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.     

Leather Insole with Acupressure Effect: New Perspectives

Some wastes contain many reusable substances of high value. Solid leather waste is one such potential waste which can be converted into value added products. This study attempts to prepare leather insoles with acupressure effect from finished leather wastes and used leather wastes. Leather with acupressure effect (LAE) was fabricated using regenerated leather. LAE was characterized physico-chemically using Fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. Foot pressure measurements were done using LAE insoles on healthy individuals. Results proved that LAE insoles were able to increase the foot pressure of the wearer and thereby created an acupressure effect in them. Wearing of footwear with LAE insoles were beneficial compared to regular insoles. LAE possessed the required mechanical properties for insole production and it was also biodegradable in nature. The study proves that these composites could be successfully used for the production of cost-effective leather goods and therapeutic footwear. Production of useful byproducts from wastes is income generating and at the same time reduces environmental pollution and a feasible technology for waste recycling has been proved in this study.     

Adsorption of Ammonium by Graphene Oxide-Based Composites Prepared by UV Irradiation and Using as Slow-Release Fertilizer

A novel sodium alginate-grafted poly(acrylic acid)/graphene oxide (NaAlg-g-PAA/GO) composite hydrogel was prepared via ultraviolet irradiation, and characterized by infrared spectroscopy spectrometer. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. It was employed to adsorb NH₄⁺ from aqueous solution and used as slow-release nitrogen fertilizers (SNFs). Result indicated that the adsorption process for NH₄⁺ reached equilibrium within 50 min, with the adsorption capacity of 6.6 mmol g^?1 even if 30 wt% GO was incorporated. The results of adsorption kinetic and isotherm were well described by the pseudo-second-order and Freundlich model. The thermodynamics analysis showed the adsorption process was spontaneous. The study indicated excellent water-holding ratio of soil with 2 wt% SNFs was 81.2%, and nitrogen release was up to 55.1% within 40 days in soil. Overall, NaAlg-g-PAA/GO could be considered as an efficient adsorbent for the recovery of nitrogen with the agronomic reuse as a fertilizer.     

A mathematical model for type II profile of concentration distribution in turbulent flows

This paper presents a mathematical model to investigate type II profile of suspension concentration distribution (i.e., the concentration profile where the maximum concentration appears at some distance above the bed surface) in a steady, uniform turbulent flow through open-channels. Starting from the mass and momentum conservation equations of two-phase flow, a theoretical model has been derived. The distribution equation is derived considering the effects of fluid lift force, drag force, particle inertia, particle–particle interactions, particle velocity fluctuations and drift diffusion. The equation is solved numerically and is compared with available experimental data as well as with other models existing in the literature. Good agreement between the observed value and computed result, and minimum error in comparison to other models indicate that the present model can be applied in predicting particle concentration distribution for type II profile for a wide range of flow conditions. The proposed model is also able to show the transition from type I profile to type II profile.     

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.