Preparation and investigation of nanozeolite ZSM-5 and its application for modification of carbon paste electrode

Thesis

Master's degree

Chemical Engineering

Abstract:

In this research, a method for the synthesis of ZSM-5 nanozeolite was presented. Then this nanozeolite was modified with CTAB surfactant and its characteristics were investigated using XRD, FT-IR, and SEM methods. This nanozeolite was used to prepare a modified carbon paste electrode (SMNZ/CPE) to measure sulfate anion. Also, the effect of factors such as different mass ratios of nanozeolite ZSM-5 and graphite, surfactant concentration, ionic strength, temperature, and pH on the potentiometric response of the modified electrode was investigated. This response remains constant in the pH range of 0.4-0.9 as well as the concentration (1-10 x 0.1-3-10 x 0.1) molar NaNO3. Under optimal conditions in a buffer solution, the voltage decreases linearly with respect to the sulfate ion concentration, and the Nernst behavior can be seen in the concentration range of (1-10 x 0.1 - 1-10 x 0.1) molar sulfate ion with a slope of 2.29 mV and a detection limit (DL) of 0.41 x 10-6. This electrode has advantages such as low resistance, fast response and high selectivity towards a wide range of different anions. Also, this electrode was used as a detector electrode to measure sulfate ions in Damavand and Nova mineral waters and iron sulfate drug. Modified carbon paste, potentiometric method, sulfate anion measurement.   

Introduction

Nano is a Greek word and its Latin equivalent is dwarf [1], which means dwarf. This prefix means one billionth in the science of scales. Therefore, one nanometer is equal to one billionth [1, 2]. This scale can be guessed better by citing concrete examples. An average human hair has a diameter of about 50,000 nm. The smallest objects visible to the naked eye have dimensions of about 10,000 nm. If we put about 10 hydrogen atoms in a line, it is equal to one nanometer [3].

Although there are many definitions about nanotechnology, but the most accurate and simple definition by Mipan [2] [2] was stated as follows: Nanotechnology is the creation of smart materials, tools and systems on the scale of 1-100 nm and taking advantage of their properties in chemical, physical, biological phenomena, etc. The ability to make objects with atomic precision allows scientists to produce materials with new optical, magnetic, thermal or electrical properties [4]. In other words, nanotechnology is a new form of manufacturing materials by controlling and manipulating their building units [3] in pre-designed structures at the nano scale [5]. Nanotechnology is the efficient production of materials, devices, and systems by controlling matter at the nanometer scale and exploiting emerging properties and phenomena that have been developed at the nanoscale. One of the important features of nanotechnology is its application in various fields. Nanotechnology in medical sciences, engineering, electronics, biology, chemistry, physics, process control, etc. It has a wide application [7,8]. Nanoparticles have been used since ancient times. Perhaps their first use was in Chinese glazes and decorative ceramics of the early dynasties of China in the 4th and 5th centuries [8].

Actually, it is not difficult to find examples of the use of metal nanoparticles. The decorative pigments of the famous Lycurgus cup in ancient Rome (fourth century AD) are an example of them [9].     In 1959, Feynman [4] published papers on the future possibilities of nanotechnology. Despite the successes achieved by many up to that time, Feynman is recognized as the founder of nanotechnology. Feynman, who later won the Nobel Prize in Physics, gave a speech that year at a dinner party hosted by the American Physical Society and unveiled the idea of ??nanotechnology to the public. The title of his speech was "There is a lot of space in the lower levels".

          The term nanotechnology was first proposed by Norio Tainguchi [5], a science professor at the University of Tokyo [11]. He used this term to describe the creation of precise materials whose dimensions are in nanometers. Minsky [6] was able to strengthen Feyman's thoughts. Minsky, the father of artificial intelligence, and his student Drexler [7], gathered a group of computer students together in an association. He occupied the minds of younger people with a series of ideas that he named nanotechnology. Drexler received his PhD in nanotechnology from MIT University in 1991 and is a pioneer in nanotechnology [12]. Ion exchange capacity depends on ion concentration, temperature and cation characteristics such as valency and atomic number. Zeolites have interconnected networks that can act as an agent to control the path of some reactions. To absorb cations, the zeolite surface is modified with the help of some metals [19]. Over several decades, a large number of zeolites have been synthesized using organic materials such as amines and alkylammonium ions. Although the irreplaceable role of these organic species, which are called as structure-directing agents [8], is not well known in the synthesis of zeolite, their structure flexibility and hydrophobicity are two important factors in determining the pore structure of the synthesized zeolite. Therefore, in the synthesis of synthetic zeolites and related microporous materials, the use of these materials has increased [13]. In addition to the known elements Al and Si, other constituent elements such as Ga, Ge, Fe and about 10 other elements including P, Li, Be, B, Mg, Co, Mn, Zn, As and Ti have been used in the synthesis of zeolites [14]. The inclusion of these elements in the structure of zeolite changes the physical and chemical properties of zeolite, including changes in pore size, changes in acidity and alkalinity, changes in ion exchange capacity, and changes in the catalytic properties of zeolites.

The ease of exchange of cations in zeolites is one of their important properties, which was first studied by Eickhorn [9] through the contact of zeolite with different salt solutions. [15]. Due to the ion exchange properties of zeolites, this compound has been used on an industrial scale as a hardener [16]. CTAB. characterizations of this nanozeolite investigated by using XRD, FT-IR, SEM techniques. After this stage, carbon paste electrode was modified by surfactant modified ZSM-5 nanozeolite and the electrochemical behavior of this modified electrode was studied using potentiometric technique. The influence of some parameters such as different mass ratio of ZSM-5 nanozeolite and graphite, surfactant concentration, ionic strength, pH and temperature was investigated on the potentiometric response of modified electrode. This response is independent of the solution pH in the range of 0.9-0.4 and remains constant in the presence of 1.0×10-4-1.0×10-3 M NaNO3. Under optimal conditions in a buffer solution, the voltage decreased linearly with the concentration of sulfate ion and discovered Nernstian behavior over wide SO42- ion concentration range (1.00×10?6 to 1.00×10?2 M) with slopes of 2.29 mV per decade and low detection limits 0.41×10?6 mol L?1. This electrode has advantages of low resistance, very fast response and good selectivity relative to a wide variety of other anions. The proposed electrode was used as an indicator electrode in the determination of sulfate in two mineral waters and ferrous sulfate tablets.