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Plastic demand is continuously growing and, with it, the amount of plastic waste. The packaging industry is by far the largest source of single-use plastic products that, after use, end up in landfills and oceans. Mechanical recycling is the solution most widely implemented in the global industry and its effectiveness and reliability have been demonstrated for processing post-industrial plastic scrap. The recycling of post-consumer plastic waste, however, requires an upgrade in the current technology to achieve complete decontamination and removal of malodorous substances embedded in the polymer. This review explores the state-of-the-art technology currently employed in the mechanical recycling of plastic waste, focusing on the progress made for the removal of volatile organic compounds emitted from recycled materials. Followed by a review of the analytical techniques that have been applied for the identification of volatile organic compounds, including, in particular, the techniques used for the identification of odor-active substances. Finally, this review gathers from literature all the volatile organic compounds and odor-active substances identified in virgin and recycled polymers, aiming to evaluate whether there is a notable difference between them based on the chemical structure of the emitted VOCs. As a result, 437 volatiles were gathered, which show the difference between post-consumer recycled plastics and the other plastic waste sources. A larger number of volatile organic compounds, especially flavor and fragrances-based substances as well as oxygenates, appear in post-consumer plastic waste compared to virgin and post-industrial plastic scrap.

For >50 years the Canary Islands have been using seawater desalinization facilities in order to satisfy the freshwater demand of their main economic activity –tourism, which continues to contribute to the economic and social progress of the archipelago. However, this desalinization process involves the production of a “waste” product known as rejected brine, which is discharged from coastal regions and islands, whether it originates from public or private facilities. Rejected brines are potentially a serious threat to marine ecosystems. However, here we demonstrate that this “waste” can be processed and reused as a nutrient mineral solution for a hydroponic production system and also a source of freshwater. The efficiency of this management process in terms of fresh-water production and water recycling economy is also discussed. The aim of this paper is to change the attitude towards rejected brines, which should be treated as potential raw material to permit high savings in the running costs of leisure and tourist facilities around the archipelago. In addition, this will also have a positive effect on the environment, making desalinization more sustainable and environmentally friendly, which is nowadays an added value in customer and user satisfaction.

Water scarcity is one of the main challenges faced by modern agriculture, leading to a substantial drop in crop productivity and a threat to food security. Thus, novel agricultural approaches are necessary and urgent to face this problem. Some natural compounds such as amino acids have been shown to increase yield and mitigate the effects of drought stress. In this study, we demonstrate that the application of pyroglutamic acid (PG) is capable of increasing lettuce yield, under field conditions with 30% less than optimal irrigation. PG treatment showed a clearly protective effect in stressed plants, enhancing their fresh weight by 37% and yield by 31%, in comparison to untreated plants. PG appears to promote drought tolerance effects in deficit irrigated lettuce plants, with several advantages. It acts by enhancing photosynthesis rate and antioxidant defences, while maintaining osmotic and water balance, without toxicity to soil microorganisms. This illustrates the potential use of PG to combat productivity losses due to water scarcity.

Salinity and drought are considered significant abiotic plant stressors with major impact on plant development that causes serious agricultural yield losses. Amongst the strategies to face this problem, the use of compounds capable of inducing abiotic stress tolerance is still little explored. Menadione sodium bisulphite (MSB), a water-soluble vitamin K3 derivative, was previously shown to prime salt stress tolerance when Arabidopsis seeds were pre-soaked with this compound. However, this method has some technical problems regarding seed storage and longevity. In order to overcome these handicaps, we assessed the effect of supplying MSB to roots to prime the response to salinity stress, analysing the effect of two NaCl concentrations (100 and 150¿mM). We selected tomato plants, the most economically important horticultural crop, as our biological model. In this new system, MSB primes salt tolerance in tomato plants by improving net photosynthesis, regulating stomatal aperture and maintaining water balance. Furthermore, MSB induces a faster proline accumulation and ion homeostasis by up-regulating several ion transporter genes, and increases antioxidant activity. As a result, a clear positive effect on plant growth was observed, indicated by the relative growth rate (RGR), These findings again highlight the potential usefulness of MSB as a priming agent for enhancing crop tolerance in the field under adverse environmental conditions.

Plastic flexible films are increasingly used in many applications due to their lightness and versatility. In 2014, the amount of plastic films represented 34% of total plastic packaging produced in UK. The flexible film waste generation rises according to the increase in number of applications. Currently, in developed countries, about 50% of plastics in domestic waste are films. Moreover, about 615,000 tonnes of agricultural flexible waste are generated in the EU every year. A review of plastic films recycling has been conducted in order to detect the shortcomings and establish guidelines for future research. This paper reviews plastic films waste management technologies from two different sources: post-industrial and post-consumer. Clean and homogeneous post-industrial waste is recycled through closed-loop or open-loop mechanical processes. The main differences between these methods are the quality and the application of the recycled materials. Further research should be focused on closing the loops to obtain the highest environmental benefits of recycling. This could be accomplished through minimizing the material degradation during mechanical processes. Regarding post-consumer waste, flexible films from agricultural and packaging sectors have been assessed. The agricultural films and commercial and industrial flexible packaging are recycled through open-loop mechanical recycling due to existing selective waste collection routes. Nevertheless, the contamination from the use phase adversely affects the quality of recycled plastics. Therefore, upgrading of current washing lines is required. On the other hand, household flexible packaging shows the lowest recycling rates mainly because of inefficient sorting technologies. Delamination and compatibilization methods should be further developed to ensure the recycling of multilayer films. Finally, Life Cycle Assessment (LCA) studies on waste management have been reviewed. A lack of thorough LCA on plastic films waste ma

Dewatering of plastic films is a highly energy-consuming recycling operation that largely affects the quality of the recycled product. Despite the importance of good drying, this operation has not been studied at laboratory or pilot plant scale. In this work, the mechanical dewatering of blown film grade high density polyethylene has been assessed by using a laboratory centrifuge. It is suggested that a plastic cake is formed under the centrifugal forces similar to the sludge cake after the filtration process. The water is retained within the plastic cake due to three phenomena: free water within the cake pores and voids, water maintained by capillarity (superficial and pendular) and water trapped due to the tortuosity of the plastic mass. The total moisture is a sum of an equilibrium moisture and a transient moisture. The equilibrium moisture depends on the centrifugal force (G) but it is independent of time. Conversely, the transient moisture is reliant on both the G-force and the centrifugation time. The experimental results showed that an optimum side length exists. The moisture content is minimized when the flake side lies between 1 and 2 cm. Finally, it has been found that the moisture content is a function of the plastic surface. Hence, the specific moisture content (the mass of water per total plastic surface) should be calculated to compare films with uneven thickness or made of different materials. In sum, the outcomes of this study may be fundamental for the further and more extensive research into the plastic films dewatering processes.

Plants are able to develop numerous defence strategies to face stress. Amongst these, higher plants are capable of demonstrating stress imprint, a mechanism related with the phenomenon of priming. This is usually defined as genetic or biochemical modifications induced by a first stress exposure that leads to enhanced resistance to a later stress. Menadione sodium bisulphite (MSB), a water-soluble addition compound of vitamin K3, was first studied as a plant growth regulator and has been later widely shown to function as plant defence activator against several pathogens in a number of plant species. We recently reported that treating Arabidopsis seeds with MSB primes salt tolerance by inducing an early acclimation to salt stress. Here we describe the analysis of the effect of MSB on cytosine methylation in a salt stress background demonstrating that one of the mechanisms underlying this early acclimation to salt stress is an epigenetic mark. Specifically, MSB leads to a hypomethylation state at the promoter region of genes involved in the biosynthesis (P5CS1) and degradation (ERD5) of proline, affecting mainly CHG and CHH sites(where H is any nucleotide except G). The epigenetic changes detected are correlated with the observed expression patterns of P5CS1 (upregulation) and ERD5 (downregulation) genes and the increase in proline accumulation.

For the majority of crops, salinity is one of the most important abiotic stresses, since about 20% of irrigated agricultural land is adversely affected by it. Menadione sodium bisulphite (MSB), a water-soluble vitamin K3 o menadione derivative, has been previously reported as a plant defence activator against several pathogens in a number of species. We have further explored the MSB effects on salt tolerance. In this study, Arabidopsis thaliana wild ecotype Col-0 plants were exposed to prolonged salt (50 mM) stress. Salt treatment resulted in severe growth inhibition. This detrimental effect was lower in terms of relative growth rate (RGR) in plants from seeds soaked in 20 mM of MSB. In these plants, the drop in RGR was nearly 30% lower than untreated plants after 7 days in salt. Furthermore, we found that the salt stress imposed was not enough to disturb photosystem II or induce the expression of several detoxification genes. These functional impairments are characteristic of ionic injuries due to high levels of reactive oxygen species (ROS). At the end of the second week of the experiment, salt-treated plants recover RGR levels close to those of the control. Under our experimental conditions plants seem to be challenged by an osmotic stress with a minimum ionic imbalance. Those from MSB-treated seeds were primed to induce an earlier proline accumulation. Although no significant expression of ROS detoxification genes was found, several transcription factors involved in ROS signalling were detected after salt addition. In this context, MSB treatment was able to prime these transcription factors, resulting in an early adaptation of plants in response to salt stress.

A magnetically recoverable catalyst consisting of copper nanoparticles (CuNPs) on nanosized silica-coated maghemite is presented. The catalyst has been prepared under mild conditions by mixing the magnetic support with a freshly prepared suspension of CuNPs obtained by fast reduction of anhydrous CuCl2 with lithium sand and a catalytic amount of DTBB (4,4′-di-tert-butylbiphenyl) as electron carrier. This copper-based catalyst has shown to be very efficient in the N-(hetero)arylation of imidazole using (hetero)aryl bromides and iodides as arylating agents under ligand-free conditions. The catalyst is easily recovered by means of an external magnet and can be reutilized in three N-arylation cycles without apparent loss of catalytic activity.

A versatile and magnetically recoverable catalyst consisting of copper nanoparticles on silica coated maghemite nanoparticles (MagSilica®) is presented. The catalyst has been prepared under mild conditions by fast reduction of anhydrous CuCl2 with lithium sand and a catalytic amount of DTBB (4,4’-di-tert-butylbiphenyl) as electron carrier, in the presence of the magnetic support. The catalyst has been fully characterized and its performance in different coupling and cycloaddition reactions of terminal alkynes has been studied. This new copper-based catalyst has shown to be very efficient and easily reusable in the Glaser alkyne dimerization reaction in THF, the multicomponent Huisgen 1,3-dipolar cycloaddition reaction in water and the three-component synthesis of propargylamines under solvent free conditions.

The heterogeneous hydrosilylation of alkynes catalysed by platinum on titania is reported. A variety of hydrosilanes react with both terminal and internal alkynes to furnish the corresponding vinyl silanes in high yields and short reaction times as well as in a regio- and stereoselective manner. The catalyst can be easily recovered and reused in several consecutive cycles.

A new methodology for the partial reduction of polycyclic aromatic and heteroaromatic hydrocarbons under mild reaction conditions is presented, the process being a reasonable alternative to the catalytic hydrogenation or the Birch reaction. The reduction protocol described is based on the use of cobalt or manganese nanoparticles generated in situ in a simple and economic way, by reduction of commercially available CoCl2·6H2O or MnCl2·2H2O in the presence of lithium sand and the corresponding PAH, acting itself as an electron carrier. The use of a deuterium-oxide-containing cobalt(II) salt allows the simple preparation of deuterium labeled products. The regiochemistry and degree of reduction in the case of 1-substituted naphthalene derivatives markedly depends on the nature of the metal-NPs used.

Nickel nanoparticles, readily prepared by reduction of nickel(II) chloride with lithium and a catalytic amount of DTBB, have been used in the transfer hydrogenation of carbonyl compounds and have been fully characterised by different means. The reaction rate of the transfer hydrogenation was found to be dependent on the acetophenone and isopropanol concentration but independent on the amount of lithium chloride. The deactivation of the catalyst after reuse has been mainly attributed to surface oxidation but not to coke formation. All the experiments performed are in agreement with the process being of heterogeneous nature. The nickel nanoparticles unveiled a superior behaviour in comparison with commercially available nickel catalysts.

Nickel nanoparticles have been found to effectively catalyse the hydrogen-transfer reduction of a variety of non-functionalised and functionalised olefins using 2-propanol as the hydrogen donor. The heterogeneous process has been shown to be highly chemoselective for certain substrates, with all the corresponding alkanes being obtained in high yields. A synthesis of the natural dihydrostilbene brittonin A is also reported based on the use of nickel nanoparticles.