Calculated values for the distribution coefficients K_d (mL g⁻¹), measured in HNO₃ 2%.

	Au3+	Ag+	Pb2+	Hg2+
FeNP-SQ1	1.57 × 106	4.70 × 103	1.28 × 105	1.86 × 105
FeNP-SQ2	2.15 × 105	3.03 × 104	5.16 × 103	3.75 × 105
FeNP-SQ3	1.32 × 106	5.78 × 103	4.86 × 103	1.69 × 103
FeNP-SQ4	8.97 × 105	6.95 × 105	7.70 × 102	5.27 × 103
FeNP control	3.58 × 103	1.55 × 103	2.56 × 102	1.69 × 103