Influence of agrochemicals on greenhouse cladding materials

A test chamber for investigation of the influence of agrochemicals (sulfur vapor) on the condensation and mechanical properties of greenhouse cladding materials was designed and constructed. The roof of the test chamber was covered by three types of polyethylene films. The exterior surfaces of the films were exposed to sun while the interior surfaces were exposed to sulfur vapor as used in rose greenhouses. At four dates, 3, 6, 9 and 12 weeks from the start of experiments, samples of the three types plastic film were tested for their mechanical (elongation at break) and anti-drop properties. It was observed that after 3 weeks of sulfur evaporation the anti-drop plastic film had lost it anti-drop properties. It was found that, after twelve weeks of sulfur evaporation the elongation at break of plastic films, were reduced to about 35% of their original value.     

Biodegradation of Starch-Based Materials

Abstract

The aim of this study was to compare three different test methods for assaying the biodegradability of starch-based materials. The materials tested included some commercial starch-based materials and thermoplastic starch film prepared by extrusion from native potato starch and glycerol. Enzymatic hydrolysis was performed using excess Bacillus licheniformis α-amylase and Aspergillus niger glucoamylase at 37°C. The degree of degradation was assayed by measuring the dissolved carbohydrates and the weight loss of the samples. The head-space test was based on carbon dioxide evolution using sewage sludge as an inoculum. The composting experiments were carried out in an insulated commercial composter bin. The degradation was evaluated visually at weekly intervals, and the weight loss of the samples was measured after composting. Good correlation was found among the three different test methods.     

Some composting and biodegradation effects of physically or chemically crosslinked poly(lactic acid)

Polylactide (PLA) crosslinked by using both triallyl isocyanurate (TAIC) and electron radiation or using dicumyl peroxide (DCP) was studied with the aim of examining the behaviour of the modified polymer under various environmental conditions. Thus, the polymer samples were subjected to composting in an industrial pile, exposed to proteinase K, or incubated in sea water. The number-average molecular weight (M_n), melt flow index (MFI), crystallinity (χ), tensile strength (σ_M) and mass loss (in the case of samples treated with proteinase K) were determined. It was found that neat PLA irradiated with high-energy electrons underwent degradation that increased during composting. As a result, the value of M_n of this polymer dramatically decreased. It appeared that PLA crosslinked with TAIC and electron radiation contained, in addition to the crosslinked phase, a phase strongly degraded by this radiation, which facilitated hydrolytic degradation during composting. The σ_M value of PLA crosslinked with TAIC and electron radiation rapidly decreased during composting, whereas that of PLA crosslinked chemically and composted for three weeks slightly increased. As the electron radiation dose increased, the mass loss of PLA containing TAIC and treated with proteinase K decreased, which indicated that the physical crosslinking of PLA hindered enzymatic degradation of this polymer. Important changes in both neat and physically crosslinked PLA incubated in sea water for nine weeks were not detected.     

Atmospheric and soil degradation of aliphatic-aromatic polyester films

The degradation of an aliphatic-aromatic biodegradable polyester film was studied under conditions of solar exposure and soil burial in a tropical area. Film samples were evaluated for changes over 40 weeks by visual examination, scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical properties, molecular weight, gel content, and thermal properties. Photodegradation played a major role in the atmospheric degradation of the film, causing it to lose integrity and mechanical properties after week 8 due to main chain scission and crosslinking. SEM micrographs and FTIR spectra indicated that photodegradation started at the exposed side of the film and propagated through the polymer matrix after week 8. FTIR spectra also indicated that subsequent photooxidation processes took place. The reduction of molecular weight of the soil burial samples was much slower than that of the non-crosslinked portion of solar exposed film samples. The reduction of number average molecular weight of the non-crosslinked solar exposed samples followed a first order reaction, whereas the soil burial samples show a surface erosion biodegradation behavior. The relationship among total solar radiation, gel content and number average molecular weight indicated that an accumulated total solar radiation of 800 MJ/m², reached in approximately 7 weeks at the exposure site, is required for PBAT mulch film integrity loss.     

冠醚修饰的C60衍生物膜的电化学性质

采用同步循环伏安(CV)和电化学石英晶体微天平(EQCM)方法研究了冠醚(二苯并-18-冠-6)修饰的C60衍生物(DBCFP)固态膜在不同电解质的乙腈溶液中的电化学性质. 选择了连有刚性基团的C60衍生物PSF与DBCFP进行对比,提出了DBCFP膜在TBA+溶液中的反应机理.     

Ultrathin conjugated polymer network films of carbazole functionalized poly(p-phenylenes) via electropolymerization

Ultrathin films of a cross-linked and chemically distinct conjugated poly(p-phenylene) network via electropolymerization are described. The amphiphilic network precursor was synthesized by incorporating the alkoxy carbazole group (-O(CH2)5Cb) to a poly(p-phenylene) (C6PPPOH) backbone. In order to investigate the combined thin film electrochemical and photophysical properties of poly(p-phenylene)s and polycarbazole conjugated polymers, C6PPPC5Cb was deposited on substrates using the Langmuir Blodgett Kuhn (LBK) method. The monolayer isotherm of the polymer, C6PPPC5Cb, showed a liquid expanded region slightly different from the parent polymer C6PPPOH. Multilayers (up to 30 layers) were transferred to different substrates such as quartz, gold coated LaSFN9 and ITO substrates for analysis. For conversion to a conjugated polymer network (CPN) film, the electroactive carbazole group was electropolymerized using cyclic voltammetry (CV) resulting in polycarbazole linking units. The differences in the film properties and corresponding changes in the electrochemical behavior indicate the importance of film thickness and electron/ion transport process in cross linked network films. From the electrochemical studies, the scan rate was found to have a considerable effect on electropolymerization with higher oxidation and reduction peak values found for the rigid network polymer compared to the uncrosslinked polymers.     

Contribution of redox-active properties of compost-derived humic substances in hematite bioreduction

The compost-derived humic substances(HS) can function as electron mediators for promoting hematite bioreduction because of its redox capacity. Humification process can affect redox capacities of compostderived HS by changing its intrinsic structure. However, the redox properties of compost-derived HS linking with hematite bioreduction during composting still remain unclear. Herein, we investigated the redox capacities of compost-derived HS, and assessed the responses of the redox capacities to t...     

Barrier and semiconducting properties of thin anodic films on chromium in an acid solution

The study of barrier and semiconducting properties of anodically formed oxide films on chromium in an acid solution was carried out using the Cr-quartz crystal electrode. The oxide film formation and growth occur through an anion vacancies transport via a low-field-assisted mechanism (H = 10⁶ V cm⁻¹). The anion diffusion coefficient, which quantitatively describes the transport of point defects within the growing film, was calculated from capacitance data using the Nernst-Planck equation for low-field limit approximation and Mott-Schottky analysis. The depletion region in the passive film, close to the film|electrolyte interface, dominates the semiconducting properties. The passive film on Cr in an acid solution behaves as an n-type semiconductor. An energy-band structure model of the passive film is given.     

钛表面二氧化钛膜中氧空位点缺陷传输性能的电化学研究

"钛/TiO2氧化膜/溶液"界面电极体系的电化学性能主要决定于钛表面的TiO2氧化物膜.本文利用多种电化学技术,结合半导体物理的Mott-Schottky分析和Einstein方程,研究了金属钛在1.0mol·L-1HClO4溶液中表面半导体TiO2氧化膜的生长及氧化膜中氧空位点缺陷在外加电场作用下的传输性能,并根据离子性电荷传输与电子性电荷传输对电场变化响应时间之不同特点,确定氧化膜中点缺陷扩散系数.结果表明,电极电位或阳极析氧反应对稳态电流(iss)、氧化膜的阳极化常数(α)、膜中电场强度()、以及膜中氧空位点缺陷的扩散系数(D0)等重要物理化学参数,均有显著影响,并依据氧化膜中的结构变化进行分析.     

Dissipation Dynamics of Doxycycline and Gatifloxacin and Accumulation of Heavy Metals during Broiler Manure Aerobic Composting

In this study, broilers were fed with heavy-metal-containing diets (Zn, Cu, Pb, Cr, As, Hg) at three rates (T1: 5 kg premix/ton feed, T2: 10 kg premix/ton feed and T3: 15 kg premix/ton feed) and Doxycycline (DOX) and Gatifloxacin (GAT) at low or high doses (T4: 31.2 mg DOX/bird/day and 78 mg GAT/bird/day, T5: 15.6 mg DOX/bird/day and 48 mg GAT/bird/day) to assess the accumulation of various heavy metals and the fate of two antibiotics in broiler manure after 35 days of aerobic composting. The results indicated that the two antibiotics changed quite differently during aerobic composting. About 14.96–15.84% of Doxycycline still remained at the end of composting, while Gatifloxacin was almost completely removed within 10 days of composting. The half-lives of Doxycycline were 13.75 and 15.86 days, while the half-lives of Gatifloxacin were only 1.32 and 1.38 days. Based on the Redundancy analysis (RDA), the concentration of antibiotics was significantly influenced by physico-chemical properties (mainly temperature and pH) throughout the composting process. Throughout the composting process, all heavy metal elements remained concentrated in organic fertilizer. In this study the Cr content reached 160.16 mg/kg, 223.98 mg/kg and 248.02 mg/kg with increasing premix feed rates, similar to Zn, which reached 258.2 mg/kg, 312.21 mg/kg and 333.68 mg/kg. Zn and Cr concentrations well exceeded the United States and the European soil requirements. This experiment showed that antibiotic residues and the accumulation of heavy metals may lead to soil contamination and pose a risk to the soil ecosystem.     

Excellent anti‐bacterial activity and surface properties of polyamide‐6 films modified with argon‐plasma and methyl diallyl ammonium salt‐graft

In this study, the effect of argon‐plasma treatment on the grafting of methyl diallyl ammonium salt (MDAA) onto polyamide‐6 film and the anti‐bacterial and surface properties of the plasma‐ and graft‐treated film were investigated. The grafting amounts of MDAA caused by argon‐plasma treatment increased with the increase in the plasma exposure time and plasma power. The analyses of Fourier transform infrared (FT‐IR) spectroscopy and electron spectroscopy for chemical analysis (ESCA) spectra revealed that the epoxy and vinyl groups of MDAA could be grafted on the argon‐plasma treated polyamide‐6 film. The survey spectra of ESCA, the patterns of atomic force microscopy (AFM), and the spectra from scanning electron microscopy (SEM) were employed to certify the surface modification of argon‐plasma treated and the argon‐plasma treated/MDAA grafted polyamide‐6 films. Argon‐plasma treatment could generate the functional group and increase the roughness on the surface of polyamide‐6 film. This phenomenon could enhance the grafting effect of MDAA. The anti‐bacterial property of argon‐plasma treated/MDAA grafted polyamide‐6 film was excellent. This argon‐plasma treated/MDAA grafted polyamide‐6 film was expected to be applied on the field of packing. Copyright © 2008 John Wiley & Sons, Ltd.     

Degradability of biodegradable plastic under controlled composting conditions

Biodegradability of poly(ß-propiolactone) (PPL), one of biodegradable plastics, was tested in a bench-scale composting reactor under controlled conditions, with uniform temperature, moisture content, and aerobiosis maintained. The composting raw mixture was prepared by mixing commercial dog food instead of real organic waste, saw dust as a bulking agent, commercial inoculum sold for acceleration of composting, and PPL in the ratio of 10:9:1:10 on dry weight basis. The degree and rate of PPL degradation were determined by comparing the difference in the CO₂ evolution for composting with and without addition of PPL. The influence of temperature on the degradability of PPL was investigated at 40, 50, and 60 °C and the optimum temperature was found to be around 40-50°C where ca. 40 wt.-% of PPL was decomposed in 8 days. The effect of inoculum on the degradability of PPL during 50 °C composting was then examined, a considerable difference (100%) being observed in the biodegradability using two different inocula.     

堆肥过程不同分子量水溶性有机物电子转移能力的演变及影响因素

利用超滤技术、电化学方法和光谱技术, 以堆肥水溶性有机物的不同分子量(MW)组分为研究对象, 分析在堆肥过程中不同分子量水溶性有机物(DOM)的组成特征、结构演变和电子转移能力变化的影响因素.结果表明, 类蛋白物质主要存在于堆肥前期的DOM(MW<1 kDa)中, 随着堆肥的进行, 类蛋白物质不断降解, 类富里酸物质持续合成, 堆肥后期类蛋白物质被完全降解, 类富里酸物质成为DOM(MW<1 kDa)主要的荧光组分.类腐殖物质是DOM(MW=1～3 kDa)、DOM(MW=3～5 kDa)和DOM(MW>5 kDa)的主要荧光组分, 堆肥过程中类腐殖质物质在3种不同分子量组分的变化各不相同, 但是堆肥后期类腐殖质物质在3个不同分子量组分的含量均高于堆肥初期. 堆肥过程中DOM(MW<1 kDa)的电子供给能力(EDC)呈降低趋势, 而电子接受能力(EAC)呈升高趋势; DOM(MW>5 kDa)的EDC在堆肥过程中呈上升趋势, 而EAC则无明显的变化规律.DOM(MW=1～3 kDa)和DOM(MW=3～5 kDa)的EDC和EAC在整个堆肥过程无明显变化规律.不同分子量组分堆肥DOM 的EAC受控于堆肥过程木质素降解产物的含量, 而其EDC变化与荧光参数和紫外参数无明显关系.     

纳米钯膜电极的制备、结构表征和特殊反应性能

用循环伏安方法制备纳米钯膜电极,运用扫描隧道显微镜和原位红外光谱等方法研究其结构和反应性能.STM图像表明,制备的纳米钯膜具有特殊的层状结构,纳米级厚度的层状晶体由直径6nm左右的Pd微晶聚集而成.发现当钯膜厚度为几个纳米时,CO的吸附表现出异常红外效应,即红外谱峰反向和红外吸收显著增强(增强因子可达42.6).纳米钯膜电极对氢的反应也具有特殊的性能,与氢向钯晶格扩散吸收过程相比较,氢吸脱附的表面过程成为主要反应.研究结果还指出,纳米钯膜电极的异常红外效应和对氢反应的特殊性能与钯膜厚度密切关联,并可归结为钯膜材料的纳米尺度效应.     

Redox Properties of Ferricyanide Ion on Layer‐by‐Layer Thin Film‐Coated Gold Electrodes; Effects of Type of Polycationic Components in the Film

The surface of a gold (Au) electrode was coated with layer‐by‐layer (LbL) thin films composed of poly(vinyl sulfate) (PVS) and different type of poly(amine)s including poly(allylamine) (PAH), poly(ethyleneimine) (PEI) and poly(diallyldimethylammonium chloride) (PDDA) and redox properties of ferricyanide ion ([Fe(CN)₆]^3?) on the LbL film‐coated Au electrodes were studied. The LbL film‐coated electrodes exhibited redox response to [Fe(CN)₆]^3? ion when the outermost surface of the LbL film was covered with the cationic poly(amine)s while virtually no response was observed on the LbL film‐coated electrodes whose outermost surface was covered with PVS due to an electrostatic repulsion between [Fe(CN)₆]^3? ion and the negatively‐charged PVS layer. The redox properties of [Fe(CN)₆]^3? ion on the LbL film‐coated electrodes significantly depended on the type of polycationic materials in the LbL film. The LbL film‐coated electrodes which had been immersed in the [Fe(CN)₆]^3? solution for 15 min exhibited redox response even in a [Fe(CN)₆]^3? ion‐free buffer solution, suggesting that [Fe(CN)₆]^3? ion is confined in the films. In the buffer solution, redox peaks were observed between +0.1 and 0.4 V depending on the type of polycations in the film. Thus, [Fe(CN)₆]^3? ion can be confined in the film and the redox potential is polycation‐dependent.     

DNA functionalized single-walled carbon nanotubes for electrochemical detection

Single-walled carbon nanotubes (SWNTs) were effectively dispersed and functionalized by wrapping with single-stranded DNA (ssDNA). The ssDNA-SWNTs attach strongly on glass substrate and easily form a uniform film, making it possible for electrochemical analysis and sensing. The film was fabricated into a working electrode, which exhibited good electrochemical voltammetric properties, such as flat and wide potential window, well-defined quasi-reversible voltammetric responses, and quick electron transfer for a Fe(CN)6(3-)/Fe(CN)6(4) system, indicating that the ssDNA-SWNTs film should be a good analytical electrode for electrochemical detection or sensing. This was demonstrated by highly selective and sensitive detection of a low concentration of dopamine in the presence of excess ascorbic acid.     

Influence of copper hexacyanoferrate film thickness on the electrochemical properties of self-assembled 3-mercaptopropyl gold electrode and application as a hydrazine sensor

A copper hexacyanoferrate film was obtained on a modified electrode prepared by self-assembly of 3-mercaptopropyltrimethoxysilane on a gold surface. The film thickness was controlled using a layer-by-layer technique to tune the electrocatalytic properties of the electrode. Two electrodes with different hexacyanoferrate film thicknesses were prepared via three immersions (AuS/CuHCF3) and six immersions (AuS/CuHCF6) of the film in the precursor solutions. Cyclic voltammetry data were obtained to determine the adequate film thickness. Scanning electron microscopy images showed a roughness increase due to the growth of the film thickness at the electrode surface. Electrochemical impedance spectroscopy showed distinct behavior for the two electrodes prepared; while diffusion and charge transfer processes can be observed in both electrodes, an additional capacitive process at intermediary frequencies was observed for the AuS/CuHCF6 electrode. The charge transfer resistance (R _ct) for the AuS/CuHCF3 electrode (19.6 Ω cm²) was lower than for AuS/CuHCF6 (27.9 Ω cm²) due to the hexacyanoferrate film thickness, since the charge transfer process demands the simultaneous diffusion of K⁺ into the surface. Cyclic voltammetry was used to evaluate the application of the AuS/CuHCF3 electrode as an electrochemical sensor, revealing a linear correlation for hydrazine concentrations.     

Biodegradability of polylactide bottles in real and simulated composting conditions

As new biodegradable polymers and their packaging applications are emerging, there is a need to address their environmental performance. In particular, there is a need to understand the time required for their complete disintegration, before these materials are deployed in commercial composting processes. Standards developed by ASTM and ISO evaluate the biodegradation of biodegradable plastic materials in simulated controlled composting conditions. However, a more detailed understanding of the biodegradation of complete packages is needed in order to have a successful composting operation. This paper investigates the biodegradation performance of polylactide (PLA) bottles under simulated composting conditions according to ASTM and ISO standards, and these results are compared with a novel method of evaluating package biodegradation in real composting conditions. Two simulated composting methods were used in this study to assess biodegradability of PLA bottles: (a) a cumulative measurement respirometric (CMR) system and (b) a gravimetric measurement respirometric (GMR) system. Both CMR and GMR systems showed similar trends of biodegradation for PLA bottles and at the end of the 58th day the mineralization was 84.2±0.9% and 77.8±10.4%, respectively. PLA bottle biodegradation in real composting conditions was correlated to their breakdown and variation in molecular weight. Molecular weight of 4100 Da was obtained for PLA bottles in real composting conditions on the 30th day. The biodegradation observed for PLA bottles in both conditions explored in this study matches well with theoretical degradation and biodegradation mechanisms; however, biodegradation variability exists in both conditions and is discussed in this paper.     

Evaluation of the aerobic composting process of winery and distillery residues by thermal methods

The possibility of using thermal analysis for a quick characterization of chemical changes was tested in the organic matter from composting materials. Differential thermal analysis (DTA), thermogravimetry (TG) and the first derivative of the TG (DTG) were calculated in oxidizing conditions on compost samples obtained from three composting piles. The composting piles were made by mixing winery and distillery residues with sewage sludge (pile 1), with cow manure (pile 2) and hen droppings (pile 3). The temperature values in the pile 1 showed a different evolution during the thermophilic stage of the composting process in relation to the piles 2 and 3. The thermophilic stage for pile 1 was 17 days, meanwhile for the piles 2 and 3 were around 80 and 110 days, respectively, and probably pile 1 was not well composted. The curves of ion current of CO₂ have been recorded in order to shed light on changes occurring in organic matter during composting. Particularly DTG curves allowed us to distinguish between well (piles 2 and 3) and poor (pile 1) stabilized organic matter. The energy released was calculated for each sample by integrating the DTA curves and these results are agreed with the previous hypothesis. Information deriving from weight losses, registered by the TG and DTG curves, enables to follow the evolution state of the organic matter and therefore changes in its stability. These data could determine the final point of the composting process of winery and distillery residues and then reduce the time for compost harvest.     

六水合硝酸镁增塑改性淀粉-聚乙烯醇复合膜的合成与性能

以六水合硝酸镁[Mg(NO₃)₂·6H₂O]为增塑剂, 采用流延法制备了增塑改性的淀粉-聚乙烯醇(PVA)复合膜, 并研究了改性后淀粉-PVA复合膜的性能. 研究结果表明, Mg(NO₃)₂·6H₂O与淀粉和PVA发生一定的相互作用, 破坏了淀粉和PVA中的结晶结构. 因此, Mg(NO₃)₂·6H₂O的加入可提高淀粉与PVA间的相容性, 改变了淀粉-PVA复合膜的力学性能, 使其拉伸强度下降, 断裂伸长率提高.