OXIDATIVE TREATMENT OF PHENOLIC WASTEWATERS: DETERMINATION OF THE EFFICIENCY OF FE-CONTAINING CATALYST

Phenol and substituted phenols are toxic organic pollutants commonly present in industrial water streams, especially in wastewater of chemical and pharmaceutical industries. However, the phenolic compounds in water can be natural origin, especially some Hungarian thermal water contains these materials. The effective removal of these toxic pollutants from wastewater is an important task of the environmental technology. The treatment of phenol in aqueous solutions has been generally carried out by oxidation of molecular oxygen from the air, at elevated pressure in the presence of catalysts (CWAO: catalytic wet air oxidation). However, the development of CWAO technique is a continuous work to find the proper reaction conditions (oxidant, catalyst, etc.). Our task has been to study the applicability of iron containing materials with different structure in the oxidative treatment of phenolic wastewaters. The catalyst samples (Fe-ZSM5 zeolite, Fe-MCM41 mesoporous silicate, Fe,Mg,Al-mixed oxide and supported Fe2O3) either were synthesized in our laboratory, or natural materials were used after thermal pretreatment (bauxite ore and red mud). XRD and BET adsorption methods were used for characterization of the catalysts. A recirculating bubble reactor was utilized to perform the oxidation of phenol in different origin waters. The reaction was followed by the determination of chemical oxygen demand (COD). All the catalyst samples tested have reasonable activity in the air oxidation at ambient temperature, however, the efficiency can be improved by using of ozone. The obtained results proved the enforceability of the cheap mineral catalysts besides the expensive synthetic ones. Keywords: phenol, catalytic wet air oxidation, Fe-MCM-41, Fe-hydrotalcite, red mu