Heterogeneous persulfate oxidation of BTEX and MTBE using Fe3O4−CB magnetite composites and the cytotoxicity of degradation products

Abstract

Groundwater contamination by organic aromatic compounds such as gasoline fuel is a serious worldwide problem because of their carcinogenic and mutagenic potential. This study evaluated the use of Fe3O4−carbon black (CB) composites for persulfate (PS) oxidation of benzene, toluene, ethylene, and xylene (BTEX) and methyl tert-butyl ether (MTBE) compounds from the aqueous solution. The characterization results of environmental scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and a superconducting quantum interference device magnetometry evidenced the successful synthesis of Fe3O4−CB composites. In addition, the in vitro cytotoxic activity and apoptotic response of these composites were investigated before and after the Fe3O4−CB/PS processes test of the BTEX and MTBE samples was performed. The effects of various operating parameters were evaluated to optimize the oxidation process, including the PS concentration, initial pH, and Fe3O4−CB amount. The results showed that increasing PS and Fe3O4−CB dosage could accelerate BTEX and MTBE oxidation when PS and Fe3O4−CB concentrations increased to 15 g L−1 and 1.0 g L−1, respectively, at a pH of 3.0. The degradation rate of BTEX and MTBE was strongly pH-dependent. Methyl thiazolyl tetrazolium assay was employed to perform a cytotoxicity study after Fe3O4−CB/PS processing treatment of BTEX and MTBE degradation products on the zebrafish (Danio rerio) embryonic cell line (ZF4), which revealed that a weak effect and apoptosis in cell viability ultimately leads to cell death. The results suggested that Fe3O4−CB assisted persulfate oxidation without elevating the temperature is a suitable and economic alternative for the ex-situ treatment of BTEX- and MTBE-contaminated aquatic environments.