Fe0还原地下水中2,4-DNT影响因素及产物

为了解零价铁(Fe0)修复污染地下水中微量2,4-二硝基甲苯 (2,4-DNT)还原规律，采用序批试验，考察地下水中常见阴离子(Cl-，NO₃-和PO₄3-)及重金属Cr(Ⅵ)对Fe0还原2,4-DNT能力的影响，并分析了Fe0还原2,4-DNT的中间产物和最终产物.结果表明:Cl-与NO₃-均能显著提高2,4-DNT的还原降解率，当反应进行120 min时，溶液中c(Cl-)由0 mmol/L增加到1 mmol/L，Fe0对2,4-DNT的还原降解率由31.4%增加到97.2%；溶液中c(NO₃-)由0 mmol/L增加到1 mmol/L，还原降解率由31.4%增加到78.9%；PO₄3-则表现为明显的抑制作用，当反应进行120 min时，溶液中c(PO₄3-)由0 mmol/L增加到1 mmol/L，还原降解率由31.4%降至2.1%.Cr(Ⅵ)能与2,4-DNT竞争Fe0提供的活性电子，当ρ〔Cr(Ⅵ)〕为20 mg/L时，Cr(Ⅵ)对Fe0还原2,4-DNT能力的抑制作用显著.Fe0还原2,4-DNT的中间产物为4-氨基-2硝基甲苯(4A2NT)和2-氨基-4硝基甲苯(2A4NT)，最终产物为2,4-二氨基甲苯(2,4-DAT).因此，在地下水硝基苯类污染物零价铁修复实践中，应考虑地下水中离子组分对反应过程的影响；2,4-DNT的还原最终产物为2,4-DAT，无法进一步降解，需后续处理. 

Products and Influencing Factors of Reductive Degradation of 2,4-DNT in Groundwater by Zero-Valent Iron

In this study,batch experiments were conducted for the purpose of understanding the reductive remediation discipline of trace quantities of 2,4-dinitrotoluene (2,4-DNT) in groundwater by zero-valent iron.Impacts of common anions in groundwater,such as Cl-,NO₃- and PO₄3- and heavy metal Cr(Ⅵ) on reductive capabilities of zero-valent iron for 2,4-dinitrotoluene (2,4-DNT) were investigated,and its final and intermedial products were analyzed.The results indicated that:Cl- and NO₃- could both remarkably promote the reductive removal rate of 2,4-DNT by zero-valent iron by the 120th min.When the concentration of Cl- and NO₃- increased from 0 to 1 mmol/L,the removal rate increased from 31.4% to 97.2% and 78.9%,respectively.In contrast,PO₄3- could remarkably inhibit the reductive process;the reductive removal rate of 2,4-DNT decreased from 31.4% to 2.1% by the 120th min when the concentration of PO₄3- increased from 0 to 1 mmol/L.However,Cr(Ⅵ) adsorbed active electrons provided by the zero-valent iron competitively with 2,4-DNT.When the concentration of Cr(Ⅵ) was 20 mg/L,the reduction of 2,4-DNT by zero-valent iron was remarkably restrained.4-amino-2-nitrotoluene (4A2NT) and 2-amino-4-nitrotoluene (2A4NT) were intermediates,and 2,4-diaminotoluene (2,4-DAT) was the final product of the reductive reaction.Therefore,in groundwater nitrobenzene pollutant remediation by zero-valent iron practice,influence of common ions on the reaction process should be taken into account.Finally,2,4-DNT was reduced to 2,4-DAT,which could not be further degraded by zero-valent iron.Therefore,follow-up treatments must be performed.