Phenol oxidation by a sequential CWPO–CWAO treatment with a Fe/AC catalyst

Abstract

Catalytic wet peroxide oxidation (CWPO) of phenol with a homemade Fe/activated carbon (Fe/AC) catalyst has been studied in a stainless steel fixed-bed reactor at different operating conditions ( T = 23–100 °C, P T = 1–8 atm, W = 0–2.5 g, and τ = 20–320 g CAT h/g Phenol). The results show that, thanks to the incorporation of Fe on the activated carbon, phenol conversion improved dramatically, reaching a 90% at 65 °C, 2 atm, and 40 g CAT h/g Phenol. However, TOC conversion values remain fairly low, (around 5% at 40 g CAT h/g Phenol), and no improvement was obtained with the inclusion of Fe. The presence of Fe seems to promote the nondesirable coupling reactions that take place in CWPO of phenol due to the condensation of the ring intermediates (the primary phenol oxidation products). These condensation products are quite refractory to CWPO at the conditions employed. Taking advantage of the high phenol conversions in CWPO and the high phenol mineralization in CWAO, along with the good stability of the Fe/AC catalyst, a CWPO–CWAO sequential treatment has been successfully performed by using a fixed-bed and trickle-bed reactor in series. A CWPO treatment at ambient conditions followed by a CWAO treatment at mild conditions (100 °C and 8 atm) is presented as high efficiency process for the decontamination of phenolic wastewaters.