Development and application of cross-linked polyethylenimine for trace metal and metalloid removal from mining and industrial wastewaters

Abstract

Pollution of water bodies by trace metals is an established problem and several studies have been conducted to deal with it. South Africa is amongst those countries whose water systems are most affected as a result of intensive mining activities. This research was dedicated to the development of an insoluble chelating polymer for use as an adsorbent for abstraction of metal ions from mining and industrial wastewaters. Polyethylenimine (PEI), well known for its metal chelating potential, was cross-linked by epichlorohydrin (ECH) in order to convert it into a water-insoluble form for direct use as an adsorbent. The binding affinity of the cross-linked polyethylenimine (CPEI) to heavy metal ions was assessed as well as its ability to be regenerated for re-use. CPEI exhibited good complexation ability to metal ions with high affinity to Cr and most divalent metal ions. The observed order of complexation was: Cr > Zn> Fe > Ni > Mn > Pb. On the other hand, it showed very poor ability to bind oxo-anions such as SeO₃ ²⁻ and AsO₂ ⁻ which has been attributed to the unavailability of suitable functional groups to interact with these ions.

Keywords:

• polyethylenimine
• cross-linking
• adsorption
• trace metals

Acknowledgment

The authors acknowledge the financial support from the University of the Witwatersrand through the Friedel Sellschop Award.