Sharif Digital Repository

The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Since in such systems the surface structure plays a key role, in the first part of this study, the performance of the hierarchical nanostructures is explored. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. The flow is considered between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics (MD) method. The size of the nanostructures and the distance between them have been studied to find whether a design with maximum flow rate exists. The nanostructures have two... 

Reverse osmosis (RO) is by far the most widely used membrane desalination process worldwide. The RO process depends on the properties of semi-permeable membranes which allow the separation of water from a salt solution by applying external pressure higher than the osmotic pressure on the seawater. The main problem in membrane separation process is the fouling of the membrane walls, which decreases the permeate flux. Having spacer filaments in the feed channel has been proven to dynamically change the concentration boundary layer and preventing fouling. The impact of spacer configurations (cavity, zigzag and submerged) on the alleviation of concentration polarization and the enhancement of... 

Nowadays, water desalination is a widely-used method for producing clean and fresh water. Recent researches in this area have mostly focused on Reverse Osmosis technology which is one of the most efficient technologies in water desalination. A new idea to increase the efficiency of a recently-designed reverse osmosis membrane called “Honeycomb Carbon Nanotube Membrane” is presented through molecular dynamics simulation. Although in this study only the inlet area of the honeycomb structure which is a Y-shaped entrance, is modeled and studied, but obviously, any improvement in the membrane inlet, equals better results at outlet which means a more efficient desalination process. Present thesis... 

Different parts of this research are focused on developing FO membranes and improving their performance. For this purpose, thin film composite (TFC) membranes with fixed composition of polyethersulfone/polyamide (PES/PA) have been used to investigate the effect of nanocomposites containing transition metal dichalcogenides (TMDs) on their performance. The support layer in all cases is PES, which is prepared through the phase inversion process and does not contain any nanofillers. The modification process takes place in the polyamide layer by dispersing the desired nanoparticles in the aqueous monomer solution necessary to form this active layer. Identification and characterization of... 

Isfahan Zirconium Production Plant (ZPP) is one of the most important plants in the nuclear industry of Islamic Republic of Iran. The wastewater of this plant contains high values of Sodium, Chloride, Nitrate and low values of Calcium, Magnesium, Zinc and Zirconium ions. Its release has been banned by international and national law because of the dangers and toxicity of its ions for the environment and living organisms. Therefore, its refinement as a compensation of Iran’s water resources in agriculture and drinking water has received a major consideration. Among the common methods to removal of these ions, membrane process method is selected due to it's major benefits such as not producing... 

Rapid preparation of a homogeneous mixture is essential for many chemical and biological applications, such as micro-scale biological-chemical agent detection, drug delivery, and DNA hybridization. Some mixing systems have a micro-scale geometry, which results in a very slow mixing process, mainly due to laminar flow in these systems. Mixing in a slow flow is performed only by molecular diffusion. In the absence of any disturbances, increased mixing is not possible simply by diffusion. Accordingly, a suitable and innovative method to improve mixing for such systems is required. Induced charge electro-osmosis is a new field of electro-osmotic flow, which performs better than conventional... 

Water is the most essential human need and the lack of fresh water soon is one of the biggest problems of mankind. One way to deal with the lack of fresh water is desalination of seawater. Seawater desalination is done by different thermal and membrane methods. In this research, the methods and history of freshwater supply methods and the role of chains in the progress of seawater desalination, and the measures taken in the field of seawater desalination have been investigated. Among the various methods discussed and proposed in this research, it was concluded that reverse osmosis membrane is available and has an acceptable economic efficiency compared to other methods. After choosing the... 

The world's freshwater resources are rapidly decreasing due to population growth, industrial and technological progress, successive droughts, climate changes, increased food demand, and poor management of water resources. Using desalination methods is one of the ways to produce the required freshwater. Several methods have been developed for desalination. The most widely used method is reverse osmosis (RO). In this thesis, an electrodialysis (ED) desalination system was designed and modeled using up-to-date and reliable articles. This modeling was done in EES software and after validating that, the effect of considering Donnan's potential was investigated. At the 60 ppt concentration of the... 

Osmotically assisted reverse osmosis (OARO) assimilates high efficiency due to non-thermal processes and accessing high salinity. This makes it suitable for high water recovery for the purpose of zero- and minimal liquid discharge desalination. Moreover, forward osmosis (FO) has low fouling efficiency which makes the operating costs of cleaning and replacement lower. This study aims at incorporating OARO and FO in a novel configuration with multiple inlet of the diluted draw solution to the regeneration section. Pinch analysis with simplifying assumptions was carried out for FO and OARO standalone stages. The results showed that pinch point in FO resides either on the beginning or at the end... 

Nowadays, water and energy shortage is the main concern of many industries. Every saving that could be done is valuable. In the first step of this project, energy recovery devices that are used in reverse osmosis systems, are reviewed and advantages and disadvantages of each system are investigated. These apparatuses save energy by recovering high-pressure energy from leaving brine and reduce the energy consumption of the device. The main focus of this study is energy consumption of the device that is used for desalination of seawater in reverse osmosis systems and on this basis, different energy recovery devices are compared. According to the investigation, results showed that most of the... 

Water is essential for human life and other organisms. Increasing population and consequent increase in water consumption has made freshwater scarcity a global problem. Desalination of saline water sources is a long-term solution to this problem. One of the most challenging issues in desalination is the management and disposal of brine. Disposal of brine into the sea and surface waters is the primary solution for brine management. Due to the environmental problems caused by the discharge of brine into the sea and surface waters, the concept of zero liquid discharge has recently been considered. In this research, an economic study of reverse osmosis-electrodialysis-crystallization structure... 

Reverse osmosis membranes are one of the most common methods of desalination of water in the world today. In the meantime, aromatic polyamide thin-film composite reverse osmosis membranes have one of the best performances and can be widely used in industry. This project aims to make surface modifications on the made raw membranes and increase the degree of crosslinking to improve the functional properties of the membrane, such as the percentage of salt rejection and the flux of permeate, and the reduction of fouling. For this purpose, polyvinyl alcohol and l-arginine along with maleic anhydride as the crosslinking agent and hexamethylene diisocyanate were used for surface modification of the... 

The current work studies the economic investigation of reverse osmosis (RO) desalination unit and multi-effect distillation (MED) considering the average global and also Iran circumstances. Technical and operational parameters are taken into account for economic modeling of both methods to choose the proper and economic method for water desalination based on different operational conditions. The cost of the desalination plants is investigated in two different parts of capital cost and operating and maintenance cost. Capital cost is divided into direct and indirect cost subsections. Based on these calcifications, the effect of economic parameters on change of capital cost and operating and... 

The purpose of this project is to correct the surface defects of the reverse osmosis membrane. The membrane tested in this project was a thin film made of three layers of polyester, polysulfone and polyamide. These three layers provide mechanical resistance to operating pressure, suitable substrate for polyamide layer synthesis and membrane selectivity, respectively.In order to improve the surface properties and modify the reverse osmosis membrane, it was first attempted to coat it with a protective layer of polyvinyl alcohol, then by modifying this layer and improving the properties of polyvinyl alcohol and synthesizing the sulfite agent on it by the esterification reaction, to the best... 

In this thesis, using superstructure concept, a method is presented to synthesize of new structures for thermal desalination processes along with their structural and operational optimization. The proposed superstructure is capable of producing various common (feed forward, backward, parallel cross feed) and non-common structures in evaporators, as well as in combination with flash stages and thermal vapor compressor. By using the GA (Genetic algorithm), the superstructure has been optimized to identify the optimal structures in both Iranian and international economic scales. Also comparisons were made between conventional structures at optimum state, to suggest superior structures at... 

Today reverse osmosis (RO) is the dominant technology for desalination. Most of commercially available RO membranes are polyamide thin film composite (TFC) types which exhibit good performance. However, the major obstacle for application of polyamide TFC RO membranes is fouling which can be mitigate by surface modification.In this research, surface modification of fabricated aromatic polyamide TFC RO membranes was carried out using UV-initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g/L). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm)... 

Due to population growth, per capita change and heterogeneous distribution of water resources, forecasts demonstrate that more than 66% of the world's population will experience water scarcity by 2025. The major concern of desalination is their management of brine, with concentrations and their associated components more than twice the input concentration. Also, when extracting oil, per 1 oil barrel, about 7 to 10 barrels of high saline water are produced. One of the most common methods for disposing of brine is direct discharge into the environment, which, due to its destructive effects, creates serious threats to marine ecosystems. Therefore, it is necessary to desalting these high saline... 

In this research, we focus on reduction of solutes in left out water from reverse osmosis membranous units (brine) with reduction of scaling factors of membrane. This research is important from that perspective that the out put brine from reverse osmosis membranous unit After purification by this method, enter into membranous system in order to increase in recovered water volume and also minimization of out put waste from membranous system and decrease the environmental damages. The method used in this research, is three processes of cooling, chemical desalination and seeding by crystal material. In this research is investigated the type and amount of matter for chemical desalination and... 

The separation ofacetic acids in binary water solutions hasbeenstudied using a reverse osmosis (RO) membrane. Thin film composite polyamide membrane is used in this study.Thin-film composite (TFC) membrane was prepared through the interfacial polymerization between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on the polysulphone support membrane.The solute permeation was carried out under applied pressure of 5 bar at 25°C. In this work the effect of various synthesis conditions on the membrane performance was investigated. Parametric studies were conducted by varyingconcentration of reactants, reaction time, curing time and curing temperature. By suitable combination of these... 

In this study, mesh-reinforced cellulose acetate (CA)-based membranes were prepared for forward osmosis (FO) by immersion precipitation. Casting composition, preparation conditions, evaporation time, coagulation bath temperature, annealing temperature, CA percent and 1,4-dioxane/acetone ratio were tested for membranes’ performance. Also, the results were compared with commercially CTA membranes. The FO membrane prepared under optimized conditions had a smooth surface similar to commercial ones. The most proper membrane (17.9 % polymer and 1,4-dioxane /acetone ratio 1.89) showed water flux of 9.3 L/m2.hr (LMH) and RSF of 0.536 mol NaCl/m2.hr. Using mesh in the membrane structure, different...