Display omitted •Unorthodox synthesis of reusable collagen-g-terpolymer-g-guar gum superadsorbent.•In situ protrusion of acrylamido propanoic acid monomer in terpolymer network.•Advanced adsorbed/unadsorbed microstructural analyses for superadsorption mechanism.•1H-/13C-NMR, XPS, FTIR, UV–vis, TGA-DSC, XRD, and isotherms-kinetics-thermodynamics.•Removals of p-nitrophenol, vitamin C/ascorbic acid, Hg(II)/Pb(II), and MB/MV. Herein, guar gum (GG)-g-(acrylic acid (AA)-co-3-acrylamido propanoic acid (AMPA)-co-acrylamide (AM))-g-cow buffing dust (CBD)/(GGTPCBD), a smart carbohydrate and protein-based doubly-grafted interpenetrating terpolymer hydrogel showing excellent physicochemical properties and recyclability was synthesized by in situ strategic allocation of AMPA during solution polymerization of AA and AM through systematic optimization of the amounts of components and reaction temperature for superadsorption of Hg(II), Pb(II), methyl violet (MV), methylene blue (MB), p-nitrophenol (PNP), and vitamin-C (vit.C). The in situ strategic protrusion of AMPA, grafting of both GG and CBD into AA-co-AMPA-co-AM, and ligand-selective superadsorption was inferred by advanced microstructural analyses of unadsorbed- and/or adsorbed-GGTPCBD using FTIR, 1H/13C NMR, O1s-/N1s-/C1s-/Pb4f7/2,5/2-/Hg4f7/2,5/2-XPS, UV–vis, TGA, DSC, XRD, DLS, SEM, EDX, % gel content, % −COOH, and pHPZC. The prevalence of covalent, ionic, and variegated interactions was rationalized by FTIR, fitting of kinetics data to the pseudosecond order model, and activation energies of adsorption. The BET and Langmuir isotherms fitted the best to MB and Hg(II)/Pb(II)/MV, respectively. Thermodynamically spontaneous chemisorption processes showed the maximum adsorption capacities (ACs) of 976.64, 859.23, 116.80, and 58.52 mg g−1 for Pb(II), Hg(II), MV, and MB, respectively, at 303 K, adsorbent dose = 0.01 g, and initial concentration of metal ions/dyes = 800/30 ppm.