Styrofoam waste (WPS) was used to prepare a grafted polymer named WPS-g-MA that was applied as an adsorbent for Ni2+ and Cd2+. The obtained polymer-metal complexes (WPS-g-MA horizontal ellipsis M, where M = Ni or Cd) were then utilized separately as a photocatalyst to enhance the degradation of methylene blue (MB) dye. The chemical structure of the WPS-g-MA and WPS-g-MA horizontal ellipsis M was confirmed by their relative functional bands that appear at FTIR chart. Energy-dispersive X-ray (EDX) spectroscopy confirmed the formation of WPS-g-MA (the presence of oxygen) and WPS-g-MA horizontal ellipsis M (the presence of Ni/Cd). The surface morphology of the polymers was investigated by scanning electron microscope (SEM) measurements. The adsorption of Ni and Cd ions onto the WPS-g-MA surface depended on the pH of the metal ions solution as well as the WPS-g-MA dosage. The adsorption performance of WPS-g-MA was calculated and found to be 70% and 80% for Ni and Cd ions, respectively, at pH = 7. The WPS-g-MA...M was used as a heterogeneous catalyst to activate peroxymonosulfates (PMSs) for the production of the sulfate radicals (the most effective and non-selective catalyst for the oxidation of organic compounds). The WPS-g-MA...M caused enhancement of the catalytic activity of PMS (27%) for MB degradation to 100% after 120 min.