Fabrication and evaluation of polysulfone nanocomposite membrane of mineral nanoparticles

Master thesis (M.Sc.)

Treatment: process design

Abstract

Currently, membranes have found a special place in different separation industries and have wide applications in various fields of separation, including solutions They have different liquids and gases. Membrane technology is one of the most widely used technologies in today's industry, whose field of application is wide ranging from water and sewage industry to food and pharmaceutical industries. Most of the membranes that are recently used in membrane gas separation processes are polymer and non-porous membranes, and the basis of their performance is the solubility-permeation mechanism. This is the mechanism at the molecular scale of the diffusion of molecules from the polymer membrane. In this mechanism, it is assumed that the molecule is absorbed on one side of the membrane and penetrates through the empty spaces of the polymer chains and is rejected on the other surface. Due to its good mechanical properties, high chemical resistance and high glass transition temperature, the polysulfone polymer is widely used in the preparation of asymmetric membranes (usually in the range of ultrafiltration and microfiltration). Polysulfone ultrafiltration membranes have very low surface wettability. Due to interactions Hydrophobicity between the membrane and hydrophobic solvents, this property will cause many blocking problems in polysulfone membranes. Also, polymer membranes cannot overcome the problem of contradiction between selectivity and permeability. In order to increase the hydrophilicity of polysulfone membranes and improve the structural properties of the membrane, there are several methods, but a few methods that have been more developed since the beginning of work are: in situ polymerization, induction solution composition, melting process and mixed bed method. In this research, clay nanoparticles have been used in the preparation of this nanocomposite membrane using the mixed bed method. With mixed bed membranes, high selectivity can be achieved with the same permeability or greater permeability compared to existing polymer membranes. By adding inorganic nanoparticles, the separation properties can be improved.

Key words: nanocomposite membrane, ultrafiltration, nanoclay, mixed bed membranes

Introduction

Current advances in chemical and similar industries are aimed at increasing the speed of processes and reducing energy consumption during the process. One of the most important and widely used processes in such industries is the separation of different materials. To carry out industrial processes, the components of the primary raw material must be separated and the product obtained from these processes must also be separated and purified. On the other hand, in most industries, considering environmental laws, the need to carry out separation processes is seen more than ever.

In fact, the importance of separation processes and related devices and equipment is so much that in many industries, most of the cost of a product is related to the costs of separating and purifying that product. For this reason, finding a simpler and less expensive separation method can be considered. In choosing an appropriate separation method, the efficiency of those methods, access to equipment, separation costs, construction costs, and energy costs should be fully evaluated, taking into account environmental issues and political issues. Also, the goals of separation in the process should be specified, in a separation process, different goals such as concentration, purification, separation and displacement of the reaction equilibrium can be considered. In this regard, membranes have been developed to separate different types of materials in solid, liquid and gas states. Although the separation method with membranes is newer than other methods such as distillation, surface adsorption, crystallization and liquid-liquid extraction, but due to its efficiency and ease of use in the last two decades, a significant expansion in its use has been observed [1]. This mechanism on a molecular scale is the diffusion of molecules from the polymer membrane. In this mechanism, it is assumed that the molecule is absorbed on one side of the membrane and penetrates through the empty spaces of the polymer chains and is rejected on the other side.In this mechanism, it is assumed that the molecule is absorbed on one side of the membrane and penetrates through the empty spaces of the polymer chains and is rejected on the other side. According to the solubility-permeation model, the penetration of molecules through the membrane is controlled by two main parameters, the diffusion coefficient and the solubility coefficient. The solubility coefficient is defined as the ratio of two absorption potentials such as partial pressure [2]. For good membrane performance, both permeability and selectivity must be high. The higher the permeability, the lower the required area of ??the membrane for gas purification, and high selectivity gives high gas purity in the same permeability conditions. In glassy polymers (polymers that are below their glass transition temperature), small molecules such as H2 and He pass quickly and large molecules such as hydrocarbons pass through the membrane slowly. Permeable polymers have low selectivity [2]. Despite all these advantages, polymeric membranes cannot overcome the problem of contradiction between selectivity and permeability. In fact, inorganic membranes such as carbon membranes have high selectivity and permeability, but it is difficult to manufacture them on a large scale, due to the need for high efficiency of membranes in polymer and inorganic membranes, a new type of membranes has recently been developed called mixed bed membranes. Mixed bed membranes are composite membranes in which solid or liquid or both are embedded as fillers in a polymer substrate [3]. Research on mixed bed membranes has been continuously increasing since 1980 with a remarkable speed. Now experimental and laboratory findings have shown the relative superiority of mixed bed membrane separation compared to pure polymer membranes. Considering the novelty of this type of membranes, there is a lot of work space for future studies [3]. In this research, the focus is on the fabrication of polysulfone nanocomposite membranes by the mixed bed method and investigating the performance of these membranes. In order to check the performance of the membrane in different conditions, permeation tests and structural analyzes have been carried out. In this research, the effect of different parameters on membrane performance and the effect of pressure on membrane permeability and selectivity have been investigated. It should be mentioned that the production of polysulfone nanocomposite membranes by mixed bed method is new and for the first time.

 Abstract

Today membranes have special place in detachment industry. They also have great use in various detachment grounds, like: liquid lotion and various gases. Today membranes technology is one of the most all-purpose technology in industries, which usage is from water and sewage industry to food and drug industry. Most of membranes which is recently used in gas and detachment are polymeric and non-spongy membranes. The basis of their application is solvation-osmosis mechanism. This mechanism in molecule criterion is polymer criterion. In this mechanism it is assumed that molecule absorb in one side of membrane and osmosis in vacuo polymeric continuum and ejection from other side of membrane.

    Since polysulfon polymeric have good mechanical property, high resistivity and high glass alternate thermal, it is largely used in bottom of asymmetric membrane (usually in olterafesiun and microfiltration) ultrafiltration poly-sulfon membranes have low saturate. Because of hydrophobic interaction between membrane and water closet soluble, this property in polysulfon membrane have great plosive problems. Polymeric membranes cannot overcome the problem of antithesis between permeability and electability.

There are so many various ways for the purpose of improving polysulfon membrane and improving organizational property of membranes but some ways which are used from the beginning of function are: polymerization, composition of faradic lotion, melt process and mixed ground way.

        In this Nano disquisition the sparks of argil are used for the purpose of preparation of Nano composite membrane. We can reach the high selectivity with the same permeability of more permeability in contrast with available polymer membrane. By adding Nano atomic mineral we can improve detachment property.