MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY --------------------------------------- VŨ VIỆT THẮNG STUDY ON PROCESS DESIGN AND BASIC DESIGN OF A PHOTOCATALYTIC REACTION SYSTEM FOR TREATMENT OF TEXTILE WASTEWATER CHEMICAL ENGINEERING MASTER THESIS OF CHEMICAL ENGINEERING …. TA HONG DUC Hanoi – 2019 17051113887301000000 STATEMENT I do hereby declare that all the data in this Master thesis is the results of investigation carried out by me in the Leibniz-Institut für Katalyse, Rostock, Germany, and that all direct and indirect sources are acknowledged as references. Hanoi, March 27th, 2019 Vũ Việt Thắng 1 ACKNOWLEDGEMENTS First of all, I would like to express my deepest appreciation to my supervisor, Dr. Ta Hong Duc, for pursuing my Master study at School of Chemical Engineering, Hanoi University of Science and Technology, granting me his endless patience, invaluable guidance and consideration at all times.
I would also like to extend my sincere thanks to Dr. Norbert Steinfeldt, Ms. Michael Sebek and my helpful friend, Mr. Karl Friedrich Iffländer for all sharing knowledges and research experiences when I was working on my topic at the Leibniz- Institut für Katalyse for six-month stay in Rostock, Germany.
I really appreciate Prof. Le Minh Thang, Dr. Dirk Hollmann and Dr. Esteban Mejia as the DAAD – ROHAN SDG Schoolarship’s co-ordinator for their helpful support and consideration so that I could have a precious opportunity to go study abroad in Rostock and could complete my thesis.
Last but not least, I would like to thank my parents for their endless love, support, and patience during all my stay abroad. I never thought that I could do it without you all. Though I cannot list all the names in this section, I feel myself very lucky when I have them, teachers, colleagues, and friends throughout my life.1 LIST OF ABBREVIATIONS AND SYMBOLS USED. I LIST OF TABLES.
II LIST OF FIGURES .1 Sizing and desizing .4 Dyeing and printing .2 Classifications, properties and applications of textile dyes. Carbon nitride material review .1 Brief introduction of g-C3N4 .2 Electronic structure of g-C3N4 .4 Methods to improve g-C3N4 photocatalytic efficiency. Materials and Methods .2 Photoreaction apparatus and procedure .1 X-ray Diffraction Analysis .2 Attenuated total reflectance - Infrared spectroscopy .3 Brunauer–Emmett–Teller method .4 Scanning transmission electron microscopy .5 UV/Vis spectra. Results and Discussion.1 Characterization of materials .1 The XRD results.
The SEM/TEM images .3 The BET method .4 The UV/Vis spectra materials .5 The ATR – IR of catalysts .6 The XPS analytic results .2 The photocatalytic activities of materials .48 Conclusions and outlook .55 5 LIST OF ABBREVIATIONS AND SYMBOLS USED ATR Attenuated total reflectance BET Brunauer–Emmett–Teller method ESR Electron spin resonance IR Infrared spectroscopy MO Methyl Orange PL Photoluminescence spectra SEM Scanning electron microscope TEM Transmission electron microscopy XRD X-ray Diffraction UV Ultra violet VIS Visible XPS X-ray photoelectron spectroscopy Fe – gC3N4 Carbon nitride material doping Iron Carbon nitride material oxidizing with Hydrogen gC3N4 – O peroxide Carbon nitride material doping with Iron and Fe – gC3N4 – O oxidizing with Hydrogen peroxide I LIST OF TABLES Table 1. Classification and examples of dyes according to the chromophore present [19]. Catalytic activity of mpg-C3N4 in the Friedel–Crafts acylation of benzene [47] .1 Summary of general characteristics of the different g-C3N4 samples .2 Near surface composition of the different catalysts determined by XPS .46 II LIST OF FIGURES Figure 1. A flow diagram for steps involved in wet processing of fabric.
Dyes for different fibers. The component of major pollutants involved at various stages of a textile manufacturing industry. Example of azo dye. Example of reactive dye (C.
Chemical structure of vat dyes. Two sulfur dyes very used. Chemical structure of C. The schematic diagram of the s-heptazine unit and s-triazine unit structure [45].
TG-DSC thermograms for heating the melamine [55]. Postulated condensation of melamine 1a [79]. Electronic structure of polymeric melon. Schematic representation of the oxidation mechanism [111].
Proposed pathway for the photocatalytic H2 production by. Comparison of the XRD spectra of g-C3N4 with those of Fe/g-C 3N4 hybrids with varying Fe contents. (a, b) Typical TEM images of CNS–CN; (c) high-resolution XPS spectra of S2p recorded from CN, CNS–CN and CNS; (d) room temperature EPR spectra of CNS–CN. Arrow direction in (d): CN, CNS–CN-1, CNS–CN-2, CNS–CN-3, CNS– CN-4; (e) schematic illustration of organic heterojunction formed between CN and CNS.
The photocatalytic testing system. XRD pattern of the prepared g-C3N4 – samples which differ in composition and/or post-treatment (* - Fe3 O4 phase). SEM images of the prepared g-C 3N4 – materials: g-C3N4 (a,b); g-C3N4 – O (c,d); Fe – g-C3N4 (e,h) and Fe – g-C3N4 – O (g,h)………………………………39 Figure 3. HAADF_STEM images of g-C3N4 - O (a,b) and Fe – g C 3N4 – O (c,d) with different magnification……………………………………………………….
a) N2 adsorption-desorption isotherms for the different samples and b) BJH pore size-distribution…………………………………………………………. a) UV-Vis spectra and b) Tauc plots from the spectra of the all g-C3N4 – samples……………………………………………………………………………. ATR-IR spectra of the different g-C 3N4 – samples……………………. XPS spectra (C1s, N1s, O1s and Fe2p) of different catalysts: pure g-C3N4, g-C3N4-O, Fe-gC3N4, and Fe-gC3N4-O…………………………………………….
ESR spectra of A) g-C3N4 and g-C3N4-O and B) Fe-g-C 3N4 and Fe-gC3N4- O (10 mg, 298 K)…………………………………………………………………. The UV-Vis spectra of MO degradation process: (a) no catalyst; (b) g- C3N4; (c) Fe – g-C 3N4; (d) g-C 3N4 – O; (e) Fe – g-C3N4 – O and (f) the HPLC determination………………………………………………………………………50 Figure 3. The PL spectra of g-C3N4 based materials……………………………51 IV INTRODUCTION Nowadays, water pollution is becoming more severe. One of the reasons comes from organic wastes and residues in industrial textile wastewater, which contains approximately 1 – 20% of the total world production of dyes compound.
In fact, from textile plants, the effluent streams have to be treated to eliminate the poisonous dye residues. Furthermore, an effective dye wastewater decolorization is usually required due to most government regulations. For dyes compound degradation, an outstanding trend in recent years is using Advanced Oxidation Processes method (AOPs), as developing photocatalysts which can degrade organic pollutant well under light energy (Ultra violet or Visible light). It opens many directions of selecting and modification semi-conductors materials as photocatalysts.
Graphitic carbon nitride (g-C3N4), a fascinating polymeric organic semiconductor, is attracting worldwide attention. g-C3N 4 possesses appropriate band positions, a band gap of 2.70 eV, high thermal stability, excellent chemical stability, and special optical features, which make it a promising metalfree photocatalyst for organic pollution degradation or water reduction under visible light irradiation. However, the photocatalytic efficiency of pure g-C3N4 is far from satisfaction due to not only the large optical band gap with limited utilization of solar energy ( λ ˂ 460 nm) but also the high recombination rate of photogenerated electron–hole pairs. From the reason above, the topic of this thesis was selected as “Study on process design and basic design of a photocatalytic reaction system for treatment of textile wastewater”, working on study and investigating the influence of iron doping and oxidation by using hydrogen peroxide on the graphitic carbon nitride based materials for organic dye compound degradation process.
LITERATURE REVIEW Industrialization plays an important role in the development of any country. Textile industry is a vital and quickly emerging industrial segment in India. The textile industry uses different resources/raw materials such as cotton, woolen and synthetic fibers. Cotton based textile industries are considered in this study.
The textile industries can also be classified into two groups viz dry and wet fabric industry. Solid wastes are generated in dry fabric industry while liquid wastes are generated in wet fabric industries. Processing operation such as desizing, scouring, bleaching, mercerizing, dying, printing and finishing stages are included in wet fabric processing industry. During fabric formation, the water utilization and waste water generation from a wet processing textile industry depends upon the operations.
The textile industry is a main creator of effluent wastewater due to a more consumption of water for its different wet processing operations. These effluent wastewater contains chemicals like acids, alkalis, dyes, hydrogen peroxide, starch, surfactants dispersing agents and soaps of metals [1]. So, in terms of its environmental impact, the textile industry is estimated to use more water than any other industry, globally and almost all wastewater discharged is highly polluted. Average sized textiles mills consume water about 200 L per kg of fabric processed per day [2].
According to the World Bank estimation, textile dyeing and finishing treatment given to a fabric generates around 17 to 20 percent of industrial waste water [2]. In India, the textiles industry consumes around 80% of the total production of 1,30,000 tons of dyestuff, due to high demand for polyester and cotton, globally [3]. These dyes in wastewater severely affect photosynthetic function in plant. They also have an impact on aquatic life due to low light penetration and oxygen consumption.
They may also be lethal to certain forms of marine life due to the occurrence of component metals and chlorine. Suspended particles can choke fish gills and kill 2 them. They also decrease the capacity of algae to make food and oxygen. Dyes are also detected to hinder with certain municipal wastewater treatment operations such as ultraviolet decontamination etc.
At present, aromatic and heterocyclic dyes are used in textile industry. The complicated and stable structure of dye is posing a greater difficulty in degradation when present not only in textile wastewater but also in any kind of complex matrix [5]. The mineralization of dyes, organic compounds and hence the toxicity of the wastewater generated by textile industry and dyes manufacturing industry is a main challenge and an ecological concern. Hence, understanding and emerging real textile wastewater treatment is ecologically noteworthy.1 Textile operations Textile industries prepare fibers; transform fibers into yarn and alter the yarn into fabric and then these fabrics goes through several stages of wet processing.
Some of the stages in wet processing of textile fabrics are revealed in Figure 1.1 [6] and are discussed in detail in the subsequent sections. A flow diagram for steps involved in wet processing of fabric 3 1.1 Sizing and desizing Textile wet processes like dyeing and printing are affected by the existence of sizing chemicals in the fabric. For instance, the occurrence of starch hampers the diffusion of the dye molecule into the yarn/fabric, which needs the elimination of starch preceding to dyeing and then printing. Enzymatic or dilute mineral acid hydrolysis or oxidation is used to remove such a sizing chemicals.
Such a hydrolysis or oxidation processes convert starch into simple water soluble products [7]. Effluent from desizing has a more biological oxygen demand (BOD) in the range of 300 – 450 ppm and pH of 4 – 5 [8] that renders it out of use. An oxidation by hydrogen peroxide can be used for the degradation of starch into CO2 and H2O. Alternatively, the problem of starch can also be eased by using enzymes that covert it into ethanol.
Distillation is used to recover this ethanol which can be used as a fuel, thus reducing the ultimate biological oxygen demand (BOD) load on the treatment [9].2 Bleaching Natural color substance in the fabric is responsible for the creamy look to the fabric. In order to get a white fabric which enables the production of bright shades, it is essential to remove natural color matter from the fabric by the process of bleaching. In earlier days, hypochlorite was being used as bleaching agents. Now days, hypochlorite is exchanged by another bleaching agents such as H2O2 and peracetic acid.
Peracetic acid is an environmentally benign alternative to hypochlorite bleaching agent. Higher luster along with less yarn destruction of the processed fabric is the one major benefits of peracetic acid [10, 11].3 Mercerization Mercerization of cotton fabrics are carried out after bleaching to give a shine and advance dye uptake. Basically, it is done by treating cotton fabric with a high concentration (about 18 – 24% by weight) of sodium hydroxide.