Environmental friendly technology for the removal of pharmaceutical contaminants from wastewaters using modified chitosan adsorbents

摘要

In the present study, new modified chitosans, cross-linked with glutaraldehyde and grafted with sulfonate (CsSLF) or N-(2-carboxybenzyl) groups (CsNCB), were synthesized and investigated as efficient and environmental friendly adsorbents for removing pharmaceuticals from polluted water matrices. To test the performance of these innovative chitosan-based sorbents, pramipexole dihydrochloride (PRM), a recently available non-ergot dopamine agonist was selected as model compound. Non-grafted chitosan was also prepared and used as reference adsorbent material for comparison with cross-linked (Cs) chitosan. Their characterization was realized via swelling tests, FTIR, SEM, and BET analysis. Alkaline conditions (pH = 10) were found to be the optimum for the adsorption process, while the reverse conditions (pH = 2) were optimum for desorption. The adsorption mechanism was also examined. Kinetic experiments were performed to study the effect of contact time on adsorption and the experimental findings were fitted to common kinetic models (pseudo-first, -second order and Elovich equations), in line with a detailed kinetic model, incorporating diffusion and localized adsorption and desorption steps. Isotherms showed the effect of initial PRM concentration and temperature (25, 45, 65 °C) on adsorption. Modified chitosans have a better behavior for PRM adsorption and the rate follows the order: CsSLF > CsNCB > Cs. The equilibrium data were fitted to the Langmuir-Freundlich model. The reuse of adsorbents synthesized was evaluated via sequential adsorption-desorption cycles.