there is provided a process for the recovery of essentially enantiomerically pure d - tartaric acid from aqueous and organic waste streams generated in the resolution of racemic 2 - amino - 2 , 3 - dimethylbutyronitrile via the formation and isolation of a crystalline monobasic tartrate salt . the recovered optically pure d - tartaric acid may be efficiently recycled to provide a sustainable resolution of racemic 2 - amino - 2 , 3 - dimethylbutyronitrile .