfided Co–Mo catalysts are widely used in this process.
The aim of this study is to prepare and improve CoMo/γ-Al2O3... 

In the past years, upstream processes have been receiving a considerable R&D investment and commercial attention. The downstream processes have, however, been overlooked causing a production bottleneck that is shifting the costs of production from up to downstream. The need to develop more efficient and cost-effective separation and purification processes is, thus, crucial in order to improve process efficiency and economics keeping the required high standards of quality for market approval. In this research, promising aqueous two-phase systems (ATPS) containing Tween 20 as a quite biocompatible non-ionic surfactant and different salts (K3Citrate and NaH2PO4) were prepared and their... 

Many parameters affect the process quality and component properties in the sheet metal forming. In this study, the use of addendum geometry and initial blanks as effective parameters in improving the quality of the manufactured workpiece. So the purpose of this study was to investigate the effects of addendm geometry on end-product quality using inverse finite element method are based on unfolding technique, Artificial Neural Network and response surface method. The design variables include thickness strains in the center and wall of the workpiece, in contrast the initial blanks estimation and the addendum geometry effects, which include length and radius flange, are considered as output...