Method for preparing silver powder by using micro-nano bubbles as crystal seeds

A method for preparing silver powder, comprising the following steps:

• (1) preparing an oxidant solution, the oxidant solution including silver nitrate or silver sulfate, having a silver concentration of 0.1-10 mol/L, and being kept at 10° C. to 50° C.;
• (2) preparing a reductant solution, the reductant solution including a reductant selected from the group consisting of a hydroxylamine compound, vitamin C, a 37% to 40% formaldehyde solution, and hydrazine hydrate, having a reductant concentration of 0.1-10 mol/L, and being kept at 10° C. to 50° C., a volume of the reductant solution being 0.5-5 times a volume of the oxidant solution;
• (3) preparing a dispersant solution, the dispersant solution including a dispersant selected from the group consisting of polyvinylpyrrolidone (PVP), poly(ethylene glycol) 400 (PEG), polyoxyethylenesorbitan monopalmitate, and glycerol and being kept at 10° C. to 50° C., a weight of the dispersant in the dispersant solution being 0.01-5 times a weight of the silver in the oxidant solution;
• (4) preparing a flocculant solution, the flocculant solution including alcohol and a flocculant selected from the group consisting of oleic acid and an oleate, a weight of the flocculant is 0.01% to 10% of the silver in the oxidant solution;
• (5) adding the dispersant solution in a reaction vessel, generating controllable micro-nano bubbles in the dispersant solution by using a micro-nano bubble generator, the micro-nano bubbles being introduced as crystal seeds, adding the oxidant solution and the reductant solution simultaneously to the dispersant solution at a flow rate of 0.1-100 L/min;
• and
• (6) discharging a mixture of the dispersant solution, the oxidant solution and the reductant solution from step (5) into a flocculation sedimentation tank, adding the flocculant solution, stirring for 1-60 min, and standing for precipitation to obtain nearly spherical silver powder having an average particle size of 0.1-10 μm,
• wherein in step (5), the oxidant solution and the reductant solution are simultaneously sprayed through micropores into the dispersant solution at a flow rate of 50 L/min and stirred at 120 rpm.