Combination of activated carbon adsorption with light-enhanced chemical oxidation via hydrogen peroxide

Abstract

A tertiary treatment scheme involving simultaneous operation of activated carbon adsorption and advanced oxidation with ultraviolet light and hydrogen peroxide, followed by “destructive regeneration” of the spent adsorbent by advanced oxidation was investigated, using phenol as a model compound. Operational parameters in each step were optimized on the basis of phenol and total organic carbon removal during selected contact times. It was found that in the first stage with adsorption/advanced oxidation, phenol was totally eliminated during the first quarter of the contact time, and 87.5% total organic carbon removal was accomplished at the end. It was further found that advanced oxidation was the dominant pathway in this operation for the disappearance of phenol, while that of total organic carbon was carried out by combined effects of adsorption and oxidative degradation. Optimum regenerating frequency for the spent activated carbon was found to be once every four batches, which was four times slower than the required frequency in the absence of advanced oxidation. In the second part of the operation, where the spent carbon was regenerated destructively via advanced oxidation, 92.5% mineralization was accomplished in the regenerating solution at the end of the optimized contact time. The economic assessment of the system considering the operation of both steps revealed that under the initial and optimized conditions, the operating cost is 2.26 USD per cubic meter of wastewater with 40 ppm phenol.