Advance treatment of chemical industrial tailwater by integrated electrochemical technologies: Electrocatalysis, electrodialysis and electro-microfiltration

In this work, a novel electrochemical process of electrocatalysis-electrodialysis-electro-microfiltration was developed for high level standard reuse of chemical industrial tailwater. The performance and mechanisms for each technique were investigated by multi-analyze methods, individually. The target species including N-heterocyclic pollutants (pyrrole, pyrimidine and pyridine), Humic Substances and salt of sodium sulfate were removed from the simulated wastewater by this process. Within electrocatalysis, pyrrole and pyrimidine were degraded prior to pyridine due to their lower Gibbs energy barriers as 6.79 kcal and 16.89 kcal, respectively, and thus were easier attacked by hydroxyl radical generated on the electrode surface. Then the pyridine together with the salt was removed efficiently during electrodialysis. The residue salt and pyridine molecules as well as the HSs were furtherly rejected by the synergistic effect of electric field and membrane by the electro-microfiltration process. Final effluent revealed a very low level of pyridine content of 0.103 mg/L, TOC of 3 mg/L, UV254 of 0.025 and a low conductivity of 33 μs/cm, consistent with an excellent removal of the target species of ∼100% pyrrole, ∼100% pyrimidine, >99% pyridine, >95% HSs and >99% salt.