Montmorillonite based clay was acid activated. Nicotine was adsorbed on
untreated and acid activated clay from its aqueous solution at either pH=6
or pH=9.26 (unadjusted pH solution). The XRD analysis revealed that the 001
basal spacing of montmorillonite after nicotine adsorption was around 1.38
nm, regardless of clay treatment or pH of adsorption. The obtained values
for basal spacing indicate that nicotine is in monolayer arrangement. In
order to investigate electrochemical properties, untreated and acid
activated clay, with and without nicotine, were used as modifier of carbon
paste electrode. Cyclic voltammetry and electrochemical impedance
spectroscopy were employed to study electrochemical response of
clay-modified electrodes toward ferrocyanide probe. The nicotine-modified
untreated clay used as paste electrode showed enhanced electrochemical
response toward ferrocyanide probe in comparison to electrode based on clay
without nicotine. On the other hand, adsorbed nicotine on acid activate clay
resulted in lower electrode activity. Electrochemical response of adsorbed
nicotine was studied at different pH. Nicotine oxidation at each of
investigated samples followed the same trend regardless of clay treatment or
pH at which adsorption was performed. For all samples, nicotine oxidation
peak potential showed linear dependence on pH in pH range from 3.7 to 9.0,
with slopes close to the value of 59 mVdec-1 expected for equal number of
protons and electrons involved in the reaction. The nicotine reduction
process was best resolved at pH = 1 at potential around -1.35 V, while the
following cathodic wave observed at potential around -1.5 V was ascribed to
the cathodic hydrogen reduction. Mechanism of electrochemical oxidation was
not influenced by pH of adsorption, i.e., nicotine form. The amount of
adsorbed nicotine was not correlated with the electrochemical activity
suggesting that only small number of adsorbed nicotine was involved in
electrochemical response.