Liquid Phase Oxidation of Phenols in Industrial Wastewater Using an Adsorbent – Catalyst Matrix

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Phenols constitute an important class of toxic organic compounds found in most refinery waste water streams. Due to its refractory nature towards conventional waste water treatment methods it requires a much more severe conditions to effect meaningful oxidation. Catalytic Wet Air Oxidation (CWAO), the most promising treatment method for phenol abatement currently has a high operation cost due largely to the absence of a suitable cost effective catalyst. The current study has investigated the use of the spent Fluidized Catalytic Cracking (FCC) catalyst as a suitable cost effective catalyst for the CWAO process and identified the appropriate operating conditions for its usage in this regard. The spent FCC catalyst has been proven to be a good adsorbent of phenol, a property not found in the fresh catalyst. Its performance as phenol adsorbent compared with activated carbon has been found to be about 16.62% that of activated carbon. It was found out that particles were agglomerated with a d25 for the fresh and spent catalyst being 48 μm and 68 μm respectively against a d50 of 68 μm and 88 μm respectively. The pore volume had also increased from 0.4 cm3/g to 0.9 cm3/g. The spent FCC unlike the fresh catalyst was found to contain Ni, V, Cu, Fe and Sr which are potential catalyst. The spent catalyst was impregnated with varying amounts of CuO, Fe2O3 and MnO2 and tested for phenol oxidation using various amounts of H2O2 as radical initiator. It was however found out that the spent catalyst impregnated with 0.97% Fe2O3 was a very effective catalyst for the catalytic wet air oxidation of phenol using 1 vol. % H2O2 as a iii radical initiator and a relatively low air pressure of 0.4 cm Hg (533 Pa) gauge and temperature of 50oC. The results were then tested with refinery stripped sour water with about 100% mineralization.
Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirement for the degree of DOCTOR OF PHILOSOPHY