Role of Nitrate in the Production of Iron-Modified Hydrochar for Arsenic Removal

This study focuses on the synthesis of a novel arsenic adsorption material, iron-modified hydrochar, by using different iron species, i.e., FeCl3·6H2O, FeSO4·7H2O, and Fe(NO3)3·9H2O. These hydrochars were prepared through a one-step hydrothermal carbonization process at 220 °C. This paper aims to explore the impact of different iron species on the characteristics of iron-modified hydrochars. XPS, XRD, SEM-mapping, and ICP-OES were employed to compare the physicochemical properties, iron binding stability, and arsenic adsorption capabilities of these iron-modified hydrochars. The results indicated that compared with FeCl3·6H2O and FeSO4·7H2O, hydrochar modified with Fe(NO3)3·9H2O exhibited a maximum iron retention rate of 84.2% and a maximum arsenic adsorption capacity of 11.19 mg/g. The study also examined the role of Fe(NO3)3·9H2O in the hydrothermal carbonization process, identifying key factors that enhance the iron content of hydrochars and improve their arsenic adsorption capacity. This research provided valuable insights into the improvement of the preparation efficiency of iron-modified hydrochars and their arsenic adsorption capabilities, revealing how different iron species influence the characteristics of hydrochars and offering beneficial information for the preparation of arsenic adsorption materials.