Mild routine to prepare Fe-Mn bimetallic nano-cluster (Fe-Mn NCs) and its magnetic starch-based composite adsorbent (Fe-Mn@SCAs) for wide pH range adsorption for Hg(Ⅱ) sewage.

• Mild routine to synthetize fe-mn bimetallic nano-cluster. • Its composite adsorption (Fe-Mn@SCAs) with corn starch was further prepared and showed selective adsorption capacity for hg (Ⅱ) as high as 324.42 mg/g. • The Fe-Mn@scas was equipped with considerable recyclability and highly selective adsorption performance for Hg (Ⅱ). • The adsorption mechanism of the Fe-Mn@scas was elaborated. The Fe-Mn bimetallic system had been applied to efficiently adsorbed heavy metal in sewage and its composites with inert matrix could overcome the ions leaching problem. After being pyrolyzed to carbon, corn starch could be used as an inert substrate. Hence, the fabrication of Fe-Mn@SCAs had a prospect in Hg(Ⅱ) sewage treatment. Herein, the Fe-Mn bimetallic system shaped with nano-cluster structure was firstly prepared through mild reaction conditions. And it was further composited with corn starch-based carbon, fabricating Fe-Mn bimetallic doped starch-based porous carbon adsorbents (Fe-Mn@SCAs). Its changes in surface structure, crystalline structure, and functional groups in compartment procedure were clarified. Batch adsorption experiments were applied to evaluate the adsorption performance for Hg(Ⅱ) and Fe-Mn@SCAs could not only complete its maximum adsorption (324.42 mg/g) within 1.5 h but also had a wide range of adsorption pH (4–7). The adsorption mechanism for Hg (Ⅱ) was elucidated carefully and summarized including porous structure, electrostatic attraction, chelation, ion exchange, and covalent coordination. Besides, thermodynamic study demonstrated that the Hg (Ⅱ) adsorption procedure was spontaneous, endothermic, and randomness. In addition, its selective adsorbability and regenerability were also excellent, having a promising prospect in the Hg (Ⅱ) sewage purification. [Display omitted] [ABSTRACT FROM AUTHOR]