The disclosure relates to methods for making carbon-supported transition metal-based nanoparticles, comprising (a) mixing at least one carbon feedstock, at least one transition metal-containing feedstock, at least one organic binder, and at least one resin binder to form a feedstock mixture, (b) extruding the feedstock mixture, and (c) heating the extruded feedstock mixture at a temperature and for a time sufficient to carbothermally reduce the transition metal-containing feedstock. Also disclosed herein are carbon-supported transition metal-based nanoparticles produced by such methods. Further disclosed herein are methods for treating water and waste streams comprising contacting the water or waste streams with the carbon-supported transition metal-based nanoparticles.