Optimization and control of Electro-Fenton process by pH inflection points: A case of treating acrylic fiber manufacturing wastewater
Optimization and control of Electro-Fenton process by pH inflection points: A case of treating acrylic fiber manufacturing wastewater
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DOI：
10.1016/j.cej.2015.01.115
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发表时间：
2015-06
影响因子：
15.1
通讯作者：
Meng Sun;Fayuan Chen;J. Qu;Huijuan Liu;Ruiping Liu
中科院分区：
文献类型：
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作者：
Meng Sun;Fayuan Chen;J. Qu;Huijuan Liu;Ruiping Liu
摘要电fenton （Electro-Fenton， EF）法在难处理废水处理中显示出巨大的潜力。然而，它的效率高度依赖于pH值，并且高昂的pH调整试剂成本极大地限制了它的大规模应用。本研究采用实验规模的EF反应器，研究了处理腈纶废水过程中pH值的变化。研究了在不同的h2o2剂量、电流密度和[fe2 + Theo]/[h2o2]（R Fe: h2o2）比下pH拐点（pH IPs）的出现，即pH的突然变化。pH - IPs出现在5 ~ 7.5 min的时间尺度上，且在降低h2o2剂量（2.5 ~ 1.0 mM）、增加电流密度（3 ~ 4.5 mA/ cm2）和升高铁铁比h2o2（0.1∶1 ~ 0.2∶1）时更有利。pH值IPs的出现表明h2o2的耗尽和COD降解的显著降低，由COD降解的准一级动力学常数(k)表示。此外，pH值出现后，Fe (OH) 3被Fe (OH) 2−和Fe (OH) 2−取代，主导机理由电化学氧化（EO）转变为电凝（EC）。在充足的h2o2存在下，Fe (OH) 3的形成几乎不影响pH的变化。在h2o2耗尽后，即pH值出现IPs，溶解的o2迅速将fe2 +氧化为fe3 +，其水解导致pH值立即升高。通过调节h2o2的用量和控制pH - IP的形貌，可以对电催化过程进行优化。
Abstract The Electro-Fenton (EF) process has shown great potential in refractory wastewater treatment. However, its efficiency is highly pH-dependent and the high reagent costs for pH adjustment greatly limit its large-scale application. This study used a bench-scale EF reactor to study pH variation during the treatment of an acrylic fiber wastewater. The appearance of pH inflection points (pH IPs), ie, sudden changes in pH, under different H 2 O 2 dosages, current densities, and ratios of [Fe 2+ Theo]/[H 2 O 2](R Fe: H 2 O 2), were investigated. The pH IPs appeared on the time scale of 5–7.5 min, and were favored at decreased H 2 O 2 dosages (2.5–1.0 mM), increased current densities (3–4.5 mA/cm 2), and elevated R Fe: H 2 O 2 (0.1: 1–0.2: 1). The appearance of pH IPs was indicative of the exhaustion of H 2 O 2 and a significant decrease of COD degradation, as expressed by the pseudo-first order kinetic constant (k) of COD degradation. Besides this, the substitution of Fe (OH) 3 by Fe (OH) 2− and Fe (OH) 2− occurred after pH IP appearance, and the dominant mechanism changed from electrochemical oxidation (EO) to electro-coagulation (EC) accordingly. In the presence of sufficient H 2 O 2, the formation of Fe (OH) 3 barely affected pH variation. After H 2 O 2 exhaustion, ie, the appearance of pH IPs, dissolved O 2 rapidly oxidized Fe 2+ to Fe 3+, the hydrolysis of which contributed to immediate pH increase thereafter. The optimization of the EF process may be achieved by adjusting H 2 O 2 doses and the control of pH IP appearance.