engleski

Dyes and zeolites - opportunities and trends

Synthetic dyes are relatively great group of organic chemicals, which are present in almost all media of everyday life, and therefore are very important to control the impacts to environment and human health. Azo dyes are the most common synthetic dyes in both number and amount produced, and they are used widely in textile, printing, pharmaceutical, cosmetic, and food industries. The reactive dyes (more recently) are present at the market, in amount of 20-30% of all produced organic dyes, because they are mostly used for dyeing of cotton (50% of world manufacturing). Reactive dye will form a covalent bond with the appropriate textile functionality. This is of great interest, since, once attached, they are very difficult to remove. One problem is that instead of reacting with the -OH groups on the cellulose, protein fibres or polyamide, the fibre-reactive group may react with the HO- ions in the alkali solution and become hydrolysed. The two reactions compete, and this unfavourable because the hydrolysed dye cannot react further. Zeolites are microporous crystalline solids with well-defined structures. Generally they contain silicon, aluminium and oxygen in their framework and cations, water and/or other molecules within their pores. Many occur naturally as minerals, and are extensively mined in many parts of the world. Others are synthetic, and are made commercially for specific uses, or produced by research scientists trying to understand more about their chemistry. More than 150 zeolites have been synthesized ; the most common are zeolites A, X, Y, and ZMS-5. Zeolites have the ability to act as catalysts for chemical reactions which take place within the internal cavities. Zeolites can also serve as oxidation or reduction catalysts, often after metals have been introduced into the framework. Because of their unique porous properties, zeolites are used in a variety of applications with a global market of several million tonnes per annum. The present study seeks to investigate possibilities of use zeolite as catalysts in different wastewater treatment processes for effective degradation of various types of organic dyes from aqueous solutions.

reactive azo dyes; zeolites; wastewater treatment

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