Light-driven in-situ synthesis of nano-sulfur and graphene oxide composites for efficient removal of heavy metal ions

Sulfur nanoparticles (SNPs) and their composites are promising for heavy metal adsorption, yet current SNPs often lack surface S2-, leading to low affinity toward heavy metal and ease of aggregation. Here, we report a simple light-driven method for facile prepare SNPs with surfaces enriched with S2- and in-situ load them onto graphene oxide (GO) to fabricate GO-S composites. Under illumination, the 1O2 generated by photosensitizer phloxine B was able to oxidize S2- into elemental SNPs. Due to the strong affinity of GO for elemental sulfur, SNPs can be monodispersed and directly in-situ loaded on the GO surface. Benefiting from the strong thiophilicity of heavy metal ions, GO-S showed 1.7-12.4 fold higher adsorption capacity for heavy metal ions, and the adsorption efficiency could reach 94-98% for Cu(II), Cd(II), Hg(II), Pb(II) and Zn(II) within 1h, ensuring the concentrations of these heavy metal ions in the treated wastewater below the maximum allowable value of integrated wastewater discharge standard (GB/8978-1996). The adsorption mechanisms include physical adsorption, electrostatic interactions and complexation. Overall, our proposed light-driven method is expected to further facilitate the facile synthesis of SNPs-modified materials and the application in the heavy metal decontamination of environmental waters. [Display omitted] •A green and simple light-driven approach for synthesis of SNPs was developed.•The prepared SNPs is rich in surface S2- which greatly improved the dispersion of SNPs.•Compared with pristine GO, GO-S showed 1.7 to 12.4 times higher adsorption capacity.