The water repellent behaviour of soils is a widely studied phenomenon given its implications for infiltration, runoff, erosion and preferential flow. However, the principles underlying the eventual penetration of water into affected soils remain poorly understood. Theoretical considerations of the energetics and kinetics involved as a water drop makes contact with a water repellent soil surface and eventually penetrates into the soil suggest three distinct stages in the overall process. These stages are 1) adhesional wetting as soil and water first make contact, followed by 2) a kinetic barrier transitional stage in which molecular reorganisation of organics on soil reduces the water-soil contact angle to allow the water drop to sit deeper over soil particles of initial contact such that there is contact with particles in directly underlying soil layers, and finally 3) branching interstitial wetting as water penetrates into the bulk soil. Studies presented here of optical microscopy, mass of soil initially wetted, penetration time through layers of soil of different thicknesses, and time-dependent measurements of contact angle, volume of water penetrated, and mass of soil wetted, all give results consistent with this model. However, only for highly water repellent soils can distinct stages in wetting be clearly resolved experimentally, presumably because only these soils have a high enough kinetic barrier in the transitional stage for good separation between stages. For less water repellent soils, while the general time dependent behaviour remains consistent with the model, the distinction between the three stages is not so easy to resolve experimentally. The roles of contact angle, particle size distribution and drop size in determining the rates of these stages is considered, and the implications of the model for understanding soil water repellency are discussed.

Anomalously high water contact angles are often measured for soils or other granular materials when using a goniometer which is designed for use with flat surfaces. For many years such high contact angles have been rationalised in terms of Cassie and Baxter, and/or Wenzel models for contact angles on non-planar surfaces, but it is becoming increasingly apparent that the theories behind these models are fundamentally flawed. Here, we present an alternative interpretation of these anomalously high contact angles which takes into consideration how a water drop sits on the particulate surface, and propose a geometric correction factor to address this anomaly. Experimental data from studies with precisely arranged needles and spheres, and model and natural soils, were used to explore this approach and examine the validity of the method. Application of the correction factor to measurements of water drops on 1 mm diameter steel spheres hydrophobised with paraffin wax gave a reduction of the measured contact angle of 140.4(+/- 0.6)degrees to a corrected contact angle of 108.2(+/- 1.0)degrees, which is within 3.5 degrees of the flat-plane contact angle for water on the wax of 111.7(+/- 0.6)degrees. For paraffin wax coated soils, measured contact angles are shown to be 15-25 degrees higher than comparable flat-plane contact angle. This correction factor may be useful in interpreting goniometer contact angle measurements of irregular surfaces since it is the flat-plane, rather than measured, contact angle which gives a measure of the polarity/hydrophobicity of the surface.

Soil water repellency, that is, the reduced ability of soils to absorb water, is thought to be caused by organic coatings with predominantly non-polar properties on soil particle surfaces. Given the important role of particle surface polarity in determining soil water repellency, we explored the use of fluorescent probes as a method for the direct in-situ determination of the distribution and polarity of organics on bulk soil surfaces, and of their molecular mobility. We used nile red and pyrene, which have both been used successfully as environmental probes in previous studies, but have not been applied before to bulk soils. The probes were either (a) co-deposited with other organics known to induce water-repellent behaviour with acid-washed sand to produce 'model soils' or (b) adsorbed directly onto sandy soils that were naturally water repellent to different degrees, and studied using fluorescence microscopy and steady-state and time-resolved fluorescence. Reliable measurements could be made using pyrene as an in-situ probe on both model and natural soils, and a viscosity/mobility probe on model soils, whereas nile red was found not to be a useful probe. On model soils, made using hexadecane (HEX), octadecane (OCT) or stearic acid (SA) on acid-washed sand, pyrene excimer formation kinetics showed a decrease in environment mobility as the organic layer changes from a liquid through to a hard wax. Spectra from pyrene adsorbed to natural soils indicated varying environmental polarity and heterogeneity within the soil samples studied. Highlights Exploration of in-situ fluorescent probes to study polarity and viscosity of organics on soils. Fluorescent probes have never been used in situ on bulk soils before. Pyrene probe shows variation in mobility, polarity and heterogeneity of organics on soils. Pyrene is a useful in-situ fluorescent probe of polarity and mobility of organics on soils.

The setup and installation of a solar power system to demonstrate the performance of various battery chemistries under two distinct storage conditions is presented in this paper. Lead acid and lithium iron phosphate batteries were installed aboveground and underground and their impact on system performance recorded.

Increasing recovery of critical raw materials (CRMs) from waste electrical and electronic equipment (WEEE) is a strategic priority to mitigate supply risks. Today, CRM recovery rates are generally low, with increases requiring new recovery processes and interface optimisation with pre-processing to ensure appropriate material flows for efficient recovery are generated. Here, results from an industrial trial to increase CRM recovery from WEEE are presented to inform development of pre-processing strategies which generate such material flows. Au, Ag, Co, Ga, Mg, Nb, Ru, Pd, Ir, Y, Nd, Sb, Ta and W are identified with XRF in components of a range of WEEE samples including within individual printed circuit board (PCB) components. CRM distribution in PCBs is mapped by visual inspection with reference to this data. Cost-effective methods to disassemble WEEE; isolate CRM bearing components, and upgrade/concentrate CRMs are evaluated for industrial adoption. A guillotine is found most suitable for LCD disassembly and separation of Au edge-contacts from PCBs, while cryocracking is best for isolation of internal components of digital media devices. Thermal PCB disassembly with a solder bath for simultaneous SMD removal and subsequent sieving to sort SMDs thereby concentrating CRMs for recovery is a promising approach. Microwave ashing of PCBs to concentrate CRMs is promising although off-gas treatment would be required. Recovery potential of identified CRMs from material streams generated is found to be poor due to lack of suitable recovery infrastructure except for precious and platinum group metals in PCBs, but available pyrometallurgical recovery permanently dissipates other CRMs present.

Photovoltaics (PV) are increasingly important for electrification in rural Sub-Saharan Africa, but what is the best battery technology to use? To explore this question, a small-scale domestic PV system for South Africa (20-year lifetime) to deliver 1.42 kWh electricity from batteries overnight with 10-h discharge was costed with various Li-ion, Pb-acid and Aquion aqueous hybrid ion batteries (AHIBs). Environmental impact; compatibility with circular economy; potential for cost-reduction through lifetime extension; and valorisation of batteries at end-of-life is discussed. Batteries are 81-93% of system costs, and battery production required over the system lifetime would emit 743, 674 and 6060 kg CO2-eq (Pb-acid, Li-ion and AHIBs respectively). Hazardous materials in Li-ion and Pb-acid batteries pose risks at end-of-life. Li-ion and AHIBs face potential resource supply constraints due to use of Co, Li and graphite. Closed-loop recycling and refurbishment of Pb-acid batteries is well established in South Africa. Currently, no African facilities for Li-ion or AHIB recycling exist, with little opportunity to retain material value from these batteries within the region. Despite lower efficiencies and shorter lifetimes, Pb-acid batteries, which are readily available from domestic manufacturing at low cost, are the current best choice for sustainable small-scale domestic PV systems in South Africa. (C) 2018 The Authors. Published by Elsevier Ltd.

In 2014 more than 1.2 billion people, which forms 16% of the world's population, were without access to electricity. Over half of these were in sub-Saharan Africa (SSA). While photovoltaics (PV) appear to offer the possibility of 'green' electricity for rural areas, PV electricity generation and storage have major environmental impacts associated with production, use, and disposal. Here we discuss sustainable solar energy generation and storage for rural SSA in the context of the 'circular economy'. We begin with the climate and geography, both physical and human, of the region, then introduce the ideas of the circular economy, and discuss silicon PV in light of these ideas. We identify a basic energy requirement for rural households and consider the sustainability of a low cost PV and energy storage system capable of meeting this requirement; and finally, we briefly discuss current developments in PV technology, and how these might be used in this application.

A study of a local industrial symbiosis involving the recovery of platinum from waste thermocouples which is then used for the preparation of catalytic electrodes suitable for dye-sensitized solar cell production is reported. The small quantity of platinum in the filaments of used thermocouples, thousands of which are discarded each year by metal foundries, can be economically recovered by conversion to chloroplatinic acid hydrate, an 'added value' product, which can then be used in the fabrication of dye-sensitized solar cell counter-electrodes. 91% recovery of platinum from filaments as chloroplatinic acid hydrate has been achieved by aqua regia digestion of manually isolated filaments. Cost-benefit analysis shows the proposed process derives sufficient value to cover landfill costs for what is left of the waste thermocouples after platinum removal; provide similar to 5 days employment; and provide 63% materials cost savings for electrode preparation in comparison to purchasing commercially available chloroplatinic acid hydrate. The proposed local industrial symbiosis would, per year, divert similar to 50 g of platinum from landfill, avoid up to 1400 kg of CO2 emissions associated with primary production of an equivalent quantity of platinum, and give enough platinum to produce catalytic electrodes for similar to 500 m(2) of dye-sensitized solar cells, which could supply clean energy for 12 homes in the locality. The process exemplifies the environmental, economic and social benefits available through adoption of circular practices, which make use of secondary materials available within the local economy by valorizing wastes. The process also overcomes economic barriers to critical raw materials (CRMs) recovery from dissipative applications. (C) 2018 The Authors. Published by Elsevier Ltd.

Variation in equine hoof conformation between farriery interventions lacks research, despite associations with distal limb injuries. This study aimed to determine linear and angular hoof variations pre- and post-farriery within a four to six week shoeing/trimming interval. Seventeen hoof and distal limb measurements were drawn from lateral and anterior digital photographs from 26 horses pre- and post-farriery. Most lateral view variables changed significantly. Reductions of the dorsal wall, and weight bearing and coronary band lengths resulted in an increased vertical orientation of the hoof. The increased dorsal hoof wall angle, heel angle, and heel height illustrated this further, improving dorsopalmar alignment. Mediolateral measurements of coronary band and weight bearing lengths reduced, whilst medial and lateral wall lengths from the 2D images increased, indicating an increased vertical hoof alignment. Additionally, dorsopalmar balance improved. However, the results demonstrated that a four to six week interval is sufficient for a palmer shift in the centre of pressure, increasing the loading on acutely inclined heels, altering DIP angulation, and increasing the load on susceptible structures (e.g., DDFT). Mediolateral variable asymmetries suit the lateral hoof landing and unrollment pattern of the foot during landing. The results support regular (four to six week) farriery intervals for the optimal prevention of excess loading of palmar limb structures, reducing long-term injury risks through cumulative, excessive loading.

To celebrate the centenary of Science Progress we offer a short survey of the progress made over the past one hundred years in the research and application of photoinduced charge transfer. After a brief historical overview and introduction to photoinduced charge transfer, we discuss developments in the theory and practice of photography, photovoltaics, photocatalysis, fluorescent probes and chemosensing.

Shranjevanje energije : 10. mednarodna konferenca o trajnostni energiji in varstvu okolja. Deseta mednarodna konferenca o trajnostni energiji in varstvu okolja - SEEP 2017 je bila organizirana od 27. do 30. junija 2017 v Bledu, in sicer Fakulteta za kemijo in kemijsko tehnologijo Univerze v Mariboru, Slovenija in Univerza za zahod Škotske. Cilj SEEP2017 je združiti raziskave na področju trajnostne energije in varstva okolja z vsega sveta. Prispevani prispevki so združeni v 18 sej, da bi bralcem zagotovili dostop do 300 prispevkov avtorjev iz 52 državam. Zahvaljujemo se uglednim plenarnim in osrednjim govornikom ter predsednikom, ki so prijazno privolili v sodelovanje na tej konferenci. Prav tako smo hvaležni vsem avtorjem za članke in člane komisije. Menimo, da znanstveni rezultati in strokovne razprave ne bodo le spodbuda za razvoj, temveč tudi za ustvarjanje novih prijateljstev in morebitnih prihodnjih znanstvenih razvojnih projektov.

Charcoals have long been used to adsorb organics from water and other substrates; we hypothesise that biochar may act in a similar way when mixed with soil, removing hydrophobic organic compounds from the soil surfaces. To test this hypothesis, we developed quantitative methods for addition of two hydrophobic organic compounds (octadecane and octadecanoic acid, commonly found in naturally hydrophobic soils) to, and their subsequent extraction from, acid washed sand (as a model for sandy soil). We then measured the quantity of the organic compounds which remained on the sand after: deposition; subsequent addition of 0, 1, 5, 10, 25 or 40 % wettable biochar; and storage for 1, 10, and 30days in solutions of pH3, 6 or 9. We found that there were small reductions in hydrophobic compound on sand with 1 and 5 % biochar additions, but that 10 % biochar removed ~50 %, and ≥25 % biochar removed ~100 %. The significance of these results in understanding the potential of wettable biochar to remove hydrophobic compounds from sandy soils, and thus act as an ameliorant of soil water repellency, is discussed.

Third generation photovoltaics (3GPV) which include dye-sensitised solar cells (DSSCs); organic photovoltaics (OPV); and perovskite solar cells, are promising green energy technologies in their infancy which hold the promise of low cost energy generation for the future. At this early stage in development, full lifecycle optimisation taking account of all parts of the product lifecycle is required to maximise the resource efficiency benefits associated with the use of these technologies to create a truly sustainable renewable energy technology. Here we examine the advantages of lifecycle optimisation for 3GPV technologies along with key aspects of design; materials selection; manufacturing processes; likely applications of the technologies; and potential recycling and refurbishment strategies. We identify features which are conducive to circular economy and identify barriers to resource efficiency for these technologies, and suggest some potential solutions and priority areas for future research.

Precious metal (PM) and copper content of dynamic-RAM modules placed on the market during 1991-2008 has been analysed by AAS following comminution and acid digestion. Linear regression analysis of compositional data ordered according to sample chronology was used to identify historic temporal trends in module composition resulting from changes in manufacturing practices, and to project future trends for use in more accurate assessment of future recycling potential. DRAM was found to be 'high grade' waste with: stable levels of gold and silver over time; 80% reduction in palladium content during 1991-2008; and 0.23 g/module/year increase in copper content with a 75% projected increase from 2008 by 2020.The accuracy of future recycling potential projections for WEEE using current methods based on static compositional data from current devices is questionable due to likely changes in future device composition. The impact on recycling potential projections of waste laptops, smart phones, cell phones and tablets arising in Europe in 2020 resulting from a 75% increase in copper content is considered against existing projections using static compositional data. The results highlight that failing to consider temporal variations in PM content may result in significant discrepancies between projections and future recycling potential. (C) 2016 The Authors. Published by Elsevier Ltd.

SummaryThe potential of biochar to ameliorate soil water repellency has not been widely studied. Previous studies have focused on the potential for biochar to induce or exacerbate existing water repellency rather than alleviate it. This study investigates the effect of adding wettable biochar to water‐repellent soil by comparing the water drop penetration times (WDPTs) of a control and biochar‐amended soil. The potential of wettable biochar to act as a physical amendment to water‐repellent soil was evaluated by mixing coarsely‐ground biochar (CGB, particle size range 250–2000 µm) or finely‐ground biochar (FGB, particle size range < 250 µm) with one strongly and one severely naturally water‐repellent soil in various quantities, and then measuring the WDPT for each mixture. When biochar particles did not fall within the size range of existing soil particles, an initial increase in both mean WDPT (WDPTM) and variation in WDPT was observed with small additions of biochar. These effects possibly result from increased surface roughness and inhibition of infiltration by the suspension of drops above the average soil–air interface at a few hydrophobic points. Both CGB and FGB reduced soil water repellency, FGB more effectively than CGB. The addition of 10% w/w FGB reduced soil WDPT by 50%, and 25% FGB eliminated repellency. Direct absorption of water by biochar and an increase in soil surface area in contact with water are the predominant physical mechanisms involved. This exploratory study suggests biochar has the potential to amend water‐repellent soil.

Mauveine, a chemical icon, is no longer commercially available. If nowadays one wanted to have a sample of the original Perkin, or Caro, mauveine, and see its colour, where would one find it? The answer is on UK Victorian 6d postage stamps from 1867-1880. This was found from a comparison with historical samples of mauveine, from both William Perkin and a Heinrich Caro sample (here analysed for the first time). These have distinctly different compositions and this was used to identify the origin of mauveine in the postage stamps, with evidence found for mauveine made by both Perkin's and Caro's synthesis.

Developments in the field of organic-inorganic lead halide perovskite based solar cells have metaphorically opened the door to an exciting new solid state photovoltaic technology that retains the low cost and processability benefits of dye sensitised solar cells (DSCs). Encouraging device efficiencies of greater than 10% on both titania and alumina, and as a planar device, have been reported in the literature. Here we report the characteristics of a series of lead iodide/bromide perovskites. As one might expect, changing the halide(s) alters the crystal structure and band gap of the perovskite which results in the possibility of vivid and colourful solar cells; a characteristic which is seen as one of the main benefits of DSCs. X-ray diffraction and scanning electron microscopy with elemental mapping via energy dispersive X-ray analysis has been used to characterise perovskites on sensitised thin films. UV-vis and diffuse reflectance has been used to study the optical characteristics of crystallised perovskite thin films. Finally device performance is evaluated and suitability for use in photovoltaic devices is discussed.

The water drop penetration time (WDPT) test is commonly used to evaluate the persistence of soil water repellency by placing water drops on the soil surface and recording the time to complete infiltration. Currently no standard protocol exists regarding the number or volume of drops applied, and often neither detail is provided when WDPT is reported. This study evaluated how mean WDPT (WDPTM) varies with drop volume and the number of drops required to obtain WDPTM within a given precision. Two naturally water-repellent soils were tested with 416 drops each of 15, 20, 80, and 200 μL. Wettable analogs of each soil were prepared and combined with the repellent soils to create various soil mixtures, to which 20- and 200-μL drops were applied. The WDPTM was found to vary significantly (α = 0.05) with drop number and volume, and the relationship likely depends largely on soil heterogeneity from variations in particle size, organic matter content, and the distribution of hydrophobic compounds within the soil. The results of this study support the following recommendations: (i) a reliable WDPTM (±10%) can be obtained with 95% confidence from 30 drops of 80- to 200-μL size (smaller drops can be used but will reflect microtopographical variability as heterogeneity increases); and (ii) water repellency class can be determined with 95% confidence from six drops and with 90% confidence from one drop, regardless of volume. Standard deviations should always be included to give some indication of the heterogeneity of water repellency within the soil.