煤气化渣活化过硫酸盐体系氧化去除菲

Removal of Phenanthrene by Coal Gasification Slag Activated Persulfate System

摘要:

采用固体废弃物煤气化渣（CGS）作为过硫酸盐（PS）的活化剂，实现对多环芳烃（PAHs）类难降解有机物菲（PHE）的高效去除。使用SEM-EDS、XPS表征了CGS的微观结构和元素组成，通过自由基掩蔽实验和EPR实验确定自由基种类；探究了CGS投加量、PS浓度、初始pH、共存物质对CGS/PS体系中菲降解效果的影响，明晰了反应机理并推测降解路径，并使用ECOSAR软件评估菲及其产物的毒性。结果表明，CGS中Fe元素质量分数为11.9%，可有效活化PS。在PHE质量浓度为1 mg/L、pH=3、CGS投加量（以PHE溶液体积计）0.7 g/L、PS浓度1 mmol/L的初始条件下，60 min后CGS/PS体系对菲的去除率达95.34%，PS的利用率达29.18%。菲降解过程符合伪一级动力学，CGS/PS体系产生了硫酸根自由基（SO4?-）和羟基自由基（HO?），且SO4?-在菲降解过程中占主要作用，共存离子HCO3-、NO3-对反应的抑制作用较显著。菲主要通过去羰基、羟基化、脱碳等反应分解为长链酸、酯，最终转化为CO2和H2O。ECOSAR模型评估发现，菲降解的中间产物毒性普遍低于菲。

Abstract:

Coal gasification slag (CGS), a kind of solid waste generated during the production of coal gasification, was used as persulfate (PS) activator to effectively remove phenanthrene (PHE), a typical polycyclic aromatic hydrocarbon difficult to eliminate from aquatic environment. The microstructure and elemental composition of CGS were characterized by SEM-EDS and XPS. The types of free radicals were determined through free radical quenching experiments and EPR experiments. The effects of CGS and PS dosages, initial pH value and coexisting substances on PHE removal in the CGS/PS system were investigated, the oxidation mechanism was explored, and the degradation pathways were predicted. ECOSAR software was used to evaluate the toxicity of PHE and its products. The results showed that 11.9% of Fe was identified in CGS, indicating that CGS was an effective PS activator. The degradation efficiency of PHE reached 95.34% after 60 minutes of reaction, with the initial conditions of PHE dosages of 1 mg/L, pH value of 3, CGS dosages of 0.7g/L and PS dosages of 1mmol/L, and the utilization rate of PS reached 29.18%. The degradation process of PHE conformed to pseudo first-order reaction kinetics，and the sulfate radical (SO4?-) and hydroxyl radical（HO?）were produced. SO4?- was found to play a dominating role during the oxidation, and HCO3- and NO3- inhibited the reaction significantly. PHE was decomposed into long-chain acids and esters through decarbonylation, hydroxylation and decarbonization, and finally converted into CO2 and H2O. The ECOSAR model evaluation found that the toxicity of intermediate products is generally lower than that of PHE.