In situ formation of bimetallic FeNi nanoparticles on sand through green technology: Application for tetracycline removal

• In situ preparation of FeNi nanoparticles on the sand via green synthesis approach. • Removal of tetracycline using GS-FeNi in batch and column study. • Both reductive degradation and sorption played crucial role the process. • Reusability of GS-FeNi showed about 77.39±4.3% removal on 4th cycle. • TC by-products after interaction showed less toxic as compared with TC. In this study, FeNi nanoparticles were green synthesized using Punica granatum (pomegranate) peel extract, and these nanoparticles were also formed in situ over quartz sand (GS-FeNi) for removal of tetracycline (TC). Under the optimized operating conditions, (GS-FeNi concentration: 1.5% w/v; concentration of TC: 20 mg/L; interaction period: 180 min), 99±0.2% TC removal was achieved in the batch reactor. The removal capacity was 181±1 mg/g. A detailed characterization of the sorbent and the solution before and after the interaction revealed that the removal mechanism(s) involved both the sorption and degradation of TC. The reusability of reactant was assessed for four cycles of operation, and 77±4% of TC removal was obtained in the cycle. To judge the environmental sustainability of the process, residual toxicity assay of the interacted TC solution was performed with indicator bacteria (Bacillus and Pseudomonas) and algae (Chlorella sp.), which confirmed a substantial decrease in the toxicity. The continuous column studies were undertaken in the packed bed reactors using GS-FeNi. Employing the optimized conditions, quite high removal efficiency (978±5 mg/g) was obtained in the columns. The application of GS-FeNi for antibiotic removal was further evaluated in lake water, tap water, and ground water spiked with TC, and the removal capacity achieved was found to be 781±5, 712±5, and 687±3 mg/g, respectively. This work can pave the way for treatment of antibiotics and other pollutants in the reactors using novel green composites prepared from fruit wastes.     

Biogenic palladium prepared by activated sludge microbes for the hexavalent chromium catalytic reduction: Impact of relative biomass

• Pd nanoparticles could be reduced and supported by activated sludge microbes. • The effect of biomass on Pd adsorption by microbes is greater than Pd reduction. • More biomass reduces Pd particle size, which is more dispersed on the cell surface. • When the biomass/Pd add to 6, the catalytic reduction rate of Cr(VI) reaches stable. Palladium, a kind of platinum group metal, owns catalytic capacity for a variety of hydrogenations. In this study, Pd nanoparticles (PdNPs) were generated through enzymatic recovery by microbes of activated sludge at various biomass/Pd, and further used for the Cr(VI) reduction. The results show that biomass had a strong adsorption capacity for Pd(II), which was 17.25 mg Pd/g sludge. The XRD and TEM-EDX results confirmed the existence of PdNPs associated with microbes (bio-Pd). The increase of biomass had little effect on the reduction rate of Pd(II), but it could cause decreasing particle size and shifting location of Pd(0) with the better dispersion degree on the cell surface. In the Cr(VI) reduction experiments, Cr(VI) was first adsorbed on bio-Pd with hydrogen and then reduced using active hydrogen as electron donor. Biomass improved the catalytic activity of PdNPs. When the biomass/Pd (w/w) ratio increased to six or higher, Cr(VI) reduction achieved maximum rate that 50 mg/L of Cr(VI) could be rapidly reduced in one minute.     

植物对纳米颗粒的吸收、转运及毒性效应

随着工程纳米颗粒的广泛使用,这些纳米材料不可避免地进入环境,对环境造成未知影响.植物是高等生物暴露于纳米颗粒的一条主要途径,工程纳米颗粒可能通过食物链使其在高营养水平生物中积累.植物与纳米颗粒间的相互作用应该受到关注和重视.已有的文献表明纳米颗粒能被植物选择性地吸收并引起植物毒性,但纳米颗粒进入植物体内的机制仍不明确.多数关于植物吸收纳米颗粒的研究是在理想条件如水培实验下开展,并且集中在植物的种子发芽或是幼苗生长阶段.描述纳米颗粒在植物体内的生物转化和在植物体内分配的报道较少,而且这方面的机制没有阐述清楚.目前有许多研究者关注纳米颗粒的植物毒性效应,但这方面的研究需要进一步深入.     

近红外长余辉纳米颗粒经小鼠眼部暴露后体内分布和代谢情况

为了研究纳米颗粒通过眼部暴露后进入体内的路径及在体内的分布和代谢情况,实验采用近红外长余辉纳米探针作为示踪剂,对小鼠进行眼部暴露,随后利用活体成像技术观察其进入小鼠体内的过程及分布情况,于暴露第4天收集代谢产物,第7天取重要脏器和血液,并检测纳米探针的存在情况.结果显示纳米探针可由眼经口腔进入胃肠道中,并且纳米颗粒暴露4天后在小鼠的粪便中检测到强荧光信号,而尿液中的荧光信号较弱,暴露7 d后在小鼠的眼睑结膜、胃及眼球中检测到强荧光信号,而其余器官的荧光信号较弱.这表明通过眼部暴露后,纳米颗粒主要分布在眼和消化系统中,最后大部分经消化系统代谢.     

土壤颗粒对纳米TiO_2悬浮稳定性作用机制的实验研究

在不含表面活性剂和含有表面活性剂两种条件下,研究了土壤颗粒对纳米TiO2(nTiO2)悬浮稳定性的影响.结果表明,土壤颗粒降低了nTiO2在水相中的悬浮稳定性.当体系中不含表面活性剂时,nTiO2在土壤大颗粒上的沉积是导致nTiO2脱稳沉淀的主要原因.在含有表面活性剂的溶液中,土壤颗粒降低nTiO2悬浮稳定性的作用变得更加明显了.一方面,表面活性剂加速了土壤颗粒本身的沉降从而增强了nTiO2在其中的沉降,另一方面,表面活性剂在土壤上的强烈吸附促进了表面活性剂-nTiO2在土壤上的沉积.扫描电镜显示,nTiO2不仅吸附在土壤大颗粒上,还会吸附在土壤小颗粒表面.3种表面活性剂中,十六烷基三甲基溴化铵(CTAB)悬浮的nTiO2与土壤颗粒共沉淀现象最明显.除了土壤对CTAB的吸附作用之外,XDLVO/DLVO能量计算显示CTAB体系中土壤颗粒与nTiO2之间存在显著第二极小值,表明nTiO2能够在第二极小值位置与土壤颗粒结合,从而与土壤颗粒一起快速沉淀.     

名山河流域黄壤无机纳米微粒对钙的吸附解吸特征

以名山河流域老冲积黄壤无机纳米微粒为对象,从纳米尺度分析钙的吸附解吸机制对土壤养分状况的影响,并采用等温吸附法和静态解吸法,比较不同土地利用方式下钙的吸附解吸特征差异.结果表明:1)不同土地利用方式土壤无机纳米微粒对钙的吸附解吸量均随钙质量浓度增加而增加,在低质量浓度范围内吸附量增加较快,在高质量浓度范围内增加趋缓,不同土地利用方式下钙的吸附能力从高到低为水田(2 580.69 mg/kg)、茶园(2 452.30 mg/kg)、旱地(1 935.10mg/ks)、林地(1 867.36mg/kg)、果园(1 520.65 mg/kg),土壤无机纳米微粒对钙的解吸率从大到小为果园、林地、旱地、茶园、水田,且解吸率随外加钙质量浓度增加而增大;2)去除土壤组分(有机质、游离氧化铁)后,无机纳米微粒对钙的吸附量及解吸量均有所增加,5种土地利用方式吸附增加量从大到小为水田、旱地、茶园、林地、果园;3)去除土壤组分前后,无机纳米微粒对钙的等温吸附均以Freundlich方程拟合效果最佳,相关系数在0.954 5～0.989 0,达到极显著水平,Langmuir方程与Temkin方程拟合效果不佳.研究表明,钙离子以非专性吸附为主,专性吸附为辅,有机质和游离氧化铁的存在会阻碍土壤对钙的吸附及解吸.     

Intracellular biosynthesis of Au and Ag nanoparticles using ethanolic extract of Brassica oleracea L. and studies on their physicochemical and biological properties

In this present study, we reported broccoli (Brassica oleracea L.) as a potential candidate for the synthesis of gold and silver nanoparticles (NPs) in green chemistry method. The synthesized metal nanoparticles are evaluated their antimicrobial efficacy against different human pathogenic organisms. The physico-chemical properties of gold nanoparticles were analyzed using different analytical techniques such as a UV–Vis spectrophotometer, Field Emission Scanning Electron Microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and a Fourier Transform Infrared spectrophotometer. In addition, gold and silver NP antimicrobial efficacy was checked by disc diffusion assay. UV–Vis color intensity of the nanoparticles was shown at 540 and 450 nm for gold and silver nanoparticles respectively. Higher magnification of the Field Emission Scanning Electron Microscopy image shows the variable morphology of the gold nanoparticles such as spherical, rod and triangular shapes and silver nanoparticles were seen in spherical shapes. The average spherical size of the particles was observed in 24–38 nm for gold and 30–45 nm for silver NPs. X-ray diffraction pattern confirmed the presence of gold nanoparticles and silver nanoparticles which were crystalline in nature. Additionally, the functional metabolites were identified by the Fourier Transform Infrared spectroscopy. IR spectra revealed phenols, alcohols, aldehydes (sugar moieties), vitamins and proteins are present in the broccoli extract which are accountable to synthesize the nanoparticles. The synthesized gold and silver NPs inhibited the growth of the tested bacterial and fungal pathogens at the concentration of 50 μg/mL respectively. In addition, broccoli mediated gold and silver nanoparticles have shown potent antimicrobial activity against human pathogens.     

Water chemistry controlled aggregation and photo-transformation of silver nanoparticles in environmental waters

The inevitable release of engineered silver nanoparticles (AgNPs) into aquatic environments has drawn great concerns about its environmental toxicity and safety. Although aggregation and transformation play crucial roles in the transport and toxicity of AgNPs, how the water chemistry of environmental waters influences the aggregation and transformation of engineered AgNPs is still not well understood. In this study, the aggregation of polyvinylpyrrolidone (PVP) coated AgNPs was investigated in eight typical environmental water samples (with different ionic strengths, hardness, and dissolved organic matter (DOM) concentrations) by using UV–visible spectroscopy and dynamic light scattering. Raman spectroscopy was applied to probe the interaction of DOM with the surface of AgNPs. Further, the photo-transformation and morphology changes of AgNPs in environmental waters were studied by UV–visible spectroscopy, inductively coupled plasma mass spectrometry, and transmission electron microscopy. The results suggested that both electrolytes (especially Ca^2 + and Mg^2 +) and DOM in the surface waters are key parameters for AgNP aggregation, and sunlight could accelerate the morphology change, aggregation, and further sedimentation of AgNPs. This water chemistry controlled aggregation and photo-transformation should have significant environmental impacts on the transport and toxicity of AgNPs in the aquatic environments.     

酸性土壤条件下纳米氧化锌长期暴露对蕹菜生长和叶绿素荧光参数的影响

为了探明酸性土壤条件下纳米氧化锌（nano-ZnO）长期暴露对蕹菜的生理生态效应，通过盆栽实验，设置7个浓度系列的nano-ZnO，70 d后测定相对叶绿素含量、生长参数和叶绿素荧光参数。结果显示，随nano-ZnO浓度升高，蕹菜相对叶绿素含量和生长参数先缓慢增加后显著下降。nano-ZnO对蕹菜生物量在根部和冠部间的分配无显著影响。相对叶绿素含量与nano-ZnO浓度呈显著负相关（r=-0.879,p<0.001）。在nano-ZnO质量比为160 mg/kg时，光合有效辐射190μmol/(m²·s)诱导的激发能过剩，但过剩激发能可通过热耗散保护机制消耗，以避免发生光损伤。酸性土壤条件下，弱光诱导的蕹菜叶绿素荧光参数对nano-ZnO长期暴露不敏感，但蕹菜的生物量累积易受nano-ZnO长期暴露的影响。     

Producing biodiesel from waste animal oil by modified ZnO

Biodiesel produced by transesterification of waste animal oil is a promising green fuel in the future. ZnO-Al₂O₃ and ZnO/Zn₂Al composition oxides were prepared by co-precipitation method and impregnation method, respectively. The above catalysts were characterized by X-ray diffraction (XRD), Brunauer--Emmett--Teller (BET) and CO₂ adsorption and temperature-programmed desorption (CO₂-TPD) and show that the high activity for the catalyst is attributed to its high alkalinity. The reaction parameters were optimized and the results show that the transesterification ratio of waste animal oil can reach 98.7% with 10% ZnO/Zn₂Al catalyst after 2 h. Moreover, 10%ZnO/Zn₂Al compound oxides can be active for the successive cycles. The glycerol as a predominant by-product after transesterification is of high purity with high use value.