Preparation of Fe catalyst coated on activated carbon for decomposition of aqueous phenol in three-phase fluidized bed reactor

Abstract

A lab-scale three-phase fluidized-bed reactor was used for removal of aqueous phenol by adsorption and decomposition. The gas, liquid and solid phases were air bubbles with or without ozone, aqueous phenol, and granular activated carbon (AC) with and without Fe on AC, respectively. Both the gas flow and liquid recirculation rate were controlled at 1 L.min-1 and the catalyst loading was 5 g per batch. The experiments were carried out using 2 L of 10 ppm phenol solution. Some intermediate products such as hydroquinone (HQ) and catechol (CC) were also detected but they were eventually decomposed to carbon dioxide and H2O. First, two types of AC (AC1 and AC2) with BET surface areas of 1,106 and 1,150 m2.g-1 and average pore diameters of 2.3 and 1.7 nm, respectively, were compared. It was found that AC1 with more mesopores removed the intermediate products better than AC2 with more micopores. Since both AC removed phenol with the same efficiency, AC1 was selected for use in all subsequent experiments. Comparison of the phenol and TOC removal efficiencies were made for the following cases: 1) only O3 from pure O2 or air, 2) only AC, 3) only Fe/AC, 4 and 5) O3 in combination with cases 2) and 3), respectively. The sequence of decreasing phenol removal efficiency was as follows: 5) (100% at 15 min) > 4) (100% at 30 min) > 3) (100% at 45 min) ≈ 2) (100% at 45 min) > 1) from pure O2 (100% at 90 min) > 1) from air (100% at 150 min). Meanwhile, the sequence of decreasing TOC removal efficiency was as follows: 4) (89% at 150 min) > 5) (83% at 150 min) > 2) (79% at 150 min) > 3) (77% at 150 min) > 1) from pure O2 (70% at 150 min) > 1) from air (negligible removal). In conclusion, the use of AC with O3 from air was a best compromise in terms of TOC removal efficiency and operation costs