电子废弃物循环利用与自愿协议式管理

随着电子废弃物数量的激增和非正规电子废弃物处理企业生产对环境影响,中国电子废弃物问题日益凸现出来.在我国,电子废弃物正成为一类重要废弃物,据估计,电子废弃物产出量以每年13～15%的速度增长,其增速是普通生活垃圾的3倍.如何解决我国电子废弃物问题不仅是环境保护的要求,也是经济发展的要求.电子废弃物的循环利用是电子废弃物管理和治理的最佳途径.电子废弃物的自愿协议式管理作为一种新的环境管理方式,对于改善电子废弃物管理现状、提高废弃物循环利用率、减少电子废弃物产生、降低电子废弃物的危害等具有广阔的应用前景.     

丝状菌污泥膨胀及其致密过程中菌丝体演替规律

为了探索丝状菌的致密途径、解决丝状菌污泥膨胀的难题,从丝状菌的自身特点及外部条件出发研究了其在污泥膨胀及致密过程中菌丝体的演替规律。研究发现,致密生长的大絮体对丝状菌的种类是有选择性的,那些丝体较弯曲、丝体强度较大、贮存能力强的菌丝体更利于形成聚集态生长。另外,研究表明,不同种类丝状菌的生长势和存贮能力不同,对底物的利用上亦存在着竞争关系。实验中存在的几个菌种对PHB颗粒的存贮能力由高到低依次为:Nostocoida limicola Ⅱ、Type 1851、Type 0701、Type 021N型菌体。     

Water Remediation: PVA-Based Magnetic Gels as Efficient Devices to Heavy Metal Removal

Scientific and technological researches are devoted to obtain materials capable of retaining different kinds of pollutants, contributing to contamination solutions. In this context, hydrogels have emerged as great candidates because of their excellent absorption properties as well as good mechanical, thermal and chemical properties. More specifically, ferrogels (magnetic gels) present the extra advantage of being easily manipulated by a permanent magnet. Here, we present the results derived from the application of ferrogels as efficient tools to extract heavy metal pollutants from wastewater samples. The gels were prepared following the method of freezing and thawing of a polyvinyl alcohol aqueous solution with magnetic nanoparticles coated with polyacrylic acid. Ferrogels were fully characterized and their ability to retain Cu²⁺ and Cd²⁺, as model heavy metals, was studied. Thus kinetics and mechanisms of adsorption were evaluated and modeled. The concentration of MNPs on the PVA matrix was key to improve the adsorption capability (approximately the double of retention is improved by the MNPs addition). The adsorption kinetics was determined as pseudo-second order model, whereas the Langmuir model was the most appropriate to explain the behavior of the gels. Finally reuse ability was evaluated to determine the real potential of these materials, the ferrogels demonstrated high efficiency up to about five cycles, retaining about 80–90% of their initial adsorption capability. All the results indicated that the materials are promising candidates able to compete with the commercial technology regarding to water remediation.     

Effects of Natural and Artificial Weathering on the Physical Properties of Recycled Poly(ethylene terephthalate)

In accelerated weathering tests, specimens are exposed to higher radiation intensity, temperature and humidity than is likely under natural weathering in order to achieve rapid degradation of the polymer in a convenient short time. In the current work, a correlation between the two environments is attempted so that a prediction of lifetimes in the natural environment can be achieved. During aging, surface flaws are created due to the chain scission process. This is initiated by the absorption of ultra-violet light and directly affects visual appearance and impact strength. After natural weathering, the material shows only plastic deformation in an impact test. However, after artificial weathering to 5000 h of UV exposure, there is a decrease of 85% in impact strength. Colour change occurs at a high rate in the early stages of UV exposure. Beyond 2000 h of exposure, the colour change approaches a steady state and a correlation between the changes under natural and artificial weathering becomes apparent for a potential prediction of lifetimes. From the analysis including the specular component (SCI), taking surface roughening into account, 1 year under natural weathering was found to be equivalent to 25 days under accelerated weathering.     

Enhanced degradation of the antibiotic tetracycline by heterogeneous electro-Fenton with pyrite catalysis

There is actually increasing concern about the accumulation of antibiotics, such as tetracycline, in soil and water bodies. There is therefore a need for efficient methods to degrade antibiotics and thus clean waters. Here we tested the degradation of tetracycline using the heterogeneous electro-Fenton-pyrite method and compared the results with the conventional electro-Fenton method. The reaction was performed with a boron-doped diamond or Pt anode and carbon-felt cathode allowing electrogeneration of H₂O₂ from O₂ reduction. Results show an increasing tetracycline mineralization using the following methods: anodic oxidation with electrogenerated H₂O₂, electro-Fenton and then electro-Fenton-pyrite using boron-doped diamond. Ion-exclusion HPLC revealed the complete removal of malic malonic, succinic, acetic, oxalic and oxamic acids. Nitrogen present in tetracycline was mainly mineralized in NH₄ ⁺. The higher efficiency of electro-Fenton-pyrite is explained by self-regulation of soluble Fe²⁺ and pH to 3.0 from pyrite catalyst favoring larger ^·OH generation from Fenton’s reaction.     

Assessing the Influence of Social Responsibility on Reputation: An Empirical Case-Study in Agricultural Cooperatives in Spain

The attention to ethics has gradually become a concurrent topic of modern companies’ management. In the last years Social Responsibility has become a key issue in the strategic agenda of competitive agriculture cooperatives. However, reputation management has not been a visible strength in the cooperative enterprises. First of all, this work theoretically analyzes the relationship between Social Responsibility and reputation in cooperatives. Later, from a practical point of view, we carry on an empirical analysis focused on the olive oil cooperatives in the south of Spain, in the province of Jaén. With respect to the previous studies on the topic, this work reveals a main reason of interest reinforcing the role of research in addressing real problems of cooperatives. The article points out the characteristics of this kind of agribusiness and shows the importance of the adoption of a responsible orientation in fostering reputation for creating sustainable competitive advantages.     

Robust optimization evaluation of reliance on locally produced foods

While local food production may be beneficial in terms of developing the local economy and reducing greenhouse gases from transportation, sustainability strategies focused on local food production may generate their own risks due to yield variability. We have developed a robust optimization (RO) model to determine the minimum amount of land (cropland and pasture) required to grow food items that would satisfy a local population’s (accounting for gender and age) calorie and nutrient needs. This model has been applied to Boone County, Missouri, which has a population of approximately 170,000. Boone County is 1790 km², with 16% of the land defined as cropland and 30% defined as pasture. The model includes 27 nutrients from 17 potential foods that could be produced: six fruits and vegetables, five grains and six animal-sourced foods. Yield estimates are based on the predominate methods of agriculture in the USA. We first run our model assuming no variability, using the midpoint yield estimates. Then, to quantify uncertainty in yield for different food types, we use historical yield data over 10 years to estimate this variability and run our RO model under these variability estimates. We compare the two model results to illustrate the impact of data uncertainty on meeting sustainable local food for communities. Solutions suggest that nutrition needs can be met for the Boone County population within the land area defined.