Singlet oxygen synergistic surface-adsorbed hydroxyl radicals for phenol degradation in CoP catalytic photo-Fenton

In recent years,there have been numerous studies on Fenton or Fenton-like reactions mediated by nonfree radicals such as singlet oxygen(1O_(2));however,there are few studies on the synergistic effect of 1O_(2) and free radicals on the degradation of organic molecules,such as phenol in Fenton reaction.In this study,a cocatalyst,CoP,commonly used in photocatalysis was synthesized using a simple two-step method,and a CoP/Fe^(2+)/AM1.5 system was constructed by introducing Fe^(2+)and simulated sunlight(AM1.5)irradiation.The newly constructed CoP/Fe^(2+)/AM1.5 system could effectively degrade various organic pollutants,including dyes,phenols,and antibiotics.Radical quenching experiments and electron paramagnetic resonance detection confirmed that there were three reactive oxygen species(ROS)in the CoP/Fe^(2+)/AM1.5 system,including·OH_(ads),·O_(2)^(-),and 1O_(2).Further,combined with the liquid chromatogram of phenol,its intermediate products,and the fluorescence diagram of o-hydroxybenzoic acid,it can be concluded that a synergistic effect exists between 1O_(2) and the surface-adsorbed·OH_(ads) in the CoP/Fe^(2+)/AM1.5 system.The controllable formation of surface 1O_(2) and·OH_(ads) was achieved through the oxidation(Co^(3+))and reduction(Pδ−)centers exposed on the CoP surface,and the synergistic effect between them results in phenol’s hydroxylation,ring-opening,and degradation.The study of this new mechanism provides a new perspective for revealing the surface interface reaction between ROS and organic pollutants.

CONVERSION RATES OF SURFACE HOX RADICALS IN BEIJING CITY

Surface OH radical concentration in Beijing City was measured by impregnated filter trapping technique-high performance liquid chromatography (IFT-HPLC). The observed concentration of OH radical showed obvious diurnal and seasonal variations, with maximum readings at noon or afternoon, similar to 80x10(6)OH/cm(3) in summer and similar to 20x10(6)-40x10(6)OH/cm(3) in fall. On the basis of measured data, the reaction rates related to the photochemical process of HO(x) (OH+HO(2)) were derived and characteristics of atmospheric chemical processes in the city were analyzed. The results showed that conversion rates of atmospheric OH and HO(2) in the summer of Beijing City were about 700x10(6) molecule/(cm(3) . s) and 600x10(6)molecule/(cm(3) . s), respectively. And the net production of OH in the air of the city mainly originated from the photolysis of the gaseous HNO(2), and the main sink of OH were the photochemical reactions with VOCs, NO(2), HCHO and CO. It was different from the clean area.

Synthesis of Chlorogenic Acid Imprinted Chromatographic Packing by Surface-initiated Atom Transfer Radical Polymerization and Its Application

A novel chromatographic packing of chlorogenic acid（CGA） molecularly imprinted polymer（MIP） based on the 5.0 ~tm silica was prepared by surface initiated atom transfer radical polymerization（SI-ATRP） with 4-vinylpyridine（4-VP） as functional monomer, ethyl glycol dimethacrylate（EDMA） as cross-linker in the mixture of methanol and water（7：3, volume ratio） under mild reaction conditions. The characteristics of CGA MIP were investi- gated by elemental analysis, thermogravimetric analysis（TGA）, Fourier transform infrared spectrometry（FTIR） and atomic force microscopy（AFM）. The effects of some chromatographic conditions such as mobile phase composition and temperature on the retention time were investigated. The adsorption capacity of the stationary phase for com- pounds was determined by frontal chromatographic technique. The results show that Freundlich isotherm fits the ex- perimental adsorption isotherm data better than Langmuir model does. The relatively high heterogeneity index values regressed with the Freundlich isotherm suggest the formation of fairly homogeneous MIP. Thermodynamic data（AAH and AAS） obtained by van＇t Hoff plots reveal an entropy-controlled separation. The CGA MIP column was shown to be successful for the separation and purification of chlorogenic acid from the extract of Honeysuckle.

Influence of Mechanical Grinding on the Interface Characteristics of Rice/Wheat Straws

The mechanical grinding method was used to make rice and wheat straw flakes and the properties of the interface of straws before and after grinding were evaluated. The particle boards were prepared using two kinds of straw flakes, respectively and their physical and mechanical properties were investigated. The results showed that the rice straw was easier to be broken when compared with wheat straw and the inner surface of cells in grinded straws was exposed remarkably. The characteristic peaks of lignin and cellulose on the surface of wheat straw were more significant than rice straw. The free-radical concentrations of straws were increased dramatically after being grinded with heating in the range from I00 ~C to 200 ~C. The surface free energy of straws was also improved after being grinded and the value in wheat straw was higher than that of rice straw, which implies that wheat straw was easier to be bonded than rice straw. The physical and mechanical properties of two kinds of straw particle boards could achieve the requirements of Chinese National Standards of GB 4897.3-2003, while wheat straw particle boards had better properties than those made from rice straws.

Activated carbon enhanced ozonation of oxalate attributed to HO·oxidation in bulk solution and surface oxidation: Effect of activated carbon dosage and pH

Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon（AC）in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals（HOU） in bulk solution and oxidation on the AC surface to the removal of oxalate was studied. We found that the removal of oxalate was reduced by tert-butyl alcohol（tBA） with low dosages of AC,while it was hardly affected by tBA when the AC dosage was greater than 0.3 g/L. tBA also inhibited ozone decomposition when the AC dosage was no more than 0.05 g/L, but it did not work when the AC dosage was no less than 0.1 g/L. These observations indicate that HOUin bulk solution and oxidation on the AC surface both contribute to the removal of oxalate. HOU oxidation in bulk solution is significant when the dosage of AC is low, whereas surface oxidation is dominant when the dosage of AC is high. The oxalate removal decreased with increasing pH of the solution with an AC dosage of 0.5 g/L. The degradation of oxalate occurs mainly through surface oxidation in acid and neutral solution, but through HOUoxidation in basic bulk solution. A mechanism involving both HOUoxidation in bulk solution and surface oxidation was proposed for AC enhanced ozonation of oxalate.

Efficient degradation of atrazine through in-situ anchoring NiCo_(2)O_(4) nanosheets on biochar to activate sulfite under neutral condition

Sulfite (S(IV)) is a promising substitute for sulfate radical-based advanced oxidation processes.Here,a composite of in-situ anchoring Ni Co_(2)O_(4)nanosheets on biochar (BC) was firstly employed as a heterogeneous activator for sulfite (Ni Co_(2)O_(4)@BC-sulfite) to degrade atrazine (ATZ) in the neutral environment.The synergistic coupling of BC and Ni Co_(2)O_(4)endows the resulting composite excellent catalytic activity.82% of the degradation ratio of ATZ (1 mg/L) could be achieved within 10 min at initial concentrations of 0.6 g/L Ni Co_(2)O_(4)@BC,3.0 mmol/L sulfite in neutral environment.When further supplementing sulfite into the system at 20 min (considering the depletion of sulfite),outstanding degradation efficiency (100%) were achieved in the next 10 min without any other energy input by the Ni Co_(2)O_(4)@BC-sulfite system.The features of the prepared catalysts and the effects of some key parameters on ATZ degradation were systematically examined.A strong inner-sphere complexation (≡Co_(2)+/Ni^(2+)-SO_(3)^(2-)) was explored between sulfite and the metal sites on the Ni Co_(2)O_(4)@BC surface.The redox cycle of the surface metal efficiently mediated sulfite activation and triggered the series radical chain reactions.The generated radicals,in particular the surface-bound radicals were involved in ATZ degradation.High performance liquid chromatography-tandem mass spectrometry (LC-MS) technique was used to detect the degradation intermediates.Density functional theory (DFT) calculations were performed to illustrate the possible degradation pathways of ATZ.Finally,an underlying mechanism for ATZ removal was proposed.The present study offered a low-cost and sustainable catalyst for sulfite activation to remove ATZ in an environmentally friendly manner from wastewater.

Significant enhancement in From granular to super-fine catalytic ozonation efficacy： powdered activated carbon

In this study, super-fine powdered activated carbon （SPAC） has been proposed and investigated as a novel catalyst for the catalytic ozonation of oxalate for the first time. SPAC was prepared from commercial granular activated carbon （GAC） by ball milling. SPAC exhibited high external surface area with a far greater member of meso- and macropores （563% increase in volume）. The catalytic perfon,nances of activated carbons （ACs） of 8 sizes were compared and the rate constant for pseudo first-order total organic carbon removal increased from 0.012 mint to 0.568 min l （47-fold increase） with the decrease in size of AC from 20 to 40 mesh （863 ~tm） to SPAC （-1.0 tim）. Furthermore, the diffusion resistance of SPAC decreased 17-fold compared with GAC. The ratio ofoxalate degradation by surface reaction increased by 57%. The rate of transformation of ozone to radicals by SPAC was 330 times that of GAC. The results suggest that a series of changes stimulated by ball milling, including a larger ratio of external surface area, less diffusion resistance, significant surface reaction and potential oxidized surface all contributed to enhancing catalytic ozonation performance. This study demonstrated that SPAC is a simple and effective catalyst fur enhancing catalytic ozonation efficacy.