| Recently, BiOX(X=Cl, Br, I) as novel semiconductor nanomaterials, havedrawn great attention in the environmental remediation due to their uniqueproperties and superior photocatalytic performance. For a long time, thewastewater treatment was foucesed on the treatmen of priority pollutants, suchas, organic pollutants, pesticides, industrial chemicals, and heavy metals. Withthe advancement of technology, pharmaceuticals and personal care products(PPCPs), as emerging contaminants in aquatic environments, have been ofgrowing concerns recently. Carbamazepine (CBZ) has been proved recalcitrantand hard to remove. Research has shown that the removal efficiencies of CBZare mostly below10%by the wastewater treatment plants (WWTPs). Thecontinuous discharge into environment enhances the possibility of its adverseeffects on public health and aquatic ecology. Therefore, it is rather imperativefor us to explore an effective treatment technology to remove CBZ compound.Heterogeneous photocatalysis is proved to be one of the most promisingtechniques for degradation of CBZ compounds.On the other hand, the increase of research and application of BiOX willinevitably result in significant exposure to environment. Can the unintendedbiological exposures of BiOX pose risk on the environment and human health?However, the toxicological information of BiOX remains lacking. Therefore, itis rather imperative for us to carry out the research and exploration for the toxicity of BiOX. In vitro cellular screening provides a rapid and efficientmethod for toxicity studies and is very suitable to develop mechanistic modelsfor understanding the toxicity mechanisms and the relationship betweenphysicochemical properties and toxicity outcome. Therefore, it is very importantto study the interaction of BiOX and the resulting effects on the organism at thecellular level as well as building evaluation methods for the safety assessment ofBiOX. Based on the above consideration, the present dissertation studied thephotocatalytic degradation of CBZ. Furthermore, the biological aspects of BiOXwere also evaluated using HaCaT cells as a research model.The main contents of this dissertation are focused on the following fiveaspects:1. A rapid method was developed for the synthesis of hierarchical BiOClmicrospheres via a diethylene glycol (DEG) mediated solvothermal route in30min solvothermal time with the assistance of ultrasound. The physicochemicalproperties of the obtained samples were characterized and the results indicatedthat both DEG and ultrasound influenced the morphology, structure, and surfacecharacteristics of BiOCl catalyst, which further determined their specificphotocatalytic performances. The as-synthesized BiOCl exhibited highphotocatalytic efficiency towards the degradation of CBZ under simulated solarirradiation. CBZ was nearly completely eliminated after150min irradiation.The photocatalytic reaction followed pseudo first-order kinetics, and the reactionrate constant was over9.48times greater than that of the commercial TiO2(P25).The enhanced photocatalytic activities could be attributed to the hierarchicalnanostructure, exposed {110} facet, special loose-packed structure, and enrichedsurface hydroxyl group. Radicals and holes trapping experiments showed that h+, OH, and O-2were involved in the photocatalytic process. The obtained resultswill provide a new sight for the synthesis of hierarchical BiOCl and broaden itsapplication in the removal of the recalcitrant pharmaceutical contaminants. 2. This study systematically investigated the photocatalytic degradation ofCBZ by hierarchical BiOCl microspheres to identify the factors affecting thekinetics of the process and to elucidate its degradation pathway. The effects ofsome key parameters including initial BiOCl dosage, CBZ concentrations,solution pH, coexisting inorganic anions (Cl, NO3, and HCO3) and cations(Mg2+, Ca2+, and Al3+) on photodegradation efficiency were examined. It wasfound that CBZ degradation followed the pseudo-first-order kinetics model withfast kinetics. The optimal concentration of BiOCl was determined to be0.8g·L-1with a rate constant (k) of0.0408, which increased with the decrease in theinitial concentration of CBZ. Changing solution pH influenced the CBZdegradation significantly and the best performance was achieved at pH=4. Thepresence of anions had minor effects on the CBZ degradation. In contrast,coexisting cations clearly slowed down the degradation efficiency, and theinhibiting effect was following the order of Al3+>Ca2+≈Mg2+. Nine reactionintermediates were assigned by HPLC-ESI-Q-TOF-MSn, and a tentativedegradation pathway was proposed. With longer experimental durations, mostreaction intermediate products would disappear without the residue of toxicintermediates. Our results show that BiOCl photocatalytic process is a promisingtechnique for removal of CBZ pharmaceuticals from water.3. The potential application of nanostructured bismuth oxychloridenanosheets (BiOCl-NS) signifies their increasing environmental release andunintended biological exposures. However, how the emerging NS interfaceswith biological systems, particularly its interaction with human cells and theresulting cytotoxic effects are completely unknown. In this study, the in vitrocytotoxicity of BiOCl-NS was investigated toward a human skin derived cellline (HaCaT). It was found that BiOCl-NS had no cytotoxicity at relatively lowconcentrations (<0.5μg·mL-1). Whereas, the higher concentrations (5-100μg·mL-1) of BiOCl-NS could trigger toxic effects on HaCaT cells, with changes in cell morphology, impairment of mitochondria and cytoskeleton, induction ofcell apoptosis, and alterations in cell cycle distribution. Flow cytometric datashowed that BiOCl-NS were effectively uptaken by HaCaT cells. Transmissionelectron microscope (TEM) images provided evidence that the NS wasendocytosed into cells and sequestered in the lysosomes, mitochondria, nuclei,and vesicles. Results of DCFH-DA assay and ROS scavenger N-acetylcysteine(NAC) experiments suggested that an oxidative stress mechanism was involvedin the cytotoxic effects of BiOCl-NS. Taken together, this work represents thefirst study on the behavior of BiOCl-NS on human cells, and constitutes the firstand essential step for the risk assessment of BiOCl nanomaterials.4. Nano-sized bismuth oxybromide (BiOBr) particles are being consideredfor applications within the semiconductor industry. However, little is knownabout their potential impacts on human health. In this study, we comparativelyinvestigated the cytotoxicity of BiOBr and titanium dioxide (TiO2) nanoparticles(NPs) using human skin keratinocyte cell line (HaCaT) as the research model.Results indicated BiOBr appeared to have less toxic effects than TiO2NPs onviability and intracellular organelles impairment. Annexin-V/propidium iodide(PI) staining showed BiOBr induced late cell apoptosis, while for TiO2, bothearly apoptosis and late apoptosis were involved. Cell cycle arrest was observedfor both NPs exposure, and more prominent in TiO2-treated cells. More cellularuptake was achieved after TiO2exposure, particularly at10μg·mL-1, thepresence of TiO2resulted in more than2-fold increase in cellular granularitycompared with BiOBr. Furthermore, TiO2had a higher potential to generateintracellular reactive oxygen species (ROS), where a2.7-fold increase in TiO2group and2.0-fold increase in BiOBr group at the same concentration of25μg·mL-1, suggesting that ROS could be responsible for their cytotoxicity. Thehigher cellular uptake and ROS stimulation should contribute to the morehazards of TiO2than BiOBr NPs. This knowledge of their impacts on HaCaT cells is a crucial component in the environmental and human hazard assessmentof BiOBr and TiO2NPs.5. Three BiOCls (BiOCl-a, BiOCl-b, and BiOCl-c) with nanosheets ornanosheets assembled microspheres with/without surface hydroxide group wereemployed to evaluate their cytotoxicity toward human HaCaT cells. The resultsshowed that the morphology and surface hydroxyl of BiOCls had a profoundeffect on their toxicity. Scanning electron microscope (SEM) images displayeddifferent interactions between BiOCls and cell membrane. Nanosheet-shapedBiOCl caused membrane damage to a greater extent than themicrosphere-shaped BiOCl, while the presence of surface hydroxyl ofmicrosphere-shaped BiOCl made it become more toxic owing to the much highlevels of oxidative stress generation. Both high levels of membrane damage andoxidative stress lead to HaCaT cell death. Furthermore, a set of experimentsincluding mitochondrial membrane potential (MMP) collapse, cell cycle arrest,and apoptosis/necrosis were conducted to propose a scenario for thetoxicological aspects of BiOCls. The data presented here will help to enable therational design of BiOCls for either reducing their unintended consequences orincreasing their application potentials. |
PDF Full Text Request