A process for desulphurisation of a gas containing sulphur oxides (SOx) in a wet scrubbing unit is described. The process comprises the step of: contacting said gas with an aqueous tricalcium aluminate hexahydrate (TCA6) scrubbing slurry to remove SOx from the gas by reaction with TCA6 to form a spent scrubbing solution comprising a calcium compound containing sulphur and oxygen, and a aluminium compound containing oxygen and hydrogen.