Removal of phenanthrene by coal gasification slag activated persulfate system
Coal gasification slag(CGS),a kind of solid waste generated during the coal gasification process,was used as persulfate(PS)activator.And the removal performance of CGS/PS for phenanthrene was evaluated,while the microstructure and elemental composition of CGS were characterized by SEM-EDS and XPS.Moreover,the species of free radicals were determined by free radical masking experiment and electron paramagnetic resonance(EPR)experiment.The effects of CGS mass concentration,PS initial concentration,initial pH and co-existing ions on the removal rate of phenanthrene in CGS/PS system were further investigated.The reaction mechanism and degradation path were discussed,and the toxicity of phenanthrene as well as its products were evaluated by ECOSAR software.The results showed that Fe element with a mass fraction of 11.9％was identified in CGS,indicating CGS an effective PS activator.The removal rate of phenanthrene reached 95.34％and the utilization rate of PS reached 29.18％after 60 min of reaction under the conditions of mass concentration 1 mg/L phenanthrene,pH=3,mass concentration 0.7 g/L CGS and 1 mmol/L PS initial concentration.The degradation process of phenanthrene conformed to pseudo first-order reaction kinetics,with CGS/PS producing SO4-·and·OH,and SO4-·playing a dominant role during the oxidation.The coexisting ions of HCO3 and NO3 exhibited significant inhibitory effect on the reaction.Phenanthrene was decomposed into long-chain acids and esters through decarbonylation,hydroxylation and decarbonization,and ultimately converted into CO2 and H2O.Meanwhile,the ECOSAR model evaluation indicated that the toxicity of intermediate products from phenanthrene decomposition was generally lower than that of phenanthrene.
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