Sharif Digital Repository

In many industrial processes there is an urgent need for flocculation of suspensions that can’t flocculate easily through the time so flocculants are wildly used in these industries. Polymeric flocculants because of less needed dose are economically used. Polymeric flocculants divided to three categories: nonionic, anionic and cationic those are almost from polyacrylamide group. Studying mechanisms of flocculation, one of the main factors that enhance flocculation is molecular weight of polymer. Hence one of the goals of this work is to improve molecular weights of synthesized polymers as much as possible that is followed by viscometery, NMR, DSC and FTIR studies and ended with jar test.... 

Using field assisted dissociation model and with a classic view the dissociation probability is calculated when it a molecule is exposed with a Ti:sapphire laser with wavenumber of 800nm and the energy of . using gradient optimization method we find a tailored two rectangular laser pulse for controlling the dissociation of C-H bond of . Using classical method reduced the complicacy of solving schrodinger equation. In our optimization method in contrast with the usual controlling method experimental data is not needed and this reduced the controlling costs.

 

The aim of this study is to mimic water oxidizing complex to find new materials and also to understand their rules in this matter. To achieve this, manganese complexes containing 2,4,6-tris (2-pyridyl)-1,3,5-Triazine, 1,10-phenanthroline, 1,10-bipyridine, Schiff base, amino acids, 2,6-pyridinedicarboxylic acid, 2-pyridinecarboxylic acid have been synthesized and characterized by elemental analysis, IR, EPR, ESI-MS, electronic absorption spectroscopy, electrochemistry, X-ray diffraction and oxygen evolution in presence of oxone and Ce(IV). It is shown that the reaction between Mn(II) complexes containing 2,4,6-tris¬(2-pyridyl)-1,3,5-Triazine, 1,10-phenanthroline, 1,10-bipyridine,... 

Natural boron consists of two stable isotopes, mass 10 (19.3%) and mass 11 (80.7%). 10B isotope has a large thermal neutron capture cross-section and it therefore, used widely in such aspects as modern industry, military equipment, medical science and so on. specially the demand of atomic energy industry for the boron isotope is increased severely. So the separation of 10B from natural boron has received very wide attention at present. There are many kinds of methods on the boron isotopes separation, such as chemical exchange reaction and distillation in boron trifluoride method, ion exchange in boric acid solution method, counter current recycle membrane cascades in boron trifluoride... 

Prediction and calculation of shielding tensors of H, C, F and P nuclei of different molecules has been the subject of much research, because these nuclei have the greatest importance in NMR experiments. The optimum wave functions and calculation method were obtained using empirical models and factorial design. Based on preliminary experiences, the following four factors at two levels were selected: electron correlation, triple-ξ valence shell, diffuse function and polarization function. The wave functions for calculating gas phase 1H and 13C chemical shifts of various types of alcohols, amines and simple hydrocarbons were optimized using empirical model. The B3LYP/6-311+G wave function is... 

Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of... 

Natural boron includes two stable isotopes 10B and 11B with 19.3 and 80.7 weight percent respectivley.10B isotope has a high thermal neutron absorption cross section. So isotope 10B material is suitable for making atomic reactor control rods. Other and even more important applications of 10B are in disclosing neutrons in order to measure neutron reactors fluxes and also are in nuclear physics laboratories and medical radiation. This isotope also is used in the pharmaceutical and the military industries. There are several methods for separating boron isotopes. Among the distillation methods, thermal diffusion of BF3, distillation of BF3, distillation of methyl borate, boric acid distillation... 

Membrane bioreactors can replace the activated sludge process and the final clarification step in municipal wastewater treatment. The combination of bioreactor and crossflow microfiltration allows for a high chemical oxygen demand (COD) reduction of synthetic wastewater. In this study, experimental data from a laboratory scale membrane bioreactor are presented. In order to investigate the influence of various operating parameters such as hydraulic retention time (HRT), biomass concentration and organic loading rate on organic pollutant removal, the pilot scale submerged membrane bioreactor (SMBR) with a Polyvinylidene Fluoride (PVDF) hollow fiber membrane module was conducted using synthetic... 

This study presents the experimental investigation, the effect of cement based chemical materials (Portland cement as a repair material No1. and 2 other cement base chemical materials) to upgrade the structural behavior of reinforced concrete slabs built with low quality (porous) concrete. The main issues focused in this investigation are: (i) the effect of repair on the flexural behavior of RC slabs in terms of ultimate capacity and ultimate mid-span deflection and ductility of specimens, (ii) the influence of repair materials on failure modes and (iii) evaluating the efficiency of different materials on decreasing the porosity of concrete by ultrasonic test. Because materials used in this... 

This study presents the experimental investigation, the effect of cement based chemical materials (Portland cement as a repair material No1. and 2 other cement base chemical materials) to upgrade the structural behavior of reinforced concrete slabs built with low quality (porous) concrete. Because materials used in this study are cement base it is expectable to behavior same as base concrete that its result is better compatibility with base structure against external factors. Other advantages of the use of these materials are consideration of economical and construction aspects. A total of four reinforced concrete column (200x200x800 mm) with low quality (porous) concrete have been built,... 

This work investigates adsorption and possible dissociation of a number of small molecules on small clusters and carbonic surface. Theoretical study of carbon monoxide adsorption on SixGe4_x(x=0–4) nano-clusters has been carried out using MPW1B95 density functional. The geometry, adsorption energy, charge distribution, and vibrational frequency of CO adsorption on all possible structures were investigated. The maximum vibrational frequency changes occur in the bridge structures while the most stable structures occur when CO adsorbs on one silicon atom in a flat surface. Adsorption energies of CO on one Si atom are by far more negative than the corresponding value for on Ge atom. Theoretical... 

Hydrodynamic mesoscopic equations are solved using boundary integral method to investigate the coarsening dynamics of two dimensional nanodroplets. The dynamics is probed by locating two drops on homogeneous, chemical heterogeneous and physical heterogeneous substrates respectively. For homogeneous substrate, the effect of different parameters like droplets distance, slip boundary condition, surface contact angle and disjoining pressure type on the dynamics is studied. Results reveal that increasing the contact angles to values larger than a critical value may qualitatively change the coarsening process and the profile of the disjoining pressure can appreciably modify the coarsening rate.... 

A droplet placed on the boundary of two solids with different wettabilities will move to the more wettable part. This is a well-known phenomenon and has been extensively used in a variety of processes and applications ranging from biological systems and ink jet printing to the commercial lab-on-a-chip. Because of its importance, many studies are conducted around this phenomenon. The difference between the equilibrium contact angles of the droplet on the two parts gives rise to an interfacial driving force which moves the droplet. Such a motion is not continuous as the droplet slides to the more wettable area, the driving force diminishes and consequently the droplet stops. A non-stop motion... 

In the present study , operation of a laboratory scale sequencing batch reactor (SBR) was evaluated to treatment of synthetic wastewaters containing ethylene glycol. Studies carried out with a plexiglass bioreactor whith effective volume of 18 lit.Aeration was supplied via two air diffusers that set at the bottom of the reactor. Synthestic wastewater containing ethylene glycol and molasses as carbon source and other nutrient such as diammonium hydrogen phosphate as phosphor source and urea as nitrogen source for biological activities was composed at the laboratory. To optimization of this reactor three parameters – aeration time, chemical oxygen demand and sudden change in arganic loading... 

We studied dynamics of droplets inside channels under surface forces created by chemicalsteps on the channel walls. A multi-component Shan-Chen lattice Boltzmann method isused for this purpose.The effects of parameters such as the channel height, viscosity anddensity ratios on the results were investigated for homogeneous and grooved substrates. Alsoan analytical solution was developed for droplets under chemical heterogeneities in channels with smooth surfaces. The solution considers a general condition, namely, asymmetry of the contact angles on the top and bottom walls, the viscosity of the gas as the second fluid and the effect of the channel height. Then using Shan-Chen lattice... 

In this thesis, we study the application of graph theory in chemistry. Such as, molecular graphs, modeling, algorithms, topologicalindicesandsoon. Themaingoalinthisresearchis collecting problems in chemistry which have mathematical models, specially in graph theory. Also we study the methods applied to them by considering the problems in chemistry with mathematical approach. In particular case, dendrimers and other structures of chemistry have been attributed to some graphs, where by studying their graphical parameters, like connectivity, independent sets, perfect matchings, isomorphism and topological indices and other parameters, we obtain some results in chemistry  

In this project, cellulose acetate butyrate (CAB) nanofibrous membranes in order to separate the contaminants of an industrial wastewater were prepared. Electrospinning process that is an effective method to fabricate nanofibers was used to prepare the membranes. Since various parameters affect this process and fibers morphology, optimization of these parameters is necessary for preparation of improved membranes. So the effect of parameters of solvent system, polymer concentration, applied voltage, distance between the tip of needle and collector, and rotational speed of collector on morphology and diameter of the nanofibers was investigated. Scanning electron microscopy (SEM) and image... 

One of the most important environmental problem across the world is global warming due to increase in greenhouse gas concentration in atmosphere. The main objective of this thesis is to try to find some ways that lead to stop or decrease, increasing trend in greenhouse gas emission, espicialy CO2. The investigation of the sources of emission of CO2 and proposed methods to decrease the rate of the emission, reveals that sepration of CO¬2 from combustion products and its storage is the only promising solution of this problem. The common feature of all propsed methods for elimination of CO¬¬2 from combustion gas, is the presence of a separation step. The addition of this separation step to... 

Optimized structure of the chlorophyll a and b molecules was obtained for LDA and GGA approximation by SIESTA package. Calculation illustrate that tails are curved in the optimized structure for both chlorophyll a and chlorophyll b molecules; in addition, Antennas, which are attached to the head of molecules, are located in optimized-spatial state. This optimized structure of chlorophyll a is similar to the calculated structure in ref [42]. Electrical dipole are calculated from ground state electron density of chlorophylls. Total electrical dipole of chlorophyll a for GGA and LDA approximation are 4.662 and 4.813 Debay, and these value for chlorophyll b are 1.435 and 1.302 Debay,... 

The main purpose of this theses is to synthesize graphene by chemical vapor deposition (CVD) of a hydrocarbon gas such as methane on the nickel foam substrate and then to characterize this kind of graphene. Graphene is a single layer of carbon atoms, discovered in 2004, which has led mankind to new eras in all fields by its extraordinary features such as extra high electron mobility, high thermal conductivity, excellent mechanical strength, optical transparence and extra high specific surface. The advantage of this method compared to other methods is that the graphene generated has a better structural quality. Graphene foam firstly, because of the continuity of the foam structure, has better...