Recovery of phosphate(V) ions from liquid waste solutions containing organic impurities
KOZIK A., HUTNIK N., MATYNIA A., GLUZIŃSKA J., PIOTROWSKI K.
Please cite as: CHEMIK 2011, 65, 7, 675-686
Struvite was continuously produced from water solutions containing phosphate(V) ions (0.20 mass %), magnesium and ammonium ions in stoichiometric proportions, as well as lactic acid (0.03 or 0.06 mass %). Reaction crystallization of struvite was carried out
in temperature 298 K in DT MSMPR type crystallizer with internal circulation of suspension. Influence of pH (from 8.5 to 10) and mean residence time of suspension in the crystallizer (from 900 to 3600 s) on product crystal size distributions, crystal phase homogeneity and shape, as well as on struvite nucleation and crystal phase growth kinetics was identified. Within the process parameter ranges tested product crystals of mean size from 28.6 to 80.0 mm, of diversified habit and size homogeneity were reported. Their linear growth rate varied from 7.68?10?9 to 2.29?10?8 m/s. The best crystals, of typical for struvite shape and required homogeneity were produced at pH 8.5 – 9 and for elongated mean residence time 3600 s. In such defined process conditions lactic acid, simulating presence of organic substance load in diluted water solution of phosphates(V), influenced course and final results of the investigated process advantageously.
Keywords: struvite, phosphate(V) ions, lactic acid, reaction crystallization, continuous DT MSMPR crystallizer, crystal size distribution, process kinetics
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