Construction of chitosan based magnetic bio adsorbent for efficient recovery of Ni(II)

Nowadays, efficient harnessing of heavy metal contamination is an urgent environmental task. Herein, magnetic bio adsorbent Fe₃O₄-graphene oxide-chitosan composite (FGOC) was constructed via one step solvothermal procedure for adsorptive recovery of Ni(II). Subsequently, interaction mechanism between FGOC and Ni(II) was deeply elucidated via combining adsorption fitting, the hard-soft acid-base (HSAB) theory calculation and spectroscopic analysis (XPS, UV-Vis and fluorescent emission spectra). Results indicate, FGOC prevails single Fe₃O₄, chitosan and graphene oxide in Ni(II) scavenging efficiency when pH > 6. Particularly, maximum adsorption percent and quantity 96.52 % and 386.09 mg·g^-1 is reached at pH = 10. After six consecutive cycles, adsorption percent and quantity are 88.41 % and 353.63 mg·g^-1. Moreover, FGOC demonstrates favorable selectivity towards Ni(II) under the coexistence of common interfering substances. Adsorption isotherm and kinetic fittings propose chemical adsorption with heterogeneous affinity. HSAB theory discloses, groups -OH, -COOH, -C(=O)NH-, -NH₂ provide strong adsorptive affinity, with electron flowing from adsorbent towards Ni(II). Furthermore, the overall affinity provided by the potential adsorption sites in each constituents are in following order: Fe₃O₄ < CS < GO. Above findings were substantiated by spectroscopic tests. This work provides reference for fabricating magnetic graphene oxide-chitosan composite towards valuable metal recovery from wastewater.