Synthesis, characterization, and secondary sludge dewatering performance of a novel combined silicon-aluminum-iron-starch flocculant.

•Silicon, aluminum, and iron were grafted onto starch chains to synthesize CSiAFS.•The sludge dewatering performance of CSiAFS was superior to PAC, PAM, and FeCl3.•CSiAFS exhibited a good dewatering efficiency over a wide range of pH (3.0–11.0).•CSiAFS had a discontinuous surface with channels which helped to sludge dewatering.