Upcycling of Cd Hyperaccumulator Biomass into a CdS@C Nanocomposite with High Photocatalytic Performance

Abstract

Phytoextraction is considered a promising technique for the remediation of Cd-contaminated soils. However, there is a risk of secondary pollution related to the disposal of Cd-enriched hyperaccumulator biomass, which largely limits the commercialization of phytoextraction. In this work, for the first time, a mesoporous carbon-supported nano CdS (CdS@C) photocatalyst was obtained by in situ upcycling of Cd-enriched Sedum plumbizincicola biomass through a combination of pyrolysis carbonization and hydrothermal reaction. Nano-CdS was identified as the mixed phase of cubic and hexagonal structures in the as-prepared CdS@C nanocomposite. The CdS@C nanocomposite exhibited considerably lower band gap energy (2.01 eV) and higher efficiency of electron–hole separation than pure CdS, indicating excellent light-harvesting capacity and photocatalytic efficiency. The significant stability and photocatalytic performance of CdS@C were demonstrated by the efficient removal of rhodamine B (RhB) and the successful treatment of dyeing wastewater by photodegradation. The impressive dye photodegradation performance was attributed to the successful formation of active species during the photocatalysis of CdS@C, such as h+, •OH, and O2•–. This work provides new insights into addressing the disposal problem of Cd-enriched hyperaccumulator biomass and developing a high-performance CdS@C photocatalyst using a facile and low-cost approach.