Petaloid MoS2@MIL-88B(Fe) nanocomposite photocatalyst utilized to achieve accurate SWASV detection of Cd2+ and Pb2+ in water under low-pressure ultraviolet irradiation

Abstract

Humic acid (HA) is an organic compound in natural water and can be complexed with heavy metal ions (HMIs), which interferes with the detection of square wave anodic stripping voltammetry (SWASV). In this study, a petaloid MoS₂@MIL-88B(Fe) nanocomposite was synthesized via hydrothermal synthesis. Leveraging its ability to generate active species under low-pressure ultraviolet (LPUV) irradiation, a MoS₂@MIL-88B(Fe)/LPUV-based pretreatment method was proposed to detect HMIs in water by disrupting the complexation between HA and HMIs, thus restoring the SWASV signals of HMIs. The microstructure, crystal structure, surface chemical state, band gap, photogenerated charge separation and recombination rates of MoS₂@MIL-88B(Fe) were investigated, along with the degradation kinetics of HA, byproducts, and active species generated during pretreatment, to elucidate both the mechanism behind the disruption of HA-HMIs complexation and the restoration of SWASV signals. Additionally, the key pretreatment parameters, such as pH, the MoS₂ to MIL-88B(Fe) mass ratio, the photocatalyst concentration, and the photolysis time, were optimized for the choice signal restoration ratio. The proposed MoS₂@MIL-88B(Fe)/LPUV-based pretreatment method was applied to real water samples, yielding a root mean square error (RMSE) of less than 0.2 μg/L compared with that of the national standard method, confirming its authenticity and feasibility.