Sharif Digital Repository

This thesis focouses on the preparation and super-swelling behavior of two superabsorbent hydrogel. In the first section, a new superabsorbent hydrogel based on agar was prepared and the effect of the ratio of some components(AA, AAM, MBA, APS and agar) on the swelling capasity of the hydrogel was studied. Maximum water absorbency of the optimized final product was found to be 614.5 g/g in distilled water. The structure of the hydrogel was characterized by FT-IR method and morphology of the samples was examined by scanning electron microscopy(SEM). Swelling behavior properties of optimized hydrogel sample in different swelling medium were investigated. In the second section, we report the... 

With the current demands in alternative methods of energy production and increased utilization of existing energy sources, microbial fuel cells have become an important field of research. In a microbial fuel cell, organic and inorganic compounds can be oxidized by microbial catabolism at the anode to generate direct electricity. A kind of microbial fuel cell (MFC) is sediment microbial fuel cell (SMFC) consists of an anode electrode embedded in the anaerobic sediment and a cathode electrode suspended in the overlying aerobic water. microorganisms produce electrons by oxidation of organic or inorganic compounds in the sediment at anode electrode, while oxygen is reduced in the water by... 

Discharging wastewater effluents to water bodies has many detrimental impacts on water quality. Thus, to prevent issues such as eutrophication and oxygen depletion, nitrogen removal is often required in wastewater treatment plants. Biological nitrification and denitrification, in comparison to physical and chemical methods, is more cost-effective and environmentally friendly, and this makes it one of the most commonly used approaches for nitrogen removal. In this work, nitrification and denitrification process and the effect of sulphate on this process is studied in a moving bed biofilm reactor (MBBR). The method used is modified LUDZACK-ETTINGER (MLE) which has an initial denitrification... 

Nitrate can be used as an oxidant in a cathode chamber of microbial fuel cell. Nitrate is known to be a pollutant of water particularly underground water and is considered a carcinogen of water. Nitrate was used in the cathode chamber of a microbial fuel cell as an oxidant that lead to simultaneous generation of electricity, removal of organic matter in anode, and removal of nitrate in the cathode. Using nitrate generated a voltage of 151 mV with an external resistance of 1000Ω. The maximum power density achieved was 1.375 mW/m2 with an external resistance of 800Ω. Seven days after the cell became operational and without the presence of a catalyst, the amount of COD had decreased by 25... 

With the aim of making a pilot in two-steps, this thesis at 4 month accomplished. In first step, municipal sewage after passing of a septic tank loaded with daily 2 or 4m3/m2 rate to a vermi-filter while removal rate of COD was 83 and 64 percent respectively. In addition, the turbidity removal rate was 92 and 83 percent respectively. The results showed that vermi-filter is a suitable and cheap way for on-site wastewater treatment that is environmentally agreeable and odorless. Furthermore, the treated sewage is suitable for irrigate and flush tank usage. In the second step, for ground water denitrification, a synthetic wastewater with high nitrate, which nitrate is initially 13.5ppm NO3-N... 

To investigate boiling heat transfer characteristics of nanofluids, transient quenching¬ experiments of a high temperature silver sphere in water-based nanofluids with Ag and TiO2 nanoparticles were performed. A silver sphere of 10 mm in diameter at the initial temperature of 700o C was quenched in the nanofluids at the temperature of 90o C. The results showed considerable reduction in the quenching ability of nanofluids compared to that of pure water. The presence of nanoparticles in water caused film boiling mode to vanish at lower temperatures depending on the mixture concentration. Computed heat transfer rates in nanofluids were lower than those in pure water. In the quenching... 

Solid oxide fuel cells as high temperature electrochemical devices draw much attention in the last decades due to their fuel flexibility, high efficiency and low pollution. However, lowering operating temperature from about 850°C to around 650°C without significant overpotential loss, in order to lower costs and increase cells life time has remained a challenge. Recently, a new family of mixed ionic and electronic conducting ceramics (MIECs) which are formulated Ln2NiO4+δ (Ln= La,Nd,Pr) and crystallized in Ruddlesden–Popper structure, have been regarded as appropriate cathode materials for the low or intermediate temperature solid oxide fuel cells (IT-SOFC). Amongst these compounds,... 

Silver and gold are precious, expensive metals and are used in various applications, such as jewellery and ornamentals, electronics and optics. In the present study, soda-lime glass surfaces firstly were activated with acidic stannous chloride solution. Then, silver and gold were coated on these surfaces via simultaneous spraying of two solution: A silver- or gold-complex bearing solution and a reducing agent (Dextrose for Ag and H2O2 for Au) bearing solution. For silver coating, the effect of various parameters such as time, reducing agent concentration, number of passes, presence and concentration of Urotrpin and Decamethylcyclopentasiloxane (DMCPS) as microstructural modifiers and... 

In this research, a novel nanofiltration membrane was used to separate nitrate from water as a nitrogen-containing compound. The membrane was fabricated by interfacial polymerization on the modified polysulfone substrate. To improve the efficiency of nitrate removal, several surface and bulk modifiers were used. As modified with LiCl and PVP polymer, the substrate matrix was modified to have the highest porosity to reduce the mass transfer resistance and the much surface area to form a polyamide layer on it. The polyamide layer was then synthesized by interfacial polymerization using a blend of MPD and PIP in different ratios (1: 1 optimum ratio) in reaction with TMC (optimum concentration... 

Industrial wastewater treatment has always been one of the significant human being problems for the years. In particular, sewage containing heavy metals that, if discharged into nature, would have irreversible effects on the ecosystem and human health. Due to their toxic nature, heavy metals will reduce the efficiency of wastewater treatment systems if they are not efficiently treated. Also, the removal of Nitrate from the wastewater, which is one of the most stable nitrogen oxides, has always been a serious human problem in the treatment of effluents due to their high solubility in water. The simultaneous presence of nitrate and heavy metals in the effluent will cause many problems in the...