Functionalization of adsorbent with different aliphatic polyamines for heavy metal ion removal: characteristics and performance.

This paper examines the characteristics of poly(glycidyl methacrylate) (PGMA) beads functionalized with different aliphatic polyamines as adsorbents and their performance in copper ion adsorption. The four aliphatic polyamines evaluated include ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). Various analytical tools, including elemental analysis, BET, and XAFS (XANES+EXAFS), were used to characterize the adsorbents in terms of their immobilized amine contents, polyamine densities, and their coordination structures for the adsorption of a typical heavy metal ion, Cu(2+). It was found that the immobilized polyamine densities followed the order of EDA>DETA>TETA>TEPA, but the immobilized amine contents followed the opposite order of TEPA>TETA>DETA>EDA. XAFS analysis for the adsorbents after copper ion adsorption revealed that the average coordination number of copper ion with the nitrogen atoms (in the range between 3 and 4) followed the order of DETA<TETA<EDA<TEPA. Hence, the molecular length and structure of the polyamines appeared to have a great effect on the adsorption performance of the prepared adsorbents. The study leads to the conclusion that among the four aliphatic polyamines, DETA-functionalized PGMA adsorbent was the most efficient one for copper ion removal because of the relatively higher amine content and lower coordination number, easier regeneration, and shorter preparation time of the adsorbent. The results provide some useful information for future studies in the selection of polyamines for adsorbent functionalization.