Carboxyl group-assisted uniform growth of MnOx nanospheres on poly(acrylonitrile) fiber for enhanced removal of organic pollutants

Development of functional fibers with efficient adsorption and catalytic properties is very important for their practical application in environmental remediation. In this study, carboxyl groups were firstly grafted onto the commercial poly(acrylonitrile) fiber (product designated as CPAN) and then used for in situ growth of manganese oxides (MnOx) nanospheres (product designated as MnOx@CPAN). Results showed that with the assistance of carboxyl groups, MnOx nanospheres (diameters 50-100 nm) could be distributed uniformly and stably on CPAN surface, and no obvious agglomeration was observed even when the amount of MnOx reached 23.4%. The resultant MnOx@CPAN showed efficient removal for organic pollutants including cationic dyes (e.g. methylene blue), phenol and antibiotic (e.g. ciprofloxacin). It was proposed that cationic dyes were removed through an adsorption-partial oxidation mechanism. The maximum adsorption capacity of methylene blue was 714 mg/g, substantially higher than the raw CPAN and most of previously reported adsorbents. Phenol was removed through a catalytic degradation process, with MnOx@CPAN as the catalyst and externally added peroxymonosulfate as the oxidant. Ciprofloxacin could be removed either through the adsorption process with CPAN as the adsorbent, or through the catalytic degradation process in the MnOx@CPAN/peroxymonosulfate system. We believe that the facile and green synthesis and excellent organic removal would make the as-synthesized MnOx@CPAN a promising candidate for organic pollutant removal.