CRYSTAL-GROWTH OF PYRITE IN AQUEOUS-SOLUTIONS - INHIBITION BY ORGANOPHOSPHORUS COMPOUNDS

The crystal growth of pyrite in aqueous supersaturated solutions at pH 6.50, 25 degrees C was investigated using the seeded growth, pH-stat technique. Crystal growth started immediately after inoculation of iro n(II) sulfide supersaturated solutions with pyrite seed crystals. The crystal growth rates measured from the desupersaturation curves were f ound to depend strongly on the relative solution supersaturation with respect to pyrite. Kinetics analysis yielded an apparent order of 3.5 +/- 0.5 suggesting a surface diffusion controlled mechanism. The prese nce of organophosphorus compounds such as 1-hydroxyethylidene-1,1-diph osphonic acid (HEDP), ,N',N'-ethylenediaminetetrakis(methylenephosphon ic acid)(ENTMP) in the supersaturated solutions at concentration level s between 0.1 and 1000 nM inhibited the crystal growth of pyrite by 70 -100% with respect to the blank experiments. Moreover, in the presence of the compounds tested the crystal growth of pyrite was preceded by well-defined induction times which increased sharply with inhibitor co ncentration. At concentration levels as low as 1 mM, crystal growth wa s completely suppressed. The presence of nitrilotris(methylenephosphon ic acid) (NTMP) had no inhibition effect on pyrite crystal growth. The influence of the inhibitors tested on the kinetics of crystal growth was attributed to the blocking of the active growth sites due to adsor ption.