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Chemosphere ; 262: 128215, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182126


The effluent from conventional treatment process (including anaerobic digestion and anoxic-oxic treatment) for pig farm wastewater was difficult to treat due to its low ratio of biochemical oxygen demand to chemical oxygen demand (BOD5/CODCr) (<0.1). In the present study, electro-Fenton (EF) was used to improve the biodegradability of the mentioned effluent and the properties of self-prepared CeO2-doped multi-wall carbon nanotubes (MWCNTs) electrodes were also studied. An excellent H2O2 production (165 mg L-1) was recorded, after an 80-min electrolysis, when the mass ratio of MWCNTs, CeO2 and pore-forming agent (NH4HCO3) was 6:1:1. Results of scanning electron microscopy (SEM), transmission electron microscope (TEM) and x-ray photoelectron spectroscopy (XPS) showed that addition of NH4HCO3 and the doping of CeO2 could increase the superficial area of the electrode as well as the oxygen reduction reaction (ORR) electro-catalytic performance. The BOD5/CODCr of the wastewater from the first stage AO process increased from 0.08 to 0.45 and CODCr reduced 71.5% after an 80-min electrolysis, with 0.3 mM Fe2+ solution. The non-biodegradable chemical pollutants from the first stage AO process were degraded by EF. The non-biodegradable pollutants identified by LC-MS/MS in the effluent from AO process including aminopyrine, oxadixyl and 3-methyl-2-quinoxalinecarboxylic acid could be degraded by EF process, with the removal rates of 81.86%, 34.39% and 7.13% in 80 min, and oxytetracycline with the removal rate of 100% in 20 min. Therefore, electro-Fenton with the new CeO2-doped MWCNTs cathode electrode will be a promising supplement for advanced treatment of pig farm wastewater.

Cério/química , Eletrólise/métodos , Nanotubos de Carbono/química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Animais , Biodegradação Ambiental , Análise da Demanda Biológica de Oxigênio , Catálise , Eletrodos , Fazendas , Peróxido de Hidrogênio/análise , Oxirredução , Suínos
J Hazard Mater ; 408: 124621, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33383458


In this research, bismuth vanadate-doped graphite felt (GF-BiVO4) was successfully prepared by sol-gel method, in which BiVO4 owned superior electro-Fenton (EF) and solar-photo-electro-Fenton (SPEF) performance. Combined with the analysis by X-ray diffractometer (XRD), field emission transmission electron microscopy (FE-TEM), nitrogen adsorption-desorption isotherms and cyclic voltammetry (CV), the changes of electrodes were reflected in structure and physicochemical properties. The doping of monoclinic BiVO4 endued GF with a higher surface area and more electro-active sites and better electrode activity in comparison to Raw-GF. Then, the GFs were used as cathodes to detect •OH concentration with coumarin (COU) as probe molecule and to evaluate photoelectric performance with ciprofloxacin (CIP) in photocatalysis, EF and SPEF processes. The results demonstrated that the concentration of •OH followed an order of SPEF> EF> photocatalysis, which was consistent with the removal rate of CIP (99.8%, 99.4% and 21.2%, respectively) on GF-BiVO4 at 5 min. Further, five degradation pathways of CIP in SPEF system were proposed including the attack on piperazine ring, oxidation on cyclopropyl group, decarboxylation and hydroxyl radical addition, oxidation on benzene group and defluorination. The study provides insights into the enhancement of EF and SPEF performance and the degradation pathway of CIP in SPEF.

J Hazard Mater ; : 124262, 2020 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-33213981


Ciprofloxacin (CIP) is ubiquitous in the environment which poses a certain threat to human and ecology. In this investigation, the physical and electrochemical properties of graphite felt (GF) anodes which affected the anodic oxidation (AO) performance, and the CIP removal effect of GF were evaluated. The GFs were used as anodes for detection of ·OH with coumarin (COU) as molecule probe and removal of CIP in a 150 mL electrolytic cell with Pt cathode (AO-GF/Pt system). The results showed that hydrophilic GF (B-GF) owned higher sp3/sp2 and more oxygen-containing and nitrogen-containing functional groups than the hydrophobic GF (A-GF). Moreover, B-GF possessed higher oxygen evolution potential (1.12 V), more active sites and stronger ·OH generation capacity. Above mentioned caused that B-GF exhibited more superior properties for CIP removal. The best efficiencies (96.95%, 99.83%) were obtained in the AO-B-GF/Pt system at 6.25 mAcm-2 after 10 min (k1, 0.356 min-1) and 60 min (k2, 0.224 min-1), respectively. Furthermore, nine degradation pathways of CIP in AO-B-GF/Pt system were summarized as the cleavage of the piperazine ring, cyclopropyl group, quinolone ring and F atom by ·OH. It provides new insights into the removal and degradation pathways of CIP with GF in AO system.

J Environ Manage ; 257: 109968, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31868637


The removal of trace antibiotics from the aquatic environment has received great interest. In this investigation, NaOH activated graphite felt (NaOH-GF) was characterized by multiple-methods, including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle, linear sweep voltammetry (LSV) and electron paramagnetic resonance (EPR). The NaOH-GF was then used as the cathode in the electro-Fenton process for oxytetracycline (OTC) degradation, the experiment was carried out in an undivided and light-proof beaker with a Pt anode and a NaOH-GF cathode at pH 3. The results showed that the modification with NaOH enhanced the antibiotics degradation efficiency of graphite felt by increasing the oxygen reduction capacity and hydroxyl radicals yielding rate. Complete OTC removal was achieved at 5.17 mA cm-2 after 40, 60 and 90 s with initial OTC concentration of 22, 44, and 66 µM, respectively. With an initial OTC concentration of 44 µM, after 30 min the removal rates of chemical oxygen demand (COD) by Raw-GF and NaOH-GF were 59.18% and 83.75%, respectively. The proposed degradation mechanism of OTC was an EF process, which consisted of hydroxylation, secondary alcohol oxidation, demethylation, decarbonylation, dehydration and deamination. This study demonstrates that NaOH activated GF cathode possesses high degradation capacity and good stability. It provides insight into the removal of non-biodegradable antibiotics and may shed light on future to its practical application.

Grafite , Oxitetraciclina , Poluentes Químicos da Água , Eletrodos , Peróxido de Hidrogênio , Ferro , Cinética , Oxirredução