PVP–Fe₃O₄ Adsorption capacity (mg g⁻¹) of four metals at 10 mg L⁻¹ in different water media. Data are mean value of three replicates ± standard deviation.

	Soft water		Sea water
	Without SRFA	With SRFA	Without SRFA	With SRFA
Cd	43.92 ± 2.56	23.66 ± 2.32	12.08 ± 0.55	11.62 ± 1.03
Cr	17.98 ± 0.86	13.87 ± 0.98	25.52 ± 1.02	22.89 ± 1.78
Ni	29.86 ± 1.45	21.23 ± 0.97	15.01 ± 1.39	13.47 ± 0.65
Pb	61.67 ± 4.57	55.33 ± 3.41	59.62 ± 3.07	20.19 ± 1.49