Herein we report the green recovery of toxic metals [namely: Cd2+, Cr3+, Mn2+, Pb2+, and Ni2+] from water utilizing a biopolymer: 2,6-pyridine dicarboxylic acid cross-linked chitosan (PDC-CCS) as the adsorbent. Adsorption studies were performed at varying experimental conditions (such as pH, adsorbent contact time, initial metal ion concentrations, etc.). At the RI-PB/def2-SVP level of theory, the Density Functional Theory (DFT) approach has been used to evaluate the adsorption energy for the metal ions. Selectivity studies were performed at pH 4.20, 5.56, 6.65 and 7.61. While Mn(II), Cd(II) and Ni(II) were strongly adsorbed at higher pH (7.5), Cr(III) and Pb(II) were seen to be strongly adsorbed at lower pH (around 4.0). Selectivity studies revealed that PDC-CCS can be utilized for simultaneous removal of the metals at pH 4.2; selective adsorption of Mn(II) at pH 5.56 as well as simultaneous-selective removal of Ni(II) and Mn(II) near neutral pH. The experimental maximum adsorption limit of PDC-CCS for Ni(II), Cd(II), Pb(II), Mn(II), and Cr(III), were found to be 1258.79, 1118.70 928.52, 829.62 and 580.21 mmol/g respectively. When compared with some relevant previously used adsorbent, PDC-CCS shows an exceptional adsorption capacity. Consequently, a successful biopolymer adsorbent for the treatment of water contaminated by hazardous metals.