A　novel　core-shell　magnetic　nanoparticle　was　synthesized　through　heterogeneous　nucleation　technique　and　utilized　to　remove　As(V)　from　water.　Both　the　magnetic　core　and　the　coating　material,　amorphous　FeOOH　shell,　were　prepared　with　iron-containing　water　treatment　residuals　(WTRs),　also　called　iron　sludge.　The　bare　magnetic　nanoparticles　(MNPs)　and　coatedmagnetic　nanoparticles　(c-MNPs)　were　characterized　by　X-ray　diffraction　(XRD),　X-ray　photoelectron　spectroscopy　(XPS),　transmission　electron　microscopy　(TEM),　Brunauer-Emmett-Teller　analysis　(BET),　vibrating　sample　magnetometer　(VSM)　and　Fourier　transform　infrared　spectroscopy　(FTIR).　The　c-MNPs,　mainly　consisting　of　maghemite　(gamma-Fe2O3)　as　the　magnetic　core　and　amorphous　FeOOH　as　the　coating　material,　could　be　easily　separated　from　water　through　a　hand-held　magnet,　the　saturation　magnetization　of　which　is　36.4　emu/g.　Freundlich　adsorption　isotherm　model　could　better　described　the　As(V)　adsorption　behavior　of　c-MNPs　than　Langmuir　model,　and　kinetic　data　could　be　described　well　by　the　pseudo-second　order　model.　The　maximum　As(V)　adsorption　capacity　of　c-MNPs　(26.05　mg/g)　was　more　than　twice　that　of　MNPs　(12.74　mg/g).　At　25　degrees　C,　0.2　g/L　of　the　c-MNPs　could　reduce　the　As(V)　from　400　mu　g/L　to　below　the　maximum　contaminant　level　(MCL)　of　10　mu　g/L　over　a　broad　pH　ranging　from　4　to　8.　The　c-MNPs　still　exhibited　effective　adsorption　in　the　presence　of　co-existing　anions　including　nitrate,　chloride,　carbonate,　and　sulfate,　whereas,　silicate　and　phosphate　had　a　negative　influence　on　the　As(V)　adsorption.　Throughout　five　consecutive　cycles,　the　adsorbents　could　still　maintain　high　As(V)　adsorption　capacity.　(C)　2020　Elsevier　B.V.　All　rights　reserved.