A facile method to prepare functional fibers with excellent adsorption and catalysis property for organic pollutant removal

J. Wang
Henan Academy of Sciences, China,

Keywords: functional fibers, Mn oxides, adsorption, catalysis, peroxymonosulfate


Development of functional materials with efficient adsorption and catalytic properties are very important for their practical application in environmental remediation. Loading nanostructures on flexible fibers or textiles seems to be one of the most promising way for preparation of functional materials due to their broad accessibility, various application forms, fast reaction kinetic, extremely low pressure drop and pretty easy solid-liquid separation. In this study, a facile method was proposed to load manganese oxides (MnOx) nanostructures, which shows excellent adsorption, oxidation and catalysis ability, on two different kinds of fibers, i.e. natural cotton fiber and synthetic poly(acrylonitrile) fiber. The method involved a one-pot in-situ sono-assisted KMnO4 reduction process with no additional reducers. To increase the uniformity and stability of MnOx nanostructures, the raw fibers were pretreated to introduce more functional groups. Specifically, cotton fiber was pretreated by dilute NaOH to activate intrinsic hydroxyl groups (product designated as BCF), while poly(acrylonitrile) fiber was grafted with carboxyl groups through the NaOH hydrolysis method (product designated as CPAN). Results showed that with the assistance of hydroxyl and carboxyl groups, MnOx nanostructures could be distributed uniformly and stably on BCF and CPAN surface, with no obvious agglomeration observed even when the amount of MnOx reached above 20%. Diameters and loading ratios of MnOx differed between the two fibers; about 15% of MnOx (diameters 10-30 nm) could be loaded on BCF, while about 23% of MnOx (diameters 50-100 nm) could be loaded on CPAN. The as-prepared MnOx loaded BCF and CPAN were then studied for their adsorption and catalysis behavior using dyes (e.g. methylene blue-MB), phenol and antibiotic (e.g. ciprofloxacin-CIP) as typical organic pollutants. Results showed both of the two functional fibers showed efficient removal performance. Under the studied conditions, MB removal equilibrium was reached within 10 minutes and solution pH showed no significant influence in a wide pH range (2-11). MB adsorption obeyed pseudo-second-order kinetic model and Langmuir model well. The calculated maximum adsorption capacity (Qm) were 46.3 mg/g for MnOx@BCF and 714 mg/g for MnOx@BCF, respectively, substantially higher than the raw BCF or CPAN and most of previously reported adsorbents. It was proposed that cationic dyes were removed through an adsorption-partial oxidation mechanism. Phenol was removed through a catalytic degradation process, with MnOx@CPAN as the catalyst and externally added peroxymonosulfate as the oxidant. CIP 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 loaded fibers a promising candidate for organic pollutant removal.