Characterization and optimization of electrodialysis with bipolar membranes with improved alkaline stability for phenol recovery from petroleum wastewater

The purity and recovery of phenol from an aqueous solution by electrodialysis with a bipolar membrane (EDBM) system mainly depend on the solution pH, possibly effective only under alkaline conditions because phenol is a very weak acid with a pK_a of 10. In this research, mono-sheet bipolar membranes with high chemical stability were successfully prepared using 1,4-diazabicyclo[2.2.2] octane (DABCO) as a quaternary ammonium group with bicyclic organic compounds. The BPMs characterization was studied using FTIR, FESEM, membrane chemical stability in alkaline solution, and electrical resistance. Comparing BPMs' performance synthesized by DABCO illustrated satisfactory results in the membrane's chemical stability and electrical resistance. The mono-sheet composite bipolar membranes are used in electrodialysis with bipolar membrane (EDBM) to remove phenol from synthetic petroleum wastewater model solution. Moreover, Response Surface Methodology (RSM) was employed as a facile method for optimizing the EDBM. In particular, the effects of current density, feed flow rate, feed concentration on the completion time (CT), and recovery efficiency (RE) of the process were investigated using the Central Composite Design (CCD) experimental design. According to the ridge and canonical analysis, the optimum operating conditions were determined at the feed concentration of 214.0 ppm, current density of 41.89, and volumetric feed flow rate of 12.84. Under these conditions, the minimum CT and maximum RE were found at 85.5 min and 75.4 %, respectively. In addition, the experimental results agreed with the prediction, suggesting that central composite design was a good technique for modeling phenol regeneration from petroleum wastewater.