Performance of a polymerization-based electrochemically assisted persulfate process on a real coking wastewater treatment

Industrial wastewater should be treated with caution due to its potential environmental risks.In this study,a polymerization-based cathode/Fe^(3+)/peroxydisulfate(PDS)process was employed for the first time to treat a raw coking wastewater,which can achieve simulta-neous organics abatement and recovery by converting organic contaminants into separable solid organic-polymers.The results confirm that several dominant organic contaminants in coking wastewater such as phenol,cresols,quinoline and indole can be induced to poly-merize by self-coupling or cross-coupling.The total chemical oxygen demand(COD)abate-ment from coking wastewater is 46.8%and the separable organic-polymer formed from or-ganic contaminants accounts for 62.8%of the abated COD.Dissolved organic carbon(DOC)abatement of 41.9%is achieved with about 89%less PDS consumption than conventional degradation-based process.Operating conditions such as PDS concentration,Fe3+concen-tration and current density can affect the COD/DOC abatement and organic-polymer yield by regulating the generation of reactive radicals.ESI-MS result shows that some organic-polymers are substituted by inorganic ions such as Cl^(-),Br^(-),I^(-),NH_(4)^(+),SCN^(-)and CN^(-),suggest-ing that these inorganic ionsmay be involved in the polymerization.The specific consump-tion of this coking wastewater treatment is 27 kWh/kg COD and 95 kWh/kg DOC.The values are much lower than those of the degradation-based processes in treating the same coking wastewater,and also are lower than those of most processes previously reported for coking wastewater treatment.

Experimental study on oxidative decomposition of nitrobenzene in aqueous solution by honeycomb ceramic-catalyzed ozonation

The ozonation of nitrobenzene in aqueous solu-tion was carried out in a semi-batch reactor to investigate the degradation efficiency,the effect factors,and the reaction mechanism,where honeycomb ceramic was used as a cata-lyst.The presence of honeycomb ceramic could improve the degradation rate of nitrobenzene by 15.46%compared to the results of ozonation alone.Under the conditions of this exper-iment,the degradation rate of honeycomb ceramic-catalyzed ozonation increased by 12.94%with the increase of the amount of catalyst from 1 to 5 blocks.The degradation rates all increased greatly with the increase of temperature and pH of the solution in the processes of honeycomb ceramic-catalyzed ozonation and ozonation alone.But,when the pH of the solution increased to 9.50,the advantage of the honey-comb ceramic-catalyzed ozonation process would be lost.The experimental findings indicated that in the processes of ozonation alone and honeycomb ceramic-catalyzed ozona-tion,nitrobenzene was primarily oxidized by•OH free radical in aqueous solution.The adsorption of nitrobenzene was too limited to have an important influence on the degradation rate of nitrobenzene.With the same total dosage of applied ozone,the multiple step addition of ozone showed much higher removal efficiency than that obtained by one step in the two processes.