Scientific Reports

Table 2 Model parameters for SCKM-1, SCKM-2, and SCKM-3 at different pH values and different initial phosphate concentrations^a.

From: Kinetic Modeling of Phosphate Adsorption by Preformed and In situ formed Hydrous Ferric Oxides at Circumneutral pH

	[PO₄³⁻]_T = 0.25 mM			[PO₄³⁻]_T = 0.50 mM			[PO₄³⁻]_T = 1.0 mM
	SCKM-1	SCKM-2	SCKM-3	SCKM-1	SCKM-2	SCKM-3	SCKM-1	SCKM-2	SCKM-3
pH=6
k₁′(min⁻¹)	—	0.0674	0.0657	—	0.0683	0.0675	—	0.0678	0.119
k₂ (min⁻¹)	—	0.0122	0.000604	—	0.0112	0.00148	—	0.0168	0.0776
k_a′ (mM⁻¹ min⁻¹)	0.433	0.519	0.508	0.242	0.285	0.278	0.134	0.235	0.214
k_d(min⁻¹)	0.0177	0.0029	—	0.0323	0.00457	—	0.029	0.00264	—
C_ss (mM mM)⁻¹^b	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45
C_ss (mM mM)⁻¹^c	0.919	1.03	0.807	1.25	1.09	0.958	1.04	0.809	0.694
PZC	—	6.74	8.04		6.79	7.66		6.61	6.19
pH=7
k₁′(min⁻¹)	—	0.0788	0.0802	—	0.108	0.106	—	0.219	0.176
k₂ (min⁻¹)	—	0.00489	0.000485	—	0.00403	0.00166	—	0.0137	0.00614
k_a′ (mM⁻¹ min⁻¹)	0.241	0.276	0.275	0.192	0.232	0.229	0.0779	0.170	0.151
k_d (min⁻¹)	0.0382	0.00223	—	0.0552	0.00138	—	0.0432	0.00288	—
C_ss (mM mM)⁻¹^b	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45
C_ss (mM mM)⁻¹^c	1.72	1.33	1.14	2.31	1.59	1.44	1.42	1.28	0.931
PZC		8.21	9.22		8.43	8.81		8.20	8.46
pH=8
k₁′(min⁻¹)	—	0.0598	0.0984	—	0.0677	0.0579	—	0.0398	0.195
k₂ (min⁻¹)	—	0.0168	0.00121	—	0.0127	0.0026	—	0.0256	0.00671
k_a′ (mM⁻¹ min⁻¹)	0.152	0.214	0.191	0.0499	0.0705	0.0847	0.0227	0.0255	0.0715
k_d(min⁻¹)	0.0470	0.0175	—	0.0275	0.00462	—	0.0279	0.0108	—
C_ss (mM mM)⁻¹^b	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45
C_ss (mM mM)⁻¹ ^c	3.68	3.06	1.85	4.26	3.24	2.03	3.29	3.07	2.37
PZC		8.55	9.91		8.73	9.35		8.19	9.46

^aThe model parameters were obtained when the influence of initial phosphate concentration was considered.
^bThe active surface sites⁷ were used for PF-HFO case.
^cThe active surface sites for ISF-HFO case were determined by using the rate constants obtained in the PF-HFO case.

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