The parameters for Langmuir and Freundlich isotherm models of Cu(ii), Cd(ii), and Zn(ii) adsorption onto GO (2 mg L⁻¹) at pH 7.8 and 6.8.

Metals	pH	Langmuir isotherms			Freundlich isotherms
		Q m (μg mg−1)	b (L μg−1)	R 2	K (μg mg−1)	1/n	R 2
Cu(ii)	7.8	36.101	0.055	0.913	2.357	0.676	0.995
	6.8	27.397	0.049	0.802	1.974	0.604	0.986
Cd(ii)	7.8	32.362	0.049	0.949	2.649	0.565	0.999
	6.8	37.594	0.021	0.939	1.178	0.720	0.988
Zn(ii)	7.8	322.581	0.003	0.992	7.032	0.529	0.943
	6.8	294.118	0.002	0.942	4.034	0.572	0.915