Experimental study of chemical oxygen demand removal by electrochemical oxidation treatment of petroleum refinery wastewater by using response surface methodology.

The current study uses a batch electro-chemical reactor with porous graphite as an anode and a stainless steel as a cathode for wastewater treatment taken from the Al-Najaf petroleum refinery plant, Iraq. On removal efficiency regarding chemical oxygen demand (COD), the impacts of operating conditions like pH (2-10), current density (5-25 mA/cm²), time (30-70 min), and NaCl addition (0-4 g/L) were explored. The findings demonstrated that both NaCl and pH have an important effect on the removal efficiency of the COD, indicating the fact that the system is regulated through the reaction situations in the bulk of the solution rather than electrooxidation regarding the chloride ions on an electrode surface. For maximizing COD removal, response surface methodology was integrated with a Box-Behnken design in parametric optimization. COD's removal percentage was determined to be 99.6% under optimized operating parameters of a current density = 25 A/cm², initial pH: 2, time = 65 min, and NaCl concentration = 3.39 g/L, with 9.85 kWh/kg-COD energy consumption, which is lower when compared to similar works. [ABSTRACT FROM AUTHOR]