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•Review of persulphate (PS) OO bond.•The behaviour of silver(I) activation.•Objections to Fe3++S2O82-→Fe2++S2O8·-.•Modified alkaline activation mechanism.•Optimal activation ...temperature.
Persulphate advanced oxidation processes (PS-AOPs) constitute an important development in the field of wastewater treatment and subsurface contamination remediation within the last two decades. Although persulphate (PS) is a very powerful oxidant, its reaction with common contaminants is relatively slow so that to achieve pollutant degradation at an acceptable rate, activation to produce reactive radicals such as sulphate and hydroxyl radicals is often necessary. Consequently, research in PS-AOPs is dominated by the search for cost-effective and sustainable activation techniques. This review provides a critical evaluation of various published techniques for the activation of PS, suggests novel explanations for important observations in the field and advances proposals to explain reaction mechanisms more consistently. Discrepancies in results and areas for further studies were identified with the view of enhancing the sustainability and reliability of PS-AOPs.
Ha Long Bay is a UNESCO World Heritage Site in Vietnam with unique natural scenery. Development and socio-economic activity impact its water quality. In the context of the Vietnam National Standards, ...historical follow-up data taken over a five-year period (2016 to 2020), for twenty-eight widely dispersed sampling sites, has been used to carry out a temporal assessment of seawater quality utilizing a Water Quality Index (WQI) method. The analysis shows that the seawater quality is generally acceptable over this period. However, the calculated WQI values for the “pandemic year” of 2020 compared to the data for 2016 to 2019, demonstrate a significantly lesser impact for the bay overall and, more specifically, for seventeen individual sites. Ten sites remain unaffected, and one site shows a significantly higher impact. This study demonstrates how the occurrence of the pandemic in 2020 may be exploited for the interrogation of anthropogenic impacts around the bay.
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•Seawater quality in Ha Long Bay, Vietnam, is impacted by anthropogenic activities.•Seawater quality was tracked from 2016 to 2020 using the Water Quality Index.•A lesser environmental impact for the pandemic year of 2020 was demonstrated.•The pandemic was exploited to interrogate anthropogenic impacts around the bay.•The COVID-19 pandemic allowed validation of the WQI and available data quality.
Scaling and biofouling are two major problems in the operation of reverse osmosis (RO) membranes. A variety of control measures are employed in practice, including the use of pulsed electromagnetic ...fields (EMF), which can avoid the use of chemical anti-fouling agents (e.g. halogen-based biocides) that may be toxic to humans or the environment. This is a fairly recent and controversial technology and, from the available documentation and literature, it is clear that the scientific basis for its purported effectiveness is not yet firmly established, although some studies suggest that beneficial effects could be possible. In particular, the various conditions under which EMF technologies are likely to be effective for real world applications have not been scientifically established. This review collates the relevant literature on the problem of scaling and biofouling in RO membranes and heat exchangersystems (e.g. cooling towers), with a particular focus on the application of pulsed EMF technologies, including the broad documentation, relevant scientific studies, proposed mechanisms of action and further research directions. This review demonstrates that a lot more systematic scientific research is needed in order to validate the application and commercialization of EMF technologies as a pretreatment to control fouling in RO membrane systems.
•Scaling and biofouling are complex, interrelated, processes that hinder current RO system efficiency and optimization.•Limitations of existing anti-biofouling and anti-scaling methods are stimulating the development of non-chemical methods.•The scientific basis of the purported effectiveness of such non-chemical methods is far from being established.
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•Radical kinetic energy is crucial to oxidation effectiveness.•Degradation by persulphate (PS) is optimised at 90°C.•The kinetic energy of radicals determines reaction type.•PS ...activation for wastewater treatment feasible using waste heat.•Radical quenching by alcohol or ice bath are equivalent.
The thermally activated persulphate (TAPS) degradation process, although recognised as an effective means for pollutant degradation, is challenged by the high cost of energy and a sub-optimal operation due to the limited elucidation of its mechanisms. In this laboratory study, it is shown that waste heat from industries such as textile dyeing is adequate for the rapid degradation and mineralisation of orange G, a typical azo dye used as the main organic probe compound, in the absence or presence of a high concentration of inorganic salts relevant to the textile industry. Other probe compounds investigated are humic acid, salicylic acid, and caffeine. The study, for the first time, highlights the important role of radical kinetic energy in determining the rate and effectiveness of TAPS mineralisation of pollutants. One effect of the kinetic energy of radicals is the existence of an optimal mineralisation temperature. For an uncatalysed persulphate activation, the optimal temperature, independent of the target pollutant, was identified as 90°C. Overall, the study provides important new insights for the design and operation of TAPS degradation processes.
The incorporation of nanomaterials into a range of polymeric materials shows great potential for developing new active food packaging systems. Although there are many suggested benefits of ...nanoparticles (NPs) in food packaging, there are also potential risks due to the possibility of such particles migrating into foodstuffs. This has obvious implications for human health and it may also negatively impact on marketing and consumer confidence. This review focuses on 2 particular types of nanomaterials: nanoclays and nanosilver, with a view to examining the effects of these on system mechanical properties (nanoclays) and antimicrobial efficacy (nanosilver). It further reports on the various migration studies, techniques for characterization, and measurement of NPs as well as the potential migration of NPs from packaging into foodstuffs. Assessment of the literature to date suggests there is an urgent need for further research in order to devise better NP detection methods and to determine the likelihood of their migration from packaging materials into foodstuffs.
Humic acid (HA) as a major constituent of natural organic matter (NOM) in raw water presents major challenges to drinking water production including membrane fouling and serving as a precursor for ...the production of disinfection byproducts (DBPs). This study demonstrates the feasibility of HA degradation by heat-activated persulfate (PS) mainly at a waste heat temperature of 40 °C, but also at 60 and 90 °C in which ∼70% TOC loss was achieved within 168, 24, and 1 h, respectively. The use of waste heat for water treatment eliminates reliance on electricity, which is a requirement for conventional advanced oxidation processes. Heat-activated PS treatment of synthetic raw water at 40 °C was also shown to significantly reduce ultrafiltration membrane fouling. Low concentration of chloride (≤0.9 mM) accelerated PS degradation of HA, but the promotion was lost at higher concentration (≥9 mM). HA spiked into tap water was degraded by PS even at 25 °C, suggesting activation by trace minerals present within regulatory limits. Overall, the results of this study promise a sustainable and low-cost water treatment option.
Advancing the design of thin-film composite membrane surfaces is one of the most promising pathways to deal with treating varying water qualities and increase their long-term stability and ...permeability. Although plasma technologies have been explored for surface modification of bulk micro and ultrafiltration membrane materials, the modification of thin film composite membranes is yet to be systematically investigated. Here, the performance of commercial thin-film composite desalination membranes has been significantly enhanced by rapid and facile, low pressure, argon plasma activation. Pressure driven water desalination tests showed that at low power density, flux was improved by 22% without compromising salt rejection. Various plasma durations and excitation powers have been systematically evaluated to assess the impact of plasma glow reactions on the physico-chemical properties of these materials associated with permeability. With increasing power density, plasma treatment enhanced the hydrophilicity of the surfaces, where water contact angles decreasing by 70% were strongly correlated with increased negative charge and smooth uniform surface morphology. These results highlight a versatile chemical modification technique for post-treatment of commercial membrane products that provides uniform morphology and chemically altered surface properties.
Thin-film composite membranes, primarily based on poly(amide) (PA) semipermeable materials, are nowadays the dominant technology used in pressure driven water desalination systems. Despite offering ...superior water permeation and salt selectivity, their surface properties, such as their charge and roughness, cannot be extensively tuned due to the intrinsic fabrication process of the membranes by interfacial polymerization. The alteration of these properties would lead to a better control of the materials surface zeta potential, which is critical to finely tune selectivity and enhance the membrane materials stability when exposed to complex industrial waste streams. Low pressure plasma was employed to introduce amine functionalities onto the PA surface of commercially available thin-film composite (TFC) membranes. Morphological changes after plasma polymerization were analyzed by SEM and AFM, and average surface roughness decreased by 29%. Amine enrichment provided isoelectric point changes from pH 3.7 to 5.2 for 5 to 15 min of plasma polymerization time. Synchrotron FTIR mappings of the amine-modified surface indicated the addition of a discrete 60 nm film to the PA layer. Furthermore, metal affinity was confirmed by the enhanced binding of silver to the modified surface, supported by an increased antimicrobial functionality with demonstrable elimination of E. coli growth. Essential salt rejection was shown minimally compromised for faster polymerization processes. Plasma polymerization is therefore a viable route to producing functional amine enriched thin-film composite PA membrane surfaces.
Pharmaceuticals and personal care products (PPCPs) and endocrine disrupting compounds (EDCs) are frequently detected in drinking water sources. This raises concerns about the formation of potentially ...more toxic transformation products (TPs) after drinking water disinfection. This study applied a combination of computational and experimental methods to investigate the biological activity of eight EDCs and PPCPs commonly detected in source waters (acetaminophen, bisphenol A, carbamazepine, estrone, 17α-ethinylestradiol, gemfibrozil, naproxen and triclosan) before and after disinfection. Using a Stepped Forced Molecular Dynamics (SFMD) method, we detected 911 unique TPs, 36% of which have been previously reported in the scientific literature. We calculated the likelihood that TPs would cause damage to biomolecules or DNA relative to the parent compound based on lipophilicity and the occurrence of structural alerts, and applied two Quantitative Structure-Activity Relationship (QSAR) tools to predict toxicity via receptor-mediated effects. In parallel, batch experiments were performed with three disinfectants, chlorine, chlorine dioxide and chloramine. After solid-phase extraction, the resulting TP mixtures were analyzed by chemical analysis and a battery of eleven in vitro bioassays covering a variety of endpoints. The laboratory results were in good agreement with the predictions. Overall, the combination of computational and experimental chemistry and toxicity methods used in this study suggest that disinfection of the studied EDCs and PPCPs will produce a large number of TPs, which are unlikely to increase specific toxicity (e.g., endocrine activity), but may result in increased reactive and non-specific toxicity.
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•Endocrine disrupting compounds (EDCs) frequently detected in drinking water sources•Raises concern that disinfection of drinking water could produce more potent EDCs•This study applied a combination of computational and experimental methods.•Chlorination decreased specific, but increased reactive & non-specific toxicity.•Toxicity less than that produced from reaction of chlorine with organic matter
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