Effect of struvite seed crystal on MAP crystallization

Liu, Zhigang; Zhao, Qingliang; Wei, Liangliang; Wu, Deli; Ma, Lei

doi:10.1002/jctb.2716

Cited by 36 publications

(19 citation statements)

References 31 publications

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“…It was found that the addition of appropriate seed crystals could increase the rate of crystallization and reduce the induction time and equilibration time significantly. 33 Our former research showed that fluorapatite/calcite mixed seed crystals can induced the removal of fluoride. 18 The mixed seed crystals of fluorapatite/calcite can only induce the formation of Ca 5 (PO 4 ) 3 F and not the formation of other solids in Table 4.…”

Section: Effect Of Coexisting Ions Effect Of Coexisting Cationsmentioning

confidence: 99%

Investigation of fluorapatite crystallization in a fluidized bed reactor for the removal of fluoride from groundwater

Deng

Zhang

Zhou

2018

J of Chemical Tech & Biotech

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BACKGROUND This work further investigates fluoride removal from groundwater by induced crystallization in batch experiments and in a fluidized bed reactor (FBR). Phosphate rock (PR), which is an abundant ore and represents the basic raw material for the phosphatic fertilizer industry, was used as seed crystal in the induced crystallization process. RESULTS Induced crystallization in FBR reduced the concentration of F− in synthetic groundwater from 9.5 mg L‐1 to <1.0 mg L‐1. Phases with the potential for precipitation were calculated through thermodynamic equilibrium modeling. The formed precipitates were identified by powder x‐ray diffraction (XRD) and scanning electron microscopy, coupled with energy dispersive spectroscopy (SEM–EDS). Finally, fluorapatite crystallization mechanisms were confirmed by the induced crystallization of Ca5(PO4)3F on the surface of PR. CONCLUSION The fluorapatite crystallization process in FBR removed F− from groundwater, and the used seed crystal PR was rich in phosphorus and that could be recovered as raw material for the phosphatic fertilizer industry. © 2018 Society of Chemical Industry

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Section: Effect Of Coexisting Ions Effect Of Coexisting Cationsmentioning

confidence: 99%

Investigation of fluorapatite crystallization in a fluidized bed reactor for the removal of fluoride from groundwater

Deng

Zhang

Zhou

2018

J of Chemical Tech & Biotech

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“…Seed crystals can significantly reduce the induction and equilibration times, especially for solutions with a lower supersaturation ratio [25]. In the present work, recycling the synthesized struvite to the reactor and injecting zeolite as an external material were applied to act as a seed substrate for struvite crystallization in the digester effluent and the concentrated seawater.…”

Section: Effect Of Seed Materialsmentioning

confidence: 99%

Use of concentrate water from seawater desalination plant as magnesium sources for struvite formation by using anaerobically digested effluent of swine wastewater

Kim

Min

et al. 2016

Desalination and Water Treatment

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Young Park (2016): Use of concentrate water from seawater desalination plant as magnesium sources for struvite formation by using anaerobically digested effluent of swine wastewater, Desalination and Water Treatment, A B S T R A C TAlthough struvite crystallization has been proven an effective process to recover nutrients from wastewater, this method has not been used widely because of the cost of the raw chemicals, such as magnesium chloride, required as supplements. In this study, in view of the high cost of supplementing magnesium, reject water from a seawater reverse osmosis process was investigated as a potential source of magnesium. The magnesium was used in the nutrient recovery process, by which struvite crystallization was performed from the anaerobically digested effluent of swine wastewater. The results of all the experiments were positive, indicating that struvite formation was successfully performed from the effluent, using the concentrate water as a magnesium source. Removal efficiencies of up to 94.5% for phosphate and 12.7% for ammonium were achieved under normal operating conditions. Seed materials were successfully used as nucleation sites to enhance the purity of the struvite and the crystal size. The removal efficiencies of phosphate and ammonia could be improved up to 97 and 84%, respectively, by adding phosphate and seed materials.

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“…The problem of lower yield in struvite precipitation, in comparison with alkaline conditions, may be minimized using a continuous crystallizer operating at conditions of constant supersaturation . It has also been reported that using MAP seed crystals increased the efficiency of the crystal crop even at low supersaturations …”

Section: Introductionmentioning

confidence: 99%

Phosphorus recovery from simulated municipal wastewater (SMW) through the crystallization of magnesium ammonium phosphate hexahydrate (MAP)

Mpountas

Papadakis

Koutsoukos

2017

J of Chemical Tech & Biotech

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BACKGROUND Phosphorus and nitrogen recovery from municipal and/or industrial wastewater treatment plants in the form of magnesium ammonium phosphate hexahydrate (MgNH4PO4·6H2O, MAP, Struvite) is an attractive alternative for the valorization of wastes. Although efforts have been focused on the recovery of nitrogen and phosphorus nutrients from wastewater at alkaline pH, removal of these nutrients in weakly acid pH is still challenging. The advantage of acid pH is that the precipitation of heavy metals in the form of insoluble hydroxides is avoided provided that their concentrations are relatively low. RESULTS The metastable zone width of solutions, supersaturated with respect to MAP at pH 6.50 was investigated. The kinetics of MAP formation both in unseeded and in seeded solutions was investigated in batch reactors at constant supersaturation. The rates of crystal growth of MAP on seed crystals showed a parabolic dependence on the relative supersaturation. The concentration of the inoculating seed crystals affected the rates of crystal growth. CONCLUSIONS It is possible to crystallize MAP at pH values of 6.50 provided that the supersaturation is sufficient. From the rate dependence on relative supersaturation (parabolic) it was concluded that the crystal growth mechanism was surface diffusion controlled for the integration of the growth units at the active crystal growth sites. Secondary nucleation, depending on the solution supersaturation, was observed within the stable domain of the metastable zone. The morphology of MAP seed crystals remained unchanged, while the mean particle size increased reaching comparable sizes irrespective of the degree of supersaturation. © 2017 Society of Chemical Industry

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Effect of struvite seed crystal on MAP crystallization

Abstract: BACKGROUND: There has been considerable controversy over the effect of seed crystal additions on crystallization of magnesium ammonium phosphate hexahydrates (MAP). In this study, batch experiments were carried out to verify this effect using synthetic solutions.

Cited by 36 publications

References 31 publications

Investigation of fluorapatite crystallization in a fluidized bed reactor for the removal of fluoride from groundwater

Investigation of fluorapatite crystallization in a fluidized bed reactor for the removal of fluoride from groundwater

Use of concentrate water from seawater desalination plant as magnesium sources for struvite formation by using anaerobically digested effluent of swine wastewater

Phosphorus recovery from simulated municipal wastewater (SMW) through the crystallization of magnesium ammonium phosphate hexahydrate (MAP)

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