Efficient removal of Cr(VI) by a 3D Z-scheme TiO2-ZnxCd1-xS graphene aerogel via synergy of adsorption and photocatalysis under visible light

Efficient and robust photocatalysts for environmental pollutants removal with outstanding stability have great significance. Herein, we report a kind of three dimensional (3D) photocatalyst presented as Z-scheme heterojunction, which combining TiO 2 and Zn x Cd 1- x S with graphene aerogel to contrast TiO 2 -Zn x Cd 1- x S graphene aerogel (TSGA, x = 0.5) through a moderate hydrothermal process. The as-prepared Z-scheme TSGA was used to remove aqueous Cr(VI) via a synergistic effect of adsorption and visible light photocatalysis. The adsorption equilibrium can be reached about 40 min, then after about 30 min irradiation under visible light (wavelength ( λ) > 420 nm) the removal rate of Cr(VI) almost reached 100%, which is much better than the performance of pristine TiO 2 and Zn 0.5 Cd 0.5 S, as well as TiO 2 graphene aerogel (TGA) and Zn 0.5 Cd 0.5 S graphene aerogel (SGA). The virulent Cr(VI) was reduced to Cr(III) with hypotoxicity after photocatalysis on TSGA, meanwhile the as-synthesized TSGA presented a good stability and reusability. The reduced graphene oxide (rGO) sheets between TiO 2 and Zn 0.5 Cd 0.5 S played a role as charge transfer mediator, promoting the photoinduced electrons transfer and photocatalysis ability of TSGA was enhanced significantly. Hence,such photocatalyst exhibits a potential application on removing heavy metals with high efficiency and stability from polluted aqueous environment.     

Effect of graphene oxide exposure on intestinal Wnt signaling in nematode Caenorhabditis elegans

Exposure to engineered nanomaterials(ENMs), such as graphene oxide(GO), can potentially induce the response of various molecular signaling pathways, which can mediate the protective function or the toxicity induction.Wnt signaling pathway is conserved evolutionarily in organisms.Using Caenorhabditis elegans as an in vivo assay model, we investigated the effect of GO exposure on intestinal Wnt signaling.In the intestine, GO exposure dysregulated Frizzled receptor MOM-5, Disheveled protein DSH-2, GSK-3(a component of APC complex), and two β-catenin proteins(BAR-1 and HMP-2), which mediated the induction of GO toxicity.In GO exposed nematodes, a Hox protein EGL-5 acted as a downstream target of BAR-1, and fatty acid transport ACS-22 acted as a downstream target of HMP-2.Functional analysis on HMP-2 and ACS-22 suggested that the dysregulation of these two proteins provides an important basis for the observed deficit in functional state of intestinal barrier.Our results imply the association of dysregulation in physiological and functional states of intestinal barrier with toxicity induction of GO in organisms.     

Mesoporous WO3-graphene photocatalyst for photocatalytic degradation of Methylene Blue dye under visible light illumination

Advanced oxidation technologies are a friendly environmental approach for the remediation of industrial wastewaters. Here, one pot synthesis of mesoporous WO_3 and WO_3-graphene oxide(GO) nanocomposites has been performed through the sol–gel method. Then, platinum(Pt) nanoparticles were deposited onto the WO_3 and WO_3-GO nanocomposite through photochemical reduction to produce mesoporous Pt/WO_3 and Pt/WO_3-GO nanocomposites. X-ray diffraction(XRD) findings exhibit a formation of monoclinic and triclinic WO_3 phases. Transmission Electron Microscope(TEM) images of Pt/WO_3-GO nanocomposites exhibited that WO_3 nanoparticles are obviously agglomerated and the particle sizes of Pt and WO_3 are ~ 10 nm and 20–50 nm, respectively. The mesoporous Pt/WO_3 and Pt/WO_3-GO nanocomposites were assessed for photocatalytic degradation of Methylene Blue(MB) as a probe molecule under visible light illumination.The findings showed that mesoporous Pt/WO_3, WO_3-GO and Pt/WO_3-GO nanocomposites exhibited much higher photocatalytic efficiencies than the pure WO_3. The photodegradation rates by mesoporous Pt/WO_3-GO nanocomposites are 3, 2 and 1.15 times greater than those by mesoporous WO_3, WO_3-GO, and Pt/WO_3, respectively. The key factors of the enhanced photocatalytic performance of Pt/WO_3-GO nanocomposites could be explained by the highly freedom electron transfer through the synergetic effect between WO_3 and GO sheets, in addition to the Pt nanoparticles that act as active sites for O2 reduction, which suppresses the electron hole pair recombination in the Pt/WO_3-GO nanocomposites.     

A metal-free composite photocatalyst of graphene quantum dots deposited on red phosphorus

A simple approach to enhance the photocatalytic activity of red phosphorus(P) was developed.A mechanical ball milling method was applied to reduce the size of red P and to deposit graphene quantum dots onto red P. The product was characterized by scanning electron microscopy, transmission electron microscopy, contact angle measurements, zeta-potential measurements, X-ray diffraction and UV–vis absorption spectroscopy. The product exhibited high visible-light-driven photocatalytic performance in the photodegradation of rhodamine B.     

Optimization, equilibrium, adsorption behavior and role of surface functional groups on graphene oxide-based nanocomposite towards diclofenac drug

Aquatic contamination of diclofenac (DCF), an emergent non-steroidal anti-inflammatory drug (NSAIDs), can result in adverse effects to many ecosystems through biomagnification. Hence, introducing effective remediation techniques to sequester the pharmaceutical wastes is highly fundamental to prevent their accumulation in the environment. Generally, adsorption has been presented as a green and efficient approach. Herein, we report the characterization and application of the novel magnetic nanocomposite ([email protected]₂O₄) derived from cobalt-based ferrite (CoFe₂O₄) and graphene oxide (GO) for DCF adsorption. For the optimization procedure, the response surface methodology (RSM) was adopted to investigate the impacts of DCF concentration (1.6–18.4 mg/L), DCF dosage (0.08–0.92 g/L), and solution pH (2.6–9.4) to find the optimum conditions for DCF removal, at 10.5 mg/L, 0.74 g/L, and pH 4, respectively. For the adsorption experiments, the kinetic, isotherm, thermodynamic, and intraparticle diffusion models were systematically studied. Moreover, we have elucidated the role of functional groups on the surface of [email protected]₂O₄ in enhancing the adsorption of DCF drug. With good removal efficiency (up to 86.1%), high maximum adsorption capacity (32.4 mg/g), [email protected]₂O₄ can be a potential candidate to eliminate DCF drug from water.     

Pd/GO/Ni电极的制备及对2,4-二氯酚的降解研究

为去除持久性氯代有机污染物2,4-二氯酚(2,4-DCP),利用电化学沉积法制备了一种新型钯/氧化石墨烯/泡沫镍(Pd/GO/Ni)电极,并通过电化学法降解2,4-二氯酚,取得良好的效果。通过扫描电镜等表征手段观察其表面形貌。结果表明:氧化石墨烯浓度为10 mol/L是制备Pd/GO/Ni电极的最佳浓度,p H为3时,Pd/GO/Ni电极对2,4-二氯酚的去除率达到90.7%。     

铋和石墨烯改性金属有机框架对碘离子的吸附性能

采用一步法制备石墨烯(GO)和铋[Bi(Ⅲ)]改性沸石咪唑酯骨架结构(ZIF-8),得到GZIF和Bi@GZIF吸附剂,并用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)及扫描电镜(SEM)对制备的吸附剂进行表征。结果显示,改性后ZIF-8晶体结构没有被破坏,表面形态及表面基团发生了变化,对碘离子的吸附能力增强,吸附速度加快,尤其是Bi@GZIF在5 min内完成吸附88.3%,最大吸附容量达197.2 mg/g。     

Graphene-supported nanoscale zero-valent iron：Removal of phosphorus from aqueous solution and mechanistic study

Excess phosphorus from non-point pollution sources is one of the key factors causing eutrophication in many lakes in China,so finding a cost-effective method to remove phosphorus from non-point pollution sources is very important for the health of the aqueous environment. Graphene was selected to support nanoscale zero-valent iron(nZVI)for phosphorus removal from synthetic rainwater runoff in this article. Compared with nZVI supported on other porous materials,graphene-supported nZVI(G-nZVI) could remove phosphorus more efficiently. The amount of nZVI in G-nZVI was an important factor in the removal of phosphorus by G-nZVI,and G-nZVI with 20 wt.% nZVI(20% G-nZVI)could remove phosphorus most efficiently. The nZVI was very stable and could disperse very well on graphene,as characterized by transmission electron microscopy(TEM) and scanning electron microscopy(SEM). X-ray photoelectron spectroscopy(XPS),Fourier Transform infrared spectroscopy(FT-IR) and Raman spectroscopy were used to elucidate the reaction process,and the results indicated that Fe-O-P was formed after phosphorus was adsorbed by G-nZVI. The results obtained from X-ray diffraction(XRD) indicated that the reaction product between nZVI supported on graphene and phosphorus was Fe3(PO4)2·8H2O(Vivianite). It was confirmed that the specific reaction mechanism for the removal of phosphorus with nZVI or G-nZVI was mainly due to chemical reaction between nZVI and phosphorus.     

Enhanced photocatalytic activities of silicon nanowires/graphene oxide nanocomposite: Effect of etching parameters

Homogeneous and vertically aligned silicon nanowires (SiNWs) were successfully fabricated using silver assisted chemical etching technique. The prepared samples were characterized using scanning electron microscopy, transmission electron microscopy and atomic force microscopy. Photocatalytic degradation properties of graphene oxide (GO) modified SiNWs have been investigated. We found that the SiNWs morphology depends on etching time and etchant composition. The SiNWs length could be tuned from 1 to 42 µm, respectively when varying the etching time from 5 to 30 min. The etchant concentration was found to accelerate the etching process; doubling the concentrations increases the length of the SiNWs by a factor of two for fixed etching time. Changes in bundle morphology were also studied as function of etching parameters. The SiNWs diameter was found to be independent of etching time or etchant composition while the size of the SiNWs bundle increases with increasing etching time and etchant concentration. The addition of GO was found to improve significantly the photocatalytic activity of SiNWs. A strong correlation between etching parameters and photocatalysis efficiency has been observed, mainly for SiNWs prepared at optimum etching time and etchant concentrations of 10 min and 4:1:8. A degradation of 92% was obtained which further improved to 96% by addition of hydrogen peroxide. Only degradation efficiency of 16% and 31% has been observed for bare Si and GO/bare Si samples respectively. The obtained results demonstrate that the developed SiNWs/GO composite exhibits excellent photocatalytic performance and could be used as potential platform for the degradation of organic pollutants.