Biosorbents have been extensively studied for heavy metal adsorption due to their advantages of low cost and high efficiency. In the study, the living and non-living biomass ofCupriavidus necatorGX_5 previously isolated were evaluated for their adsorption capacity and/or removal efficiency for Cd (II) through batch experiments, SEM and FT-IR investigations. The maximum removal efficiency rates for the live and dead biomass were 60.51% and 78.53%, respectively, at an optimum pH of 6, a dosage of 1 g/L and an initial Cd (II) concentration of 5 mg/L. The pseudo-second-order kinetic model was more suitable for fitting the experimental data, indicating that the rate-limiting step might be chemisorption. The Freundlich isotherm model fit better than the Langmuir isotherm model, implying that the adsorption process of both biosorbents was heterogeneous. FT-IR observation reflected that various functional groups were involved in Cd (II) adsorption: –OH, –NH, C=O, C–O and C–C groups for the living biomass and –OH, –NH, C–H, C = O, C–N and N–H groups for the dead biomass. Our results imply that non-living biosorbents have a higher capacity and stronger strength for absorbing Cd (II) than living biomass. Therefore, we suggest that dead GX_5 is a promising adsorbent and can be used in Cd (II)-contaminated environments.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13065-023-00977-4.