Magnetic solid-phase extraction of metal ions: Comparison of adding Schiff base to the extraction medium vs. magnetite modification with Schiff base

[Display omitted] •Cd & Pb were extracted by magnetite (Mag) in presence of Schiff base (SB).•SB addition protocol outperformed previously reported SB-modified Mag.•Adding Vanillin SB significantly improved Mag extraction performance. In the present work, two protocols were compared for magnetic solid phase extraction (MSPE) of Cd(II) and Pb(II) from aqueous medium. The first novel protocol involved adding Schiff base into the extraction medium using either magnetite (Mag) or magnetic carbon nanotubes (MCNT). It was found that adding vanillin Schiff base (VSB) with Mag to the extraction medium caused a double increase in the MSPE recovery and adsorption of Cd(II) and Pb(II). Unexpectedly Mag gave almost similar results as MCNT when adding VSB. Figures of merits were estimated and application on real water samples gave high recoveries. The second protocol involved magnetite modified with Schiff bases. Comparing both protocols revealed that the first protocol is better than the second protocol in terms of application on real waters and adsorption capacity. Furthermore, the first protocol avoided sorbent modification and offered a wider working pH range for Pb(II); while the second protocol offered re-usability of the Schiff base modified sorbent and avoided repetitive Schiff base preparation.