Hexametaphosphate cross-linked chitosan beads for the eco-efficient removal of organic dyes: tackling water qualityHexametaphosphate cross-linked chitosan beads for the eco-efficient removal of organic dyes: tackling water quality Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2023-04-272021enThere is an increasing trend of developing various low-cost grafted natural amino polysaccharides for the biosorptive removal of noxious dye effluents like Malachite green (MG) and anionic Reactive Red–195 (RR-195) dyes from aqueous solution. Chemically cross-linked chitosan microsphere (CTS-HMP), a promising non-toxic biosorbent possessing high charge density and thermal stability was prepared by using hexametaphosphate as ionic cross-linker. Batch biosorption experiments were carried out under different temperatures (298, 308 and 318 K), pH (2.0–10.0), initial concentrations (25–250 mg L−1), adsorbent dosage (0.01–0.1 g) and contact times (0–180 min) to understand the optimum experimental conditions and simultaneously evaluate the adsorption isotherms and kinetics of CTS-HMP. Biosorption equilibrium was established in 120 and 60 min for MG and RR-195 removal process. The pseudo-equilibrium process was best described by the pseudo-second-order kinetic (R2 ≥ 0.98), Freundlich and Temkin isotherm model (R2 ≥ 0.90). The removal rate of MG and RR-195 gradually increased (69.40 and 148 mg g−1) at 250 mg L−1 of initial concentration till 100 and 50 min of contact period in a single contaminant system, though the removal efficiency of acid dye was ~2 times higher compared to basic dye under optimum conditions (p < 0.05; t-test). Thermodynamic parameters indicated exothermic (MG) and endothermic (RR-195) nature of spontaneous dye removal. The activation energy of sorption (Ea) was <50 kJ mol−1 which highlighted the importance of physical adsorption process. Therefore, the obtained results clearly validate the sustainable utilization of CTS-HMP as a promising functionalized chitosan microparticles/agent for removing dye effluents from the contaminated aqueous phase.http://creativecommons.org/licenses/by/4.0/Journal of Environmental Management280 Raval Nirav Mukherjee Santanu Shah Nisha K. Gikas Petros Γκικας Πετρος Kumar Manish Elsevier Hexametaphosphate Malachite green Reactive red–195 Biosorption Chitosan Thermodynamic