Dezhi Chen,Shoujun Wang,Zhiming Zhang,Hongying Quan,Yachao Wang,Yijie Jiang,Matthew J. Hurlock,Qiang Zhang
The efficient removal of endocrine-disrupting pollutants (EDCs) from water is a crucial issue for improving the quality of drinking water. Herein, hierarchically structured carbon composites (HCCs) composed of carbon-polyhedron decorated carbon nanosheets were fabricated using the zeolite imidazole framework-8 (ZIF-8) as the precursor in the presence of molten NaCl. The as-prepared hierarchical carbon composites showed higher specific surface areas, more defects, high N-doping, and hydrophilicity compared with the NaCl-free ZIF-8-derived carbon polyhedrons (CPs). In addition, the as-prepared HCCs exhibited boosted adsorption performances for the removal of the model EDC, namely carbamazepine (CBZ), surpassing CPs and commercial powdered activated carbon (AC). The adsorption kinetics showed that HCCs possessed a higher sorption rate as compared to CPs and AC. In the initial 5 min, the adsorption amount of CBZ on HCCs reached 94.9% of the adsorption quantity at equilibrium. Furthermore, the maximum adsorption capacity of CBZ on HCCs is 248.7 mg g−1, which is superior to that of CPs and AC. X-ray photoelectron spectroscopy characterizations indicated that the predominant factors for controlling the adsorption of CBZ on HCCs are π–π electron donor–acceptor interactions and hydrogen bonding, although, some of the adsorbed CBZ molecules were decomposed by oxidation. Finally, a fixed-bed experiment demonstrated that the HCCs have great potential as a filler for the purification of tap water.
Forty strains of Mn-oxidizing microalgae (MnOMs) with different Mn 2+ oxidation mechanisms were identified from two aquatic environments. Among them, three strains of isolates ( Chlamydomonas sp. WH1–1, Chlamydomonas sp. WH1–4 , and Chlorella sp. WH2–5) oxidize Mn 2+ by increasing the ambient pH and by secreting Mn oxidation factors (e.g., superoxide-production enzymes and/or other Mn oxidases) into the extracellular environment at the same time. In carbamazepine (CBZ) removal by MnOMs and/or Bio-MnOx, the combination of MnOMs and Bio-MnOx significantly increased the CBZ (1 mg/L) removal efficiency from 36.05% (by MnOMs alone) and 20.11% (by Bio-MnOx alone) to 80.13% by two synergistic mechanisms. One of the synergistic mechanisms was confirmed as that the Mn 2+ was re-oxidized by MnOMs to Bio-MnOx, which can promote the CBZ removal, and another was the mutual exchange of degradation products of CBZ as shared reactants between MnOMs and Bio-MnOx. The degradation intermediates of CBZ were analyzed using high-performance liquid chromatography-tandem mass spectrometry , based on which the CBZ degradation pathway by MnOMs and Bio-MnOx was proposed. These findings expand existing knowledge on the Mn 2+ oxidation mechanisms of MnOMs, and indicate that MnOMs and their generated Bio-MnOx are promising for the removal of CBZ or other pharmaceutical contaminants from wastewater.
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