Academic literature on the topic 'Reactive dyes Chemistry'

Advanced oxidation processes (AOPs), namely the Fenton oxidation, ozonation, electrochemical oxidation, and photocatalysis, are potential alternative techniques for dye removal from textile effluents. Their inherent ability to completely mineralize pollutants including those recalcitrant to biodegradation and to be compatibly integrated in conventional technologies present grounds for consideration of AOPs as alternative wastewater treatment options. Advanced oxidation involves generation and subsequent reaction of various radicals and reacting species with the target compounds. This chapter discusses the fundamentals and chemistry and efficiencies of the Fenton process, ozonation, electrochemical oxidation, and photocatalysis processes for complete dye removal from wastewater. The reaction mechanisms, performance, and factors affecting efficiency are discussed.

Volumetric analysis is a chemical analytical procedure based on measurement of volumes of reaction in solutions. It uses titration to determine the concentration of a solution by carefully measuring the volume of one solution needed to react with another. In this process, a measured volume of a standard solution, the titrant, is added from a burette to the solution of unknown concentration. When the two substances are present in exact stoichiometric ratio, the reaction is said to have reached the equivalence or stoichiometric point. In order to determine when this occurs, another substance, the indicator, is also added to the reaction mixture. This is an organic dye which changes color when the reaction is complete. This color change is known as the end point; ideally, it will coincide with the equivalence point. For various reasons, there is usually some difference between the two, though if the indicator is carefully chosen, the difference will be negligible. A typical titration is based on a reaction of the general type aA+bB → products where A is the titrant, B the substance titrated, and a:b is the stoichiometric ratio between the two. Some indicators include Litmus, Methyl Orange, Methyl Red, Phenolphthalein, and Thymol Blue. Titration can be applied to any of the following chemical reactions: • Acid–base • Complexation • Oxidation–reduction • Precipitation Only acid–base and oxidation–reduction titration will be treated here, though the fundamental principles are the same in all cases. Acid–base titration involves measuring the volume of a solution of the acid (or base) that is required to completely react with a known volume of a solution of a base (or acid). The relative amounts of acid and base required to reach the equivalence point depend on their stoichiometric coefficients. It is therefore critical to have a balanced equation before attempting calculations based on acid–base reactions. Below we define some of the common terms associated with acid–base reactions. A molar solution is one that contains one mole of the substance per liter of solution. For example, a molar solution of sodium hydroxide contains 40 g (NaOH=40 g/mol) of the solute per liter of solution. As described in chapter 13, the concentration of a solution expressed in moles per liter of solution is known as the molarity of the solution.

The many different nitrogen-containing oxygenated volatile organic compounds that are present in the troposphere play important roles in the chemistry of our atmosphere. They can be emitted directly into the atmosphere, such as in the case of amides that are widely used as organic solvents, starting materials, or intermediates in different industries (e.g., synthetic polymers, manufacture of dyes, and synthesis of pesticides). Amides are formed in situ as intermediate products in the degradation of amines (e.g., see Tuazon et al., 1994; Finlayson-Pitts and Pitts, 2000). Nitrogen-containing oxygenated organic compounds are formed in the atmosphere also via reactions of alkoxy (RO) and alkyl peroxy radicals (RO2) with NO or NO2 leading to alkyl nitrates, alkyl nitrites, and peroxy acetyl nitrates. However, primary sources of these organic species have also been suggested such as diesel and other engines and biomass burning (e.g., see Simpson et al., 2002). Alkyl nitrates (RONO2) have been detected in both the urban and the remote troposphere (e.g., see Roberts, 1990; Walega et al., 1992; Atlas et al., 1992; Ridley et al., 1997; and Stroud et al., 2001; see also section I-D). Nitrates are formed as minor products in the reaction of peroxy radicals with NO. The nitrate yield increases with the size of peroxy radicals and can be as high as 20–30% for large (>C6) radicals (Calvert et al., 2008). Peroxyacyl nitrates (RC(O)O2NO2) are important constituents of urban air pollution. They have been identified in ambient air (e.g., see Bertman and Roberts, 1991; Williams et al., 1997, 2000; Nouaime et al., 1998; Hansel and Wisthaler, 2000; also see section I-D). They are formed from photochemical reactions via RC(O)O2 + NO2. A major role of these compounds is their capacity to act as a reservoir for NOx that can be transported from polluted urban to remote regions that are poor NOx regions and where their presence can increase NOx levels (Roberts, 1990). As with other volatile organic compounds (VOCs), once released to the atmosphere, nitrogen-containing organic compounds are expected to undergo degradation primarily via reaction with hydroxyl and nitrate radicals, reaction with ozone, and photolysis. Thermal decomposition is an important loss process for the peroxyacyl nitrates.

It has been realized that various chemical reactions are accelerated under irradiation of MW. Such Microwave chemistry is known as time-saving, clear and eco-friendly. MW ovens are world-wide domestic tools for cooking which can serve meals quickly. Regardless of its convenience, few understand the essential mechanism of MW ovens. For better understanding of MW chemistry, authors think it is necessary for to introduce elementary knowledge by holding a 1-day program of experiments by using microwave (MW) ovens.“Science with microwave oven”, 1-day program which we developed and named “Hirameki T