Mineralization of organic matter from vinasse using physicochemical treatment coupled with Fe2+-activated persulfate and peroxymonosulfate oxidation

Application of advanced oxidation process for wastewater treatment has gained more attention recently. In this study, the efficiency of coagulation–flocculation pretreatment coupled with sulfate radical-based advanced oxidation process (SR-AOP) in the removal and mineralization of organic matter of sugarcane vinasse was evaluated. For coagulation–flocculation, jar-test experiment was carried out with ferric chloride as coagulant and the removal of TOC, color and UV₂₅₄ was determined. The results revealed that by using 15 g/L of coagulant, 70 % of TOC removal and nearly 100 % of UV₂₅₄ and color removal were achieved. The pretreated vinasse was then subjected to SR-AOP. In this study, sulfate radical was generated using persulfate (PS) and peroxymonosulfate (PMS) activated by Fe(II). The effect of reaction time, oxidants to Fe(II) ratio and pH on the TOC removal efficiency were investigated. For the effect of reaction time, the TOC removal was found to increase significantly for the first 5 min. TOC removal was found to increase with increasing concentration of Fe(II) for PMS. However, for Fe(II)/PS, the TOC removal efficiency was decreased with increasing Fe(II) concentration. Both Fe(II)/ PMS and Fe(II)/PS showed the highest TOC removal efficiency when the oxidation was carried out at pH 7. By using the selected optimum condition, nearly 70 and 49 % of TOC removal were achieved for PMS/Fe(II) and PS/Fe(II), respectively. Therefore, it can be concluded that SR-AOP can be a promising alternative method for TOC removal from sugarcane vinasse.

Keywords
Waste treatment; Radical; Total organic carbon; Wastewater; Coagulation–flocculation