Ferrous sulfide-containing passivator for removing heavy metal from soil and preparation method and use thereof

A method, comprising:

• 1) dissolving a sulfide in an alkaline solution to form a mixed solution with a pH of 12-13;
• 2) adding sodium silicate to the mixed solution and stirring for 0.5-1 hour at 20-40° C.;
• 3) adding an aqueous solution of a ferrous salt to the mixed solution containing sodium silicate, and allowing to react at 40-60° C. for 2-3 hours;
• where, with decrease of the pH of the mixed solution, sodium silicate is converted into silica nanoparticles, and the ferrous salt reacts with the sulfide to form ferrous sulfide;
• and
• 4) further adding an aqueous solution of an organic modifier to the mixed solution, and allowing to react at 40-60° C. for 1-2 hours to form a passivator slurry comprising surface-modified ferrous sulfide doped with silicon dioxide;
• filtering the passivator slurry through suction filtration to form a filter cake passivator or spray drying the passivator slurry to form a dry powdery passivator.