MgFe2O4/MgO (S-sample) and a novel V-modified MgFe2O4/MgO (V-sample) nanocomposites were successfully synthesized using the reverse coprecipitation method and were carefully characterized by X-ray diffractometry, Infrared and 57Fe Mössbauer spectroscopies, magnetization, electron microscopy (both transmission and scanning) and surface area analysis to comprehend their structural, morphological, hyperfine and magnetic properties before and after P adsorptions. MgFe2O4 and V-modified MgFe2O4 phases (with 30 nm average in “diameter”) govern the nanocomposite magnetic properties and these phases are chemically stable in phosphate-rich effluents. 50 nm in size MgO phase is responsible for P adsorption, but it showed chemical corrosion, as suggested by surface analysis. Adsorption kinetic revealed that there are two controlling steps: film and intraparticle diffusion. The nanocomposite materials fitted better to the Freundlich isotherm model, indicating that the adsorption site distribution for P is heterogeneous, and a multilayer adsorption mechanism is favored. Multicycle reuse experiments with secondary sewage effluent were performed, and the adsorption capability of the V-sample over 3 consecutive adsorption cycles was 11 mg g−1, a value 30 % higher than that found for the S-sample. The desorption efficiency of the V-sample was about 97 %, while the S-sample reached 76 %. The V-substituted composite is a promising nanoadsorbent for water remediation process in phosphate-rich effluents and should be also tested in remediation of other contaminants.