The ternary magnetically recyclable N-K2Ti4O9/MnFe2O4/PANI composites with PANI standing for polyaniline at different N-K2Ti4O9/MnFe2O4 ratios were successfully synthesized by an in situ oxidative polymerization method. The ternary N-K2Ti4O9/MnFe2O4/PANI composites possess a hierarchical core-shell structure with PANI forming the shell around the N-K2Ti4O9 core and the MnFe2O4 nanopartides embedded in the PANI shell. Photocatalytic activity of the composites was investigated by the degradation of Rhodamine B (RhB) under visible light irradiation, and the synergistic effect induced by compounding was quantitatively evaluated by the proposed synergistic factor. The results show that the binary PANI-based composites exhibit higher photocatalytic activity as compared with the parent materials. This is due to the big adsorption capacity high utilization ratio of visible light and the enhanced charge carrier transfer of PANI. With PANI connecting MnFe2O4 and N-K2Ti4O9 to form heterojunction interfaces of N-K2Ti4O9/PANI and MnFe2O4/PANI, the separation of electron-hole pairs can be more enhanced, as a result, the ternary composites display better photocatalytic activity than the binary composites. It is obvious that PANI plays a vital role for the synergistically enhanced photocatalytic effect. (C) 2014 Elsevier B.V. All rights reserved.