Competitive Adsorption of Cadmium (II) from Aqueous Solutions onto Nanoparticles of Water Treatment Residual

Table 3

Kinetics model parameters and determination coefficients () and standard error of estimate (SE) for cadmium adsorption by nWTR in single-ion and multi-ion systems at different initial solution pH values.

Models	Parameter	pH 5		pH 7		pH 9
		Single-ion	Multi-ion	Single-ion	Multi-ion	Single-ion	Multi-ion
Elovich	α mg g^−1 min^−1	1.0 × 10^9	595876	1.1 × 10^8	552163	3.3 × 10^6	531042
	mg g^−1	2.3 × 10^−4	2 × 10^−3	3.0 × 10^−4	3 × 10^−3	6.0 × 10^−4	8 × 10^−3
		0.956	0.993	0.989	0.977	0.988	0.871
	SE	2078	169	697	191	535	119
First-order	min^−1	−0.409	−0.004	−0.384	−0.003	−0.726	−0.002
	μg g^−1	10.53	7.797	10.27	7.405	10.50	6.654
		0.805	0.95	0.977	0.948	0.961	0.933
	SE	0.237	0.225	0.226	0.161	0.211	0.127
Parabolic diffusion	μg g^−1 min^−1/2	4199	76.86	3575	51.57	1681	22.83
	μg g^−1	52113	4788	37087	3091	12783	1326
		0.956	0.796	0.989	0.891	0.988	0.964
	SE	3111	557	2672	255	1409	60
Power function	mg g^−1	1.0	1.0	1.0	1.0	1.0	1.0
	min^−1	0.027	0.078	0.031	0.075	0.040	0.069
		0.955	0.889	0.982	0.920	0.975	0.892
	SE	0.012	0.016	0.005	0.011	0.012	0.025