Preparation and Characterization of Polymer-Coated Magnetic Nanoparticles: Assessment of Heating Ability and Pollutants Remediation Efficiency

Abstract

Abstract : Chlorophenols (CPs) are hazardous compounds widely used in industries including plastic, papers, textiles, steel, pharmaceuticals, dyes, pesticides, insecticides, and herbicides. However, their environmental persistence leads to their accumulation in soil and water, thereby posing significant risks to ecosystems and human health. In this work, we synthesized various types of iron oxide magnetic nanoparticles (MNPs), either coated with polymers (i.e. PVP, Chitosan, Starch) or doped with metal ions (i.e. Co2+, Ni2+, Zn2+) and studied their catalytic efficiency in degrading two common organic CP contaminants: 4-Chlorophenol (4-CP) and 2-Chlorophenol (2-CP). All MNPs were thoroughly characterized using XRD, FTIR, VSM, TEM, and SEM-EDX. These characterization techniques confirmed the formation of uniform nanosized particles (~ 8-15 nm), highly crystalline cubic spinel structures, and superparamagnetic behavior. The CPs degradation studies showed that both polymer-coated MNPs (PMNPs) and metal-doped MNPs (MMNPs) were effective at eliminating CPs although at different efficiencies. Interestingly, the metal-doped MNPs, especially CoF2O4, exhibited outstanding performance, achieving complete degradation of 50 ppm 4-CP and 2-CP within 15 and 80 seconds, respectively. These enhancements are attributed to the spinel ferrite structure, intrinsic peroxidase-like activity, stability of the redox pair in octahedral sites, and reduced particle sizes. Additional factors such as pH, catalyst dosage, pollutant concentration, H2O2 levels, and temperature were also tested and were found to influence degradation. Reusability studies demonstrated that the different as-synthesized NPs could be reused for six consecutive cycles without significant loss of activity (~99% for CoFe2O4, 91.1% for PVP-coated MNPs, and 76.97% for bare Fe3O4). Interestingly, the application of an alternating magnetic field (AMF) generating heat dissipation from MNPs significantly accelerated the degradation process compared to mechanical stirring. For instance, 100% degradation for 50 ppm 4-CP was reached within 10 minutes under AMF, while within the same time-fame, and without mechanical shaking nor, AMF, only 4% degradation was achieved. According to our knowledge, these promising results using AMF to degrade CPs are presented for the first time. This underscores the promise of such metal-doped MNPs as fast, efficient, and reusable nanocatalysts for potential industrial wastewater treatment involving chlorophenol contaminants.