Summary: In this study, novel methods were used to recover the by‐product of the reaction between Al‐based composites and water for hydrogen generation as effective means to reduce the cost of hydrogen generation. The results suggest that α‐Al2O3 which is prepared from the reaction by‐product after 24 h ball milling has particle size distributions of 0.57, 1.34, and 2.865 μm for standards d10, d50, and d90, respectively. Sn was partially separated from the hydrolysis by‐product of the Al‐based composites. AlOOH was synthesized through carbonation of the remaining liquid solution after Sn separation. X‐ray diffraction and inductively coupled plasma mass spectrometry were used to characterize the phase compositions and metal element contents, respectively. In addition, a physicochemical mechanism for Sn separation was established. [ABSTRACT FROM AUTHOR]