TY - JOUR
T1 - Novel Demonstration of Heterogeneous Redox Catalysis Using a Rotating Pencil Lead
AU - Mills, Andrew
AU - Andrews, Rachel
AU - O'Rourke, Christopher
AU - Hitchman, Michael
PY - 2017/8/1
Y1 - 2017/8/1
N2 - Heat-treated, pencil lead, in powder or rod form, is used as a heterogeneous redox catalyst for the oxidation of
chloride to chlorine by Ce(IV) ions in 0.5 M H2SO4 and 2 M NaCl solution. When the lead is used in ground up powder form,
the resulting decay of the Ce(IV) is first order over 3 half-lives and gives a chlorine yield of 79%. When a rotating 2 mm
diameter, heat-treated form of the pencil lead is used in the same test system, the kinetics of Ce(IV) yields a series of different
first order rate constants, k1, as a function of rod rotation speed, ω. A plot of k1 versus ω0.7 yields a good straight line, which
accords with the hydrodynamics of the system and the assumption that the rate of Ce(IV) reduction, by chloride, depends
upon the rate of mass transport of the Ce(IV) ions to the surface of the pencil lead rod. The gradient of the plot allows a value
for the diffusion coefficient for Ce(IV) ions in 0.5 M H2SO4 and 2 M NaCl solution to be calculated, namely: (2.7 ± 0.1)x10-6
cm2 s
-1
) which compares favourably with those reported previously.
AB - Heat-treated, pencil lead, in powder or rod form, is used as a heterogeneous redox catalyst for the oxidation of
chloride to chlorine by Ce(IV) ions in 0.5 M H2SO4 and 2 M NaCl solution. When the lead is used in ground up powder form,
the resulting decay of the Ce(IV) is first order over 3 half-lives and gives a chlorine yield of 79%. When a rotating 2 mm
diameter, heat-treated form of the pencil lead is used in the same test system, the kinetics of Ce(IV) yields a series of different
first order rate constants, k1, as a function of rod rotation speed, ω. A plot of k1 versus ω0.7 yields a good straight line, which
accords with the hydrodynamics of the system and the assumption that the rate of Ce(IV) reduction, by chloride, depends
upon the rate of mass transport of the Ce(IV) ions to the surface of the pencil lead rod. The gradient of the plot allows a value
for the diffusion coefficient for Ce(IV) ions in 0.5 M H2SO4 and 2 M NaCl solution to be calculated, namely: (2.7 ± 0.1)x10-6
cm2 s
-1
) which compares favourably with those reported previously.
U2 - 10.5923/j.jlce.20170504.04
DO - 10.5923/j.jlce.20170504.04
M3 - Article
VL - 5
SP - 86
EP - 93
JO - Journal Of Laboratry Chemical Education
JF - Journal Of Laboratry Chemical Education
SN - 2331-7450
IS - 4
ER -