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.     

Environmental Impact Assessment of Polylactide(PLA)/Chicken Feathers Biocomposite Materials

The aim of this study is to analyse the environmental impacts (EIs) of the process of preparation of new biocomposite materials obtained from polylactide (PLA) and chicken feathers (CFs). Two CFs stabilization methods and different percentages of CFs have been studied. The EIs of these new composites were compared to the impact of virgin PLA. Cradle-to-gate life cycle inventories were assessed for 0–35% v/v of CFs in a CFs/PLA biocomposite. Two CFs stabilization processes, autoclave and surfactant, were tested and compared with the aim to prioritize one of them from the environmental point of view. A composite plate of 184?×?184?×?2.2 mm³ was defined as the functional unit. Autoclave stabilization process exhibited lower environmental impact compared with surfactant stabilization process mainly due to both the lower requirements of electricity and water and the reduced pollution loads of the generated wastewater. Thus, the autoclave process was selected as the standard method when comparing the EIs of the proposed CFs/PLA biocomposites. In this sense, the addition of CFs to PLA matrix proportionally reduces all the EIs compared to pure PLA due to the replacement of PLA with CFs. This behaviour can be explained because the PLA production accounts for the 99% of the impact of the biocomposite. Consequently, CFs conveniently stabilized might be an alternative raw material to prepare CFs/PLA biocomposites with less environmental impact compared to pure PLA.     

“No fences make bad neighbors” but markets make better ones: cap-and-trade reduces cross-border SO2 in a natural experiment

The clean air interstate rule (CAIR) was a regional cap-and-trade program announced in 2005 which covered 27 eastern US states and sought to reduce sulfur dioxide emissions from coal-fired power plants. The rule was later vacated after a court found that the non-targeted design of the program did not comply with the Clean Air Act provision to regulate interstate air pollution. Using a custom air pollution dispersion model, I calculate the interstate SO₂ pollution from 493 coal-fired power plants across the United States between 1997 and 2020. In a difference-in-differences setup with plants not covered by CAIR in the control group, I estimate the treatment effect of the program on overall- and cross-border SO₂ emissions and find a 24% reduction in overall emissions and reduces the risk that a plant violates air quality standards across state borders by 2–4%. I report evidence of heterogeneous treatment effects where the reduction in overall emissions attributed to CAIR is lower among plants transporting SO₂ in excess of 1% of the National Air Quality Standards to another state.

     

Comprehensive and high-resolution emission inventory of atmospheric pollutants for the northernmost cities agglomeration of Harbin-Changchun, China: Implications for local atmospheric environment management

Using a bottom-up estimation method, a comprehensive, high-resolution emission inventory of gaseous and particulate atmospheric pollutants for multiple anthropogenic sectors with typical local sources has been developed for the Harbin-Changchun city agglomeration (HCA). The annual emissions for CO, NOx, SO₂, NH₃, VOC_S, PM_2.5, PM₁₀, BC and OC during 2017 in the HCA were estimated to be 5.82 Tg, 0.70 Tg, 0.34 Tg, 0.75 Tg, 0.81Tg, 0.67 Tg, 1.59 Tg, 0.12 Tg and 0.26 Tg, respectively. For PM₁₀ and SO₂, the emissions from industry processes were the dominant contributors representing 54.7% and 49.5%, respectively, of the total emissions, while 95.3% and 44.5% of the total NH₃ and NOx emissions, respectively, were from or associated with agricultural activities and transportation. Spatiotemporal distributions showed that most emissions (except NH₃) occurred in November to March and were concentrated in the central cities of Changchun and Harbin and the surrounding cities. Open burning of straw made an important contribution to PM_2.5 in the central regions of the northeastern plain during autumn and spring, while domestic coal combustion for heating purposes was significant with respect to SO₂ and PM_2.5 emissions during autumn and winter. Furthermore, based on Principal Component Analysis and Multivariable Linear Regression model, air temperature, relative humidity, electricity and energy consumption, and the urban and rural population were optimized to be representative indicators for rapidly assessing the magnitude of regional atmospheric pollutants in the HCA. Such indicators and equations were demonstrated to be useful for local atmospheric environment management.     

Estimation of the spatial covariance in Universal Kriging: Application to forest inventory

This paper presents a simple least squares procedure for estimating the spatial covariance and compares it with the numerically more difficult restricted maximum likelihood procedure. Thereafter, it compares design-based and kriging techniques for the estimation of spatial averages in the context of double sampling, as used in forest inventory, where terrestrial sample plots are combined with auxiliary information based on aerial photographs. A case study illustrates the theory.     

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.