高铁酸钾-过硫酸钠降解萘的效能及机理研究

Study on efficacy and mechanism of naphthalene degradation by potassium ferrate and sodium persulfate

为了绿色且高效地治理多环芳烃萘污染地下水,采用高铁酸钾-过硫酸钠体系降解萘,考察高铁酸钾和过硫酸钠的摩尔比、pH值和温度对萘降解效果的影响,并探究反应动力学和降解机理。研究显示,当温度为25℃,pH值为5.0,高铁酸钾和过硫酸钠的摩尔比为1∶2时,在50 min时萘最佳降解率为82.3%。采用一级反应动力学方程对萘的降解曲线进行拟合,发现其反应速率k为0.0302 min^(-1),远高于高铁酸钾体系的0.0074 min^(-1)和过硫酸钠体系的0.0034 min^(-1)的总和,表明高铁酸钾-过硫酸钠体系存在协同作用。通过对高铁酸钾-过硫酸钠体系中Fe(Ⅱ)和Fe(Ⅲ)质量浓度变化测定,显示该体系可以活化过硫酸钠且Fe(Ⅱ)和Fe(Ⅲ)质量浓度变化与萘的降解试验结果吻合。采用自由基猝灭试验和电子顺磁共振(Electron Paramagnetic Resonance,EPR)技术探究高铁酸钾-过硫酸钠体系中的活性氧化物种,发现羟基自由基(·OH)和硫酸根自由基(·SO_(4)^(-))都参与了萘的降解过程。采用气相色谱-质谱联用仪(Gas Chromatography and Mass Spectrometry,GC-MS)分析确定了3种萘的中间产物,并提出了一种可能的降解途径。研究发现,萘在降解过程中可被转化为低毒或无毒物质,表明高铁酸钾-过硫酸钠体系对萘的降解是一个渐进降低毒性的过程,可以有效降低环境风险。总之,高铁酸钾-过硫酸钠联合体系作为一种高效的清洁技术,可为治理多环芳烃萘污染地下水提供一定的理论指导。

To greenly and effectively remediate PAH-naphthalene contaminated groundwater,the degradation of naphthalene using a potassium ferrate-sodium persulfate system was investigated,and the effects of molar ratio,pH,and temperature on the degradation effect of naphthalene were examined.The reaction kinetics and degradation mechanism were also studied.It was shown that at a temperature of 25℃,a pH of 5.0,and a molar ratio of 1:2 between potassium ferrate and sodium persulfate,the optimum degradation of naphthalene was 82.3% within 50 min.Moreover,the degradation curve of naphthalene was fitted using the first-order reaction kinetic equation and the reaction rate(k)for the potassium ferrate-sodium persulfate system was found to be 0.0302 min^(-1),which was much higher than the sum of those of potassium ferrate system(0.0074 min^(-1))and sodium persulfate system(0.0034 min^(-1)).This demonstrates the synergistic effect of the potassium ferrate-sodium persulfate system.The changes in the mass concentrations of Fe(Ⅱ)and Fe(Ⅲ)in the potassium ferrate-sodium persulfate system show that the system can activate sodium persulfate and that the changes in the mass concentrations of Fe(Ⅱ)and Fe(Ⅲ)are consistent with the results of the naphthalene degradation tests.The reactive oxide species in the potassium ferrate-sodium persulfate system are probed using radical scavenging experiments and EPR techniques,and both·OH and·SO_(4)^(-) are found to be involved in the degradation of naphthalene.The presence of three naphthalene intermediates in the degradation of naphthalene by the potassium ferrate-sodium persulfate system was analyzed and determined using GC-MS and a possible degradation pathway was suggested.It is found that naphthalene is converted to less toxic or non-toxic substances during degradation,indicating that the degradation of naphthalene by the potassium ferrate-sodium persulfate system is a gradual reduction in toxicity and can effectively reduce environmental risks.Overall,the combined system of potassium ferrate and sodium persulfate can be used as an efficient clean-up technology and provide some theoretical guidance for the remediation of PAH-naphthalene-contaminated groundwater.