Controlled surface multifunctional groups over halloysite nanotube enabling reinforced lead adsorption in vitro

Lead pollution particularly in blood seriously threatens the health of people, thereby, efficient removal of lead becomes very emergent. Natural adsorbents with surface specific functionality might be promising and selective for the alternative adsorption of lead. To explore the effects of different functional ligand modifications on lead(II) adsorption over halloysite nanotube (HNTs), HNTs adsorbents grafted with (3-Aminopropyl) trimethoxysilane (APTES), (3-Mercaptopropyl) trimethoxysilane (MPTMS), Ethylenediaminetetraacetic acid (EDTA), D-Cystine and Dimercaptosuccinic acid (DMSA) were constructed and ensuingly characterized. The well-defined nanotube structure with abundant functional moieties by grafting speficial organic groups as binding sites was demonstrated as novel clay adsorbents. The practical affecting factors on the Pb(II) adsorption including solution pH, initial concentration, temperature, and contact time were investigated in detail. The adsorption kinetics of Pb(II) over the targeted adsorbents obey the pseudo-second-order model. The optimized HNTs-Cys was demonstrated to afford outstanding Pb(II) adsorption capability (Qmax = 365.02 mg g−1) within 10 min and biocompatibility performance and anti-biological fouling ability with a specific 98 % lead removal efficiency from the stimulated blood, outperforming other functional counterparts. The Pb(II) adsorption mechanism by the synergetic chelating interaction of functional moieties of the resulting adsorbents including carboxyl, sulfydryl and amino groups was further indentified through preciously deconvoluting the X-ray photoelctron spectra result. The weakened zeta potential value of functional HNTs further validates the dominant coordination effect of present organic moieties rather than the electrostatic interaction. More importantly, we demonstrated that the high and reinforced selective adsorption of Pb(II) in the stimulated blood by HNTs-Cys when introducing various ions interference, and the adsorptive capacity can be maintained at 70 mg g−1 albiet in mixed system (100 mg/L).