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In this work, a novel graphite intercalation compound (GIC) particle electrode was used for the adsorption of Reactive Black 5 (RB5), Indigo Carmine (IC), Sudan Black B (SBB), Methyl Orange (MO) and Eosin Yellow (EY) dyes. GIC can be electrochemically regenerated in a three-dimensional (3D) electrochemical reactor to recover its adsorptive capacity. RB5, IC, SBB, MO, and EY can undergo mineralisation and oxidation during the electrochemical treatment. Various adsorption kinetics and isotherm models were used to characterise the adsorption behaviour of GIC.
Several adsorption kinetics were modelled using linearised and non-linearised rate laws to evaluate the viability of the sorption process. Non-linear models best fitted with the kinetic data in the order: Elovich>Bangham>Pseudo-second-order>Pseudo-first-order. The Langmuir adsorption isotherm was calculated to have a dye loading capacity of 0.6166 mg/g by linear regression analysis. In addition, a dye loading capacity of 1.4369 mg/g was predicted by the non-linear regression method. The R2-values were between 0.9999 to 1.000 for both linearised and non-linearised Langmuir adsorption.
The results showed that Redlich-Peterson and SIPS isotherm models yielded better fitness to experimental data than the Langmuir type. The best dye removal efficiency achieved was approximately 93% for RB5 using a current density of 45.14 mA/cm2, whereas the highest TOC removal efficiency achieved was 85.28% using a current density of 45.14 mA/cm2. On the other hand, response surface methodology (RSM) optimisation results showed that dye and TOC removal efficiencies were 89.98% and 78.67%, respectively, using a current density of 10.40 mA/cm2 to treat an initial dye concentration of 30 mg/L RB5 at 10 mins of electrolysis time. The current efficiency achieved was 38.07%. The energy consumption for RB5 removal was 15.62 kWh/kg RB5, and the energy consumption for TOC removal was 134.80 kWh/kg TOC, indicating that minimal electrical energy was required for the electrochemical treatment of dyes.
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