Homogenous Electro-Fenton degradation of phenazopyridine in wastewater using a 3D Printed filter-press flowcell: Optimization via response surface methodology

Abstract

Background

Most studies on Advanced Oxidation Processes (AOPs) for wastewater treatment focus on small-scale batch reactors, highlighting the need for large-scale continuous systems to remove emerging pollutants like biorecalcitrant pharmaceuticals.

Methods

In this study, the treatment of synthetic phenazopyridine (PHP) wastewater at a pre-pilot scale by homogeneous electro-Fenton (HEF) process using a continuous filter-press flowcell in full recirculation is presented. Moreover, operational parameters were optimized using a three-level full-factorial central composite design (CCD) method within the framework of a design of experiments (DOE) approach.

Significant findings

Results indicated that the HEF process could be well expressed using a quadratic mathematical equation with significant statistical meaning (F-value=18.68 and P-value=0.001). Optimized operational parameters were pH≅3, initial PHP=2 mg L^-1, Fe²⁺=0.72 mg L^-1, and voltage=5 V which led to a predicted and actual PHP removal percent of 74.89 and 75.14±1.2 %. Oxidation of PHP was validated using size-exclusion chromatography analysis. The results of this study pave the way for techno-economic evaluations of continuous pilot HEF process given the successful applicability DOE method for the process optimization and modularity of filter-press flowcells (multiple stacks and reactors in series concept) for the purification of actual pharmaceutical wastewater.