Removal of polymethyl methacrylate nanoplastics and silver nanoparticles by a novel ferrofluid-COF-aminated natural cotton-based hydrogel nanosorbent

Abstract

In this work, an innovative nanosorbent is assembled based on the combination of Fe2VO6 ferrofluid, silane covalent organic frameworks (COFs) and gelatin/aminated natural cotton/chitosan hydrogel (FF-SiCOF@Gel-ANC@Ch.Hgel). The developed nanomaterial was fully identified using several characterization techniques such as FTIR, electron microscopy, XRD and XPS; and was then studied as an effective nanosorbent for removal of organic nanopollutants such as polymethyl methacrylate nanoplastics (PMMA) and inorganic nanopollutants such as silver nanoparticles from water. Optimization of experimental parameters such as reaction duration, nanosorbent mass, nanopollutant concentration, solution pH, temperature and medium ionic strength revealed promising removal efficiencies towards both nanopollutants with 98.3% and 99.2% recovery for Ag and PMMA nanopollutants, respectively. Kinetic studies confirmed that the adsorptive removal of both nanosorbent followed via a pseudo-second order chemisorption process. Thermodynamic investigations highlighted that spontaneity of the chemisorption process in terms of negative ΔG° values. Industrial scale applicability was confirmed with interestingly high removal efficiencies toward both nanopollutants (99.45% and 96.80% for Ag and PMMA, respectively) in industrial wastewater. Furthermore, proposed nanosorbent showed appreciable recyclability with little decrease in removal efficiencies (from 95.30% to 91.00% and from 97.20% to 93.00% for Ag and PMMA respectively) after 5 adsorption/regeneration cycles. Considering nanosorbent comparatively high adsorption capacities, together with its industrial applicability and reusability, it was proposed as a promising candidate for wastewater treatment applications. The green aspects in this study were investigated in terms of reusing the recovered Ag@FF-SiCOF@Gel-ANC@Ch.Hgel as a potential nanocatalyst in reductive degradation of sulfasalazine drug, a potentially hazardous pollutant. High degradation rates were deduced at optimal conditions providing 2.3 min−1pseudo-first order rate constant with only 3.18% drop in the catalytic activity after 5 successive reduction/regeneration cycles. This accounts for the promising potential of recycled Ag@FF-SiCOF@Gel-ANC@Ch.Hgel as reductive degradation catalyst for targeted water treatment applications.