Electrochemical Dechlorination of 3-chlorophenol with Palladium-Loaded Carbon Felt Electrode

Electrochemical dechlorination with Pd-loaded electrodes offers an effective method for detoxification of wastewater. Electro-reductive dechlorination of 3-chlorophenol (3-CP) with Pd loaded on carbon felt (Pd/CF) was investigated. Pd was loaded on carbon felt by electrolytic method. The prepared electrodes were characterized by XRD, SEM, EDS, S-TEM and CV. The sizes of the Pd particles loaded on CF were found in the range of 100–400 nm. The preparing conditions including loading amount of Pd and loading currents were investigated. Moreover, the reduction conditions including electrolytes, reductive currents and recycle times were also studied. The Pd/CF cathodes with Pd loading of 0.5 mg/cm2, preparing current of 5 mA, electrolyte concentration of 30 mmol/L NaCl and 30 mmol/L CH3COONa were used to reduce 3-CP for dechlorination. When CH3COONa was used as the electrolyte, the current was 5 mA, the initial pH was 7.5, the initial 3-CP concentration was 1 mmol/L and the degradation rate of 3-CP could reach 95.81% after reduction of 150 min under an argon atmosphere. The electrochemical reduction of 3-CP was confirmed to follow the first-order rate law. 3-CP was qualitatively dechlorinated to phenol on electrodes with Pd. The fact that active hydrogen formed on palladium during preliminary electrolysis could be proved by the dechlorinated 3-CP in non-electroreduction after preliminary electrolysis. A possible reduction pathway was proposed based on the results.

Impact of Carbon Felt Electrode Pretreatment on Anodic Biofilm Composition in Microbial Electrolysis Cells

Sustainable technologies for energy production and storage are currently in great demand. Bioelectrochemical systems (BESs) offer promising solutions for both. Several attempts have been made to improve carbon felt electrode characteristics with various pretreatments in order to enhance performance. This study was motivated by gaps in current knowledge of the impact of pretreatments on the enrichment and microbial composition of bioelectrochemical systems. Therefore, electrodes were treated with poly(neutral red), chitosan, or isopropanol in a first step and then fixed in microbial electrolysis cells (MECs). Four MECs consisting of organic substance-degrading bioanodes and methane-producing biocathodes were set up and operated in batch mode by controlling the bioanode at 400 mV vs. Ag/AgCl (3M NaCl). After 1 month of operation, Enterococcus species were dominant microorganisms attached to all bioanodes and independent of electrode pretreatment. However, electrode pretreatments led to a decrease in microbial diversity and the enrichment of specific electroactive genera, according to the type of modification used. The MEC containing isopropanol-treated electrodes achieved the highest performance due to presence of both Enterococcus and Geobacter. The obtained results might help to select suitable electrode pretreatments and support growth conditions for desired electroactive microorganisms, whereby performance of BESs and related applications, such as BES-based biosensors, could be enhanced.