Fe3O4-based materials are widely used for magnetic separation from wastewater.However,they often suffer from Fe-leaching behavior under acidic conditions,decreasing their ac-tivity and limiting sustainable practical applications.In this study,covalent organic frame-works(COFs)were used as the shell to protect the Fe3O4 core,and the Fe3O4@COF core-shell composites were synthesized for As(Ⅲ)removal from acid wastewater.The imine-linked COFs can in situ grow on the surface of the Fe3O4 core layer by layer with[COFs/Fe3O4]mol ratio of up to 2∶1.The Fe-leaching behavior was weakened over a wide pH range of 1-13.Moreover,such composites keep their magnetic characteristic,making them favorable for nanomaterial separation.As(Ⅲ)batch adsorption experiments results indicated that,when COFs are used as the shell for the Fe3O4 core,a balance between As(Ⅲ)removal efficiencies and the thickness of the COF shell exists.Higher As(Ⅲ)removal efficiencies are obtained when the[COFs/Fe3O4]mol ratios were＜1.5∶1,but thicker COF shells were not beneficial for As(Ⅲ)removal.Such composites also exhibited better As(Ⅲ)removal performances in the pH range of 1-7.Over a wide pH range,the zeta potential of Fe3O4@COF core-shell compos-ites becomes more positive,which benefits the capture of negative arsenic ions.In addition,thinner surface COFs were favorable for mass transfer and facilitating the reaction of Fe and As elements.Our study highlights the promise of using COFs in nanomaterial surface protection and achieving As(Ⅲ)depth removal under acidic conditions.

Wenjun Huang;Haomiao Xu;Xiaoshuang Liu;Longlong Wang;Shutang Li;Leipeng Ji;Zan Qu;Naiqiang Yan

School of Environmental Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China;Shanghai Institute of Pollution Control and Ecological Security,Shanghai 200092,China

环境科学学报（英文版）

[1]Wenjun Huang;Haomiao Xu;Xiaoshuang Liu;Longlong Wang;Shutang Li;Leipeng Ji;Zan Qu;Naiqiang Yan-.Surface protection method for the magnetic core using covalent organic framework shells and its application in As(Ⅲ)depth removal from acid wastewater)[J].环境科学学报（英文版）,2022(05):1-9

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