Coated magnetic nanoparticles and methods for attracting, isolating, and/or removing of particulate waste from environments are provided. A coated magnetic nanoparticle may include an iron-containing core surrounded by a hydrophobic or amphiphilic coating. This coating can include a functional group based on PDMS such as C-PDMS, PDMS-co-APMS, and/or PDMS-OH block copolymers. The magnetic nanoparticles may be synthesized in air or air-free in an inert gas. The magnetic nanoparticles may be introduced into, for example, an aqueous environment to bind with waste contained therein through an adsorption process. The magnetic nanoparticles and bound waste may be attracted and removed from the environment by introducing an external magnetic field.