<p>Ascorbic acid cross-linked cellulose agar beads (AA-CLCAB) were synthesized in a green method and successfully used as an effective adsorbent for the selective removal of mercury (II) ions from aqueous medium. The AA-CLCAB were well characterized by swelling study, FTIR, SEM, EDS, TGA, BET and UV–Vis spectroscopic analyses. The effect of pH, adsorbent dose, contact time, initial mercury ion concentration and temperature were investigated to find out the favourable experimental conditions. The adsorption experimental data followed pseudo-second-order kinetic model and were found to fit well with both Langmuir (maximum monolayer adsorption capacity of 247.6&#xa0;mg/g) and Freundlich isotherm models. Redlich-Peterson isotherm model, a hybrid of Langmuir and Freundlich isotherms is used to explain this dual mode of adsorption in a better way. The negative value of ΔG˚ and positive value of ΔH˚ obtained from the thermodynamic study, indicated that the adsorption process is spontaneous and endothermic. 100% removal of mercury ions was achieved with 500 beads at pH 5. 0.1&#xa0;M HCl was utilised as a desorbing agent to completely desorb mercury ions in a two-step elution process. AA-CLCAB showed a good regeneration ability which was 63% of the initial mercury uptake after five cycles. The material showed no interference in presence of different co-ions for Hg(II) removal. The eco-friendly cellulose-agar composite beads, cross-linked with ascorbic acid, have good stability, reusability and great potential in Hg(II) removal.</p>