This work evaluated the novel application of biochars derived from potassium (K)-rich feedstock (banana peels (BB) and cauliflower leaves (CB)). The sorptive property of the produced biochars was evaluated with multi-element Copper (Cu(II)), Cadmium (Cd(II)) and Led (Pb(II)) sorption experiments. Morphologies of the pre- and post-sorption samples were characterized using SEM/EDS and XRD spectra analyses. The produced biochar was further subjected to mono-element sorption studies to explore the effect of the pH value of the sorbate solution on the removal efficiency of Cu(II), Cd(II) and Pb(II) ions. Biochar productivity was noticeably high (61.44 and 64.66% for BB and CB, respectively) due to the catalytic action of K during the pyrolytic conversion of the feedstock. K-minerals were the predominant on the XRD patterns of both biochars. Metal sorption capacity of BB was much greater than that of CB due to its higher electrostatic attraction, which was the predominant mechanism governed sorption process. Sorption of metal ions onto BB and CB was pH-dependent as the sorption capacity increased significantly with the increase of the pH value of sorbate solutions (6.0 with Cu(II), Pb(II) and 8.0 with Cd(II)). Dynamics of metal ions sorption onto biochars showed competitive sorption following the order: Pb(II) > Cu(II) > Cd(II). •The XRD patterns showed the excellent crystallinity of both banana peel biochar (BB) and cauliflower leaves biochar (CB).•Apparent sorption of heavy metals was rapid during the first 5–10 h, and the equilibrium was reached at 24 h.•Pseudo-second-order was the best model describing the sorption of Pb(II) and Cd(II) onto both biochars (R2 > 0.94).•Sorption capacity (Smax) of heavy metal was higher in BB as compared to other biochar reported in literature.