Letter pubs.acs.org/journal/estlcu
A Novel Electro-Fenton Process with H2O2 Generation in a Rotating Disk Reactor for Organic Pollutant Degradation Fangke Yu,†,‡ Minghua Zhou,*,†,‡ Lei Zhou,†,‡ and Rudan Peng†,‡ †
Key Laboratory of Pollution Process and Environmental Criteria, Ministry of Education, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China ‡ Tianjin Key Laboratory of Urban Ecology Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China S Supporting Information *
ABSTRACT: The feasibility of the electrogeneration of H2O2 and degradation of an organic pollutant by a novel electro-Fenton (EF) process was demonstrated using dual rotating graphite felt disks to supply oxygen instead of the traditional aeration method, with methyl orange (MO) as the model pollutant. The effects of rotating speed, current density, and pH on the generation of hydrogen peroxide (H2O2) were investigated. At a current density of 50 A/m2, a rotating speed of 10 rpm, and a pH of 3, the concentration of H2O2 reached 116 mg/L in 1 h, which was much higher than that at 0 rpm (37 mg/L). The complete removal of 25 mg/L MO was achieved within 15 min, while the total organic carbon removal efficiency reached 58.7% at 2 h, which was almost 3-fold higher than that at 0 rpm (14.9%). The rotation of disk cathodes resulted in the efficient production of H2O2 without oxygen aeration, offering a potentially cost-effective EF method for degrading organic pollutants.
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INTRODUCTION The electro-Fenton (EF) process has been used in a noteworthy fashion in the effective decontamination of water/wastewater containing toxic and persistent pollutants such as pesticides, organic synthetic dyes, pharmaceuticals, and personal care products.1−3 This technology can be used to significantly enhance the oxidation power of H2O2 in an acidic medium by adding Fe2+ as a catalyst to form •OH, as shown in equations O2 + 2H+ + 2e− → H 2O2
(1)
Fe 2 + + H 2O2 → Fe3 + + •OH + OH−
(2)
rather than a gas diffusion electrode could lead to a high rate of H2O2 generation and fast abatement of contaminant dyes.6 It is well-known that a rotating biological contactor (RBC) is effective in utilizing oxygen even without aeration in wastewater treatment,17 and that it has a low level of energy consumption because of the use of a low rotation speed.18 Inspired by this practice, a novel electro-Fenton process with H2O2 generation in a rotating disks reactor was invented for the first time, in which two round graphite felt disks were positioned in parallel as cathodes. This process design eliminated the aeration requirement that is known to have an extremely low oxygen utilization efficiency in common electro-Fenton processes. The feasibility and performance of this novel process were evaluated here using a model azo dye, methyl orange (MO). A dramatic increase in the rate of H2O2 generation was observed in this rotating disk reactor, and consequently, faster removal of MO was achieved by this novel electro-Fenton process.
To achieve a high yield of H2O2, various carbonaceous materials have been widely tested as cathodes, including carbon/graphite felt,4−6 activated carbon fiber,7 carbon sponge,8 O2/gas diffusion electrode,9,10 carbon nanotubepolytetrafluoroethylene (PTFE),11−13 and graphite-PTFE.14 Usually, this process requires the sparging of oxygen or air into the solution. For example, some researchers obtained H2O2 generation rates of 0.11 and 0.44 mg h−1 cm−2 at O2 flow rates of 8.4 and 24 L/h, respectively.13,15,16 The oxygen utilization efficiency, based on the fraction of oxygen that ended up in the H2O2 from the total amount of oxygen supplied through sparging, was
