Efficient removal of uranium, cadmium and mercury from aqueous solutions using grafted hydrazide-micro-magnetite chitosan derivative

Magnetic chitosan microparticles are functionalized by grafting a new hydrazide derivative to produce HAHZ-MG-CH, which is applied to the sorption of metal cations. The functionalization (appearance of new groups) and synthesis mechanisms are confirmed using elemental analyses, FTIR and XPS spectrometry, TGA and EDX analysis, SEM observation and titration. HAHZ-MG-CH bears high nitrogen content (approximate to 10.9 mmol N g(-1)). Maximum sorption capacities at pH 5 reach up to 1.55 mmol U g(-1), 1.82 mmol Hg g(-1) and 2.67 mmol Cd g(-1). Sorption isotherms are preferentially fitted by the Langmuir model. In acidic solutions, the sorbent has a marked preference for Hg(II) over U(VI) and Cd(II), while at mild pH uranyl species are preferentially bound. The sorbent has a lower affinity for Cd(II) in multicomponent solutions. Sorption occurs within 60 min of contact. The pseudo-first-order rate equation fits well kinetic profiles. HCl solutions (0.5 M) successfully desorb all the metal ions (yield exceeds 97% at the first cycle). The sorbent can be recycled for 5 cycles of sorption and desorption: the loss in efficiencies does not exceed 8%. The sorbent removes Hg(II), Cd(II) and Pb(II) from local contaminated groundwater at levels compatible with irrigation and livestock uses but not enough to reach the levels for drinking water regulations.