A process for selectively removing and recovering sulfur dioxide from a sulfur dioxide-containing source gas, the process comprising: contacting a feed gas stream comprising the source gas in a sulfur dioxide absorber with a buffered aqueous absorption medium comprising a salt of a polyprotic carboxylic acid, thereby absorbing sulfur dioxide from the feed gas stream into the absorption medium and producing an exhaust gas from which sulfur dioxide has been removed and a sulfur dioxide-enriched absorption liquor comprising aqueous absorption medium and sulfur dioxide absorbed therein; heating the sulfur dioxide-enriched absorption liquor in an absorption liquor stripper to desorb sulfur dioxide from the sulfur dioxide-enriched absorption liquor and thereby produce a regenerated aqueous absorption medium and a sulfur dioxide-enriched stripper gas; recirculating regenerated aqueous absorption medium to the sulfur dioxide absorber for further absorption of sulfur dioxide from further flow of the feed gas stream, wherein divalent sulfur oxyanion impurities accumulate in the aqueous absorption medium recirculated between the absorption liquor stripper and the sulfur dioxide absorber; and contacting an anion exchange feed stream comprising at least a portion of the aqueous absorption medium recirculated between the absorption liquor stripper and the sulfur dioxide absorber with an anion exchange resin, thereby selectively removing divalent sulfur oxyanion impurities from the anion exchange feed stream to produce a treated aqueous absorption medium from which impurities have been removed and an anion exchange resin charged with impurities removed from the anion exchange feed stream, wherein the anion exchange feed stream is acidified prior to contact with the anion exchange resin to convert at least a portion of the polyprotic carboxylic acid salt therein to the corresponding acid. contacting a feed gas stream comprising the source gas in a sulfur dioxide absorber with a buffered aqueous absorption medium comprising a salt of a polyprotic carboxylic acid, thereby absorbing sulfur dioxide from the feed gas stream into the absorption medium and producing an exhaust gas from which sulfur dioxide has been removed and a sulfur dioxide-enriched absorption liquor comprising aqueous absorption medium and sulfur dioxide absorbed therein; heating the sulfur dioxide-enriched absorption liquor in an absorption liquor stripper to desorb sulfur dioxide from the sulfur dioxide-enriched absorption liquor and thereby produce a regenerated aqueous absorption medium and a sulfur dioxide-enriched stripper gas; recirculating regenerated aqueous absorption medium to the sulfur dioxide absorber for further absorption of sulfur dioxide from further flow of the feed gas stream, wherein divalent sulfur oxyanion impurities accumulate in the aqueous absorption medium recirculated between the absorption liquor stripper and the sulfur dioxide absorber; and contacting an anion exchange feed stream comprising at least a portion of the aqueous absorption medium recirculated between the absorption liquor stripper and the sulfur dioxide absorber with an anion exchange resin, thereby selectively removing divalent sulfur oxyanion impurities from the anion exchange feed stream to produce a treated aqueous absorption medium from which impurities have been removed and an anion exchange resin charged with impurities removed from the anion exchange feed stream, wherein the anion exchange feed stream is acidified prior to contact with the anion exchange resin to convert at least a portion of the polyprotic carboxylic acid salt therein to the corresponding acid.