Search

In this study, a new hybrid system composed of a photo-catalysis (UV/ZnO) process combined with an electro-Fenton (EF) process equipped with a micro porous graphite air diffusion cathode (MPGADC) was used to treat petroleum refinery wastewater (PRW). The hybrid system was operated in a batch recycle mode and its performance was investigated and optimized using a response surface methodology (RSM). Three operating parameters affecting on the removal efficiency (RE%) of chemical oxygen demand (COD) were investigated including current density (2–10 mA/cm2), ZnO dosage (0.05–0.35 g/L), and Fe2+concentration (0.05–0.15 mM). Results showed that the optimum operating conditions can be achieved using a current density of 6.44 mA/cm2, with ZnO dosage of 0.35 g/L, and concentration of Fe2+ ions at 0.05 mM in which RE% of 90.15% was obtained with requiring a total electrical energy consumption (EEC T) of 19.102KWh/m3. Furthermore, analysis of variance (ANOVA) exhibited a high value of determination coefficient (R2) close to 98.24% indicating a satisfactory fit between the obtained regression model and the experimental results. Moreover, ANOVA results revealed that current density has the most significant effect on RE% with a contribution of 52.41% followed by ZnO dosage and Fe 2 + concentration both of them with a contribution of 11.64%. The comparison between the individual photo-catalysis process and hybrid process showed that RE% increases from 77.83% to 90.15% making an enhancement by 15.83% in RE% while EEC T decreased from 27.171to 19.102KWh/m3 making a reduction by 29.7% in EEC T. Hence, combining EF with photo-catalysis process improves the efficiency and reduced the required energy in comparison with the individual photo-catalysis process. Therefore, the combined process could be considered as an alternative, sustainable, green and cost-effective method for treatment of refinery wastewaters. [Display omitted] • A novel photocatalysis-ElectroFenton system was applied successfully for treatment wastewater. • The optimum conditions were: current density of 6.44 mA/cm2, Fe2+concentration of 0.05 mM, Zn O 2 dosage of 0.35 g/l. • A maximum COD removal (RE% = 90.15% %) with a lower energy consumption (EEC T = 19.102kWh/m3) were achieved after operation of 40 min. • Reaction time was the most effective parameter followed by Z n O 2 dosage, Fe2+ concentration, and current density. • EF+UV/ZnO in comparison with UV/ZnO alone results in an enhancement of 15.83% in RE% and a reduction by 29.7% in EEC T. [ABSTRACT FROM AUTHOR]

A low-cost micro porous graphite air diffusion cathode (MPGADC) has been utilized successfully for the in-situ hydrogen peroxide generation via O 2 reduction in 0.05 M Na 2 SO 4. Using a tubular electrochemical reactor with a novel design composed of MPGADC as a cathode and a hollow cylinder porous graphite as an anode, a maximum of 68 mg/ L of H 2 O 2 was produced at a current density of 25 mA/cm2, an air flow rate of 3 L/min, and a pH value of 3. Electro-Fenton (EF) process was adopted to remove the chemical oxygen demand (COD) from the wastewater of Al-Dora petroleum refinery in Iraq using this new style of tubular electrochemical reactor. Based on the response surface methodology (RSM) with Box-Behnken design (BBD), the effect of EF operating parameters on the COD removal was investigated. The optimal conditions for maximizing COD removal efficiency (RE%) with lowering specific energy consumption (SEC) using EF process were determined to be a current density of 6.66 mA/cm2, Fe2+ concentration of 0.80 mM, and an electrolysis duration of 60 min, in which RE% of 94% with SEC of 3.75 kWh/kg COD were achieved. In addition, the results demonstrated that the current density has the greatest influence on the COD removal, followed by electrolysis duration and then Fe2+ concentration. Furthermore, current density has the greatest impact on the specific energy consumption, followed by time, while Fe2+ concentration has a negligible effect. The high R2 value (98.33%) confirmed the goodness of fitting the model equation. These results established the viability of employing the new cathode design for the EF process in treatment of petroleum refinery wastewaters. [Display omitted] • Low-cost micro porous graphite air diffusion cathode was utilized for COD removal from wastewater using electro Fenton. • The effects of various operational parameters on COD removal(RE%) were evaluated and optimized by RSM. • The new cathode generated a maximum of 68 mg/ L of H 2 O 2 at current density of 25 mA/cm2 and air flow rate of 3L/min. • Current density has the greatest influence on the RE%, followed by electrolysis duration and Fe2+ concentration. • The optimal conditions were current density of 6.66 mA/cm2, Fe2+ concentration of 0.80 mM, and 60 min, in which RE% and SEC were 94% and 3.75 kWh/kg COD. [ABSTRACT FROM AUTHOR]