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CATALYTIC SCREENING OF COPPER BEARING ZEOLITE BASED CATALYSTS IN CWPO OF MODEL PHENOLIC WASTEWATER IN BATCH AND FIXED BED REACTOR

Phenols are important industrial chemicals of environmental concern and are some of the major hazardous compounds in industrial wastewater due to their poor biodegradability, phytotoxic and antimicrobial properties, as well as their suspected carcinogenic and mutagenic properties. Phenolic wastewater therefore requires a special consideration prior to its release into the environment. One example of industrial effluent that contains significant amounts of phenolics is olive oil mill wastewater (OOMW) – the liquid waste generated in the olive oil production process that contains a number of harmful organic contaminants such as lignin, tannins and polyphenolic compounds. It is estimated that more than 4.6 Mt of olive-mill wastewater is produced each year at the European level alone. Even though the European Commission has adopted the legislation that prohibits the release of untreated OOMW into the environment, over 90 % of olive mills releases its wastes directly to streams (58 %), sea (11.5 %) and soil (19.5 %) without any prior treatment. Its high polluting charges that are measured in BOD5 and COD levels up to 35 g dm-3 as well as the presence of phenols and polyphenols that can constitute up to 20 wt. % of total organic content and their proven toxicity towards the microorganisms used in the aerobic biological processes make direct conventional biological treatment inapplicable. Therefore, in the current research studies that address this issue, the focus of investigation is on developing viable treatment processes that will reduce or eliminate toxic content of the OOMW and improve the biodegradability of such effluents by removing from them compounds such as phenol and tyrosol. Copper containing 13X zeolite based pelleted catalyst (dP= 0.4 - 0.6 mm) was prepared, characterized, thermally stabilized and used in the catalytic screening in wet peroxide oxidation of model wastewater (tyrosol and phenol aqueous solutions) to determine its intrinsic catalytic properties. The experiments were performed in a suspension batch and adiabatic continuous fixed bed reactors under mild reaction conditions with low energy consumption (T ≤ 323 K, 500 mg dm-3 organic compound(s), stoichiometric oxidant amount, 1 g of catalyst). It was found that the prepared catalyst showed promising activity in both reactor systems yielding over 50 % conversions of targeted organic contaminants at 323 K and 600 rpm in the suspension reactor and 303 K and the flow of 1 ml/min in the fixed bed reactor. Leaching of active metal component of the catalyst was observed in the batch operation mode, and minimized using postsynthesis thermal treatment. During preliminary runs in the continuous adiabatic fixed bed reactor, excesive ammounts of oxygen were formed in the catalyst bed indicating unefficient decomposition of hydrogen peroxide to form water and oxygen instead of hydroperoxyl radicals and disrupting the flow distribution yielding somewhat lower conversions.

catalytic wet peroxide oxidation, transition metal zeolite catalysts, phenolic wastewater treatment

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