Sonolysis of Per- And Poly Fluoroalkyl Substances (PFAS): A meta-analysis

•PFAS sonolysis parameter meta-analysis.•Optimum pH, frequency and temperature derived for PFOX sonolysis.•Degradation occurs via adsorption bubble and headgroup removal.•PFOA/S sonolysis produces only CO2, H2, H+, and F-•Oxidative agents alter degradation mechanism.Human ingestion of Per- and Polyfluoroalkyl Substances (PFAS) from contaminated food and water is linked to the development of several cancers, birth defects and other illnesses. The complete mineralisation of aqueous PFAS by ultrasound (sonolysis) into harmless inorganics has been demonstrated in many studies. However, the range and interconnected nature of reaction parameters (frequency, power, temperature etc.), and variety of reaction metrics used, limits understanding of degradation mechanisms and parametric trends. This work summarises the state-of-the-art for PFAS sonolysis, considering reaction mechanisms, kinetics, intermediates, products, rate limiting steps, reactant and product measurement techniques, and effects of co-contaminants. A meta-analysis showed that mid-high frequency (100-1,000 kHz) sonolysis mechanisms are similar, regardless of reaction conditions, while the low frequency (20-100 kHz) mechanisms are specific to oxidative species added, less well understood, and generally slower than mid-high frequency mechanisms. Arguments suggest that PFAS degradation occurs via adsorption (not absorption) at the bubble interface, followed by headgroup cleavage. Further mechanistic steps toward mineralisation remain to be proven. For the first time, complete stoichiometric reaction equations are derived for PFOA and PFOS sonolysis, which add H2 as a reaction product and consider CO an intermediate. Fluorinated intermediate products are derived for common, and more novel PFAS, and a naming system proposed for novel perfluoroether carboxylates. The meta-analysis also revealed the transition between pseudo first and zero order PFOA/S kinetics commonly occurs at 15-40 µM. Optimum values of; ultrasonic frequency (300 – 500 kHz), concentration (>15-40 μM), temperature (≈20°C), and pH range (3.2 – 4) for rapid PFOX degradation are derived by evaluation of prior works, while optimum values for dilution of PFAS containing firefighting foams and applied power require further work. Rate limiting steps are debated and F- is shown to be rate enhancing, while SO42- and CO2 by products are theorised to be rate limiting. Sonolysis was compared to other PFAS destructive technologies and shown to be the only treatment which fully mineralises PFAS, degrades different PFAS in order of decreasing hydrophobicity, is parametrically well studied and has low-moderate energy requirements (several kWh g-1 PFAS). It is concluded that sonolysis of PFAS in environmental samples would be well incorporated within a treatment train for improved efficiency

Effects of Dynamic Pricing on the Design and Operation of Distributed Energy Resource Networks

This paper presents a framework for the use of variable pricing to control electricity imported/exported to/from both fixed and unfixed residential distributed energy resource (DER) network designs. The framework shows that networks utilizing much of their own energy, and importing little from the national grid, are barely affected by dynamic import pricing, but are encouraged to sell more by dynamic export pricing. An increase in CO2 emissions per kWh of energy produced is observed for dynamic import and export, against a baseline configuration utilizing constant pricing. This is due to feed-in tariffs (FITs) that encourage CHP generation over lower-carbon technologies. Furthermore, batteries are shown to be expensive in systems receiving income from FITs and grid exports, but for the cases when they sell to/buy from the grid using dynamic pricing, their use in the networks becomes more economical

Ultrasonic degradation of perfluorooctane sulfonic acid (PFOS) correlated with sonochemical and sonoluminescence characterisation

Sonolysis has been proposed as a promising treatment technology to remove per- and polyfluoroalkyl substances (PFASs) from contaminated water. The mechanism of degradation is generally accepted to be high temperature pyrolysis at the bubble surface with dependency upon surface reaction site availability. However, the parametric effects of the ultrasonic system on PFAS degradation are poorly understood, making upscale challenging and leading to less than optimal use of ultrasonic energy. Hence, a thorough understanding of these parametric effects could lead to improved efficiency and commercial viability. Here, reactor characterisation was performed at 44, 400, 500 and 1000 kHz using potassium iodide (KI) dosimetry, sonochemiluminescence (SCL), and sonoluminescence (SL) in water and PFOS solution. Then the degradation of PFOS (10 mg / L in 200 mL solution) was investigated at these four frequencies. At 44 kHz, no PFOS degradation was observed. At 400, 500 and 1000 kHz the amount of degradation was 96.9, 93.8 and 91.2%, respectively, over four hours and was accompanied by stoichiometric fluoride release, indicating mineralisation of the PFOS molecule. Close correlation of PFOS degradation trends with KI dosimetry and SCL intensity was observed, which suggested degradation occurred under similar conditions to these sonochemical processes. At 1000 kHz, where the overall intensity of collapse was significantly reduced (measured by SL), PFOS degradation was not similarly decreased. Discussion is presented that suggests a solvated electron degradation mechanism for PFOS may occur in ultrasonic conditions

Per- and poly-fluoroalkyl substance remediation from soil and sorbents: a review of adsorption behaviour and ultrasonic treatment

Per- and poly-fluoroalkyl substances (PFAS) are xenobiotics, present at variable concentrations in soils and groundwater worldwide. Some of the current remediation techniques being researched or applied for PFAS-impacted soils involve solidification-stabilisation, soil washing, excavation and disposal to landfill, on site or in situ smouldering, thermal desorption, ball milling and incineration. Given the large volumes of soil requiring treatment, there is a need for a more environmentally friendly technique to remove and treat PFASs from soils. Sorbents such as granular/powdered activated carbon, ion exchange resins and silicas are used in water treatment to remove PFAS. In this work, PFAS adsorption mechanisms and the effect of pore size, pH and organic matter on adsorption efficacy are discussed. Then, adsorption of PFAS to soils and sorbents is considered when assessing the viability of remediation techniques. Sonication-aided treatment was predicted to be an effective removal technique for PFASs from a solid phase, and the effect of varying frequency, power and particle size on the effectiveness of the desorption process is discussed. Causes and mitigation strategies for possible cavitation-induced particle erosion during ultrasound washing are also identified. Following soil remediation, degrading the extracted PFAS using sonolysis in a water-organic solvent mixture is discussed. The implications for future soil remediation and sorbent regeneration based on the findings in this study are given

Ultrasonic degradation of perfluorooctane sulfonic acid (PFOS) correlated with sonochemical and sonoluminescence characterisation

Sonolysis has been proposed as a promising treatment technology to remove per- and polyfluoroalkyl substances (PFASs) from contaminated water. The mechanism of degradation is generally accepted to be high temperature pyrolysis at the bubble surface with dependency upon surface reaction site availability. However, the parametric effects of the ultrasonic system on PFAS degradation are poorly understood, making upscale challenging and leading to less than optimal use of ultrasonic energy. Hence, a thorough understanding of these parametric effects could lead to improved efficiency and commercial viability. Here, reactor characterisation was performed at 44, 400, 500 and 1000 kHz using potassium iodide (KI) dosimetry, sonochemiluminescence (SCL), and sonoluminescence (SL) in water and PFOS solution. Then the degradation of PFOS (10 mg / L in 200 mL solution) was investigated at these four frequencies. At 44 kHz, no PFOS degradation was observed. At 400, 500 and 1000 kHz the amount of degradation was 96.9, 93.8 and 91.2%, respectively, over four hours and was accompanied by stoichiometric fluoride release, indicating mineralisation of the PFOS molecule. Close correlation of PFOS degradation trends with KI dosimetry and SCL intensity was observed, which suggested degradation occurred under similar conditions to these sonochemical processes. At 1000 kHz, where the overall intensity of collapse was significantly reduced (measured by SL), PFOS degradation was not similarly decreased. Discussion is presented that suggests a solvated electron degradation mechanism for PFOS may occur in ultrasonic conditions

The Climate Domesday Book

The Climate Domesday Book includes contributions from climate-conscious writers, artists, research scientists, designers and activists from Australia and the UK. The book is a speculative design, intended to provoke public thought and action on the climate emergency and to explore new ways of communicating through design and technology. It demonstrates how design research can bring together diverse disciplinary perspectives, to re-present and amplify a plurality of voices from across temporal and geographic zones. As a speculative design with multi-modal forms of communication (writing, talking, reading, listening, watching), its final manifestation is intended to show the power of human ingenuity and common cause. It is a book as a curated event; as a programme; as a protest; as a survey of ideas. It owes its coming into being to 1960’s counterculture, to the grand ideas of R.Buckminster Fuller and to the electric information age books of Marshall McLuhan, Jerome Agel and Quentin Fiore. In the creation of an experimental hybrid print-digital book on a topic as essential as the future of energy and the planet, design research becomes more than assembling and packaging (a ‘first order’ concern) but an uncertain, collaborative, and activist mode of knowledge-making (a ‘fourth order’).1 It attempts to make sense of a complex challenge (saving planetary species from extinction), invites dialogue between readers and writers and – eventually – stimulate action. It is a speculative design that provides space for contemplation, for inspiration, for engaging the pragmatic and the imaginary. “But it’s just a book. How can a book make a difference?” To which we would respond: “What world-changing events in the world have not been book-inspired?” We want it to be the first book of many: for others to take our technology, our designs and our ideas and make their own Climate Domesday Book in their city. Our Book-of-the-Future is a book, podcast, music video, poem, a window onto ground-breaking science, a manifesto-in-the-making, a clarion call, a gallery-within-a-gallery, a cultural census, a design of possibilities. It is more than a work of art. It is a design with purpose

Challenges of multimodality: Language and the body in social interaction

This article reflects on recent challenges emerging from the study of language and the body in social interaction. There is a general interest in language and the body across disciplines that has invited a reconceptualization of the broader issues relative to action, cognition, culture, knowledge, social relations and identities, spatiality and temporality. The study of social interaction focuses on how multimodal resources - including language and bodily movements - are holistically and situatedly used in building human action. This article discusses some consequences and challenges of putting the body at the center of attention: it repositions language as one among other modalities, and invites us to consider the involvement of entire bodies in social interaction, overcoming a logo-centric vision of communication, as well as a visuo-centric vision of embodiment. These issues are developed through a series of conversation analytic studies, firstly of classic topics in linguistics like deixis, then of more recent topics, such as mobility and sensoriality