Due to the carcinogenicity and high environmental mobility of arsenic (As), its contamination in the groundwater environment is widespread, continuously threatening human health through the food chain. The adsorption technologies for As removal, which demonstrate simplicity and cost-effectiveness, have received much attention. Despite these merits, the difficult separation between adsorbent and As-contaminated water in traditional adsorption limited the development of large-scale applications. An adsorbent of Fe-Mn-Cu ternary oxide modified with magnetite (FMCTO@Fe