RESUMO
Organic pollutants in electroplating wastewater can be removed by photodegradation, however the effect mechanism of heavy metal ions on photocatalytic activity still remains unknown. Herein, we firstly reported the self-assembly synthesis of titanium dioxide/reduced graphene oxide (TiO2/rGO) composites for phenol-4-sulfonic acid (PSA) removal, and investigated the effects of Cu2+ ions on photocatalytic efficiency. During the self-assemble process, rGO nanosheets were connected together to form network macropores, and simultaneously induced the deposition of hierarchically nanostructured TiO2 microspheres. The synergetic effects of TiO2 microspheres and rGO nanosheets improved the photocatalytic activity by enhancing light adsorption ability, stabilizing electron-hole separation and decreasing band gap energy. The Cu2+ ions in wastewater showed positive and negative effects on PSA photodegradation. In the photocatalytic reaction, the electron-induced reduction reaction of Cu(II) into Cu(0) or Cu(I) took place, which inhibited electron-hole recombination and thus enhanced photocatalytic activity. However, the high chemical stability of PSA-Cu(II) complex compounds held back PSA photodegradation. The appropriate concentrations of Cu2+ ions at around 25 mg/L accelerated PSA photodegradation over TiO2/rGO composites. The PSA degradation into CO2 and H2O was performed by using hydroquinone, benzoquinone and maleic acid as degradation intermediates. Hence, TiO2/rGO composites are novel multifunctional photocatalysts to purify electroplating wastewater.
RESUMO
Design and fabrication of novel adsorbents to remove heavy metal ions in continuous-flow wastewater remained a great challenge. Inspired by the hierarchical architecture and biomineralization process of nacre, we firstly constructed hydroxyapatite/chitosan (HA/CH) layered composites. The brick-and-mortar characteristics of HA/CH layered composites improved their flexure strengths up to 3.08 MPa so that the hierarchical architectures could not be destroyed even under high-pressure drop. HA/CH layered composites had the hierarchical microstructures analogous to plate towers, facilitating the separation of adsorbents from water. The interlaminar macropores in the layered composites contributed to the transfer of continuous-flow wastewater. The Pb(II), Cd(II) and Hg(II) ions in wastewater showed similar adsorption trends, and their adsorption amounts arrived at 295.96, 192.37 and 127.38 mgâ¯g-1 after 6 days, respectively. Among the above heavy metal ions, the HA/CH layered composites possessed the best Pb(II) adsorption ability due to forming lead hydroxyapatite rods and CH-Pb complexes. The Pb(II) adsorption performances of HA/CH layered composites matched well with Elovich equation, pseudo-first-order and pseudo-second-order kinetics models, revealing the heterogeneous chemisorption mechanism at adsorbent/wastewater interfaces. Therefore, the nacre-like HA/CH layered composites with appropriate mechanical property and excellent adsorption capacity are a novel platform for heavy metal removal in continuous-flow wastewater.
RESUMO
The surgical resection of melanoma may cause skin wounds, and the remaining melanoma cells bring a great risk of tumor recurrence. To overcome the above problem, we for the first time constructed lanthanum-doped chitosan (La-CS) hydrogels with excellent wound healing and antitumor functions. The La element was uniformly dispersed within whole hydrogels, and part of La3+ ions reacted with CS to form La-CS complex. The complexation interaction between La3+ ions and CS significantly improve the La3+ release performances of La-CS hydrogels. The as-released La3+ ions from the composite hydrogels selectively inhibited the proliferation of B-16 melanoma cells, but showed lower toxic side effects to L929 skin fibroblast cells. Moreover, the La3+ ions triggered the apoptosis of B-16 cells through Bcl-2/Bax pathway, as confirmed by the Annexin Vand PI double staining, flow cytometry, and Western blot results. The in vivo tumor models of C57 mice revealed that the La-CS hydrogels had more significant relapse-inhibition effects on B-16 melanoma cells than the pure CS hydrogels. At the same time, the in vivo wound healing was accelerated by the multifunctional hydrogels. The exciting finding provides a critical and promising strategy in the construction of La-doped hydrogels for oncotherapy.
RESUMO
In anaerobic conditions, the acclimation of activated sludge was studied with sodium lactate as the electron donor and 2,4,6-trichlorophenol as the electron acceptor. Metabolic characteristics of dechlorination were the focus of this study. The result showed highly efficient dechlorination on 2, 4, 6-trichlorophenol that the conversion rate reached to 100% in 9 - 24 h when initial concentrations of sodium lactate and 2,4, 6-trichlorophenol were 20 mmol x L(-1) and 40 - 80 µmol x L(-1), respectively. The intermediate product 2,4-dichlorophenol was found in low concentration (< 4.22 µmol x L(-1)). And 4-chlorophenol and phenol were the main products. Ortho chlorophenol (2, 4, 6-trichlorophenol, 2, 4-dichlorophenol) can be converted rapidly by acclimated sludge, while the further conversion of 4-chlorophenol and phenol was limited. The residues of anaerobic metabolism were degraded by aerobic sludge, among which 4-chlorophenol (initial concentration of 33 mol x L(-1)) removal rate was up to 100% under aerobic conditions. The acclimated bacteria can rapidly transfer Fe(III) and humus (AQDS) into reductive Fe(II) and AQH2DS which indicated that the dissimilatory iron reducing bacteria was enriched in the acclimated sludge. The electron mediator [Fe(III) and AQDS] significantly accelerated the dechlorination rate. The acclimated sludge could perform extracellular respiration dechlorination with electron mediators.