Biosynthetic amyloid fibril CsgA-Fe3O4 composites for sustainable removal of heavy metals from water

Abstract

Removal of heavy metals from water has been a hot topic. However, few studies have been conducted for the tricky low concentration range. Experimental designs often have heavy metal concentrations much higher than the actual environmental loading, which leads to poor practical results of adsorbent materials. This study showed that amyloid fiber CsgA-Fe3O4 composites are ideal for the removal of heavy metals from water, especially at low concentrations. We constructed CsgA-Fe3O4 composites by fusing short functional peptides that specifically bind to Fe3O4 magnetic nanoparticles. The CsgA-Fe3O4 composites achieved 98.73 %, 98.43 %, and 93.00 % removal of 1 mg/L Cu2+, Cd2+, and Pb2+, respectively. Moreover, the adsorption rate remained above 80 % after six repeated adsorptions, indicating that CsgA-Fe3O4 was highly reusable. Meanwhile, the high removal rate (>90 %) of heavy metals in the simulated wastewater demonstrated the excellent environmental stability of CsgA-Fe3O4. Finally, by FT-IR and XPS characterization, we found that the adsorption mechanism of CsgA-Fe3O4 is mainly the complexation of surface oxygen-containing functional groups and heavy metal ions. In general, the CsgA-Fe3O4 composite is an efficient, inexpensive, and sustainable adsorption material for mitigating low concentrations of difficult-to-treat heavy metal pollution in water bodies.