Lightweight Polypropylene Composites Reinforced by Long Switchgrass Stems

Switchgrass (SG) stems with lengths up to 10 cm have been used as reinforcement to make lightweight composites with polypropylene (PP) webs. The long SG stems, with simple cut or split and without chemical treatment, were used directly in the composites. Utilizing SG stems for composites not only increases the values of SG but also provides a green, sustainable and biodegradable material for the composites industry. Lightweight composites are preferred, especially for automotive applications due to the potential saving in energy. In this research, the effects of manufacturing parameters on the properties of composites have been studied. Although the tensile properties of SG stem are significantly worse than jute fiber, SG stem with low bulk density is found to better reinforce the lightweight composites. Compared with the jute-PP composites of the same density (0.47 g/cm³), composites reinforced by the split SG stems have 56% higher flexural strength, 19% higher modulus of elasticity, 15% higher impact resistance, 63% higher Young’s modulus, 52% lower tensile strength, and similar sound absorption property. The SG-PP composites with optimized properties have the potential to be used for industrial applications such as the support layers in automotive interiors, office panels and ceiling tiles.     

Supercritical water oxidation of tannery sludge: Stabilization of chromium and destruction of organics

The supercritical water oxidation (SCWO) of industrial tannery sludge was investigated to understand the simultaneous destruction of organic pollutants and recovery of high content chromium. Experiments were performed in a batch reactor at temperatures of 350–500 °C, reaction time of 150–300 s and different oxygen ratios, to exhibit the effect of operation conditions. Results showed that removal efficiency of chemical oxygen demand (COD) increased with higher temperature, larger oxidant amount and reaction time; a maximum value of 96% was obtained. Meanwhile, destruction yield was much higher under supercritical conditions than that in subcritical water. In addition, removal efficiency of Cr from sludge reached more than 98% under all conditions; higher temperature played a positive role. Further, leaching toxicity tests of heavy metals in solid products were conducted based on toxicity characteristic leaching procedure. All heavy metals except nickel showed a greatly reduced leaching toxicity through their stabilization. The chromium oxide recovered in ash was amorphous below 550 °C, so that the structure of Cr could not be identified by X-ray diffraction pattern. Special attention should be paid on nickel as its leaching toxicity increased due to the corrosion of reactor surface under severe reaction conditions.     

Health risk assessment for consumption of fish originating from ponds near Dabaoshan mine, South China

Mining effluents are a potential source of toxic metals in the surrounding aquatic ecosystem and pose a potential health risk to humans from fish consumption. The objective of this paper is to assess the impact of the long-term Dabaoshan mining operation on heavy metal accumulation in different fish species. Heavy metal accumulation (lead (Pb), cadmium (Cd), zinc (Zn), and copper (Cu)) in four tissues (liver, muscle, intestine, and gills) of five carp species (Hypophthalmichthys molitrix, Ctenopharyngodon idellus, Megalobrama amblycephala, Aristichthys nobilis, and Carassius auratus auratus) from two fishponds exposed to effluent waters from Dabaoshan mine, South China. The bioaccumulation factor (BAF) and target hazard quotients were calculated to assess potential health risks to local residents through fish consumption. Levels of heavy metals varied depending on the analyzed tissues. C. auratus auratus accumulated the higher Pb, Cd, Zn, and Cu in the intestine compared with other fish species. Liver of all five species contained high concentrations of Pb, Cd, Zn, and Cu. The BAF for the studied metals showed a descending order of Cd?>?Zn?>?Cu?>?Pb for fishpond 1 and Zn?>?Cd?>?Cu?>?Pb for fishpond 2. Risk assessments suggested that potential human health risk may be present due to high Pb and Cd concentration in the muscle of some fish species exceeding the national and international limits, although the target hazard quotients were less than one.     

Coarsening of extracellularly biosynthesized cadmium crystal particles induced by thioacetamide in solution

A novel coarsening route for extracellularly biosynthesized cadmium nanocrystals was investigated for the first time. In this process, the white rot fungus Coriolus versicolor was employed to take up cadmium ions and synthesize extracellular cadmium crystal particles. The coarsening of the particles was induced by thioacetamide under certain conditions. Scanning electron microscopy showed that the formed cadmium crystal particles were coarsened from about 100 nm to 2-3 μm. The corresponding energy-dispersive X-ray spectra confirmed the presence of proteins in the particles. The maximum removal efficiency of Cd(II) increased from 17% to 87%, and the corresponding sorption capacity of biomass increased from 4 to 24 mg g⁻¹ with the completion of the coarsening process. The properties of the coarsened particles were also examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD analysis of fungal mycelial pellets embedded with the coarsened particles confirmed the formation of cubic crystalline cadmium sulfide particles. The TEM results suggest that the coarsened particles were composed of clusters of several smaller particles. The changes in the functional groups on the biomass surface were studied through Fourier transform infrared spectroscopy. Based on the results above, a possible mechanism for the formation and coarsening of cadmium crystal particle is also discussed.     

SCR反应器内各关键部件对系统压力损失特性影响的研究

选择性催化还原(selective catalytic reduction,SCR)脱硝反应器的关键部件对系统压力损失特性的影响非常明显.针对某电厂1×300 MW锅炉机组的SCR脱硝反应器,采用数值模拟和实验研究的方法研究了各关键部件对系统压力损失特性影响.通过研究确定了SCR反应器的最优设计方案,即关键部件1设计为...     

纳米二氧化钛的改性及光催化氧化烷烃研究

催化剂的表面结构是影响催化反应的重要因素之一.利用原位红外(In-situ FT-IR)、X射线衍射(XRD)和紫外-可见漫反射(UV-Vis DRS)等现代物理技术考察了热处理改性对纳米 TiO2的表面结构、晶相结构、粒子大小、比表面积和吸光性能的影响,采用In-situ FT-IR光谱着重研究了纳米TiO2催化剂上环己烷光催化降解机制及催化剂的结构特性与催化反应之间的相关性.研究表明,400 ℃条件下热处理纳米TiO2具有最佳光催化活性,适宜的表面结构、晶相结构、吸光能力及晶化度是纳米TiO2光催化剂高催化活性的主要原因.借助In-situ FT-IR光谱,观察到环己烷氧化的主要产物是CO2和H2O,同时捕捉到了中间产物CO以及乙酸,提出了环己烷光催化降解的可能机理.     

漓江流域红壤区生态恢复过程中植被结构动态和生物量变化

利用时空替代原理,选取漓江流域红壤区退化生态系统恢复过程中具有代表性的草丛、灌丛、针叶林、针阔混交林、常绿阔叶林5个阶段作为演替序列,研究自然恢复过程中各演替阶段的植被结构动态和生物量变化。结果表明：随着草丛→灌丛→针叶林→针阔混交林→次生常绿阔叶林正向演替的进行,在未形成成熟而稳定的顶极群落之前,物种丰富度、物种多样性指数、植被生物量及生产力都呈增大趋势。退化群落通过自然恢复总是向着结构更复杂、更完善的方向发展。根据恢复过程中植被的动态变化规律,提出了一些人工促进植被恢复的建议．     

用微波辐照消除磺基水杨酸污染物

介绍了利用微波辐照去除废水中磺基水杨酸污染物的技术。处理废水时,先用活性炭吸附污染物,然后,将滤出的活性炭用微波幅照,使其再生,即可有效地消除废水中有机物的污染。实验表明,对废水中磺基水杨酸的去除率可达 ９７ ４％。     

天然消化道粘膜保护剂思密达的成分及物相分析

分析研究了天然消化道粘膜保护剂思密达的化学成分、物相组成和矿物形态,查明其基本矿物成分为钙钠质蒙脱石,系由天然膨润土经过精细加工而成。本实验结果有助于合理开发利用我国丰富的膨润土及其它药用矿石