Heterogeneous catalytic degradation of organic compounds using nanoscale zero-valent iron supported on kaolinite: Mechanism, kinetic and feasibility studies

Herein, nano zero-valent iron (NZVI) particles were anchored on kaolinite (K) for preparation of a mesoporous heterogeneous catalyst (marked as NZVI@K) in Fenton-like oxidation of Acid Black 1 (AB1) dye. The properties of morphological, physico-chemical and textural of catalyst were characterized using powder X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscope (TEM), field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectrometer (EDS) techniques. Results indicated that NZVI particles with 40-80 nm diameter were incorporated successfully on K surface and iron was predominantly in Fe form. Prior oxidation experiments, adsorption studies were performed to determine the equilibrium point and also modeling (kinetic and isotherm) of the process. Fenton-like oxidation showed a better performance in decolorization of AB1, compared to adsorption process. The excellent reusability and high stability were found for NZVI@K during four consecutive use cycles. Under optimum operational conditions (pH: 2.0, catalyst dose: 0.3 g/L, H2O2 amount: 4.0 Mm), over 98% of dye (30 mg/L) and 76% of TOC were removed within 120 min reaction. A tentative mechanism was proposed for decomposition of H2O2 and production of reactive oxidizing species, based on the results of quenching tests. Decreasing decolorization rate in the presence of anions obeys the order of bicarbonate > chloride > nitrate > sulfate. A significant synergistic effect was detected when NZVI@K were coupled with H2O2. Reducing removal efficiency and the scavenging effect were observed at excessive concentrations of both catalyst and oxidant. Integration of adsorption and oxidation processes using NZVI@K coupled with H2O2 can be introduced as a promising technique for efficient decolorization of wastewaters, due to high adsorption capacity, good catalytic activity and minimal iron leaching. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.