Characteristics and mechanism of Pb(II) adsorption/desorption on GO/r-GO under sulfide-reducing conditions.

Highlights • The adsorption capacity of Pb(II) on GO was 2–8 times higher than that of r -GO. • Decrease of adsorptive sites on GO-Pb(II) by Na 2 S induces Pb(II) desorption. • Released Pb(II) reacts with OD to form a stable dissolved Pb(II)-OD complex. Graphical abstract Abstract Compared with graphene oxide (GO), r -GO (the reduced form) has a lower adsorption capacity for heavy metal ions and, therefore, generates concern over the release of adsorbed contaminants when GO adsorbent is discharged into a reducing environment. This study reveals that the maximum adsorption capacity of Pb(II) on GO and r -GO was 937.65 and 92.99 mg g⁻¹ respectively. GO was reduced to r -GO by sulfide, causing 2.59–6.46% of the adsorbed Pb(II) to be released and was stably dispersed as a Pb(II)-oxidative debris (OD) complex. Our results provide valuable information about heavy metal transportation in environments containing GO under different redox conditions. [ABSTRACT FROM AUTHOR]