Removal of phenol from industrial wastewater using nanotechnology

Master's Thesis in Nano Chemical Engineering

Abstract

Removal of phenol from industrial wastewater using nanotechnology

In this research, the photocatalytic removal of phenol as a model of organic pollutant in a fluidized bed reactor under ultraviolet and visible radiations has been studied. The effects of important parameters such as pH, catalyst concentration, phenol concentration and nanocomposite synthesis methods on the photocatalytic removal of phenol have been investigated. The concentration of removed phenol was measured quantitatively as a function of irradiation time in a visible-ultraviolet spectrophotometer, and the nanocomposites used in this work consist of semiconductor nanoparticles of ZnO, CuO, and TiO2. According to the results of the experiments, the kinetics of phenol removal follows pseudo-first-order kinetics. The results showed a significant dependence of the photocatalytic removal of phenol on the active compounds. The results show that in both methods of nanocomposite synthesis (mechanical mixing and wet impregnation), nanocomposite c has the best phenol removal rate under visible and ultraviolet radiations. The percentage of phenol removal with this nanocomposite was 53.11 and 55.20 under visible and ultraviolet radiations, respectively, in the mechanical mixing method. Also, the percentage of phenol removal with this nanocomposite in the wet impregnation method, under visible and ultraviolet radiations, was measured as 62.76 and 63.88, respectively. In all experiments, the optimum pH was 5. Keywords: nanocomposite, spectrophotometer, ultraviolet and visible radiation, wet saturation, nanotechnology, nanotechnology, the ability to produce new materials, tools and systems with Taking control at the molecular and atomic level and using their properties at the nano scale. Nanoscience is the study and research of devices and structures that exist in the smallest dimension unit (100) nanometers or smaller. It follows from the above definitions that nanotechnology is not a field but a new approach in all fields. Nanotechnology has applications in various fields, including food, medicine, medical diagnosis and biotechnology, to electronics, computers, communications, transportation, energy, environment, materials, air and space, and national security. The wide applications of this field and its social, political and legal consequences have raised this technology as a transdisciplinary and transsectoral field.

The first spark of nanotechnology in the year It was published in 1959 (of course, at that time it was not yet known by this name). In this year, Richard Feynman introduced the idea of ??nanotechnology during a speech entitled "There is a lot of space at low levels". He presented the theory that in the near future we will be able to directly manipulate molecules and atoms. The word nanotechnology was first used by Noriotainguchi, a professor at Tokyo University of Science, in 1974. He used this term to describe the manufacturing of precise materials (devices) whose dimensional tolerance is in the order of nanometers. In 1986, this term was recreated and redefined by Kiarik Drexler[1] in a book titled "The Engine of Creation: The Beginning of the Nanotechnology Era". He investigated this term in a deeper way in his doctoral dissertation and later developed it in a book titled "Nanosystems, molecular machines, how to make and calculate them". The goal of nanotechnology is molecular production or atom-by-atom and molecule-by-molecule construction of materials and machines by programmed robot arms on a nanometer scale [2,1]. rtl;"> The increase in the world population and the decrease in drinking water resources have caused concerns about the supply of drinking water needed by different countries around the world, and the lack of water, which is intensified as a result of the increase in environmental pollution, has caused the supply of sanitary water needed by people to become one of the basic problems of the world today.Diseases caused by the pollution of water sources kill thousands and maybe tens of thousands of people in the world every day, while the possibility of water recycling will provide access to a suitable source for various uses. Recently, with the introduction of new technologies such as biotechnology and nanotechnology, new materials and solutions for water treatment and industrial and agricultural wastewater have been introduced or are being introduced. The use of nanometer filters has created a huge revolution in the recycling and reuse of water resources. The applications of nanotechnology in this regard include: nanosensors, nanofilters, nanophotocatalysts, nanoporous materials, nanoparticles, the capabilities of these technologies in water purification have been evaluated according to the types of pollution in different parts of Iran.

Researchers are looking for the development of a unique method for wastewater treatment that without the use of expensive chemicals, water quality compared to the methods that are currently used, it will increase significantly. The last stage of water purification is the removal of very small living organisms, which is currently using chlorine as a disinfectant. But in this case, even after purification, there will be many organic compounds in the water. Chlorine removes microorganisms from water. But it reacts with organic pollutants and produces non-degradable and toxic byproducts that cannot be removed from water. The transfer of these substances to the environment and their use in agriculture and other industries can cause dangerous health problems.

Wastewater treatment with the help of photocatalyst can replace the third stage of treatment, which is chlorine disinfection, to remove living organisms and organic compounds at the same time and turn wastewater into a suitable water source. Naturally, tiny living organisms convert large organic compounds into smaller particles. But since these compounds are non-biodegradable, some kind of energy must be used to break them down. This energy is provided by ultraviolet rays of sunlight and is used together with photocatalysts. The energy released from the reaction of the photocatalyst cell can destroy micro-organisms and break down non-biodegradable compounds. This process is economically viable due to the possibility of reusing the photocatalysts. Catalytic particles are either homogeneously dispersed in the solution or deposited as membrane structures that enable the chemical decomposition of pollutants.

The effect of adding different metals in improving the catalytic activity is known and scientists have used it to remove trichloroethylene[2] from underground water. The research of Rice University Environmental Nanotechnology Center[3] shows that gold and palladium nanoparticles are very effective catalysts for removing TCE pollution from water. The advantages of removing TCE with palladium are well known, but this method is somewhat expensive.

1-2-1- Nanotechnology and water purification

By using nanotechnology, the number of atoms in contact with molecules can be increased. TCE and as a result increased the efficiency of this catalyst several times compared to common catalysts. Researchers at Rice University have developed a new method to produce titanium nanocrystals with a high specific surface area (more than 250 m2/g) for the removal of organic aromatics. These materials are able to photooxidize many molecules under UV radiation. Also, C60 is a very good photocatalyst, whose efficiency is hundreds of times higher than titania in the market. Production of free radicals by concentrated C60 in water enables the decomposition of pollutants. Due to the applications and capabilities of nanotechnology in the water and wastewater industry, many companies use this technology in water and wastewater treatment, and for this reason, the use of products and productions based on nanotechnology has increased today. These products often include nano filters and various types of sensors that are used to detect substances and particles in water.

It is not too late that one of the main and important goals in the law of establishing industrial companies and factories in Iran is to protect the environment and prevent its pollution.