A novel electro-fenton process for water treatment: reaction-controlled pH adjustment and performance assessment.

A novel electro-Fenton (E-Fenton) process was developed, in which the desired pH for an effective E-Fenton reaction and for a neutral treated media could be obtained by utilizing the reaction-released H+ and OH- in stead of chemical addition. In the laboratory-scale process using three chambers, the substrate solution pH > 4.0 was designed to be adjusted in situ through three sequencing steps: (I) pH reduction, (II) pH keeping for the effective E-Fenton reaction, and (III) pH recovery to neutral while the E-Fenton reaction continued. Experimental results demonstrated that such three-step pH adjustment was successfully achieved in this novel E-Fenton process, and that the pH adjustment was controlled by the E-Fenton reaction process. The performance of the novel process was assessed in terms of dimethyl phthalate (DMP) degradation in aqueous solution. The results revealed that the novel process was effective to reduce the DMP concentration and the total organic carbon (TOC) at steps II and III. Also, through experiments, the initial DMP solution pH > 4.0 was selected to be reduced to 3.5 in Step I of the process. This pH adjustment not only allowed the E-Fenton reaction to occur in its favorable pH range, but also benefited any potential subsequent biological treatment process or a final discharge. Moreover, the iron species could be recycled in the process.