As a natural, non-toxic adsorbent, chitosan is well suited for the removal of heavy metals and antibiotics. In this study, chitosan was modified with polypropylene glycol and itaconic anhydride to improve the mechanical properties of chitosan, and the polypropylene glycol-itaconic anhydride-chitosan adsorbent was successfully prepared. The adsorbent was characterised and analysed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis and X-ray photoelectron spectroscopy (XPS). The effects of the different conditions on the adsorption of Pb2+ and cephalexin were investigated. The Langmuir adsorption isotherm model showed that the maximum adsorption capacities of Pb2+ and cephalexin could reach 431.73 mg g−1 and 153.72 mg g−1, respectively. The possible adsorption mechanism of Pb2+ and cephalexin was discussed.