South African Journal of Chemistry
On-line version ISSN 1996-840X
DARKO, Godfred et al. Pre-concentration of toxic metals using electrospun amino-functionalized nylon-6 nanofibre sorbent. S.Afr.j.chem. (Online) [online]. 2012, vol.65, pp. 14-22. ISSN 1996-840X.
This paper presents a new approach for pre-concentrating toxic metals (As, Cd, Ni and Pb) in aqueous environments using an amino-functionalized electrospun nanofibre sorbent. The sorbent, composed of nanofibres of average diameter 80 ± 10 nm and specific surface area of 58 m2 g-1, exhibited fast adsorption kinetics (<20 min) for As, Cd, Ni and Pb. The optimal pH for the uptake of As, Cd, Ni and Pb were 5.5, 6.0, 6.5 and 11, respectively. The adsorption process best fitted the Freundlich isotherm and followed the first-order kinetics. The highest pre-concentration achieved using the sorbent was 41.99 (Ni in treated wastewater). The capacity of the sorbent to pre-concentrate the toxic metals was compared with those of aqua regia and HNO3+H2O2 digestions. The pre-concentration factors achieved for Cd in river water samples can be ranked as aqua regia digestion (0.73) > adsorption (0.34) > HNO3+H2O2 (0.23) digestion. A similar trend was observed for Ni in river water as well as Ni and Cd in tap water samples. Pb ions in the river water samples were pre-concentrated slightly better using the two digestion methods (pre-concentration factors ~22) compared to adsorption method (pre-concentration factor ~21). The use of the electrospun amino-functionalized nanofibre sorbentpresents an efficientand cost-effective alternative for pre-concentration of toxic metals in aqueous environments.
Keywords : Electrospinning; pre-concentration; heavy metals; nylon-6.