Solvent and method for recycling SO2 from industrial waste gas

The invention belongs to the field of gas purification technology. An ionic liquid is adopted as an absorbent to remove sulfur dioxide (SO2) in industrial waste gas. An ionic liquid aqueous solution containing a piperazine or piperazine derivative tetrabutyl halogenated quaternary ammonium salt ionic liquid is adopted as the absorbent, the total mass content of the ionic liquid in the absorbent is 20%-50%, and the adopted absorption temperature is 40-60 DEG C. SO2 in gas flow is removed through countercurrent contact with the ionic liquid aqueous solution, the ionic liquid aqueous solution absorbing SO2 is regenerated to separate out SO2 gas, and the ionic liquid aqueous solution obtained after regeneration is circulated to the absorption step for anew absorbing. The ionic liquid aqueous solution is adopted as the recyclable SO2 gas absorbent, has high absorption efficiency, and has no secondary pollution.