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

Figure 4

Pseudo-second-order plot for the adsorption of Cd(II) (a and b) and Cu(II) (c and d) on PS and Na-PS depending on the initial concentration. Note: PS means Pisha sandstone; Na-PS means Pisha sandstone modified with Na⁺.

(a)

(b)

(c)

(d)