ACCELERATION OF PROBERTITE PRECIPITATION IN BORAX SOLUTIONS BY POLYELECTROLYTES

In this study, the importance of surface charge in the precipitation o f probertite (NaCaB5P9 . 5H(2)O) in borax solution was shown. By contr olling the surface charge with polyelectrolytes, the removal of calciu m ions from the borax solution in the form of probertite, which is the most difficult impurity to remove, was studied. The use of only 5 ppm cationic polyelectrolyte and 0.2% of probertite seed crystals was suf ficient to reduce the calcium ion concentration to the 200 ppm level i n 2 hours. By comparison with the 50-60 hours precipitation time from clear solution to the same level of calcium concentration, it was conc luded that polyelectrolytes can be used as tailor-made additives to co ntrol precipitation.