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Catalytic screening of transition metal zeolite based catalysts in cwpo of model and real phenolic wastewater

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. During the extraction process excessive amount of phytotoxic wastewater that contains a number of harmful organic contaminants such as lignin, tannins and polyphenolic compounds is produced. 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 that can constitute up to 20 wt. % of total organic content make this wastewaters challenging for treatment. Conventional biological treatment is not applicable for the treatment of OOMW due to the presence of phenols and polyphenols and their proven toxicity towards the microorganisms used in the aerobic biological processes. 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 the most toxic compounds present in them such as phenol and tyrosol. Several zeolite based catalysts containing different active metal (Cu, Fe, Co, Ni) and different zeolite support (types FAU and BETA) were prepared, characterized and used in the catalytic screening catalytic wet peroxide oxidation of model (tyrosol and phenol aqueous solutions) and real polyphenolic wastewater (OOMW) to determine their catalytic properties. The use of active catalysts resulted in successfully operating the process under mild conditions with low energy consumption. It was found that copper and iron containing catalysts showed promising activity, while the stability of the active metal component was best in catalysts prepared using commercial FAU UOP zeolite.

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

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