Dan Yuan,Shungang Wan,Rurong Liu,Mengmeng Wang,Lei Sun
A novel material of self-shaped ZnO-embedded biomass carbon foam pellets (ZnO@BCFPs) was successfully synthesized and used as fluidized particle electrodes in three-dimensional (3D) electro-peroxone systems for metronidazole degradation. Compared with 3D and 2D + O3systems, the energy consumption was greatly reduced and the removal efficiencies of metronidazole were improved in the 3D + O3system. The degradation rate constants increased from 0.0369 min−1and 0.0337 min−1to 0.0553 min−1, respectively. The removal efficiencies of metronidazole and total organic carbon reached 100% and 50.5% within 60 min under optimal conditions. It indicated that adding ZnO@BCFPs particle electrodes was beneficial to simultaneous adsorption and degradation of metronidazole due to improving mass transfer of metronidazole and forming numerous tiny electrolytic cells. In addition, the process of metronidazole degradation in 3D electro-peroxone systems involved hydroxyethyl cleavage, hydroxylation, nitro-reduction, N-denitrification and ring-opening. The active species of ·OH and ·O2−played an important role. Furthermore, the acute toxicity LD50and the bioconcentration factor of intermediate products decreased with the increasing reaction time.Keywords:electro-peroxone process;particle electrode;metronidazole;degradation mechanism;detoxification
Menghan Sun,Jinshuo An,Zonglin Pan,Guoqing Feng,Xinfei Fan,Chengwen Song,Tonghua Wang
Electrochemical filtration process (EFP) which adopted the coal-based carbon membrane (CCM) as both anode and filter was successfully applied for organic wastewater treatment and presented the promising prospects. In this work, a further enhancement on the wastewater treatment performance of EFP was achieved through the simple Fe 2+ addition (Fe-ECM). The mechanism of the enhanced treatment performance for Fe-ECM system was explored and the effect of operational parameters on the wastewater treatment performance of Fe-ECM system were studied. Results showed that Fe-ECM system established an almost 100% removal efficiency for 250 ppm RhB simulated wastewater when 13.2 μM Fe 2+ was added in the system, which was much higher than that of membrane filtration by CCM or electrochemical filtration carbon membrane (ECM) system. The performance enhancement of Fe-ECM system was attributed to the Fenton process: the hydrogen peroxide (H 2 O 2 ) was electrochemically generated on CCM via the reaction between H 2 O and dissolved oxygen, thus more hydroxyl radical (·OH) was produced in the Fe-ECM system compared with the ECM system through Fenton reaction between the generated H 2 O 2 and Fe 2+ in the solution. Moreover, the Fe-ECM system displayed a good applicability for the decontamination of different organic wastewater and a good reusability was observed for several cycles operation. This work provided an alternative way to enhance the organic wastewater treatment performance of ECM process.
Huilan Lian,Ping Xiang,Yinghao Xue,Yuzhu Jiang,Mengying Li,Jingyu Mo
The significant removal efficiency of microcystis aeruginosa was presented using Pt/Ti anode and activated carbon fiber/nickel foam (ACF/Ni) cathode by addition of Fe 2+ slightly in a wide range of initial pH (3–9). Results showed that about 93% of the Microcystis aeruginosa cells were removed within 15 min for Pt/Ti-ACF/Ni–Fe 2+ system. Dosage of Fe 2+ , current density, and initial pH had remarkable effects on the removal efficiency of microcystis aeruginosa. The mechanism of algae removal in the Pt/Ti-ACF/Ni–Fe 2+ electrochemical system was revealed by the comparison between Pt/Ti-ACF/Ni–Fe 2+ process and classical Fenton process, the analysis on Microcystis aeruginosa and ACF/Ni by SEM, the specific surface area and pore size analysis of ACF, and the determination of UV 254 , OD 620 and microcystin-LR (MC-LR). Results showed that the main mechanism of this system was the electro-Fenton process, which was accompanied by electro-adsorption, electro-floatation, and electro-coagulation process. And the cooperation mechanism on the electrochemical removal system was further speculated. With the breakdown of algal cells during the electrolysis, the MC-LR and other substances released from the cells were effectively degraded. Besides, the new cathode exhibited favorable and stable reusability . This study built up a high-efficiency algae removal system, which broke through the limits of narrow working pH range and large consumption of exogenous chemicals in electro-Fenton process.
Volatile organic compound (VOC) elimination technologies have been investigated to alleviate health damage and to reduce serious environmental risks. The degradation of hydrophobic and refractory VOCs calls for advanced oxidation processes with high degradation efficiency and low-level toxic byproduct generation. In this study, core-shell Fe 3 O 4 @C was employed as an advanced oxidation microreactor for hydrophobic and refractory VOC removal during the Fenton process, and octane was chosen as a typical target pollutant. The average octane removal efficiency increased by 41.6%, while the main byproduct concentrations decreased by 65.8% in the initial 60 min compared with Fe 3 O 4 . Density functional theory (DFT) calculations revealed the key role of Fe O C bond during the regeneration of Fe(II) species, and the enhanced octane adsorption process by the carbonyl sites. Calculation of mass transfer enhancement factor proved that the carbon shell was critical during mass transfer process. The advanced oxidation mechanism was investigated by detection and measurement of byproducts and hydroxyl radicals and XPS analysis. The synergism and the octane degradation pathway was proposed based on the two main types of reactions. This core-shell Fenton system suggests a promising approach for catalyst and microreactor design in advanced oxidation technologies for refractory VOCs removal.
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