Preparation of activated carbons doped with iron oxide for removing phenol within pilot-scaled three-phase fluidized bed

Abstract

Activated carbons doped with iron oxide were prepared for decomposition of aqueous phenol in three-phase fluidized bed reactor. The gas, liquid and solid phases in the reactor were ozone, aqueous phenol and Fe/activated carbon, respectively. Two types of activated carbon (AC-US and AC-TH) with average pore diameter of 2.3 and 1.7 nm and specific surface area of 1,060 and 1,154 m2/g, relatively were to use in this work. Based on laboratory-scaled investigation AC-TH was selected used in large-scaled experiments. 5 wt.% Fe on activated carbons were prepared by two techniques, namely wet impregnation (IMA) and incipient wetness impregnation (IMB). After impregnated and calcined at 500°C under nitrogen gas, 5%CAT-TH-A-500 could be prepared from IMA and 5%CAT-TH-B-500 form IMB. With 10 wt.% of Fe precursor, 10%CAT-TH-B-500 was prepared. With 5 wt.% of Fe precursor and calcined at 200°C under ambient air, 5%CAT-TH-B-200 was prepared. All activated carbons combined with ozone could provide detectable phenol and TOC removal efficiency. The sequence of phenol removal efficiency in a period of 60 minutes was as follows: 5%CAT-TH-B-500 + O3 (99%) = 5%CAT-TH-A-500 + O3 (99%) > AC-TH + O3 (98%) > 10%CAT-TH-B-500 + O3 (97%) > 5%CAT-TH-B-200 + O3 (90%) > only O3 (67%). The sequence of TOC removal efficiency at 360 min was as follows: AC-TH + O3 (92%) > 5%CAT-TH-B-200 + O3 (81%) > 5%CAT-TH-A-500 + O3 (71%) = 10%CAT-TH-B-500 + O3 (71%) > 5%CAT-TH-B-500 + O3 (69%) > only O3 (52%). However, AC-TH and 5%CAT-TH-B-200 could provide the hightest efficiency for TOC removal. In pilot-scaled three-phase fluidized bed reactor, the experiments were carried out using 200 L of 20 ppm aqueous phenol with AC-TH + O3 and 5%CAT-TH-B-200 + O3. It was found that 5%CAT-TH-B-200 exhibited with good stability even after repeated use in three consecutive runs (1,080 minutes) in pilot-scaled system. Usable lifetime of 18 hours could be verified from experiments using re-used activated carbon