Characterization, Dissolution, and Solubility of Zn-Substituted Hydroxylapatites [(Zn_xCa_1−x)₅(PO₄)₃OH] at 25°C

Table 2

Analytical data and solubility determination of the Zn-substituted hydroxylapatites (25°C and initial pH 2.00).

Sample	Dissolution time (h)	pH	Concentration (mmol/L)				Average	(kJ/mol)	Average; (kJ/mol)
			Zn	Ca	P
(Zn0.00Ca1.00)5(PO4)3OH	7200	4.95	0.0000	6.8916	3.5385	−57.85	−57.75	−6311.58	−6311.03
	7920	4.98	0.0000	6.8941	3.5578	−57.63		−6310.34
	8640	4.96	0.0000	6.9015	3.5207	−57.77		−6311.17
(Zn0.02Ca0.98)5(PO4)3OH	7200	4.96	0.0055	6.4824	3.2091	−58.30	−58.21	−6273.53	−6273.00
	7920	5.00	0.0052	6.4624	3.1978	−58.03		−6271.98
	8640	4.96	0.0061	6.4774	3.2075	−58.29		−6273.48
(Zn0.04Ca0.96)5(PO4)3OH	7200	4.95	0.0442	6.2927	2.8960	−58.67	−58.47	−6234.97	−6233.84
	7920	4.99	0.0428	6.3302	2.8905	−58.38		−6233.33
	8640	4.99	0.0443	6.3376	2.9283	−58.36		−6233.21
(Zn0.06Ca0.94)5(PO4)3OH	7200	5.09	0.0797	5.4544	2.1479	−58.42	−58.60	−6192.92	−6193.93
	7920	5.05	0.0800	5.4494	2.1599	−58.69		−6194.45
	8640	5.05	0.0803	5.4643	2.1631	−58.68		−6194.41
(Zn0.08Ca0.92)5(PO4)3OH	7200	5.20	0.1025	4.5511	1.6278	−58.43	−58.59	−6152.30	−6153.22
	7920	5.16	0.1043	4.6260	1.6223	−58.68		−6153.72
	8640	5.16	0.1048	4.6434	1.6304	−58.66		−6153.63
(Zn0.10Ca0.90)5(PO4)3OH	7920	5.56	0.0541	2.5026	0.8662	−57.99	−58.05	−6109.13	−6109.47
	8640	5.54	0.0566	2.4951	0.8717	−58.11		−6109.81
(Zn0.12Ca0.88)5(PO4)3OH	7920	5.55	0.0536	2.7671	1.0083	−57.88	−58.00	−6067.83	−6068.52
	8640	5.51	0.0554	2.7446	1.0331	−58.12		−6069.22
(Zn0.14Ca0.86)5(PO4)3OH	7920	5.91	0.0142	1.7239	0.6199	−57.36	−57.48	−6024.22	−6024.89
	8640	5.87	0.0138	1.7079	0.6457	−57.59		−6025.57
(Zn0.16Ca0.84)5(PO4)3OH	7920	6.14	0.0101	1.2296	0.7606	−56.44	−56.63	−5978.31	−5979.39
	8640	6.09	0.0108	1.1927	0.7458	−56.81		−5980.46
(Zn0.17Ca0.83)5(PO4)3OH	7920	6.02	0.0076	2.2766	1.0067	−56.14	−56.38	−5956.27	−5957.67
	8640	5.95	0.0117	2.0809	0.9673	−56.63		−5959.06
(Zn0.19Ca0.81)5(PO4)3OH	7920	5.90	0.0084	2.4043	0.9030	−45.85	−45.96	−5856.88	−5857.53
	8640	5.86	0.0092	2.3978	0.9040	−46.08		−5858.19