The production of pure NaCl by the antisolvent crystallisation of NaCl center dot 2H(2)O and a consecutive recrystallisation step

NaCl . 2H(2)O crystals formed by antisolvent crystallisation with N,N-dimet hylisopropylamine (DMiPA), were recrystallised batchwise into NaCl at 0.2 d egrees C and 0.5 degrees C in pure brines and in brines containing 5 wt% DM iPA. In all experiments the recrystallisation brought about a strong purifi cation of the solid phase. The average DMiPA concentration in the NaCl . 2H (2)O crystals was approximately 1000 ppm, whereas the DMiPA concentration i n the NaCl product was between 1 and 6 ppm. Both the DMiPA concentration in the mother liquor and the recrystallisation temperature influenced the ave rage NaCl crystal size and the rate at which the recrystallisation took pla ce significantly. (C) 1999 Elsevier Science B.V. All rights reserved.