Abstract
Wastewater is contaminated with inorganic and organic compounds through a number of activities including industrial, agricultural and human activities. Current wastewater treatment technologies such as membrane technology, ion exchange, electrolysis and bioremediation are not always efficient in removing these contaminants to parts per billion (ppb) levels. New techniques need to be developed that are reasonably inexpensive, easy to use, environmentally friendly and more efficient in removing toxic metals and other compounds to acceptable levels. Adsorption of toxic contaminants in water using polyethyleneimine (PEI)-based composite materials has the potential to meet these criteria. This work reports on the synthesis of branched PEI, its insoluble form (CPEI) and its cross-linking with multi-walled carbon nanotubes (MWCNTs) to form PEI-MWCNT nanocomposites. The PEI-MWCNT polymeric nanocomposite adsorbents were evaluated for the removal of Cr6+ and Pb2+ from contaminated water.
Branched PEI was used as the polymer material of choice because of its chelating properties and the ability to add specific functional groups on its structure. Functionalized MWCNTs (0.5 - 2.5% w/w), with average diameter of 25 nm were incorporated into PEI to provide mechanical robustness to the resulting nanocomposite polymers. The presence of acidic functional groups on the functionalized materials (CPEI and PEI-MWCNTs) was confirmed by measuring the surface charge as a function of pH (zeta potential measurements). Fourier transform infrared (FTIR) analysis confirmed the formation of a new bond between the functional groups on the MWCNTs and PEI, as evidenced by the appearance of a –C=O peak at 1716 cm-1 in the FTIR spectra of PEI-MWCNTs. Batch adsorption and kinetic studies were carried out to evaluate the performance of the PEI-MWCNT nanocomposite materials for the removal of Cr6+ from simulated water samples...
M.Sc. (Chemistry)