Fabrication of polyacrylonitrile ultrafiltration membrane containing TiO2 nanoparticles in order to separate cationic polyacrylamide from coal washing factory effluent

Number of pages: 119 File Format: word File Code: 31777
Year: 2016 University Degree: Master's degree Category: Chemical - Petrochemical Engineering
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  • Summary of Fabrication of polyacrylonitrile ultrafiltration membrane containing TiO2 nanoparticles in order to separate cationic polyacrylamide from coal washing factory effluent

    Master's Thesis in Nano Chemical Engineering

    Abstract

     

    The purpose of this study is to separate cationic polyacrylamide from the effluent of Parodeh Tabas coal washing plant using membrane filtration process. It is a polymer. The primary membrane was prepared using polyacrylonitrile (PAN) by phase inversion process, and then they were prepared using hydrolysis as chemical modification and heat treatment as physical modification for maximum wastewater separation. Also, TiO2 nanoparticles have been used by two methods of self-assembly and mixing with polymer solution in order to increase the anti-clogging properties of the membrane surface. In order to check the performance of the membrane, the feed solution of 10 ppm of cationic polyacrylamide was prepared according to the factory feed and the retention rate and flow rate were measured at a pressure of 3 bar and a temperature of 25 degrees Celsius. According to what has been desirable in this study, besides the retention of 98% of polyacrylamide, it has been possible to achieve different fluxes according to the type of membrane used. The amount of flux in the membranes without nanoparticles was about 125.4 L/m2.hr, while for the membrane combined with TiO2 nanoparticles in the self-assembly method, this value was improved by about 45% and for the method of mixing in the polymer solution, it was improved by 32%. The clogging tests of the constructed membranes show that the membranes containing TiO2 nanoparticles have less clogging compared to normal membranes. FT-IR analyzes show the chemical groups on the surface of the membrane before and after hydrolysis. The surface SEM images do not show a noticeable change in the surface morphology of the membranes after modification in the presence of TiO2 nanoparticles, while the EDX analysis confirms the presence of TiO2 nanoparticles. The contact angle analysis shows that the hydrophilicity of the membrane surface in the presence of TiO2 nanoparticles increases more with the self-assembly method than with the mixing method.

    Key words: TiO2 nanoparticles, antifouling, polyacrylonitrile, polyacrylamide, self-assembly, mixing

    Introduction

     

    Due to the ever-increasing crisis of lack of water needed not only for domestic and agricultural use, but also in the industry sector, efforts to purify and return a significant part of consumed water to the consumption cycle are increasing. According to the report of the Ministry of Energy of the Islamic Republic of Iran, the amount of water consumption in the industry sector accounts for about 1.5% of the country's total water consumption, equivalent to 1.5 billion cubic meters. Therefore, with the development of science and technology such as membrane processes, a huge part of this water can be returned to the industrial cycle. Membrane processes such as nanofiltration [1] (NF), ultrafiltration [2] (UF) and reverse osmosis [3] (RO) are increasingly used in the recovery and reuse of wastewater and drinking water treatment. rtl;"> 

    This factory was designed and implemented in the first phase in order to supply coke needed for Isfahan iron smelting factory. The nominal capacity of this factory, which is the largest coal washing factory in the country, is 300 tons per hour. After the coal is extracted from Pardoh mines, which contains about 50% tailings, it is transferred to the coal washing plant for purification and separation from the tailings. Then the coal enters the rotary breaker to granulate and reduce the size of the coal. After the various operations performed on coal in order to granulate and ash it, the most important part of the coal washing plant, i.e., the flotation section, is used. In this section, coal is granulated and finely mixed with water. The process of flotation is actually the separation of solid from solid (separation of coking coal from tailings) due to the difference in particle density] 2. [

              Six cells are active in the flotation part, these cells have a diameter of 4 meters and a height of 8 meters, and their capacity is 300 tons per hour.The primary feed flow (a mixture of water and coal) enters it from a height of 2 meters above the cell, then it enters below, or the foamer, from a height of 1.5 meters from the bottom of the cell. The reason for adding the foaming agent is actually the creation of bubbles, which causes the particles with lower density, which is high-quality coal, to be placed on the surface of the bubbles and exit from the top of the cell in the form of small heads, and the tailings also remain at the bottom of the cell due to the higher density, and are removed. will be Also, the tailings from the flotation along with the effluent also enters the thickener. Thickener is a part of the water recovery plant that includes a 5400 m3 pool. In the last stage, due to the presence of suspended particles in the wastewater, coagulants are used for sedimentation - under the name of coagulation and flocculation process - and reuse of water. rtl;"> 

    Coagulation and flocculation[4] is a physical and chemical unit in the pretreatment process[5]. In this process, fine suspended particles are converted into coarse particles and settled by coagulants [6]. For this process, organic or inorganic materials and materials with high molecular mass such as polymers can be used. Flocculation is a type of coagulation and flocculation process that uses polymers to settle suspended particles, which are divided into three categories: cationic, anionic and neutral. Cationic polymers are widely used in the treatment of wastewater containing mineral particles. Most of the polymers used in the flocculation process are linear polymers [3-11].

    For suspensions with different concentrations and particle sizes, polymers with different molecular masses are used. The most important factors affecting the efficiency of the coagulation process of ions in aqueous solution (ionic strength of water), concentration of humic substances, pH, water temperature and type of coagulant are. In the process of coagulation and flocculation, the growth of clots occurs in several successive stages:

    dispersion of polymer in the environment

    penetration of polymer in the solid-liquid interface

    absorption of polymer on the surface of the liquid collision of particles carrying the absorbed clot with another particle

    absorption Clot on the second particle to create a bridge and form a micro-clot

    Growth of micro-clots through successful collisions and absorption

    Breaking of clots created by stress

    Each step occurs according to its own kinetics and the final results depend on the relative speed of different steps. Therefore, for example, if the absorption phase is much faster than the growth phase, there will be many small flocs, while if the growth speed is higher, the flocs will be larger and fewer in number [12]. The use of water-soluble organic polymers has been very common in the pretreatment of drinking water and industrial wastewater for the past 40 years. Initially, the United States of America used these polymers for pre-treatment operations, and with the passage of 15 years since the first use of polymers for pre-treatment operations in the United States, more than half of the units with pre-treatment processes used one or more polymers to increase the efficiency of this process [13]. Acrylamide is formed. Polyacrylamide is a family of polymers or copolymers that can vary in molecular mass, charge type, charge density and other properties. Polyacrylamide is a cheap synthetic chemical and does not have harmful effects on the environment [13]. The demand market for this material in 2012 was reported to be 3.95 billion dollars and it is expected that this amount will reach 6.9 billion dollars by 2019 with an annual growth of 4.7%. This polymer is widely used in industries containing mineral waste to settle suspended particles in industrial waste. This polymer exists in three types: cationic, anionic and neutral.

  • Contents & References of Fabrication of polyacrylonitrile ultrafiltration membrane containing TiO2 nanoparticles in order to separate cationic polyacrylamide from coal washing factory effluent

    List:

     

     

    First speech: study on polyacrylamide separation methods and familiarization with membrane processes. 1

    1-1 Introduction of coal washing plant. 3

    1-2 Introduction of coagulation and coagulation process. 4

    1-3 Introduction of polyacrylamide. 6

    1-4 The need to treat wastewater containing polyacrylamide. 10

    1-5 Polyacrylamide isolation methods. 12

    1-6 polymer absorption with surface adsorbents. 12

    1-7 membrane and membrane processes. 13

    1-7-1 History 13

    1-7-2 Membrane definition 14

    1-7-3 Advantages of using membrane technology. 17

    1-7-4 types of membranes 17

    1-7-4-1 division based on membrane type 18

    1-7-4-2 division based on membrane structure 18

    1-7-4-3 division of membranes in terms of function 20

    1-7-5 types of membrane separation processes. 21

    1-7-6 Comparison of filtration methods. 24

    1-7-7 separation mechanisms. 26

    1-7-8 methods of functioning of membrane processes. 28

    1-7-9 Obstruction in membranes 29

    1-7-10 Methods to prevent or reduce membrane clogging 33

    1-7-10-1 Choosing the right membrane. 33

    1-7-10-2 pre-treatment of fluid entering the membrane 33

    1-7-10-3 improvement of operation conditions. 34

    1-7-10-4 Modifying the surface of manufactured membranes 34

    1-7-10-4-1 Physical method. 34

    1-7-10-4-2 chemical method. 34

    1-7-11 preparation of composite ultrafiltration membranes using mineral particles. 35

    1-7-11-1 deposition of mineral particles on the membrane surface directly. 35

    1-7-11-2 placement of nanoparticles in the membrane matrix 36

    1-7-12 methods to reduce clogging. 36

    1-7-13 Cleaning 37

    1-7-13-1 Hydraulic cleaning. 37

    1-7-13-2 Mechanical cleaning. 38

    1-7-13-3 Electrical cleaning. 38

    1-7-13-4 Chemical cleaning. 38

    1-8 studies done 40

    Second speech: experiences. 46

    2-1 Equipment and materials used 47

    2-2 Membrane preparation process 48

    2-2-1 Fabrication of polyacrylonitrile membrane by phase inversion method. 48

    2-2-2 Making suitable polyacrylonitrile membrane. 51

    2-3 Membrane surface modification by heat treatment and hydrolysis method 51

    2-4 Combination of membrane with titanium dioxide nanoparticles. 52

    2-4-1 Self-assembly of titanium dioxide nanoparticles on the surface of polyacrylonitrile membrane. 53

    2-4-2 Mixing titanium dioxide nanoparticles in polymer solution. 53

    2-5 Evaluation of membrane performance 54

    2-6 Pure water flux. 57

    2-7 Retention. 58

    8-2 Fracture threshold and hole size calculation. 59

    2-8-1 Measuring polyethylene glycol concentration. 61

    2-9 Checking the degree of membrane clogging 62

    2-10 Checking the morphology of the membrane 63

    2-10-1 Checking the morphology of the membrane prepared with a scanning electron microscope (SEM) 64

    2-10-2 Checking the hydrophilicity of the membrane with contact angle analysis. 65

    2-7-3 Investigating the chemical structure of the membrane 66

    2-10-4 X-ray Energy Diffraction Spectroscopy (EDX) 67

    Third speech: discussion and conclusion. 69

    Introduction 70

    3-1 Fabrication of polyacrylonitrile membrane. 70

    3-2 chemical modification of membrane 73

    3-3 thermal modification of polyacrylonitrile membranes. 76

    3-4 Investigating the performance and structure of the thermally modified membrane. 76

    3-5 Membrane modification using nanoparticles. 80

    3-5-1 Effect of self-assembly of titanium dioxide nanoparticles on the membrane surface 81

    3-5-2 Effect of mixing titanium dioxide nanoparticles in polymer solution. 83

    3-6 Comparison between two methods of adding nanoparticles. 85

    3-7 Scanning electron microscope analysis of the membrane surface 86

    3-8 X-ray energy diffraction analysis (EDX) 90

    3-9 Measurement of fracture threshold. 93

    3-10 investigation of membrane surface hydrophilicity 95

    3-8 investigation of membrane clogging 97

    Fourth speech: conclusion and suggestions. 101

    4-1 Conclusion. 102

    4-2 suggestions 104

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Fabrication of polyacrylonitrile ultrafiltration membrane containing TiO2 nanoparticles in order to separate cationic polyacrylamide from coal washing factory effluent