N-doped porous bowl-like carbon with superhigh external surface area for ultrafast degradation of bisphenol A: Key role of site exposure degree.

High-temperature nitrogen (N) doping boosts the activity of biochars for peroxymonosulfate (PMS) activation, but the N heat loss causes the unsatisfactory catalytic efficiency. Improving the surface area for obtaining the high exposure of N sites is a promising solution. Herein, a soft template-KHCO3 etching strategy is used to synthesize the N-doped porous bowl-like carbon (NPBC) with ultrahigh external surface area (1610.8 m2 g-1). The bowl-like structure eliminates inert bulk interior and allows unobstructed mass transfer of reactants onto both outer and inner surfaces, while the large pore channels by KHCO3 etching further improves the exposure degree of limited N sites. Although NPBC has only 0.43% N content, 93.1% of bisphenol A (BPA) is removed within 1 min through the electron-transfer pathway by fully utilizing the N active centers, and the kinetic rate constant (k) reaches 5.29 min-1, exceeding reported values by 2-270 times. Moreover, the NPBC/PMS system possesses excellent applicability for various organics and conditions, effectively mineralizes BPA and reduces effluent biotoxicity. A quantitative index W representing N exposure degree is first proposed and shows high linearity with the k values of BPA degradation (R2=0.992, 0 

Sulfide-modified zero-valent iron activated periodate for sulfadiazine removal: Performance and dominant routine of reactive species production.

In this work, sulfide-modified zero-valent iron (S-Fe0) was used to activate periodate (IO4-, PI) for sulfadiazine (SDZ) removal. 60 µM SDZ could be completely removed within only 1 min by S-Fe0/PI process. Compared with other oxidants including H2O2, peroxymonosulfate (PMS), peroxydisulfate (PDS), S-Fe0 activated PI exhibited better performance for SDZ removal but with lower Fe leaching. Compared with Fe0/PI process, S-Fe0/PI process could reduce more than 80% Fe0 and PI dosage. Inorganic ions and nature organic matters had negligible effect on SDZ removal in S-Fe0/PI system inducing its good SDZ removal efficiency in natural fresh water. 80.2% SDZ still could be removed within 2 min after 7th run. S-Fe0/PI process also exhibited 2.5 - 20.1 folds enhancement for various pollutants removal compared with Fe0/PI process. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical tests, and density functional theory (DFT) calculation were conducted to confirm the presence of sulfurs could enhance the reactivity of S-Fe0 thus increased the efficiency of PI activation for antibiotics removal. Electron paramagnetic resonance spectroscopy (EPR) tests, radical quenching experiments, quantitative detection and DFT calculation were performed to illustrate the role of multiple reactive species in SDZ removal and the dominant pathway of multiple reactive species production. IO3·, ·OH, O2-·, 1O2, FeIV, and SO4·- all participated in SDZ removal. ·OH played the major role in SDZ removal and the dominant routine of ·OH production was IO4- â†’ O2-· â†’ H2O2 â†’ ·OH. Meanwhile, S-Fe0/PI process could efficiently mineralize SDZ and reduce the toxicity. Comparison with other PI activation approaches and SDZ treatment techniques further demonstrated S-Fe0 was an efficient catalyst for PI activation and present study process was a promising approach for antibiotics removal.

Sulfadiazine removal by peroxymonosulfate activation with sulfide-modified microscale zero-valent iron: Major radicals, the role of sulfur species, and particle size effect.

Sulfide-modified zero-valent iron (S-Fe0) is regarded as a promising method to enhance the catalytic activity of Fe0 for peroxymonosulfate (PMS) activation. However, the roles of sulfidation and the application of the sulfidation treatment method are worth to further investigation. In our study, the effects of the S/Fe ratio, Fe0 dosage, and initial pH on sulfadiazine (SDZ) removal were investigated. The characterization of S-Fe0 with SEM, XPS, contact angle and Tafel analysis confirmed that the formation of sulfur species on the Fe0 surface could enhance the catalytic performance of Fe0. S2- played the major role and SO32- played the minor role in accelerating the conversion of Fe3+ to Fe2+. EPR tests, radical quenching and quantitative determination experiments identified •OH as playing the major role and SO4•- also playing an important role in SDZ removal in S-Fe0/PMS system. Sulfidation produced no notable change in the role of •OH and SO4•-. A possible degradation pathway of SDZ was proposed. Effect of sulfidation on various sizes of Fe0 was also studied which demonstrated that the smaller sizes of Fe0 (< 8 µm) were more effective in the sulfidation method treatment. S-Fe0/PMS system also showed a good performance in removing antibiotics in natural fresh water.

Assessment and prediction of the effect of ageing on the adsorption of nonylphenol in black carbon-sediment systems.

Black carbon (BC) is a promising sediment amendment, as proven by its considerable adsorption capacity for hydrophobic organic pollutants and accessibility, but its reliability when used for the removal of pollutants in natural sediments still needs to be evaluated. For example, the ageing process, resulting in changing of surface physicochemical properties of BC, will decrease the adsorption capacity and performance of BC when applied to sediment pollution control. In this study, how the ageing process and BC proportion affect the adsorption capacity of BC-sediment systems was modelled and quantitatively investigated to predict their adsorption capacity under different ageing times and BC additions. The results showed that the ageing process decreased the adsorption capacity of both BC-sediment systems, due to the blockage of the non-linear adsorption sites of BC. The adsorption capacity of rice straw black carbon (RC)-sediment systems was higher than that of fly ash black carbon (FC)-sediment systems, indicating that RC is more efficient than FC for nonylphenol (NP) pollution control in sediment. The newly established model for the prediction of adsorption capacity fits the experimental data appropriately and yields acceptable predictions, especially when based on parameters from the Freundlich model. However, to fully reflect the influence of the ageing process on BC-sediment systems and make more precise predictions, it is recommended that future work considering more factors and conditions, such as modelling of the correlation between the adsorption capacity and the pore volume or specific surface area of BC, be applied to build an accurate and sound model.

Fate of 14C-bisphenol F isomers in an oxic soil and the effects of earthworm.

Bisphenol F (BPF) pollution in environment increased, but the studies on its fate and uptake in soil-earthworm systems were limited. Using 14C-tracers, environmental fate of BPF isomers in an oxic rice soil with/without earthworm Metaphire guillelmi was studied. After 59 days of incubation, mineralization increased in the order of 2,2'-BPF (18.7% ±â€¯0.3% of the initial amount) < 2,4'-BPF (21.7% ±â€¯0.2%) < 4,4'-BPF (26.9% ±â€¯0.1%). About 70% was converted to bound residues (BRs) and most of the BRs resided in the humin fraction by physical entrapment and ester-linkages. M. guillelmi decreased the mineralization and BRs of 4,4'-BPF in soil, indicating that earthworm increased the ecological risk of 4,4'-BPF. About 5.2% ±â€¯0.1% of the initial amount was accumulated in M. guillelmi and mostly in gut. Considerable amounts of the accumulated 4,4'-BPF were present as earthworm-bound residues (earthworm-BRs). The elimination of 4,4'-BPF from M. guillelmi was very slow, and there was still 96.2% of the initial accumulated radioactivity presented in earthworm after 5 days of depuration. The results of this study firstly provide the isomer - specific partitioning of three BPF isomers in an oxic soil and the uptake and depuration of 4,4'-BPF in earthworm during soil incubation.