| Metadata | Details |
|---|
| Publication Date | 2024-08-01 |
| Journal | Sakarya University Journal of Science |
| Authors | Gökçe Didar DeÄermenciÌ |
| Institutions | Kastamonu University |
| Analysis | Full AI Review Included |
- Core Achievement: Demonstrated highly efficient electrochemical degradation of caffeine (a persistent organic pollutant) using an advanced oxidation process (EAOP) driven by a Boron-Doped Diamond (BDD) anode.
- Performance Metrics: Achieved optimal caffeine removal of 98.5% (for 25 mg L-1 initial concentration) in just 45 minutes under optimized conditions.
- Kinetic Model: Caffeine degradation followed pseudo-first-order kinetics, with the maximum rate constant (k1) reaching 0.0496 min-1.
- Key Drivers: The degradation rate was primarily controlled by the applied current density (J) and the supporting electrolyte (SE) concentration (K2SO4).
- Optimal Configuration: The most effective and energy-efficient system utilized a current density of 20 mA cm-2, 50 mM K2SO4, a minimal anode-cathode distance (2 mm), and a cost-effective Stainless Steel (SS) cathode.
- Energy Consumption: Electrical energy consumption under optimal conditions was calculated to be 18.25 kWh m-3.
- Material Stability: BDD electrodes proved suitable due to their high overpotential for oxygen evolution and inert surface, enabling high production of oxidizing hydroxyl radicals.
| Parameter | Value | Unit | Context |
|---|
| Anode Material | Boron-Doped Diamond (BDD) | N/A | 12 ”m thick diamond layer on Niobium substrate. |
| Optimal Current Density (J) | 20 | mA cm-2 | Maximized degradation rate; higher J increases energy cost. |
| Optimal Electrolyte Concentration | 50 | mM K2SO4 | Reduced average cell voltage to 5.4 V, lowering energy consumption. |
| Optimal Anode-Cathode Distance | 2 | mm | Shortest distance tested; minimized voltage and energy consumption. |
| Optimal Initial pH | 3 | N/A | Fastest degradation rate (k1 = 0.0496 min-1); pH tends to increase during electrolysis. |
| Optimal Caffeine Concentration (C0) | 25 | mg L-1 | Degradation rate decreases as C0 increases due to byproduct competition. |
| Maximum Removal Efficiency | 98.7 | % | Achieved at 25 mM K2SO4 after 120 minutes. |
| Optimal Energy Consumption (Ec) | 18.25 | kWh m-3 | At 20 mA cm-2, 50 mM K2SO4, pH 3. |
| Maximum Reaction Rate (k1) | 0.0496 | min-1 | Pseudo-first-order rate constant at optimal conditions. |
| Cathode Material (Cost-Effective) | Stainless Steel (SS) | N/A | Provided lowest energy consumption compared to Graphite and BDD cathodes. |
| Operating Temperature | 25 | °C | Maintained constant using a cooling/heating circulator. |
- Reactor Configuration: Experiments utilized an undivided cylindrical glass electrochemical batch cell (400 mL volume) with continuous magnetic stirring (600 rpm) to ensure efficient mass transfer.
- Electrode Setup: A single BDD electrode (35 cm2 active area) served as the anode. Cathodes (50 cm2 area) tested included Stainless Steel (SS), Graphite, and BDD, immersed 7 cm deep.
- Power Supply and Control: The system was operated in galvanostatic mode using a constant current power supply (GW Instek, PSW 80-40.5), allowing precise control of current density (5-20 mA cm-2).
- Electrolyte Preparation: Potassium sulfate (K2SO4) was added as the supporting electrolyte, with concentrations varied between 10 mM and 50 mM to assess conductivity effects.
- pH Management: Initial solution pH (3, 5.8, or 10) was set using 1 M H2SO4 or 1 M NaOH prior to electrolysis; no buffer was used, and pH drift was monitored throughout the run.
- Analytical Measurement: Caffeine concentration was quantified using a UV-Vis spectrophotometer (DR 6000, HachLange) at a wavelength of 273 nm.
- Performance Evaluation: Degradation efficiency and energy consumption (Ec, kWh m-3) were calculated, and kinetic analysis was performed using the pseudo-first-order model via the Microsoft Excel solver add-in tool.
- Pharmaceutical Wastewater Treatment: Direct application for the removal and mineralization of persistent pharmaceutical compounds (PPCPs) like caffeine from hospital and industrial effluents.
- Water Reclamation and Reuse: Use of BDD-based electrochemical advanced oxidation processes (EAOPs) as a tertiary treatment step to ensure trace organic contaminants are eliminated before water is discharged or reused.
- Electrode Technology Supply: High-demand market for robust, long-lifetime BDD electrodes, which are superior to conventional materials (e.g., Pt, RuO2) due to their chemical inertness and high oxidizing power.
- Disinfection and Sterilization: Generation of powerful oxidizing species (hydroxyl radicals) enables effective disinfection in water systems without relying solely on chlorine.
- Industrial Process Water Cleanup: Treatment of complex industrial wastewaters containing refractory dyes, pesticides, or other organic pollutants that resist biological degradation.
View Original Abstract
In this study, the purification of caffeine by electrochemical oxidation, one of the advanced oxidation processes, was systematically investigated. A boron-doped diamond electrode was used as the anode, which has a high potential for the production of large amounts of hydroxyl radicals. The effects of applied current density, initial pH, supporting electrolyte concentration, cathode type, anode-cathode distance, and initial caffeine concentration were evaluated. The results showed that the electrochemical degradation rates of caffeine follow pseudo-first-order kinetics, with rate constants ranging from 0.0154 to 0.0496 min-1 depending on the operating parameters. The applied current density and the electrolysis time proved to be the most important parameters influencing both caffeine degradation and energy consumption. However, varying the initial caffeine concentration and the concentration of the supporting electrolyte also influenced the caffeine degradation rates. Changing the anode-cathode distance and the type of cathode has no effect on the rate of caffeine degradation, but it does have an effect on energy consumption. A current density of 20 mA cm-2, a supporting electrolyte concentration of 50 mM K2SO4, an anode-cathode distance of 2 mm, a cathode type of stainless steel, and an initial solution pH of 3 were found to be optimal values for the degradation of a solution containing 25 mg L-1 caffeine in 45 minutes using a boron-doped diamond anode. Finally, it was found that the pH value of the solution tended to increase during electrolysis.