Table 4.

Metal cations concentration (mg/L) after adsorption and desorption tests. The Q values for the adsorption test calculated as Q = $\frac{\left(C_o-C_e\right)V}{W}$ is also reported (see the Experimental section).

Sample	Zn2+	Cd2+	Pb2+	Cu2+
Metal cations concentration after adsorption test (mg/L)
GSil3A	<lod *	<lod *	0.013	<lod *
GSil3B	0.028 ± 0.009	0.035 ± 0.008	0.017 ± 0.004	0.062 ± 0.008
GSil12A	0.007 ± 0.002	0.008 ± 0.001	0.015 ± 0.005	0.015 ± 0.005
GSil12B	0.019 ± 0.008	0.014 ± 0.007	0.027 ± 0.005	0.067 ± 0.008
Metals concentration after desorption test (mg/L)
GSil3A	<lod	<lod	<lod	0.014 ± 0.008
GSil3B	<lod	<lod	0.055 ± 0.004	0.13 ± 0.01
GSil12A	0.114 ± 0.005	0.016 ± 0.002	0.209 ± 0.006	0.31 ± 0.02
GSil12B	<lod	<lod	0.021 ± 0.002	<lod
Q values for adsorption test (mg/g sample)
GSil3A	0.383	0.383	0.383	0.383
GSil3B	0.120	0.120	0.120	0.120
GSil12A	0.341	0.341	0.341	0.341
GSil12B	0.111	0.111	0.111	0.110

* Limit of detection (lod) for Zn²⁺, Cd²⁺, Pb²⁺, Cu²⁺ are: 4.2 ng/L, 0.8 ng/L, 0.5 ng/L, 0.5 ng/L respectively.