3.4.2. Electro-kinetic evaluation
Tafel analysis was performed to understand the electro-kinetics
in terms of redox behavior and polarization resistance (RP) of the
biocatalyst during the operation of SBES. Low value of the slope
connected to the oxidation process indicated the requirement of
lower activation energy that makes oxidation more favorable
(Chandrasekhar and Venkata Mohan, 2012). The same theory is
applicable in the case of reduction slope. SBES operation documented
higher oxidation reactions over reduction reactions.
During SBES operation, lower oxidation slope was observed on
20th day of operation (0.126 V/dec) followed by 10th day
(0.154 V/dec), 0th day (0.184 V/dec) and 30th day (0.114 V/dec)
(Fig. 5). Reduction reaction showed minor variations with respect
to time. Lower reduction slope was observed on 20th day
(0.217 V/dec) followed by 10th day (0.221 V/dec), 0th day
(0.228 V/dec) and 30th day (0.234 V/dec). Observed lower oxidation
slope during SBES operation on 20th day indicated favorable
conditions for substrate oxidation by the biocatalyst which was
well supported by the observed higher H2 production. Values of
reduction slopes were relatively higher than that of oxidation
slope. This might be due to rapid consumption of H+ for H2 production
by H2 producers in the presence of dehydrogenase, which
facilitated the accessibility of H+ through redox reactions.
Observed results correlated well with the improvement in H2
production.