Nucleation in the formation of struvite: state of art

Morita, Dione Mari; Avila, Renan de Luca; Aidar, Fernando Ngan

doi:10.1590/S1413-41522019113711

Dione Mari Morita ^**Autor correspondente: dmmorita@usp.br

Universidade de São Paulo - São Paulo (SP), Brasil.

http://orcid.org/0000-0002-0506-0972

Renan de Luca Avila

Universidade de São Paulo - São Paulo (SP), Brasil.

http://orcid.org/0000-0002-9284-8310

Fernando Ngan Aidar

Universidade de São Paulo - São Paulo (SP), Brasil.

http://orcid.org/0000-0002-2044-9839

*Autor correspondente: dmmorita@usp.br

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Figura 1 -
Variação das concentrações das espécies de fósforo em função do pH: (A) em diferentes temperaturas; (B) em diferentes intensidades iônicas; (C) em diferentes concentrações totais de fósforo.

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Figura 2 -
Tempo de indução em função da razão de supersaturação obtidos por diferentes autores.

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Tabela 1 -
Influência do cálcio na formação da estruvita.

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Tabela 2 -
Reações consideradas pelos pesquisadores que estudaram os aspectos termodinâmicos da formação e dissolução da estruvita.

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Tabela 3 -
Valores da constante do produto de solubilidade de atividade (pK_S0) da estruvita obtidos por diferentes pesquisadores.

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M g 3 H P O 4 . 3 H 2 O ↔ 3 H 2 O + H P O 4 2 - + M g 2 + -5,8 (KPS) Musvoto et al. (2000), Çelen et al. (2007)

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M g H P O 4 . 3 H 2 O ↔ 3 H 2 O + H P O 4 2 - + M g 2 + -5,8 (KPS) Musvoto et al. (2000), Çelen et al. (2007)

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M g 3 H P O 4 . 8 H 2 O ↔ 8 H 2 O + 2 P O 4 3 - + 3 M g 2 + -25,2 (KPS) Musvoto et al. (2000), Mehta e Batstone (2013), Song et al. (2015)

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M g 3 P O 4 2 . 8 H 2 O ↔ 8 H 2 O + 2 P O 4 3 - + 3 M g 2 + -25,2 (KPS) Musvoto et al. (2000), Mehta e Batstone (2013), Song et al. (2015)

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[P-PO₄] (mM)	[Mg] (mM)	[N-NH₃] (mM)	[Ca] (mM)	Faixa de pH	Condições nas quais a estruvita foi formada	O que aconteceu fora dessas condições?	Escala	Meio de cristalização	Referência
1,64	1,64	3,28	0, 0,82; 1,64; 3,28	9,0	Mg:Ca > 2:1	Formou apenas “fosfato de cálcio amorfo”	laboratório	Água ultrapura com íons CO₃adicionados	*Le Corre et al. (2005*LE CORRE, K.S.; VALSAMI-JONES, E.; HOBBS, P.; PARSONS, S.A. (2005) Impact of calcium on struvite crystal size, shape and purity. Journal of Crystal Growth, v. 283, n. 3-4, p. 514-522. https://doi.org/10.1016/j.jcrysgro.2005.06.012 https://doi.org/10.1016/j.jcrysgro.2005.... )
6,13	3,07; 6,13; 12,26	122,6	3,07; 6,13; 12,26	7,8; 8,7; 9,2; 10,5	8,0 < pH < 9,0 e P:Ca > 2:1	Formou apenas “fosfato de cálcio” amorfo	laboratório	Efluente de criadouros de animais confinados	*Wang et al. (2005*WANG, J.; BURKEN, J.G.; ZHANG, X.; SURAMPALLI, R. (2005) Engineered struvite precipitation: Impacts of component-ion molar ratios and pH. Journal of Environmental Engineering, v. 131, n. 10, p. 1433-1440. https://doi.org/10.1061/(ASCE)0733-9372(2005)131:10(1433) https://doi.org/10.1061/(ASCE)0733-9372(... )
2,58	3,61	20,63	1,81; 3,61; 7,22	9,5	Mg:Ca > 2:1	A formação de estruvita foi inibida, para pH > 11, formou apenas MgOH₂	laboratório	Efluente sintético de criadouro de porco	*Song et al.* (2007**SONG, Y.; YUAN, P.; ZHENG, B.; PENG, J.; YUAN, F.; GAO, Y. (2007) Nutrients removal and recovery by crystallization of magnesium ammonium phosphate from synthetic swine wastewater. Chemosphere, v. 69, n. 2, p. 319-324. https://doi.org/10.1016/j.chemosphere.2007.06.001 https://doi.org/10.1016/j.chemosphere.20... )
3,0	2,5	7,5	2,17	7,5; 8,5; 9,5; 10,5; 11,5	Para qualquer pH < 10,5; mesmo para Mg:Ca = 1,2	Formaram Ca₃PO₄, CaHPO₄, Mg₃PO₄ ou MgOH₂ amorfos	laboratório	Água de torneira com alta concentração de Ca	*Hao et al. (2008*HAO, X.D.; WANG, C.; LAN, L.; VAN LOOSDRECHT, M.C.M. (2008) Struvite formation, analytical methods and effects of pH and Ca 2+. Water Science and Technology, v. 58, n. 8, p. 1687-1692. https://doi.org/10.2166/wst.2008.557 https://doi.org/10.2166/wst.2008.557... )
2,2; 2,0; 2,7	24,6; 19,9; 20,8 respectivamente	2,2; 2,1; 12,0 respectivamente	4;8; 3,9; 4,1 respectivamente	7,79; 9,57; 7,86 respectivamente	pH = 7,86 e N:P = 4; concluíram que o Ca não influencia na formação da estruvita	Formou Mg₃(PO₄)₂.10H₂O com material amorfo para pH = 7,79; e fosfatos de Mg e Ca para pH = 9,57	piloto	Efluente de indústria de peixes congelados	Crutchik e Garrido (2011CRUTCHIK, D.; GARRIDO, J.M. (2011) Struvite crystallization versus amorphous magnesium and calcium phosphate precipitation during the treatment of a saline industrial wastewater. Water Science and Technology, v. 64, n. 12, p. 2460-2467. https://doi.org/10.2166/wst.2011.836 https://doi.org/10.2166/wst.2011.836... )
10,7	17,5	38,7	20,0	7,0 a 10,0	pH = 9,0 em relação de atividades Ca²:Mg²⁺ < 0,2:1	Somente carbonato de cálcio precipitou na água residuária real (filtrado do digestor anaeróbio de uma indústria de laticínios) em pH 9,0 a 10,0	laboratório	Solução sintética para avaliar efeito do cálcio e real para determinar remoção de cálcio	Huchzermeier e Tao (2012HUCHZERMEIER, M.P.; TAO, W. (2012) Overcoming Challenges to Struvite Recovery from Anaerobically Digested Dairy Manure. Water Environment Research, v. 84, n. 1, p. 34-41.)
15,5	0 a 9,6	7,0	0 a 16,0	5,07 a 10,93	Em pH > 7,9 e Mg:Ca > 4:1 obtém-se estruvita com alta pureza (> 98%)	Hidroxiapatita - em Mg:Ca < 1:9 e 8,0 < pH < 10,5; brushita - em pH < 6,5 e Mg:Ca < 4:1; Newberita - em pH < 6,0 e Mg:Ca > 4:1; monetita - CaHPO₄ em pH < 6,5 e Mg:Ca < 1:4; whitloquita - em 6,5 < pH > 8,5 e Mg:Ca de 4:1 a 1:4	Laboratório	Mistura de soluções de MgCl₂; CaCl₂; NH₄Cl, Na₃PO₄ e NaH₂PO₄ 0,1 M	*Muster et al. (2013*MUSTER, T.H.; DOUGLAS, G.B.; SHERMAN, N.; SEEBER, A.; WRIGHT, N.; GÜZÜKARA, Y. (2013) Towards effective phosphorus recycling from wastewater: Quantity and quality. Chemosphere, v. 91, n. 5, p. 676-684. https://doi.org/10.1016/j.chemosphere.2013.01.057 https://doi.org/10.1016/j.chemosphere.20... )
16,7	16,7	16,7	3,3; 5,6; 8,4; 16,7; 20,9 e 33,4 respectivamente	7,5; 8,0; 9,0; 10,0 e 11,0	Todas, mas com diferentes purezas. O aumento da relação Ca:Mg e do pH ocasionou redução na pureza.	A porcentagem de estruvita era menor que 50% em Ca:Mg ≥ 1:1 e em pH ≥ 10,0. O outro precipitado formado era hidroxiapatita em valores de pH 7,5 e 8,0. Em pH 10,0 e 11,0, forma-se fosfato de cálcio amorfo e Mg₃PO₄.22H₂O e Mg₃PO₄.6H₂O	laboratório	Água desionizada com adição de cloreto de cálcio e cloreto férrico	Yan e Shih (2016YAN, H.; SHIH, K. (2016) Effects of calcium and ferric ions on struvite precipitation: A new assessment based on quantitative X-ray diffraction analysis. Water Research, v. 95, p. 310-318. https://doi.org/10.1016/j.watres.2016.03.032 https://doi.org/10.1016/j.watres.2016.03... )

Reação	logk ou logK_PS onde especificado	Referência
$H_{2} O \leftrightarrow H^{+} + {O H}^{-}$	14,0	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.), *Hanhoun et al.* (2011HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... ), Rahaman et al. (2014**RAHAMAN, M.S.; MAVINIC, D.S.; MEIKLEHAM, A.; ELLIS, N. (2014) Modeling phosphorus removal and recovery from anaerobic digester supernatant through struvite crystallization in a fluidized bed reactor. Water Research, v. 51, p. 1-10. https://doi.org/10.1016/j.watres.2013.11.048 https://doi.org/10.1016/j.watres.2013.11... )
${{N H}_{3} + H^{+} \leftrightarrow N H}_{4}^{+}$	9,24	Webb e Ho (1991WEBB, K.M.; HO, G.E. (1991) Struvite (MgNH4PO4.6H2O) solubility and its application to a piggery effluent problem. In: WORKSHOP ON APPROPRIATE TECHNOLOGY FOR ENVIRONMENTALLY SUSTAINABLE DEVELOPMENT. Anais… ASEAN, Perth, Australia: Remote Area Developments Group, p. 39-45.), Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.), Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Doyle e Parsons (2002DOYLE, J.D.; PARSONS, S.A. (2002) Struvite formation, control and recovery. Water Research, v. 36, n. 16, p. 3925-3940.), Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.), Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... ), *Hanhoun et al.* (2011HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... ), Rahaman et al. (2014**RAHAMAN, M.S.; MAVINIC, D.S.; MEIKLEHAM, A.; ELLIS, N. (2014) Modeling phosphorus removal and recovery from anaerobic digester supernatant through struvite crystallization in a fluidized bed reactor. Water Research, v. 51, p. 1-10. https://doi.org/10.1016/j.watres.2013.11.048 https://doi.org/10.1016/j.watres.2013.11... )
${{H C O}_{3}^{-} \leftrightarrow C O}_{3}^{2 -} + H^{+}$	-10,33	Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... )
$H^{+} + {P O}_{4}^{3 -} \leftrightarrow {H P O}_{4}^{2 -}$	12,32	Webb e Ho (1991WEBB, K.M.; HO, G.E. (1991) Struvite (MgNH4PO4.6H2O) solubility and its application to a piggery effluent problem. In: WORKSHOP ON APPROPRIATE TECHNOLOGY FOR ENVIRONMENTALLY SUSTAINABLE DEVELOPMENT. Anais… ASEAN, Perth, Australia: Remote Area Developments Group, p. 39-45.), Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.), Doyle e Parsons (2002DOYLE, J.D.; PARSONS, S.A. (2002) Struvite formation, control and recovery. Water Research, v. 36, n. 16, p. 3925-3940.), Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... ), *Hanhoun et al.* (2011HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... ), Rahaman et al. (2014**RAHAMAN, M.S.; MAVINIC, D.S.; MEIKLEHAM, A.; ELLIS, N. (2014) Modeling phosphorus removal and recovery from anaerobic digester supernatant through struvite crystallization in a fluidized bed reactor. Water Research, v. 51, p. 1-10. https://doi.org/10.1016/j.watres.2013.11.048 https://doi.org/10.1016/j.watres.2013.11... )
$H_{3} {P O}_{4} \leftrightarrow H_{2} {P O}_{4}^{-} + H^{+}$	-2,1	Webb e Ho (1991WEBB, K.M.; HO, G.E. (1991) Struvite (MgNH4PO4.6H2O) solubility and its application to a piggery effluent problem. In: WORKSHOP ON APPROPRIATE TECHNOLOGY FOR ENVIRONMENTALLY SUSTAINABLE DEVELOPMENT. Anais… ASEAN, Perth, Australia: Remote Area Developments Group, p. 39-45.), Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.), Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.), *Hanhoun et al.* (2011HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... ), Rahaman et al. (2014**RAHAMAN, M.S.; MAVINIC, D.S.; MEIKLEHAM, A.; ELLIS, N. (2014) Modeling phosphorus removal and recovery from anaerobic digester supernatant through struvite crystallization in a fluidized bed reactor. Water Research, v. 51, p. 1-10. https://doi.org/10.1016/j.watres.2013.11.048 https://doi.org/10.1016/j.watres.2013.11... )
${H P O}_{4}^{2 -} + 2 H^{+} \leftrightarrow H_{3} {P O}_{4}$	9,37	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... )
${H P O}_{4}^{2 -} + H^{+} \leftrightarrow H_{2} {P O}_{4}^{-}$	7,20	Webb e Ho (1991WEBB, K.M.; HO, G.E. (1991) Struvite (MgNH4PO4.6H2O) solubility and its application to a piggery effluent problem. In: WORKSHOP ON APPROPRIATE TECHNOLOGY FOR ENVIRONMENTALLY SUSTAINABLE DEVELOPMENT. Anais… ASEAN, Perth, Australia: Remote Area Developments Group, p. 39-45.), Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.), Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.), Doyle e Parsons (2002DOYLE, J.D.; PARSONS, S.A. (2002) Struvite formation, control and recovery. Water Research, v. 36, n. 16, p. 3925-3940.), Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... ), *Hanhoun et al.* (2011HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... ), Rahaman et al. (2014**RAHAMAN, M.S.; MAVINIC, D.S.; MEIKLEHAM, A.; ELLIS, N. (2014) Modeling phosphorus removal and recovery from anaerobic digester supernatant through struvite crystallization in a fluidized bed reactor. Water Research, v. 51, p. 1-10. https://doi.org/10.1016/j.watres.2013.11.048 https://doi.org/10.1016/j.watres.2013.11... )
${S O}_{4}^{2 -} + H^{+} \leftrightarrow {H S O}_{4}^{-}$	1,99	Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.)
$C a ({O H)}_{2} \leftrightarrow {C a}^{2 +} + 2 {O H}^{-}$	-5,2	*Musvoto et al. (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Mehta e Batstone (2013*MEHTA, C.M.; BATSTONE, D.J. (2013) Nucleation and growth kinetics of struvite crystallization. Water Research, v. 47, n. 8, p. 2890-2900. https://doi.org/10.1016/j.watres.2013.03.007 https://doi.org/10.1016/j.watres.2013.03... )
$M g ({O H}_{2}) . 6 H_{2} O \leftrightarrow 6 H_{2} O + {M g}^{2 +} + 2 {O H}^{-}$	-10,9 (K_PS)	Mehta e Batstone (2013MEHTA, C.M.; BATSTONE, D.J. (2013) Nucleation and growth kinetics of struvite crystallization. Water Research, v. 47, n. 8, p. 2890-2900. https://doi.org/10.1016/j.watres.2013.03.007 https://doi.org/10.1016/j.watres.2013.03... )
$M g ({O H)}_{2} \leftrightarrow {M g}^{2 +} + 2 {O H}^{-}$	-11,16 (K_PS)	*Musvoto et al.* (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Çelen et al. (2007**ÇELEN, I.; BUCHANAN, J.R.; BURNS, R.T.; ROBINSON, R.B.; RAMAN, D.R. (2007) Using a chemical equilibrium model to predict amendments required to precipitate phosphorus as struvite in liquid swine manure. Water Research, v. 41, n. 8, p. 1689-1696. https://doi.org/10.1016/j.watres.2007.01.018 https://doi.org/10.1016/j.watres.2007.01... )
${M g}^{2 +} + {O H}^{-} \leftrightarrow M g {O H}^{+}$	2,6	Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.), Doyle e Parsons (2002DOYLE, J.D.; PARSONS, S.A. (2002) Struvite formation, control and recovery. Water Research, v. 36, n. 16, p. 3925-3940.), *Hanhoun et al.* (2011HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... ), Rahaman et al. (2014**RAHAMAN, M.S.; MAVINIC, D.S.; MEIKLEHAM, A.; ELLIS, N. (2014) Modeling phosphorus removal and recovery from anaerobic digester supernatant through struvite crystallization in a fluidized bed reactor. Water Research, v. 51, p. 1-10. https://doi.org/10.1016/j.watres.2013.11.048 https://doi.org/10.1016/j.watres.2013.11... )
${M g}^{2 +} + H_{2} O \leftrightarrow {M g O H}^{+} + H^{+}$	-11,44	Webb e Ho (1991WEBB, K.M.; HO, G.E. (1991) Struvite (MgNH4PO4.6H2O) solubility and its application to a piggery effluent problem. In: WORKSHOP ON APPROPRIATE TECHNOLOGY FOR ENVIRONMENTALLY SUSTAINABLE DEVELOPMENT. Anais… ASEAN, Perth, Australia: Remote Area Developments Group, p. 39-45.), Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... )
${C a}_{10} ({{P O}_{4})}_{6} ({O H)}_{2} \leftrightarrow 10 {C a}^{2 +} + 6 {P O}_{4}^{3 -} + 2 {O H}^{-}$	-114 (K_PS)	*Musvoto et al.* (2000**MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.)
${C a}_{3} {{(P O}_{4})}_{2} . x H_{2} O \leftrightarrow 3 {C a}^{2 +} + 2 {P O}_{4}^{3} + x H_{2} O$	-31,45 (K_PS)	*Musvoto et al.* (2000**MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.)
${C a}_{3} {{(P O}_{4})}_{2} \leftrightarrow 3 {C a}^{2 +} + 2 {P O}_{4}^{3 -}$	-32,7 (K_PS)	*Musvoto et al.* (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Mehta e Batstone (2013**MEHTA, C.M.; BATSTONE, D.J. (2013) Nucleation and growth kinetics of struvite crystallization. Water Research, v. 47, n. 8, p. 2890-2900. https://doi.org/10.1016/j.watres.2013.03.007 https://doi.org/10.1016/j.watres.2013.03... )
${C a}_{8} (H {{P O}_{4})}_{2} ({{P O}_{4})}_{4} 5 H_{2} O \leftrightarrow 8 {C a}^{2 +} + 2 H {P O}_{4}^{2 -} + 4 {P O}_{4}^{3 -} + 5 H_{2} O$	-94,16 (K_PS)	*Musvoto et al.* (2000**MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.)
$C a {H P O}_{4} \leftrightarrow {C a}^{2 +} + {H P O}_{4}^{2 -}$	-2,7 (K_PS)	*Musvoto et al. (2000*MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.)
$C a {H P O}_{4} . 2 H_{2} O \leftrightarrow {C a}^{2 +} + {H P O}_{4}^{2 -} + 2 H_{2} O$	-6,6 (K_PS)	*Musvoto et al.* (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Mehta e Batstone (2013**MEHTA, C.M.; BATSTONE, D.J. (2013) Nucleation and growth kinetics of struvite crystallization. Water Research, v. 47, n. 8, p. 2890-2900. https://doi.org/10.1016/j.watres.2013.03.007 https://doi.org/10.1016/j.watres.2013.03... )
${C a}_{5} ({{P O}_{4})}_{3} (O H) \leftrightarrow 5 {C a}^{2 +} + 3 {P O}_{4}^{3 -} + {O H}^{-}$	-57,8 (K_PS)	*Muster et al.* (2013**MUSTER, T.H.; DOUGLAS, G.B.; SHERMAN, N.; SEEBER, A.; WRIGHT, N.; GÜZÜKARA, Y. (2013) Towards effective phosphorus recycling from wastewater: Quantity and quality. Chemosphere, v. 91, n. 5, p. 676-684. https://doi.org/10.1016/j.chemosphere.2013.01.057 https://doi.org/10.1016/j.chemosphere.20... )
$H_{2} {P O}_{4}^{-} + {M g}^{2 +} \leftrightarrow M g H_{2} {P O}_{4}^{+}$	0,45	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.), Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.), Doyle e Parsons (2002DOYLE, J.D.; PARSONS, S.A. (2002) Struvite formation, control and recovery. Water Research, v. 36, n. 16, p. 3925-3940.), *Hanhoun et al.* (2011HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... ), Rahaman et al. (2014**RAHAMAN, M.S.; MAVINIC, D.S.; MEIKLEHAM, A.; ELLIS, N. (2014) Modeling phosphorus removal and recovery from anaerobic digester supernatant through struvite crystallization in a fluidized bed reactor. Water Research, v. 51, p. 1-10. https://doi.org/10.1016/j.watres.2013.11.048 https://doi.org/10.1016/j.watres.2013.11... )
$H_{2} {P O}_{4}^{-} + {M g}^{2 +} \leftrightarrow M g {P O}_{4}^{-} + 2 H^{+}$	-12,96	Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... )
$H_{2} {P O}_{4}^{-} + {M g}^{2 +} \leftrightarrow M g H {P O}_{4} + H^{+}$	-4,3	Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... )
$H {P O}_{4}^{2 -} + {M g}^{2 +} \leftrightarrow M g H {P O}_{4}$	2,43	Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.), Doyle e Parsons (2002DOYLE, J.D.; PARSONS, S.A. (2002) Struvite formation, control and recovery. Water Research, v. 36, n. 16, p. 3925-3940.), *Hanhoun et al.* (2011HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... ), Rahaman et al. (2014RAHAMAN, M.S.; MAVINIC, D.S.; MEIKLEHAM, A.; ELLIS, N. (2014) Modeling phosphorus removal and recovery from anaerobic digester supernatant through struvite crystallization in a fluidized bed reactor. Water Research, v. 51, p. 1-10. https://doi.org/10.1016/j.watres.2013.11.048 https://doi.org/10.1016/j.watres.2013.11... ), Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Bouropoulos e Koutsoukos (2000**BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.)
${P O}_{4}^{3 -} + {M g}^{2 +} \leftrightarrow M g {P O}_{4}^{-}$	4,80	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.), *Babic-Ivancic et al.* (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.), Doyle e Parsons (2002DOYLE, J.D.; PARSONS, S.A. (2002) Struvite formation, control and recovery. Water Research, v. 36, n. 16, p. 3925-3940.), Hanhoun et al. (2011**HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... )
${M g}_{3} {H P O}_{4} . 3 H_{2} O \leftrightarrow 3 H_{2} O + {H P O}_{4}^{2 -} + {M g}^{2 +}$	-5,8 (K_PS)	*Musvoto et al.* (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Çelen et al. (2007**ÇELEN, I.; BUCHANAN, J.R.; BURNS, R.T.; ROBINSON, R.B.; RAMAN, D.R. (2007) Using a chemical equilibrium model to predict amendments required to precipitate phosphorus as struvite in liquid swine manure. Water Research, v. 41, n. 8, p. 1689-1696. https://doi.org/10.1016/j.watres.2007.01.018 https://doi.org/10.1016/j.watres.2007.01... )
${M g}_{3} {H P O}_{4} . 8 H_{2} O \leftrightarrow 8 H_{2} O + {2 P O}_{4}^{3 -} + {3 M g}^{2 +}$	-25,2 (K_PS)	*Musvoto et al.* (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Mehta e Batstone (2013MEHTA, C.M.; BATSTONE, D.J. (2013) Nucleation and growth kinetics of struvite crystallization. Water Research, v. 47, n. 8, p. 2890-2900. https://doi.org/10.1016/j.watres.2013.03.007 https://doi.org/10.1016/j.watres.2013.03... ), Song et al. (2015**SONG, Y.; QIAN, F.; GAO, Y.; HUANG, X.; WU, J.; YU, H. (2015) PHREEQC program-based simulation of magnesium phosphates crystallization for phosphorus recovery. Environmental Earth Sciences, v. 73, n. 9, p. 5075-5084. https://doi.org/10.1007/s12665-015-4340-8 https://doi.org/10.1007/s12665-015-4340-... )
${M g}_{3} ({{P O}_{4})}_{2} . 22 H_{2} O \leftrightarrow 3 {M g}^{2 +} + 2 {P O}_{4}^{3 -} + 22 H_{2} O$	-23,1 (K_PS)	*Musvoto et al.* (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Mehta e Batstone (2013MEHTA, C.M.; BATSTONE, D.J. (2013) Nucleation and growth kinetics of struvite crystallization. Water Research, v. 47, n. 8, p. 2890-2900. https://doi.org/10.1016/j.watres.2013.03.007 https://doi.org/10.1016/j.watres.2013.03... ), Song et al. (2015**SONG, Y.; QIAN, F.; GAO, Y.; HUANG, X.; WU, J.; YU, H. (2015) PHREEQC program-based simulation of magnesium phosphates crystallization for phosphorus recovery. Environmental Earth Sciences, v. 73, n. 9, p. 5075-5084. https://doi.org/10.1007/s12665-015-4340-8 https://doi.org/10.1007/s12665-015-4340-... )
${M g}^{2 +} + {N H}_{3} \leftrightarrow M g {N H}_{3}^{2 +}$	0,24*	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.)
${M g}^{2 +} + 2 {N H}_{3} \leftrightarrow {(M g {N H}_{3})}_{2}^{2 +}$	0,20	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.)
${M g}^{2 +} + 3 {N H}_{3} \leftrightarrow {(M g {N H}_{3})}_{3}^{2 +}$	-0,3*	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.)
${N a}^{+} + H_{2} {P O}_{4}^{-} \leftrightarrow {N a H P O}_{4}^{-} + H^{+}$	-6,01	Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... )
${N a}^{+} + H {P O}_{4}^{2 -} \leftrightarrow N a H {P O}_{4}^{-}$	0,85	Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.)
${N H}_{4}^{+} + {H P O}_{4}^{2 -} \leftrightarrow {N H}_{4} {H P O}_{4}^{-}$	1,3	Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... )
${N H}_{4}^{+} + {S O}_{4}^{2 -} \leftrightarrow {N H}_{4} {S O}_{4}^{-}$	1,03	Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... )
${S O}_{4}^{2 -} + {M g}^{2 +} \leftrightarrow M g {S O}_{4}$	2,37	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ), Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.)
${M g}^{2 +} + {N H}_{4}^{+} + {P O 4}_{3}^{-} + 6 H_{2} O \leftrightarrow M g {N H}_{4} {P O}_{4} . 6 H_{2} O$	13,26	Webb e Ho (1991WEBB, K.M.; HO, G.E. (1991) Struvite (MgNH4PO4.6H2O) solubility and its application to a piggery effluent problem. In: WORKSHOP ON APPROPRIATE TECHNOLOGY FOR ENVIRONMENTALLY SUSTAINABLE DEVELOPMENT. Anais… ASEAN, Perth, Australia: Remote Area Developments Group, p. 39-45.), Bouropoulos e Koutsoukos (2000BOUROPOULOS, N.C.; KOUTSOUKOS, P.G. (2000) Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, v. 213, n. 3-4, p. 381-388.), *Musvoto et al.* (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Mehta e Batstone (2013MEHTA, C.M.; BATSTONE, D.J. (2013) Nucleation and growth kinetics of struvite crystallization. Water Research, v. 47, n. 8, p. 2890-2900. https://doi.org/10.1016/j.watres.2013.03.007 https://doi.org/10.1016/j.watres.2013.03... ), Song et al. (2015**SONG, Y.; QIAN, F.; GAO, Y.; HUANG, X.; WU, J.; YU, H. (2015) PHREEQC program-based simulation of magnesium phosphates crystallization for phosphorus recovery. Environmental Earth Sciences, v. 73, n. 9, p. 5075-5084. https://doi.org/10.1007/s12665-015-4340-8 https://doi.org/10.1007/s12665-015-4340-... )
$C a {C O}_{3} \leftrightarrow {C a}^{2 +} + {C O}_{3}^{2 -}$	-8,22 (K_PS)	*Musvoto et al.* (2000**MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.)
$C a M g {{(C O}_{3})}_{2} \leftrightarrow {C a}^{2 +} + {M g}^{2 +} + 2 {C O}_{3}^{2 -}$	-16,7 (K_PS)	*Musvoto et al.* (2000**MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.)
$M g {C O}_{3} . 3 H_{2} O \leftrightarrow {M g}^{2 +} + {C O}_{3}^{2 -} + 3 H_{2} O$	-5,19 (K_PS)	*Musvoto et al.* (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Çelen et al. (2007**ÇELEN, I.; BUCHANAN, J.R.; BURNS, R.T.; ROBINSON, R.B.; RAMAN, D.R. (2007) Using a chemical equilibrium model to predict amendments required to precipitate phosphorus as struvite in liquid swine manure. Water Research, v. 41, n. 8, p. 1689-1696. https://doi.org/10.1016/j.watres.2007.01.018 https://doi.org/10.1016/j.watres.2007.01... )
$H {C O}_{3}^{-} + {M g}^{2 +} \leftrightarrow M g H {C O}_{3}^{+}$	1,07	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... ) e Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... )
${M g}^{2 +} + {H C O}_{3}^{-} \leftrightarrow {M g C O}_{3} + H^{+}$	-7,35	Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... )
${C O}_{3}^{2 -} + {M g}^{2 +} \leftrightarrow M g {C O}_{3}$	-8,2	*Musvoto et al.* (2000MUSVOTO, E.V.; EKAMA, G.A.; WENTZEL, M.C.; LOEWWENTHAL, R.E. (2000) Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors. Water SA, v. 26, n. 4, p. 417-438.), Bhuyian, Mavinic e Beckie (2007**BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... )
${M g}^{2 +} + {C l}^{-} \leftrightarrow M g {C l}^{+}$	-0,135	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... )

pK_S0	Condições em KSo foi determinada	Referência
12,76 ± 0,56	Água residuária de suinocultura, [P_solúvel] = 65 mg.L^-1, [N-NH₃] = 1830 mg.L^-1, [Mg] = 170 mg.L^-1, pH entre 6,8 e 8,5, temperatura = 25ºC	Webb e Ho (1991WEBB, K.M.; HO, G.E. (1991) Struvite (MgNH4PO4.6H2O) solubility and its application to a piggery effluent problem. In: WORKSHOP ON APPROPRIATE TECHNOLOGY FOR ENVIRONMENTALLY SUSTAINABLE DEVELOPMENT. Anais… ASEAN, Perth, Australia: Remote Area Developments Group, p. 39-45.)
14	Dissolução de 40 mg de estruvita marcada com o radioisótopo ³²P em 20 mL de água redestilada e soluções diluídas de NaCl 0,030, 0045, 0,06 M, temperatura = 25ºC	*Aage et al. (1997*AAGE, H.K.; ANDERSEN, B.L.; BLOM, A.; JENSEN, I. (1997) The solubility of struvite. Journal of Radioanalytical and Nuclear Chemistry, v. 223, n. 1-2, p. 213-215. https://doi.org/10.1007/BF02223387 https://doi.org/10.1007/BF02223387... )
13,26 ± 0,04	Produção de estruvita em laboratório. Dissolução desta estruvita e de estruvita coletada em sobrenadante de digestor de sistema EBPR em água desionizada tamponada, temperatura = 25 ± 0,5ºC	Ohlinger, Young e Schroeder (1998OHLINGER, K.N.; YOUNG, T.M.; SCHROEDER, E.D. (1998) Predicting struvite formation in digestion. Water Research, v. 32, n. 12, p. 3607-3614. http://dx.doi.org/10.1016/S0043-1354(98)00123-7 http://dx.doi.org/10.1016/S0043-1354(98)... )
13,36 ± 0,28	Água sintética; [Pt] = 310 a 1.860 mg.L^-1; [N-NH₃] = 410 a 1.568 mg.L^-1; [Mg] = 240 a 552 mg.L^-1 = temperatura 25ºC; pH = 7,4; [NaCl] = 0,15 mol.L^-1	Babic-Ivancic et al. (2002BABIC-IVANCIC, V.; KONTREC, J.; KRALJ, D.; BRECEVIC, L. (2002) Precipitation diagrams of struvite and dissolution kinetics of different struvite morphologies. Croatica Chemica Acta, v. 75, n. 1, p. 89-106.)
14,10 ± 0,16	Dissolução de cristais de estruvita em água destilada; pH = 7,01 a 9,52; temperatura de 20ºC	*Rahaman et al.* (2006**RAHAMAN, M.S.; MAVINIC, D.S.; BHUYIAN, M.I.H.; KOCH, F.A. (2006) Exploring the determination of struvite solubility product from analytical results. Environmental Technology, v. 27, n. 9, p. 951-961. https://doi.org/10.1080/09593332708618707 https://doi.org/10.1080/0959333270861870... )
13,55 ± 0,54	Dissolução de cristais de estruvita no sobrenadante do digestor da ETE Annacis Island; pH = 5,62 a 8,77; temperatura de 20ºC
13,53 ± 0,45	Dissolução de cristais de estruvita no sobrenadante do digestor da ETE Lulu Island; pH = 5,89 a 9,02; temperatura de 20ºC
13,45 ± 0,37	Dissolução de cristais de estruvita no sobrenadante do digestor da ETE Penticton; pH = 6,45 a 8,97; temperatura de 20ºC
13,69 ± 0,02	Dissolução de cristais de estruvita em água desionizada contendo solução de NaCl 0,01; 0,02; 0,04 e 0,06 M; pH = 7,4; temperatura de 20ºC	Bhuyian, Mavinic e Beckie (2007BHUYIAN, M.I.H.; MAVINIC, D.S.; BECKIE, R.D. (2007) A Solubility and thermodynamic study of struvite. Environmental Technology, v. 28, n. 9, p. 1015-1026. https://doi.org/10.1080/09593332808618857 https://doi.org/10.1080/0959333280861885... )
13,36 ± 0,07	Dissolução de cristais de estruvita em água desionizada contendo solução de NaCl 0,01; 0,02; 0,04 e 0,06 M; pH = 7,4; temperatura de 25ºC
13,26 ± 0,06	Urina e água sintética; [P-PO₄] = 4,2 a 14,2 mM; [N-NH₄] = 291 a 508 mM; [Mg] = 1,08 a 15,6 mM; [Ca] = 0,7 ± 0,1 mM; temperatura = 25ºC; pH = 9,0; intensidade iônica = 0,32 a 0,56 M	Ronteltap, Maurer e Gujer (2007RONTELTAP, M.; MAURER, M.; GUJER, W. (2007) Struvite precipitation thermodynamics in source-separated urine. Water Research, v. 41, n. 5, p. 977-984. http://dx.doi.org/10.1016/j.watres.2006.11.046 http://dx.doi.org/10.1016/j.watres.2006.... )
11 a 12	Efluente de digestor anaeróbio tratando água residuária de indústria de melaço, [NH₄]=1400 mg.L^-1; [Mg²⁺]=21 mg.L^-1; [] = 24 mg.L^-1; [Ca²⁺] = 21 mg.L^-1; [K⁺] = 2.150 mg.L^-1; sólidos dissolvidos totais = 7.600 mg.L^-1; pH = 7,9, temperatura = 37ºC	Türker e Çelen (2010TÜRKER, M.; ÇELEN, I. (2010) Chemical equilibrium model of struvite precipitation from anaerobic digester effluents. Turkish Journal of Engineering and Environmental Sciences, v. 34, n. 1, p. 39-48. https://doi.org/10.3906/muh-1008-15 https://doi.org/10.3906/muh-1008-15... )
13,17 ± 0,01	Água sintética; [PO₄] = 4 mM; [Mg] = 4 mM e [NH₄] = 4 mM; temperatura = 25ºC; pH = 8,5; 9,0; 9,5 e 10,0; intensidade iônica = 0,0159 M	*Hanhoun et al. (2011*HANHOUN, M.; MONTASTRUC, L.; AZZARO-PANTEL, C.; BISCANS, B.; FRECHE, M.; PIBOULEAU, L. (2011) Temperature impact assessment on struvite solubility product : a thermodynamic modeling approach. Chemical Engineering Journal, v. 167, n. 1, p. 50-58. http://dx.doi.org/10.1016/j.cej.2010.12.001 http://dx.doi.org/10.1016/j.cej.2010.12.... )
14,0	Água sintética; []= 2 mM; [] = 2,2 mM; [Mg²⁺]= 6,0 mM; temperatura 25ºC; pH = 8,5; 3 g.L^-1 de estruvita adicionada	Crutchik e Garrido (2016CRUTCHIK, D.; GARRIDO, J.M. (2016) Kinetics of the reversible reaction of struvite crystallisation. Chemosphere, v. 154, p. 567-572. https://doi.org/10.1016/j.chemosphere.2016.03.134 https://doi.org/10.1016/j.chemosphere.20... )

K_{S o} = (a_{{M g}^{2 +}}) . (a_{{N H}_{4}^{+}}) . (a_{{P O}_{4}^{3 -}}) = \{(γ_{{M g}^{2 +}}) . [{M g}^{2 +}])\} . \{{(γ}_{{N H}_{4}^{+}}) . [{N H}_{4}^{+}]\} . \{{(γ}_{{P O}_{4}^{3 -}}) . [{P O}_{4}^{3 -}]\}

P_{s} = \frac{K_{P S}}{{(α}_{{M g}^{2 +}}) . (α_{{N H}_{4}^{+}}) . (α_{{P O}_{4}^{3 -}})} = \frac{K_{S 0}}{{(α}_{{M g}^{2 +}}) . (γ_{{M g}^{2 +}}) . (α_{{N H}_{4}^{+}}) . (γ_{{N H}_{4}^{+}}) . (α_{{P O}_{4}^{3 -}}) . (γ_{{P O}_{4}^{3 -}})}

S_{a} = \frac{a_{{M g}^{2 +}} . a_{{P O}_{4}^{3 -}} . a_{{N H}_{4}^{+}}}{{(a_{{M g}^{2 +}} . a_{{P O}_{4}^{3 -}} . a_{{N H}_{4}^{+}})}_{e q}} = \frac{I A P}{K_{S 0}}

t_{i n d} = \frac{1}{J} = \frac{1}{Ω} e x p [\frac{β . v^{2} . φ^{3}}{{K_{B}^{3} . T}^{3} . z^{2} . {(l n S_{a})}^{2}}] = \frac{1}{Ω} e x p [\frac{β . v^{2} . φ^{3}}{{(2,3 . K_{B} T)}^{3} . z^{2} . {(l o g S_{a})}^{2}}]

[1] *Autor correspondente: dmmorita@usp.br

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Nucleation in the formation of struvite: state of art

ABSTRACT