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

Table 2

Equilibrium model parameters and determination coefficients () and standard error of estimate (SE) for cadmium adsorption by nWTR in single-ion and multi-ion systems.

Model	Parameter	nWTRs		µWTRs		mWTRs
		Single-ion	Multi-ion	Single-ion	Multi-ion	Single-ion	Multi-ion
Langmuir	(mg g^−1)	47	16.67	4.60	2.50	2.80	1.75
	(L mg^−1)	53.19	117	24.15	235.85	0.36	223
		0.96	0.86	0.95	0.81	0.95	0.78
	SE	9.46 × 10^−5	1.5 × 10^−3	0.001	1.1 × 10^−2	0.001	1.9 × 10^−2
Freundlich	(mL g^−1)	18928	171.5	549.44	12.4	205.6	9.71
		0.401	0.848	0.1736	0.898	0.39	0.880
		0.94	0.96	0.91	0.98	0.97	0.98
	SE	0.31	0.255	0.35	0.162	0.18	0.163
Elovich	(μg g^−1)	33333	10000	2000	500	1250	2000
	(L mg^−1)	4.21	1.00	0.129	0.99	0.089	0.99
		0.96	0.92	0.89	0.42	0.95	0.02
	SE	0.10	0.125	0.21	1.32	0.14	1.23
Temkin	(kJ mol^−1)	0.771	0.92	22	48	17	24
	(L mg^−1)	1.33	1.34	1.42	1.01	3.45	5.46
		0.96	0.97	0.93	0.68	0.85	0.87
	SE	0.054	0.035	0.056	0.088	0.1	0.063
Fowler–Guggenheim	(kJ mol^−1)	0.736	0.917	1.31	1.38	6.58	10.46
	(L mg^−1)	0.556	1.86	0.023	0.035	0.106	0.131
		0.93	0.99	0.94	0.94	0.90	0.97
	SE	0.047	0.016	0.048	0.044	0.48	0.247
Kiselev		5.256	−0.697	6.029	1.18	4.83	−0.177
	(L mg^−1)	44.07	0.008	22.26	0.004	0.281	0.004
		0.96	0.99	0.95	0.99	0.95	0.99
	SE	213	0.005	118	0.007	0.97	0.004
Hill–de Boer	(L mg^−1)	0.354	2.98	0.036	0.008	0.003	0.005
	(kJ mol^−1)	2.496	−3.023	3.846	15.073	14.6	4.078
		0.96	0.96	0.98	0.38	0.99	0.69
	SE	0.06	0.053	0.04	1.238	0.10	0.194