Removal of Cd(II) and Cu(II) from Aqueous Solution by Na⁺-Modified Pisha Sandstone

Table 2

Parameters for the competitive solution of Cd(II) and Cu(II) on PS and Na-PS.

Metal	Material	a	b	c	R ^2
Cd	PS	0.80	1.61	−0.30	0.97
	Na-PS	0.94	1.75	−0.41	0.98
Cu	PS	0.35	−0.16	2.07	0.99
	Na-PS	0.30	−0.11	2.16	0.99

Note: PS means Pisha sandstone; Na-PS means Pisha sandstone modified with Na⁺.