Preparation and characterization of Pd/Fe bimetallic nanoparticles immobilized on Al2O3/PVDF membrane: Parameter optimization and dechlorination of dichloroacetic acid

Using a liquid–solid phase inversion method, a hybrid matrix poly(vinylidene fluoride)(PVDF) membrane was prepared with alumina(Al2O3) nanoparticle addition. Pd/Fe nanoparticles(NPs) were successfully immobilized on the Al2O3/PVDF membrane, which was characterized by Scanning Electron Microscopy(SEM) and Transmission Electron Microscopy(TEM). The micrographs showed that the Pd/Fe NPs were dispersed homogeneously. Several important experimental parameters were optimized, including the mechanical properties, contact angle and surface area of Al2O3/PVDF composite membranes with different Al2O3 contents. At the same time, the ferrous ion concentration and the effect of hydrophilization were studied. The results showed that the modified Al2O3/PVDF membrane functioned well as a support. The Al2O3/PVDF membrane with immobilized Pd/Fe NPs exhibited high efficiency in terms of dichloroacetic acid(DCAA) dechlorination. Additionally, a reaction pathway for DCAA dechlorination by Pd/Fe NPs immobilized on the Al2O3/PVDF membrane system was proposed.     

Co-adsorption of gaseous benzene, toluene, ethylbenzene, m-xylene (BTEX) and SO2 on recyclable Fe3O4 nanoparticles at 0-101% relative humidities

We herein used Fe3O4 nanoparticles(NPs) as an adsorption interface for the concurrent removal of gaseous benzene, toluene, ethylbenzene and m-xylene(BTEX) and sulfur dioxide(SO2), at different relative humidities(RH). X-ray diffraction, Brunauer–Emmett–Teller, and transmission electron microscopy were deployed for nanoparticle surface characterization.Mono-dispersed Fe3O4(Fe2O3·Fe O) NPs synthesized with oleic acid(OA) as surfactant, and uncoated poly-dispersed Fe3O4 NPs demonstrated comparable removal efficiencies.Adsorption experiments of BTEX on NPs were measured using gas chromatography equipped with flame ionization detection, which indicated high removal efficiencies(up to(95 ± 2)%) under dry conditions. The humidity effect and competitive adsorption were investigated using toluene as a model compound. It was observed that the removal efficiencies decreased as a function of the increase in RH, yet, under our experimental conditions, we observed(40 ± 4)% toluene removal at supersaturation for Fe3O4 NPs, and toluene removal of(83 ± 4)% to(59 ± 6)%, for OA-Fe3O4 NPs. In the presence of SO2, the toluene uptake was reduced under dry conditions to(89 ± 2)% and(75 ± 1)% for the uncoated and coated NPs, respectively, depicting competitive adsorption. At RH 100%,competitive adsorption reduced the removal efficiency to(27 ± 1)% for uncoated NPs whereas OA-Fe3O4 NPs exhibited moderate efficiency loss of(55 ± 2)% at supersaturation.Results point to heterogeneous water coverage on the NP surface. The magnetic property of magnetite facilitated the recovery of both types of NPs, without the loss in efficiency when recycled and reused.     

小麦和水稻对纳米硒的吸收和转运

通过水培试验,研究了不同粒径纳米硒(Se NPs)和不同p H条件对小麦(Triticum aestivum L.)及水稻(Oryza sativa L.)吸收、转运硒的影响.结果表明,小麦和水稻对不同粒径(50、100和150 nm) Se NPs的吸收规律不同. 24 h和72 h处理下,小麦根系对3种粒径Se NPs的吸收无显著差异,但其地上部中的硒含量(以干重计,下同)在50 nm Se NPs处理下达到最高,分别为(1. 89±0. 47)μg·g-1和(5. 18±1. 51)μg·g-1.硒在小麦体内的转运系数也在50 nm Se NPs处理24 h时显著高于其他粒径Se NPs处理2. 38倍(P 0. 05).对于水稻而言,50 nm Se NPs处理24 h时根系中的硒含量分别比100 nm和150 nm Se NPs处理增加了11. 18%和41. 81%,但在72 h时3种粒径Se NPs处理间根系对硒的吸收无显著差异.同时,硒在水稻中的地上部含量和转运系数也在50 nm Se NPs处理达到了最大值.另外,p H条件也会影响植物对硒的吸收和转运. Se NPs处理24h时,小麦根系在p H为6时对硒的吸收量最大,并高于亚硒酸盐处理89. 47%,但在p H为4时小麦对硒的转运能力最强.水稻在p H较低时(p H为3. 5和5. 5),对Se NPs的吸收量显著低于亚硒酸盐,且Se NPs在p H为3. 5时更易转运.以上结果表明水稻和小麦均可以吸收Se NPs,并且在p H较低的环境下Se NPs粒径越小越容易在植物体内转运.     

纳米氧化锌粒径对人工湿地性能及微生物群落的影响

纳米颗粒(nanoparticles,NPs)具有较小的粒径(1～100 nm),其生物毒性与粒径的大小紧密相关.在进水COD约200. 0 mg·L~(-1),NH_4~+-N约12. 5 mg·L~(-1)和溶解性总磷约4. 0 mg·L~(-1)的条件下连续运行28 d,研究了3种不同粒径的纳米氧化锌(ZnO NPs)对水平潜流人工湿地微生物群落结构和多样性的影响,同时结合湿地脱氮性能的变化,探讨了湿地中微生物群落结构和多样性与其处理性能的相互关系.结果表明,3种粒径(15、50和90 nm)的ZnO NPs(10 mg·L~(-1))对COD的去除无明显差异,而对脱氮则表现出明显的粒径效应.高通量测序发现,人工湿地系统中硝化菌属的丰度明显低于反硝化菌属,硝化过程是制约湿地脱氮性能的关键因素.暴露于不同粒径的ZnO NPs后,微生物群落结构发生不同程度的变化,与较大粒径(50 nm和90 nm)的ZnO NPs相比,15 nm的ZnO NPs对硝化菌属的抑制更为显著.     

Size and shape effects of MnFe2O4 nanoparticles as catalysts for reductive degradation of dye pollutants

• Size and shape-dependent MnFe₂O₄ NPs were prepared via a facile method. • Ligand-exchange chemistry was used to prepare the hydrophilic MnFe₂O₄ NPs. • The catalytic properties of MnFe₂O₄ NPs toward dye degradation were fully studied. • The catalytic activities of MnFe₂O₄ NPs followed Michaelis–Menten behavior. • All the MnFe₂O₄ NPs exhibit selective degradation to different dyes. The magnetic nanoparticles that are easy to recycle have tremendous potential as a suitable catalyst for environmental toxic dye pollutant degradation. Rationally engineering shapes and tailoring the size of nanocatalysts are regarded as an effective manner for enhancing performances. Herein, we successfully synthesized three kinds of MnFe₂O₄ NPs with distinctive sizes and shapes as catalysts for reductive degradation of methylene blue, rhodamine 6G, rhodamine B, and methylene orange. It was found that the catalytic activities were dependent on the size and shape of the MnFe₂O₄ NPs and highly related to the surface-to-volume ratio and atom arrangements. Besides, all these nanocatalysts exhibit selectivity to different organic dyes, which is beneficial for their practical application in dye pollutant treatment. Furthermore, the MnFe₂O₄ NPs could be readily recovered by a magnet and reused more than ten times without appreciable loss of activity. The size and shape effects of MnFe₂O₄ nanoparticles demonstrated in this work not only accelerate further understanding the nature of nanocatalysts but also contribute to the precise design of nanoparticles catalyst for pollutant degradation.     

纳米银的植物毒性研究进展

纳米银因其具备良好的催化、超导性能及杀菌消毒活性,广泛应用于食品加工业及医药等领域,是目前市场上最为常见的金属纳米材料。纳米银的大量生产和应用大大增加了其向环境释放的机会,同时也增加了其对环境及人类健康的潜在风险。植物是生态系统中重要组成部分,纳米银可通过植物积累进入食物链,因此对纳米银的植物毒理学研究尤为重要。纳米银的植物毒性与其被植物体吸收、迁移及转化有关。它可影响植物种子的萌发、苗期的生理生化过程和细胞结构等营养生长,也影响植物的开花、结实等生殖过程,并影响DNA的稳定性。但目前纳米银的毒性是否由银离子引起尚未确定。     

pH、离子强度及电解质种类对纳米氧化锌聚集和溶解的影响

本文初步探讨了不同pH、离子强度及电解质种类对纳米氧化锌(ZnO NPs)稳定性(聚集沉降和溶解)的影响.沉降实验表明,pH越靠近零电荷点(~pH9.2),ZnO NPs聚集体尺寸越大,沉降速度越快,稳定性越低;中性pH条件下,随着离子强度的增加,ZnO NPs ζ电位绝对值减小,聚集体尺寸相应变大,沉降速度加快,稳定性降低.中性pH时ZnO NPs ζ电位为正值,阴离子较阳离子更易使ZnO NPs聚集沉降,且SO2-4的影响远大于Cl-.溶解实验显示,pH2—11,Zn2+都会释放到溶液中,pH>7.5,ZnO NPs溶解量<5%;pH<6,超过60%的Zn2+释放到溶液中.中性条件下,离子强度越高,ZnONPs越易溶解,且Ca2+对纳米氧化锌溶解的促进作用强于Na+.这表明离子对纳米氧化锌溶解的促进可能源于阳离子与颗粒表面的离子交换机制.     

Influence of phosphate on deposition and detachment of TiO2 nanoparticles in soil

We examined influence of phosphate on transport of TiO₂ NPs in soil. Deposition was reduced at higher pH and by adsorption of phosphate in soil. Release was more for NPs initially deposited at higher pH. Release was more for NPs initially deposited in the presence of phosphate. Surface roughness and charge heterogeneity play a role in the deposition/ release. The widespread use of TiO₂ nanoparticles (NPs) makes inevitable their release into the soil. Phosphate is also widespread within soil, and is likely copresent with TiO₂ NPs. However, the influence of phosphate on deposition/release— and thereby on transport— of TiO₂ NPs in soil is yet to be elucidated. In this study we conducted saturated column experiments to systematically examine the transport of TiO₂ NPs in soil amended with phosphate at different ionic strengths (ISs) (1, 10, 100 mmol/L NaCl) and pHs (4 and 9). Results show that the deposition of TiO₂ NPs decreased with decreasing IS, increasing pH, and when soil absorbed phosphate. These observations are qualitatively in agreement with Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy calculations, because the repulsive energy barrier is larger and secondary minimum depth is smaller at a lower IS, higher pH, and in the presence of phosphate. Accordingly, both primary- and secondary-minimum deposition were inhibited. Interestingly, although the deposition was less at higher pH and in the presence of phosphate, the subsequent spontaneous detachment and detachment by reduction of solution IS in these cases were greater. In addition, the presence of phosphate in the solution can cause a small quantity of attached TiO₂ NPs to detach, even without perturbations of physical and chemical conditions. Our study was the first to investigate the influence of phosphate on detachment of TiO₂ NPs and the results have important implication for accurate prediction of fate and transport of TiO₂ NPs in subsurface environments.     

磁性纳米颗粒对不同模式生物的毒性研究

磁性纳米颗粒在生物医学等领域应用广泛,而其毒性研究尚未深入,对生物的影响及作用机制仍未阐明。本文综述了磁性纳米颗粒近年来对于细胞、鼠、家兔和秀丽隐杆线虫的毒理学研究,为磁性纳米颗粒的应用提供参考。     

量子点对Cu2+诱导L02细胞毒性的影响及机理研究

量子点(QDs)和Cu~(2+)可能共存于肝脏,对肝细胞产生联合毒性,威胁人体健康。本研究以人胚肝细胞(L02)为研究对象,考察了低/无毒的QDs(3.6%的细胞致死率)对Cu~(2+)诱导L02细胞毒性的影响及相关机理,为其可能的健康和环境风险提供参考。结果显示,QDs的加入使得Cu~(2+)的细胞毒性有了很大的提高,细胞存活率最高下降了26.0%,两者表现为协同作用;另外QDs存在使得Cu~(2+)细胞蓄积量增大,伴随着Cu~(2+)天然解毒蛋白CTR1和ATP7A等表达水平的升高,从侧面印证了Cu~(2+)的蓄积量增加对细胞的影响;同时,QDs的存在使得细胞乳酸脱氢酶(lactate dehyfrogenase,LDH)泄露相对于Cu~(2+)单独处理组提高,暗示QDs可能破坏了细胞膜,导致Cu~(2+)在细胞内蓄积量增加,从而使细胞毒性增加,两者的联合毒性表现为协同作用。