Removal of copper from contaminated soil by use of poly(amidoamine) dendrimers

This study characterizes poly(amidoamine) (PAMAM) dendrimers of various generations and terminal functional groups for removal of copper(II) in a sandy soil. Effects of dendrimer dose, generation number, pH, terminal functional groups, and ionic strength on the removal efficiency were investigated through a series of column tests. Over 90% of copper initially sorbed in the soil was removed by use of approximately 66 bed volumes of 0.10% (w/w) of a generation 4.5 dendrimer with carboxylate terminal groups at pH 6.0. On the basis of equal equivalent dose, dendrimers of lower generation removed more copper. Lowering pH enhanced copper removal for all dendrimers tested. In contrast, types of terminal groups (carboxylate, amine, or hydroxyl) showed a modest effect on the removal efficiency. Results from a sequential extraction procedure suggested that dendrimers removed primarily exchangeable and carbonate-bound copper. The residual copper in treated soil is predominantly bound with soil organic matter (SOM), which is much less available physical-chemically or biologically. Spent dendrimers were recovered through nanofiltration with a commercially available nanofilter. Upon acid regeneration, recovered dendrimers were reused and performed as well as the virgin dendrimers. The dendrimers may be used as reusable, high-capacity extracting agents for in situ removal of heavy metals from contaminated soils.