The present study is focused on the removal of Hg (II) ions from aqueous environment using a new nanobiocomposite (NBC) hydrogel modified by triethylene tetra amine (TETA-NBC) and $\beta$-cyclodextrin (CD-NBC). Optimization of various parameters was done using 4-level Box-Behnken design. Maximum mercury removal (97.9{\%}; 70.1{\%}) and uptake (407.9. mg/g; 292.1. mg/g) was noted at central values of various parameters (pH: 6.0, time: 6. h, initial metal: 250. mg/L, biomass dosage: 0.6. g/L). Mode of biosorption was evaluated using equilibrium studies. Among the various equilibrium and kinetic models, Freundlich isotherm and fractional power model exhibited the best fit. Intraparticle diffusion and Boyd plot suggested two-phase diffusion in case of CD-NBC and single phase diffusion in case of TETA-NBC. The mechanism was further elucidated using SEM, EDX and FT-IR analysis. Spectroscopic analysis showed a higher mercury uptake due to enhanced surface roughness, less compaction and higher availability of functional groups in case of TETA-NBC compared to CD-NBC. Ex situ studies were conducted using a packed bed column in upflow mode. TETA-NBC could be reused upto six cycles. Comparative studies using Amberlite (commercial resin) showed that TETA-NBC could serve as alternative and cost effective agent for remediation of mining wastewater.