A process (10) for at least partially removing hydrogen cyanide from synthesis gas includes feeding a synthesis gas (30) containing hydrogen cyanide to a gas-liquid contacting stage (18) and, in the gas-liquid contacting stage (18), contacting the synthesis gas with an aqueous washing solution (36) comprising at least one dissolved metal salt, with metal cations of the metal salt being capable of forming metal cyanide complexes and/or metal cyanide precipitates, and weak acid anions of the metal salt serving to buffer the pH of the washing solution in a range between 6 and 10. Hydrogen cyanide is washed from the synthesis gas by the washing solution to form a treated synthesis gas (38) and a spent washing solution (40). From time to time or continuously, at least a portion of the spent washing solution is withdrawn from the gas-liquid contacting stage. The treated synthesis gas (38) is also withdrawn from the gas-liquid contacting stage.