Simultaneous Emerging Contaminant Removal and H2O2 Generation Through Electron Transfer Carrier Effect of Bi─O─Ce Bond Bridge Without External Energy Consumption

Abstract Conventional advanced oxidation processes (AOPs) require significant external energy consumption to eliminate emerging contaminants (ECs) with stable structures. Herein, a catalyst consisting of nanocube BiCeO particles (BCO‐NCs) prepared by an impregnation‐hydrothermal process is reported for the first time, which is used for removing ECs without light/electricity or any other external energy input in water and simultaneous in situ generation of H2O2. A series of characterizations and experiments reveal that dual reaction centers (DRC) which are similar to the valence band/conducting band structure are formed on the surface of BCO‐NCs. Under natural conditions without any external energy consumption, the BCO‐NCs self‐purification system can remove more than 80% of ECs within 30 min, and complete removal of ECs within 30 min in the presence of abundant electron acceptors, the corresponding second‐order kinetic constant is increased to 3.62 times. It is found that O2 can capture electrons from ECs through the Bi─O─Ce bond bridge during the reaction process, leading to the in situ production of H2O2. This work will be a key advance in reducing energy consumption for deep wastewater treatment and generating important chemical raw materials.

mixed with 50 mL of the actual wastewater (35 °C) in an appropriate volume glass beaker.
The suspension was stirred throughout the experiment.At certain intervals, 3 mL reaction suspension was collected with a syringe and filtered with a filter (0.45 µm) for follow-up analysis.
Three-dimension excitation emission matrix (3D-EEM) fluorescence spectra of various samples were obtained on an F-7000 spectrometer (HITACHI) with a xenon excitation source, and slits were set to 5 nm for both excitation and emission.The excitation wavelengths were incremented from 200 to 450 nm in 5-nm steps; for each excitation wavelength, the emission was detected from 300 to 550 nm in 5-nm steps.
FTIR.The attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was tested with a TENSOR FTIR spectrophotometer (Bruker Scientific Inc.) with a single ATR accessory.To prepare an ATR sample, 1 g L -1 catalyst was added to a 100 ppm CIP aqueous solution.The suspension was stirred at room temperature for approximately 30 min to establish adsorption/desorption equilibrium between the pollutant and the catalyst.Then the suspension was collected followed by filtration, the solid particles were collected and dried at approximately 50 °C to form the powder samples.
The FTIR spectra of these powder samples and fresh samples supported on KBr pellets at a fixed sample amount (1 wt%) were recorded on a Nicolet 8700 FTIR spectrophotometer (Thermo Fisher Scientific Inc., USA).
Raman and in situ EPR measurements.in situ Raman spectra for various catalyst were tested with an HR Evolution Raman spectrophotometer (HORIBA Scientific Inc.).The catalyst was placed directly into the reaction cell and scanned from 200 to 2000 cm -1 at a resolution of 1 cm-1 for 60 s with 40 mW 532 nm laser light irradiation.
For the EPR spectra measurement, BMPO/TEMP-trapped EPR signals were detected in different air-saturated methanol/aqueous dispersions of the corresponding samples using a Bruker A300-10/12 EPR spectrometer at room temperature (25°-30°).The center field is 3500 G, sweep width is 100 G, modulation frequency is 100 kHz.To detect • OH, 0.01 g of the prepared powder sample was added to 500 µL of water.Then, 100 µL of the above suspension, 20 µL of BMPO (250 mM) was mixed thoroughly and then left to stand for 1 min before being drawn into a capillary for detection.To detect HO 2 , the steps were the same as above except that water was replaced with methanol.To detect 1 O 2 , the steps were the same as that of detecting • OH except that BMPO was replaced with TEMP.
Quantification of  OH by the TPA probe method.The generation of  OH in the BCO-NCs aqueous dispersion was quantitatively measured using the terephthalic acid (TPA) probe method, in which the trapping of  OH by TPA could generate the strongly fluorescent 2-hydroxyl-terephthalic acid (2-HTPA).The TPA solution was prepared with 4 mM of TPA and 12 mM of NaOH mixture.In a typical procedure, 50 mL of the TPA solution and 0.05 g of the catalyst powder were placed in a beaker.The pH value was adjusted to 6-6.Reaction Time (min) 5 using the aqueous hydrochloric acid solution.Then, continuous magnetic stirring at 35 °C throughout the experiment.At given time intervals, 3 mL aliquots were collected and filtered through a Millipore filter (pore size 0.45 µm) to detect the 2-HTPA (  OH) production based on the fluorescence intensity.The fluorescence intensity of the produced 2-HTPA was detected by a CARY ECLIPSE fluorescence spectrophotometer.The excitation and emission wavelengths of the detector were set at 310 and 425 nm, respectively.

Figure S4 .
Figure S4.The proposed degradation pathways in the BCO-NCs system.

Figure S5. a
Figure S5. a Satellite map of printing and dyeing wastewater sampling sites.b Changes in COD of printing and dyeing wastewater during the purification process.c Fluorescence EEMs spectrum of raw printing and dyeing wastewater; d Printing and dyeing wastewater after 60 min of BCO-NCs self-purification system treatment.

Figure S6 .
Figure S6.Effect of different concentrations of H 2 O 2 on CIP removal.

Figure S7. a
Figure S7. a Fluorescence spectral changes observed during the self-purification of BCO-NCs in terephthalic acid solution.(Excitation wavelength is 310 nm).b, c  OH concentration standard curve constructed using a series of known concentrations of 2-hydroxyterephthalic acid (hTPA).

Table S1 .
Comparison of the catalytic performance with the previous reported catalysts.