LAUSR

Spent caustic wastewater from petrochemical industries is a complex concoction of various pollutants, not only making it a threat to the environment, but also very difficult to treat using conventional treatment processes. In this study, electrocoagulation with iron electrodes was investigated as an option for the removal of sulfide from synthetic spent caustic. The pH of the treatment (3–12), the electrode distance (1–4 cm), the treatment duration (15–60 min), and the current density (1.4–20.8 mA/cm2) were varied, and their contribution to sulfide removal percent was investigated. The results showed that as current density increased to 7.4 mA/cm2 there was a pronounced increase in sulfide removal. Beyond that, increasing the current density slightly improved removal results. Interestingly, it was also observed that with process times above 30 min and a voltage of 20 V, the initial pH had no impact on removal percentage. After the parametric study of contributing factors, response surface methodology was used for further scrutiny and optimization. Under optimum conditions of electrode distance = 3 cm, voltage = 11 V, and treatment duration of 30 min, a sulfide removal of nearly 93% was obtained which showed the effectiveness of the proposed electrocoagulation process.