α−FeOOH@HTC with abundant oxygen vacancy enhances the adsorption of As(III) in different phosphate environments

The interaction process between phosphorus and arsenic is of great significance for controlling arsenic pollution by iron oxide minerals. In this work, the α−FeOOH@hydrothermal carbonisation (HTC) composites with abundant oxygen vacancy were synthesized by a hydrothermal method using HTC as a carrier and were used for the removal of arsenic in different phosphate environments. The surface hydroxyls (OHs) in α−FeOOH promote the production of OVs on the surface of the composite and improve the adsorption capacity of As(III). The experiment results showed that the maximum adsorption capacity of α−FeOOH@HTC on As(III) under the influence of PO43−, HPO42−, and H2PO4− were 8.76 mg∙g−1, 10.67 mg∙g−1 and 10.21 mg∙g−1, respectively. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis showed that after adsorption, a characteristic peak of As(III) was generated on the FeOOH@HTC surface. The possible adsorption mechanism for As (III) by α−FeOOH@HTC is the surface complexation and precipitation of M−OH as well as Fe−OH−Fe with As (III). After the application of composite materials in rice seedling hydroponic experiments, it was found that they have a certain degree of biological safety, providing a theoretical basis for reducing arsenic pollution. This work studies the adsorption behavior of OVs on As(III) and provides a new approach to address arsenic contamination in water.