•The plastic films recycling rates are still very low.•Further research should be directed towards closed-loop recycling systems.•Deinking process and other decontamination technologies are ...required.•Multilayer films recycling technologies are still underdeveloped.•Life Cycle Assessment study is needed to evaluate the impacts on the environment.
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 management systems was identified.
The Rifian Corridor was a seaway between the Atlantic Ocean and the Mediterranean Sea during the late Miocene. The seaway progressively closed, leading to the Messinian Salinity Crisis in the ...Mediterranean Sea. Despite the key palaeogeographic importance of the Rifian Corridor, patterns of sediment transport within the seaway have not been thoroughly studied.
In this study, we investigated the upper Miocene sedimentation and bottom current pathways in the South Rifian Corridor. The planktic and benthic foraminifera of the upper Tortonian and lower Messinian successions allow us to constrain the age and palaeo-environment of deposition. Encased in silty marls deposited at 150–300m depth, there are (i) 5 to 50m thick, mainly clastic sandstone bodies with unidirectional cross-bedding; and (ii) 50cm thick, mainly clastic, tabular sandstone beds with bioturbation, mottled silt, lack of clear base or top, and bi-gradational sequences. Furthermore, seismic facies representing elongated mounded drifts and associated moat are present at the western mouth of the seaway.
We interpret these facies as contourites: the products of a westward sedimentary drift in the South Rifian Corridor. The contourites are found only on the northern margin of the seaway, thus suggesting a geostrophic current flowing westward along slope and then northward. This geostrophic current may have been modulated by tides. By comparing these fossil examples with the modern Gulf of Cadiz, we interpret these current-dominated deposits as evidence of late Miocene Mediterranean overflow into the Atlantic Ocean, through the Rifian Corridor. This overflow may have affected late Miocene ocean circulation and climate, and the overflow deposits may represent one of the first examples of mainly clastic contourites exposed on land.
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•H2 photoproduction from binary mixtures of C-3 alcohols on 0.5% Pt/TiO2 was studied.•Propan-2-ol transformation was affected by the presence of traces of other alcohols.•Propan-2-ol ...dehydrogenate to acetone both in the liquid and gas phase.•Propan-1-ol and ethanol also yield the C-1 alkane.•Competitive reactions were proved useful for mechanistic studies.
The effect of alcohol structure on photocatalytic production of H2 from C-3 alcohols was studied on 0.5% Pt/TiO2. A C-2 alcohol (ethanol) was also included for comparative purposes. For individual reactions from 10% v/v aqueous solutions of alcohols, hydrogen production followed the order ethanol ≈ propan-2-ol > propan-1-ol > propane-1,2,3-triol > propane-1,2-diol > propane-1,3-diol. The process was found to be quite sensitive to the presence of additional alcohols in the reaction medium, as evidenced by competitive reactions. Therefore, propan-2-ol conversion was retarded in the presence of traces of the other alcohols, this effect being particularly significant for vicinal diols. Additional experiments showed that adsorption of alcohols on Pt/TiO2 followed the order propane-1,2,3-triol > propane-1,2-diol > propane-1,3-diol > propan-1-ol > ethanol > propan-2-ol. Adsorption studies (DRIFT) and monitoring of reaction products showed that the main photocatalyzed process for propan-2-ol and propan-1-ol transformation is dehydrogenation to the corresponding carbonyl compound (especially for propan-2-ol both in the liquid and the gas phase). In the case of liquid-phase transformation of propan-1-ol, ethane was also detected which is indicative of the dissociative mechanism to lead to the corresponding C-1 alkane. All in all, competitive reactions proved to be very useful for mechanistic studies.
Polyamide (PA) reverse osmosis (RO) membranes suffer performance decay when exposed to oxidizing species, limiting their lifetime and increasing operation costs. This article aims at reviewing the ...effect of chlorine species on the performance and characteristics of PA-membranes. Experimental evidence supporting different competing mechanisms for chlorine-polymer interaction will be presented, together with the influence of operational parameters. Additionally, an overview of different modification methods that exist to render PA-membranes more chlorine-resistant is given.
Sr1-xLaxTiO3 (SLT; 0 ≤ x ≤ 0.5) powder samples were synthesised at room temperature by a mechanochemical method from SrO, La2O3 and TiO2 mixtures in 90 min. The obtained SLT samples as potential ...anode materials in solid oxide fuel cells (SOFCs) were investigated. The microstructure, electrical conductivity and chemical compatibility with yttria-stabilised zirconia (YSZ) were studied. The powder samples had a nanometric character after milling. After a subsequently heating at 900 °C, the particle size slightly increased, but still remained nanometric. At this high temperature, a good chemical compatibility with YSZ was found. The x = 0.2 sample gave the best electrical conductivity values, i.e. 0.23 W cm−2. These features make such as-obtained samples good candidates to be used as anodes in SOFCs.
•Mechanosynthesis and full characterisation of cubic Sr1-xLaxTiO3 system.•Potential applicability of the mechanosynthesis for obtaining SOFCs anodes.•Anodes with the appropriated microstructure for building SOFCs.•Sr0.8La0.2TiO3 suitable as anode in the SOFCs and compatible with the electrolyte.
The differentiation of pure turbidites and contourites from mixed deposits —as the bottom current reworked sands (BCRS) — in sedimentary cores and outcrops from the modern or ancient records is still ...challenging. An accurate evaluation of facies associations calls for detailed understanding of processes controlling these deep-water systems and how they record interactions of along- and down-slope processes. Connecting features to processes is of particularly relevant in the study of contouritic drifts that include sandy deposits. This research describes and interprets BCRS within a Pleistocene contouritic drift located along the middle continental slope of the Gulf of Cadiz. Seismic, wireline, and sedimentological analyses of sediment samples were applied to core material representing a muddy drift that hosts sandy deposits. A sedimentary sequence, comprising five facies (F1 to F5) is defined here; it records background sedimentation influenced by the initial deposition of a gravity-driven flow followed by bottom current reworking. It is moderately bioturbated and contains distinctive trace fossil assemblages, often dominated by ichnofabrics of the Planolites and Thalassinoides. These assemblages represent intermittent deposition between down-slope and along-slope processes during relatively short time scales. The sequence is defined as a partial bi-gradational contourite sequence including BCRS reworked from underlying turbiditic deposits due to the interaction of down- and along- slope processes within the contouritic drift and its adjacent contouritic channel. Longer-term trends include an increase and subsequent decrease in both sediment supply and bottom currents. The sedimentary facies model presented here represents a new end member for a mixed turbiditic-contouritic system in which turbiditic flows influence a contourite drift. As such, it may support basic sedimentological interpretation and petroleum exploration strategies.
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•Sedimentological study of the interaction between down- and along-slope processes;•A contourite drift containing reworked turbidites is described;•Turbidites are subjected to reworking and winnowing by bottom currents;•Contourite drifts are not only formed by contourite deposits;•The vertical trend in the sedimentary sequence presented records long- and short- term variation in turbidite-contourite interactions.
Atmospheric electricity has been intensively studied during the last 30 years after the discovery in 1989 of different forms of upper atmospheric electrical discharges (so–called Transient Luminous ...Events) triggered by lightning in the troposphere. In spite of the significant number of investigations that led to important new results unveiling how lightning produces a zoo of transient electrical discharges from the upper troposphere to the mesosphere, there is still no clear understanding about how all sort of TLEs – including those that occur inside thunderclouds – can contribute to the chemistry of the atmosphere both at the local and global scale. This review paper aims at presenting a perspective on the TLE atmospheric chemistry research done in the past, in the present as well as to describe some of the challenges that await ahead to find the true scientific importance of the non-equilibrium atmospheric chemistry triggered by TLEs. This review comes to conclude that while the global chemical impact of elves and halos are almost negligible, the large scale chemical impact of sprites, blue jets and blue starters and that of impulsive cloud corona discharges might be non–negligible in terms of their possibly measurable contribution to important greenhouse gases such as ozone and nitrous oxide (N2O). Being the third strongest greenhouse gas (after carbon dioxide and methane) and by having the ability to deplete ozone, precise determination of atmospheric N2O sources is of increasing and pressing demand. A new era in atmospheric electricity is just emerging in which dedicated scientific space missions (ISS–LIS, ASIM) together with geostationary lightning sensors (since 2016) and new micro–scale and parameterizations of TLEs in general atmospheric chemistry circulation models will hopefully help to start clarifying the full role of TLEs in the chemistry of the atmosphere.
•The global chemical impact of elves and halos are almost negligible.•Sprites N2O production could contribute to the chemical balance of the mesosphere lower thermosphere.•Blue jets and impulsive coronas in thunderclouds may have a measurable contribution to greenhouse gases such as O3 and N2O.•New micro-scale modeling of streamer clusters are needed. Validation and chemical verification of such models are crucial.•Parameterizations of TLEs in general atmospheric chemistry circulation models are needed.
Plant growth-promoting rhizobacteria (PGPR) are free-living bacteria which actively colonize plant roots, exerting beneficial effects on plant development. The PGPR may (i) promote the plant growth ...either by using their own metabolism (solubilizing phosphates, producing hormones or fixing nitrogen) or directly affecting the plant metabolism (increasing the uptake of water and minerals), enhancing root development, increasing the enzymatic activity of the plant or “helping” other beneficial microorganisms to enhance their action on the plants; (ii) or may promote the plant growth by suppressing plant pathogens. These abilities are of great agriculture importance in terms of improving soil fertility and crop yield, thus reducing the negative impact of chemical fertilizers on the environment. The progress in the last decade in using PGPR in a variety of plants (maize, rice, wheat, soybean and bean) along with their mechanism of action are summarized and discussed here.
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