A new eco-friendly method for efficient recovery and reuse of phenols in a semi-coke wastewater

Abstract

Phenols in wastewater (WW SCP ) from semi-coke production pose a serious threat to human health and ecological environment due to its high concentration, high toxicity, and difficult-to-degrade characteristics. Single treatment method, such as extraction or catalytic conversion, has the problems of secondary pollution, high processing cost, and low catalytic efficiency. In light of the problems, this study developed an ecofriendly WW SCP treatment by the synergistic process of extraction and catalytic conversion, which can convert phenols in a WW SCP into anisoles. Using response surface method (RSM), the wastewater treatment process was optimized. The concentration of phenols in the WW SCP was optimally reduced from 5509 mg L −1 to 105 mg L −1 after three times of extraction with cyclohexane/dimethyl carbonate (DMC) as the extractant at 25 °C for 1 min of each extraction and the extract yield of phenols up to 98%. The phenols extracted from the WW SCP were completely converted over Na-CH 3 ONa/ γ -Al 2 O 3 at 213.48 °C for 2.00 h with phenols/DMC molar ratio of 1 : 4.00. Therefore, the synergistic process of extraction and catalytic conversion provides a pollution-free and more economic strategy for treating WW SCP . • A simple and green extraction- catalytic coupling process is proposed to treat Semi-coke wastewater. • Dimethylcarbonate is used not only as an extractant, but also as a O -methylating reagent for volatile phenol reaction. • Optimizing process conditions through response surface methodology.