Green rGO/FeNPs nanocomposites activated peroxydisulfate for the removal of mixed 17ß-estradiol and estriol.

Reduced graphene oxide/iron nanoparticles (rGO/FeNPs) synthesized by the chemical method have been used in Fenton oxidation of organic contaminants, yet little is known about biosynthesized rGO/FeNPs using green tea extract (GT) as how to activate persulfate in sulfate radical-based advanced oxidation processes. In this study, rGO/FeNPs were used to activate peroxydisulfate (PDS) for 17ß-estradiol (ßE2) and estriol (E3) removal. The rGO/FeNPs-PDS system removed 83.6% of ßE2 and 62.5% of E3 within 240 min, which was confirmed by a combination of adsorption and degradation via both radical and non-radical pathways. Four main reactive species in ßE2 and E3 degradation were observed, i.e., hydroxyl radical (·OH), sulfate radical (SO4·-), singlet oxygen (1O2) and electron transfer, with the respective contributions of ·OH (32.9 and 34.7%), SO4·- (16.1 and 19.7%), 1O2 (12.2 and 14.1%) and electron transfer (8.0 and 7.2%). Analysis of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), Electron Paramagnetic Resonance (EPR) and electrochemical measurements all indicated that beside the well-known role of Fe, CO from rGO through the generation of ·OH, SO4·-, 1O2 and electron transfer, as well as GT through electron transfer also participated in the activation of PDS. Finally, the degradation pathways of ßE2/E3 were proposed. Overall, this study provides a new insight into the biosynthesis of rGO/FeNPs to activate PDS for the oxidation of mixed emerging contaminants.

Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes.

Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g., wetland inputs. Here, we investigate how mangroves and saltmarshes influence coastal carbonate chemistry and quantify the contribution of alkalinity and dissolved inorganic carbon (DIC) outwelling to blue carbon budgets. Observations from 45 mangroves and 16 saltmarshes worldwide revealed that >70% of intertidal wetlands export more DIC than alkalinity, potentially decreasing the pH of coastal waters. Porewater-derived DIC outwelling (81 ± 47 mmol m-2 d-1 in mangroves and 57 ± 104 mmol m-2 d-1 in saltmarshes) was the major term in blue carbon budgets. However, substantial amounts of fixed carbon remain unaccounted for. Concurrently, alkalinity outwelling was similar or higher than sediment carbon burial and is therefore a significant but often overlooked carbon sequestration mechanism.

Aerobic denitrification by Paracoccus sp. YF1 in the presence of Cu(II).

This study of Cu(II)'s impact on aerobic denitrification of Paracoccus sp. YF1 revealed that the denitrification rate decreased markedly from 99.8%, 98.0%, 68.7% to 16.3% when the concentrations of Cu(II) rose from 0, 0.01 mM, 0.05 mM to 0.1 mM, respectively. This outcome was confirmed by the successful test of OD600, total protein and enzyme activities. As the concentration of Cu(II) increased from 0 to 0.1 mM, the total protein contents declined over a period of 48 h, and the activities of nitrate reductase (NR) and nitrite reductase (NIR) decreased remarkably during the first 24 h in a NO3- sufficient state. Meanwhile, the reduction of NO3- and NO2- was positively correlated with the expression level of NR and NIR. The removal rate of nitrate in the control treatment and different concentration of Cu(II) treatment fitted approximately to the zero-order model. Scanning electron microscopy (SEM) confirmed that the cell surfaces of Paracoccus sp. YF1 were disrupted when exposed to 0.1 mM Cu(II). The adsorption of Cu(II) onto the cells' surface was confirmed by Energy dispersive spectrometer (EDS), Fourier transform infrared spectra (FTIR), and X-ray photoelectron spectroscopy analysis (XPS). The insights obtained here regarding the influence of Cu(II) on aerobic denitrification will be of great significance for the treatment of heavy metals and nitrite co-existing sewage.

Effects of cetyltrimethylammonium bromide on the morphology of green synthesized Fe3O4 nanoparticles used to remove phosphate.

In this paper, iron oxide nanoparticles (IONPs) are successfully synthesized using Eucalyptus leaf extract in the presence of cetyltrimethylammonium bromide (CTAB) to enhance the dispersion and reduce aggregation of IONPs. CTAB was used as a stabilizing and capping agent in biosynthesis of IONP was observed. The particle size decreased from 183.9±30.1nm to 89.8±17.1nm as the concentration of CTAB increased from 0 to 0.4mM CTAB, indicating that CTAB reduce the aggregation of IONPs and enhance the reactivity. In addition, the removal efficiency of phosphate declined from 95.13% to 89.58% when the CTAB concentration increased from 0.4 to 10mM, indicating that a CTAB impacted on micelles and lipophilic biomolecules in Eucalyptus leaf extract, and hence affected the formation of IONPs. Furthermore, SEM image showed that the smaller spherical with some irregularly shaped CTAB-IONPs having a diameter of 80-90nm in the presence of 0.4mM CTAB were observed. The date from EDS, FTIR and TGA suggested that the CTAB capped on the surface of CTAB-IONPs, while XRD showed that zero-valent iron and iron oxide were formed. Finally, the formation mechanism of IONPs was proposed.