Electrochemical filtration carbon membrane derived from coal for wastewater treatment: Insights into the evolution of electrical conductivity and electrochemical performance during carbonization

A novel electrochemical filtration carbon membrane (ECM) was developed from caking coal via self-bonding in this work. The evolutions of chemical structure, morphology, carbon microstructure from nonconductive precursor membrane to conductive ECM during carbonization were systemically investigated by FTIR, SEM, Raman and XRD. The evolution mechanism of electrical conductivity and electrochemical performance of ECM was proposed and discussed. The electrochemical filtration performance of ECM was evaluated by using the phenol as simulated pollutant in wastewater treatment. It was found that the precursor membrane underwent the violent thermal decomposition and condensation during carbonization. The electrical conductivity and electrochemical performance of ECM depended strongly on carbonization temperature (CT), which was attributed to the evolution of carbon microstructure such as the growth of the conductive carbon clusters and defect graphite lattices (active sites) as CT increased. The electrochemical filtration performance of ECM on phenolic water was strongly correlated to its electrochemical properties. The higher electrochemical activity of ECM would result in the better electrochemical filtration performance. The ECM obtained at 950 °C exhibited the optimal overall performance, and its phenol and COD removal rates were up to 91.65% and 81.89% under the applied voltage of 2.0 V, respectively. The mechanism of electrochemical oxidation involved in ECM included the direct oxidation and indirect oxidation, in which the indirect oxidation was caused by the electro-catalytic activity of minerals existed in ECM.