Natural melanin/TiO2 hybrids for simultaneous removal of dyes and heavy metal ions under visible light

© 2019 Melanin has attracted researchers’ attention in recent years due to its intriguing properties and various applications in different fields. Here, we fabricated a highly efficient photocatalytic material through utilizing the natural melanin (NM) isolated from textile scraps like yak hair wastes. A simple one-step process was employed to synthesize titanium dioxide (TiO2) nanoparticles on the surface of NM. The synthesized NM/TiO2 hybrids exhibited prominent photocatalytic activity for the simultaneous removal of methyl orange (MO) and hexavalent chromium ions (Cr (VI)) under visible light irradiations, which constitute ∼45 % of the solar light. Our results revealed that NM served as a base material with abundant catechol groups to form C-O-Ti bonds with TiO2 nanoparticles, which narrowed the band gap and broadened the light response of the hybrids. The working mechanism of NM/TiO2 hybrids for the simultaneous removal of dyes (MO) and heavy metal ions (Cr (VI)) was thoroughly explored and proposed. This work highlighted the potential of the NM/TiO2 hybrids for textile dyeing effluent treatment with more efficient utilization of solar spectrum. Our work also opens a pathway for the design of advanced NM-based functional materials from various NM-enriched wastes such as human hair wastes, squid ink, etc.