Preparation of Fe/C-Mt composite catalyst and ofloxacin removal by peroxymonosulfate activation

Abstract

In recent years, montmorillonite (Mt) has started to be used as a carrier for catalysts and widely utilized inexpensive adsorbent due to its unique structure. However, the used Mt might cause solid-waste pollution without proper dispose. In order to realize the resource utilization of solid waste, a new strategy for preparing high-performance catalysts was proposed using waste Mt-based materials as precursor, providing a new way to reuse abandoned Mt materials. In this study, the waste Mt was obtained by using iron hydroxide oxide (FeOOH) and hexadecylpyridinium chloride (CPC) to simulate the process of adsorption of contaminants (tetracycline, TC) on the montmorillonite composite. The iron oxide/Carbon-Montmorillonite (Fe/C-Mt) composite catalysts were successfully prepared at 700 °C pyrolysis temperature, reconstructing metal and carbon catalytic sites on Mt through the conversion of FeOOH to Fe3O4 and the organic precursors to graphite carbon. According to the investigation of catalytic performances, the sample after pyrolysis of montmorillonite modified by FeOOH, CPC and TC (Fe/CPC/TC-Mt-p) was determined as the optimum catalyst to activate peroxymonosulfate (PMS), and reaching the degradation efficiency of 96.2% in this oxidation system to treat target pollutants (ofloxacin, OFL). The increase of catalyst dosage and PMS concentration promoted the degradation effect of OFL, while initial pH and anionic species in the solution had little effect. Meanwhile, the synergistic effect of metal and carbon catalytic sites enables this system to have high oxidation activity. Here, Fe/CPC/TC-Mt-p/PMS system was developed with accelerating the generation of 1O2, making 1O2 the major reactive oxygen species for OFL degradation. In addition, Fe/CPC/TC-Mt-p catalyst has good stability, and could reach the initial degradation level of OFL after being regenerated by high temperature pyrolysis. This study provides a novel routine to applications of waste mineral materials and improving treatment efficiency of antibiotic wastewater through PMS activation.