Highly efficient and selective adsorption of heavy metal ions by hydrazide-modified sodium alginate

In the present study, a new potential adsorbent for the separation and removal of heavy metal ions was prepared using hydrazide modification. Characterization of structural and chemical properties of the absorbent indicated the dialdehyde sodium alginate (DSA) grafted adipic acid dihydrazide (AAD) plays a crucial role. The adsorption process correlated well with Freundlich isotherm and pseudo-second-order kinetics models. Additionally, the adsorption capacities for Hg2+, Pb2+, Cd2+, and Cu2+ were 7.833, 2.036, 4.766, and 3.937 mmol g-1, respectively. The thermodynamic parameter for the sorption demonstrated the process is endothermic and spontaneous. FT-IR and XPS analysis revealed the combination of chelation interactions and ion exchange between nitrogen, oxygen atoms and heavy metal ions. Moreover, after 10 times adsorption-desorption recycles, the adsorption efficiency of the adsorbent was slightly decreased. In conclusion, the as-prepared adsorbent has great potential in practical water pollution purification.