Coagulation Behavior and Floc Properties of Dosing Different Alkaline Neutralizers into the Fenton Oxidation Effluent
2018
Xu, Min | Wu, Changyong | Li, Yanan | Zhou, Baoying | Xue, Hao | Yu, Yin
Neutralization is the necessary operation to ensure the Fenton effluent pH. In situ coagulation can be induced during neutralization. In this study, three types of alkaline neutralizers (Ca(OH)₂, NaOH, and Ca(OH)₂ + NaOH) were added into the Fenton oxidized PSE to control the effluent pH of 6 to 9. The coagulation behavior, floc structure, and properties were investigated. The results indicated that the coagulation with the adding of three neutralizers can remove 9.68 to 24.02% of the TOC. Ca(OH)₂ exhibited the highest TOC removal efficiency at the dosage of 0.4 g/L. Charge neutralization ability was in the following order: Ca(OH)₂ > Ca(OH)₂ + NaOH > NaOH. Ca(OH)₂ and Ca(OH)₂ + NaOH showed the increase of floc growth rate with the increase of agent dosage, especially for Ca(OH)₂ + NaOH. Moreover, Df of NaOH flocs was higher than that of Ca(OH)₂ and Ca(OH)₂ + NaOH, indicating the floc formed by NaOH was more compact than that of Ca(OH)₂. The main coagulation process of three neutralizers was different, and it was also affected by the agent dosage (or pH). When the dosage was 0.35 g/L (pH 6–7.5), the complexation, adsorption, and bridging were the predominant processes while charge neutralization gradually became the main coagulation process for Ca(OH)₂ and Ca(OH)₂ + NaOH with the increase of dosage (pH 7.5–9).
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