A magnetic coagulant (a new selective water treatment agent in the form of black powder) was prepared from acid-modified fly ash compounded with magnetite according to a specific proportion (mflyash/mmagnetite/VHCl02 g:1 g:1 mL). Fly ash was obtained from Hefei Power Plant, and its main chemical components are listed in Table 1. Magnetite (Fe3O4; red and black
amorphous powder, chemical grade) was provided by Sinopharm Chemical Reagent Co. Ltd. The other reagents used were analytical grade