Effect of Chemical Treatment of Multi-Walled Carbon Nanotubes with Various Oxidizing Agents on its Preconcentration Performance of Some Metals

Multi-walled carbon nanotube was oxidized with various oxidizing agents (nitric acid, hydrogen peroxide and ammonium persulphate) to produce multi-walled carbon nanotubes of various surface properties. The oxidized sorbents were used for the preconcentration of some metals (Mn2+, Pb2+, Cu2+, Cd2+, Zn2+) from environmental waters prior to their determination by flame atomic absorption spectroscopy. The best preconcentration performance was achieved with nitric acid-oxidized carbon nanotubes (sorbent CNT-NA) at pH 9. The effect of hydrogen peroxide treatment of carbon nanotubes was similar to nitric acid treatment in terms of increasing recovery at pH 9 and at pH5. A preconcentration method was optimized using CNT-NA. Comparing the analytical performance of CNT-NA with non-oxidized carbon nanotubes (sorbent CNT-NO) indicated that CNT-NA gave wider limit of linearity, higher sensitivity and lower limits of quantification. Applying the optimized method on environmental waters (tap water, reservoir water and stream water) gave spike recovery in the range 81-106 %.