title: Carbon nanotube membrane stack for flow-through sequential regenerative electro-Fenton.
abstract: Electro-Fenton is a promising advanced oxidation process for water treatment consisting a series redox reactions. Here, we design and examine an electrochemical filter for sequential electro-Fenton reactions to optimize the treatment process. The carbon nanotube (CNT) membrane stack (thickness ∼ 200 μm) used here consisted of 1) a CNT network cathode for O2 reduction to H2O2, 2) a CNT-COOFe(2+) cathode to chemical reduction H2O2 to (•)OH and HO(-) and to regenerate Fe(2+) in situ, 3) a porous PVDF or PTFE insulating separator, and 4) a CNT filter anode for remaining intermediate oxidation intermediates. The sequential electro-Fenton was compared to individual electrochemical and Fenton process using oxalate, a persistent organic, as a target molecule. Synergism is observed during the sequential electro-Fenton process. For example, when [DO]in = 38 ± 1 mg L(-1), J = 1.6 mL min(-1), neutral pH, and Ecell = 2.89 V, the sequential electro-Fenton oxidation rate was 206.8 ± 6.3 mgC m(-2) h(-1), which is 4-fold greater than the sum of the individual electrochemistry (16.4 ± 3.2 mgC m(-2) h(-1)) and Fenton (33.3 ± 1.3 mgC m(-2) h(-1)) reaction fluxes, and the energy consumption was 45.8 kWh kgTOC(-1). The sequential electro-Fenton was also challenged with the refractory trifluoroacetic acid (TFA) and trichloroacetic acid (TCA), and they can be transferred at a removal rate of 11.3 ± 1.2 and 21.8 ± 1.9 mmol m(-2) h(-1), respectively, with different transformation mechanisms.
authors.affiliation: Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University , Tianjin 300071, China.
authors.forename: Guandao
authors.initials: G
authors.lastname: Gao
authors.forename: Qiaoying
authors.initials: Q
authors.lastname: Zhang
authors.forename: Zhenwei
authors.initials: Z
authors.lastname: Hao
authors.forename: Chad D
authors.initials: CD
authors.lastname: Vecitis
mesh_terms: D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D004566:Electrodes; D004867:Equipment Design; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D008567:Membranes, Artificial; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010084:Oxidation-Reduction; D014238:Trichloroacetic Acid / Q000737:chemistry; D014269:Trifluoroacetic Acid / Q000737:chemistry; D014865:Waste Disposal, Fluid; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D008567:Membranes, Artificial; D037742:Nanotubes, Carbon; D014238:Trichloroacetic Acid; D006861:Hydrogen Peroxide; D007501:Iron; D014269:Trifluoroacetic Acid