engleski

Advanced oxidation processes for wastewater treatment

Advanced oxidation processes (AOPs) have been defined as water treatment processes that involve an input of energy, either chemical, electrical or radiative, into water matrix to produce highly reactive radical intermediates that can degrade a wide range of organic contaminants. AOPs for water and wastewater treatment are based on generation of hydroxyl radicals to initiate the oxidation. There are different methods for generating hydroxyl radicals that may be applied in AOPs: photochemical and electrochemical oxidation, photolysis of hydrogen peroxide and ozone, Fenton and Fenton ''like'' reactions, TiO2 photocatalysis, wet oxidation, sonolysis, &#947 ; ; ; -rays irradiation and high voltage electrical discharge. In Fenton reaction generation of hydroxyl radicals is based on the decomposition of hydrogen peroxide by ferrous ions according to the equation: Fe2+ + H2O2 &#61614 ; ; ; Fe3+ + OH- + OH&#8226 ; ; ; . Fenton ''like'' reagent (Fe(III)/H2O2) is also proved to be very efficient in catalyzing generation of hydroxyl radicals, although much slower due to the lower reactivity of ferric ion toward hydrogen peroxide. Compared to other AOPs Fenton-type processes are relatively cheap and easily operated and maintained. The only disadvantage is that the large amount of iron salt addition could result in a troublesome sludge problem. In order to take advantage of the oxidizing power of Fenton's reagent yet eliminate the separation of iron salts from solution, Fe0/H2O2 system was successfully applied in dye wastewater treatment. Recent investigations indicate that the presence of zeolites can enhance efficiency of Fenton-type wastewater treatment, as well as other AOPs like: ozone and peroxone processes. Furthermore, results of dye wastewater treatment obtained by high voltage electrical discharge in combination with various type of zeolites shows that the small amount of zeolites can significantly influence overall process efficiency of decolorization and mineralization of organic contaminants as well.

Fenton; ozone; peroxone; wastewater; mineralization; decolorization

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