Decontamination of Hg(II) from aqueous solution using polyamine-co-thiourea inarched chitosan gel derivatives

Ethylenediamine (EDA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA) had been successfully introduced into the structure of thiourea (TC) modified chitosan (CS) by using formaldehyde as linkage, respectively. The resulted materials, TC-CS, TC-EDA-CS, TC-TETA-CS, and TC-TEPA-CS were characterized and employed as adsorbents in batch experiment for the Hg(II) removal. We have found the modification enhanced the Hg(II) adsorption significantly in comparison with raw CS. Hg(II) adsorption amounts for all adsorbents increased gradually and reached maxima at pH ≥ 4.0. The adsorption of Hg(II) achieved an equilibrium state within 12 h with the process drove by the pseudo-second-order model. The ionic strength had no remarkable inhibition effect on Hg(II) adsorption. While the Hg(II) adsorption capacities of the adsorbents were strongly related with the modifier types and the length of the incorporating amino ligands. Langmuir model described Hg(II) adsorption well with the maximum adsorption capacities of prepared adsorbents in order of TC-EDA-CS (217.1 mg/g) > TC-CS (164.8 mg/g) > TC-TETA-CS (149.7 mg/g) > TC-TEPA-CS (140.6 mg/g) at room temperature. The FT-IR and XPS investigations implied that Hg(II) ion adsorption mechanism was characterized by a complexation reaction process. Adsorbents could be readily regenerated and had great reusability potential in Hg(II) ions capture from aqueous solution.