Abstract
In this study, coagulation, ozone (O3) catalytic oxidation, and their combined process were used to pretreat actual coking wastewater. The effects on the removal of chemical oxygen demand (COD) and phenol in coking wastewater were investigated. Results showed that the optimum reaction conditions were an O3 mass flow rate of 4.1 mg min−1, a reaction temperature of 35 °C, a catalyst dosage ratio of 5:1, and a O3 dosage of 500 mg·L−1. The phenol removal ratio was 36.8% for the coagulation and sedimentation of coking wastewater under optimal conditions of 25 °C of reaction temperature, 7.5 reaction pH, 150 reaction gradient (G) value, and 500 mg·L−1 coagulant dosage. The removal ratios of COD and phenol reached 24.06% and 2.18%, respectively. After the O3-catalyzed oxidation treatment, the phenols, polycyclic aromatic hydrocarbons, and heterocyclic compounds were degraded to varying degrees. Coagulation and O3 catalytic oxidation contributed to the removal of phenol and COD. The optimum reaction conditions for the combined process were as follows: O3 dosage of 500 mg·L−1, O3 mass flow of 4.1 mg·min−1, catalyst dosage ratio of 5:1, and reaction temperature of 35 °C. The removal ratios of phenol and COD reached 47.3% and 30.7%, respectively.
Highlights
Coking wastewater is generated by coal coking and mainly includes residual ammonia water, gas cold sewage, and sewage generated by chemical product refinement [1]
The remaining ammonia water contains high concentrations of ammonia, phenol, cyanide, and oil, which are the main sources of coking wastewater [2]
When the O3 dosage increased to 500 mg·L−1, the removal efficiency of phenol increased significantly, and the highest removal ratio was 24.2%
Summary
Coking wastewater is generated by coal coking and mainly includes residual ammonia water, gas cold sewage, and sewage generated by chemical product refinement [1]. Coking wastewater is a series of phenolic substances, cyanide, petroleum substances, sulfides, ammonia nitrogen and other organic compounds emitted during the coking industry. High-concentration organic wastewater, known as phenol-containing wastewater, mainly contains phenol, cyanide, benzene, ammonia, oil, and high solid suspension. The remaining ammonia water contains high concentrations of ammonia, phenol, cyanide, and oil, which are the main sources of coking wastewater [2]. The wastewater of sulfide and oil is collectively referred to as phenol cyanide wastewater This wastewater has large amounts of water and a complex composition, and it is a typical refractory wastewater in the coking industry. The main organic substances in coking wastewater are phenols, benzenes, heterocyclic compounds, and polycyclic compounds [4]
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