Comparison of the effect of copper(II) and zinc(II) ions in phosphorus mineral fertilizer industry wastewater on size -dependent linear growth rate of struvite crystals in phosphorus recycling process

摘要

Kinetic parameters of struvite continuous reaction crystn. in phosphate(V), Mg and NH4 ions and Cu(II) or Zn(II) ions- contg. aq. solns. were detd. Calculations were based on kinetic model for ideal MSMPR (mixed suspension mixed product removal) crystallizer assuming a dependence of struvite crystal growth rate on its size RE SDG (Rojkowski exponential, size-dependent growth) model. The presence of Cu(II) ions (0.2-0.5 mg/kg of feed) resulted in increasing the linear growth rate of struvite crystals from 1.35.10(-8) to 1.42.10(-8) m/s, resp., whereas nucleation rate decreased from 1.01.10(15) to 2.58.10(14) 1/(s.m(3)). The Zn(II) ions concn. varied from 0.2 to 2.0 mg/kg of feed and influenced the process disadvantageously. The linear crystal growth rate decreased from 1.64.10(-8) to 1.30-10(-8) m/s, resp., while nucleation rate increased from 1.14.10(13) to 3.9140(15) 1/(s.m(3)). The crystallization was also favored by low pH and elongated up to 3600 s mean residence time of suspension in a crystallizer. The struvite manufactured under the conditions had high quality.