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Occupational Threat of Recycling Spent Lithium-Ion Batteries by Vacuum Reduction.

Here's a fun paper I came across this morning: Occupational Threat of Recycling Spent Lithium-Ion Batteries by Vacuum Reduction, Keyi Lin, Mi Lin, and Jujun Ruan ACS Sustainable Chemistry & Engineering 2022 10 (46), 15297-15304

An excerpt of the introduction is kind of fun, although we should be clear that the theory that we will someday recycle all the batteries we keep hyping (when we're not hyping hydrogen) is largely just that, theoretical. Right now the bulk of the world's growing inventory of batteries is electronic waste, rather problematic electronic waste at that. Don't worry. Be happy. There's lots of talk about recycling batteries, just like there is lots of talk - more than half a century of it - about how solar and wind will destroy the nuclear industry while providing 100% of the world's energy someday after we're all dead and done with our personal consumption.

Here's some battery recycling talk, unusual inasmuch it actually raises issues of human and environmental health in doing so:

Lithium-ion batteries (LIBs) are called “white oil” (1) because they are replacing traditional energy sources. With the greenhouse effect becoming more and more serious, countries around the world have issued relevant policies to promote the use of LIBs and other new energy. (2,3) According to the statistical data of new energy vehicles released by the European Union, the output of electric vehicles is expected to reach 200–500 million by 2028. (4) Just as a coin has two sides, the wide application of batteries will also cause some problems. The cycle of charging and discharging reduces its working performance, and the service life of lithium battery is about 3–10 years. (5) Therefore, the output of spent LIBs will gradually increase. Thus, it is very necessary for us to research on spent LIBs. (6,7) Spent LIBs contain a lot of metal resources, (8−11) which can bring considerable economic effects. (12,13) In addition to economic benefits, the recovery of spent LIBs has strategic significance, such as Li (14) and Co. (15) The recycling technology of spent LIBs is also constantly developing, (16,17) and environmentally unfriendly technologies are eliminated. (18,19) Vacuum reduction (20) is encouraged to be used in the resource recovery of spent LIBs because it claims to be efficient (21,22) and environmentally friendly. (23) Zhang et al. (24) researched under vacuum and at 600–1000 °C and found that LiCoO2 is selectively converted from the anode to Co or cobalt oxide and Li2CO3 by carbothermal reduction. Meanwhile, Huang et al. (20) prepared LiAl5O8 and LiAlO2 under vacuum reduction.

However, it is irresponsible to blindly issue an environmentally friendly definition. The interior of the spent LIB is not entirely composed of metal elements; it has binders and conductive agents. (19) Polyvinylidene fluoride (PVDF) is a common organic binder, which has chemical stability and excellent thermal, so it is widely used in the attaching the cathode to the Al foil of LIBs. (25,26) However, fluoride was added to PVDF to improve its performance. In the process of battery treatment, it is inevitable that fluoride (such as HF) will leak, (27) which is an environmental problem that needs high attention. (28,29) In addition to the binder, halogen elements are also added to the conductive agent inside the spent LIB, for example, LiPF4, LiPF6, and LiClO4. (30) The decomposition of these substances will not only cause irreversible damage to the battery but also damage the ecology when released into the environment. (31) The organic electrolyte in the spent LIB will react quickly when it comes in contact with the water molecules and releases toxic gases (such as aldehydes, ketones, and phosphorus pentafluoride) in the atmosphere. (32,33) Hence, it may cause environmental pollution inadvertently.

Some studies have focused on the possible pollution caused by spent LIBs. Due to improper supervision, spent LIBs have caused serious environmental problems and are considered as “hazardous wastes.” Spent LIB contains “toxic” elements [such as Li (5–7%), Mn (5–11%), plastic diaphragm (7%), electrolyte materials (15%), Ni (5–20%), and Co (5–25%)]. (34) When exposed to the environment, these substances will enter the water environment, soil environment, and atmospheric environment, causing irreversible effects on human beings and ecology. (35,36) There is pollution when the spent LIB is naturally exposed, and it will also bring pollution during its recycling process. (37) For example, in the process of LIB discharge, toxic and harmful substances will be produced. (38) The released substances will corrode the iron shell outside the spent LIB, leading to electrode leakage and seriously threatening the environment and human health. (39) Some directly released toxins can directly damage human nerves and induce body problems. (40) Because the original intention of LIB design is convenient to use, (41) it is inevitable that there will be many problems when recycling. However, few people pay attention to the specific threats of the recycling process.

The purpose of this study is to evaluate the possible pollution in the process of vacuum reduction of spent LIBs, conduct an occupational threat assessment, and study the pollutant generation pathway. Occupational threats refer to the threats that occur with a certain frequency in the work process and that the professional practitioners are exposed to. This paper mainly studies the threats caused by occupational exposure. In this paper, the following experiments were carried out: (1) The particulate matter 10 (PM10) of vacuum tube furnace accessories was collected and analyzed to assess the threat of exposure to heavy metals. (2) The gas produced in the process of vacuum reduction of spent LIBs and the organic residues after the reaction were collected to determine the pollutants in gas and organic residues and analyze their exposure threat. (3) The process of vacuum reduction of spent LIBs was simulated by molecular dynamics to analyze the formation principle and pathway of pollutants. (4) Through the analysis of the experimental results, the corresponding occupational threat control measures were formulated. This experiment will help to make up for the blank of risk assessment of vacuum reduction spent LIB technology, improve the defects of this technology, and promote the popularization and industrial application of this technology...

I added the bold and italics for some excerpts I found particularly juicy, in particular to "Few people pay attention..."

Of course, few people pay attention to the second law of thermodynamics, which is why we hear so much bullshit rhetoric about how energy storage, which always wastes energy is supposed to be "green."

What we call "green," is mining poor people to mine (or recycle) so we bourgeois types can declare ourselves "green."

"Blessed are the oblivious, for they shall inherit the Earth..."

Well they have inherited the Earth, and frankly, to state it baldly, they're fucking it up, speeding, accelerating, toward making it unlivable.

Some figures from the text:

The caption:

Figure 1. Flow chart of risk assessment and formation mechanism of toxic substances generated in the vacuum reduction process of recovering spent LIBs.

The caption:

Figure 2. (a) Equilibrium state mixture model of organic matters.; (b) molecular dynamics simulation result of the organic matter mixture model at 400 °C; (c) molecular dynamics simulation result of the organic matter mixture model at 600 °C. (b-1) Details of molecular dynamics simulation results of organic matter mixture model at 400 °C; (c-1) details of molecular dynamics simulation results of organic matter mixture model at 600 °C.

The caption:

Figure 3. Pollution formation path in the vacuum reduction process of spent LIBs.

The authors of this paper are Chinese, and of course, back when the Chinese were poor, Westerners mined poor people there to "recycle" our stuff. There are lots of interesting papers in the literature about the concentration of heavy metals and swell flame retardants in the plasma of Chinese children as a result.

China is now a wealthy country of course, so they're well on their way to restricting the mining of its population to bear the health and environmental costs of making Americans green through recycling.

Don't worry. Be happy.

The world, led by the racist fascist Elon Musk, is successfully mining cobalt slaves in the "Democratic Republic" of Congo to make our batteries, and there's no reason we can't mine them to recycle them for us. As for the "think only happy thoughts" belief that recycling cobalt will make cobalt mining obsolete, I note that everyone is happily carrying on about how the battery industry is expanding. I attended a lecture recently which made a point that should have been obvious, but somehow isn't: You cannot rely on recycling for material supply when material is in use, particularly when use is increasing. Moreover, even with infinite energy, which we don't have, recycling always involves material loss, and the other word for material loss is "pollution."

I trust you're enjoying a long weekend.


Live, 1979

Parasite gives wolves what it takes to be pack leaders

This came in on my Nature News Feed:

Parasite gives wolves what it takes to be pack leaders


Study is one of the few to show the behavioural effects of Toxoplasma gondii in wild animals.

It's probably open sourced, but if not, some excerpts:

Wolves infected with a common parasite are more likely than uninfected animals to lead a pack, according to an analysis of more than 200 North American wolves1. Infected animals are also more likely to leave their home packs and strike out on their own.

The parasite, Toxoplasma gondii, makes its hosts bold — a mechanism that increases its survival. To reproduce sexually, T. gondii must reach the body of a cat, usually when its host is eaten by one. That becomes much more likely if the parasite alters the host’s behaviour, making it foolhardy. Research results are mixed, but in rodents, infection generally correlates with decreased fear of cats and increased exploratory behaviour. Physical and behavioural changes have also been found in people: testosterone and dopamine production is increased and more risks are taken.

Warm-blooded mammals can catch the parasite by eating an infected animal or ingesting forms of T. gondii shed in the faeces of infected cats. After a period of acute infection, semi-dormant cysts form in muscle and brain tissue, and persist for the rest of the host’s life. Up to one-third of humans might be chronically infected.

Unique data set

T. gondii is known to infect wildlife, but few studies have examined its behavioural effects. In one work, infected hyenas in Kenya became more likely to be eaten by lions2. Connor Meyer and Kira Cassidy, wildlife ecologists at the University of Montana in Missoula, thought of a rare opportunity to link infection with behaviour in wild wolves: data on grey wolves (Canis lupus) collected intensively in Yellowstone National Park, Wyoming, over nearly 27 years. Some wolves in Yellowstone live near, and sometimes steal prey from, cougars (Puma concolor), which are known to carry the parasite. Wolves could become infected by eating the cats — or their faeces.

The team looked at 256 blood samples from 229 wolves, which had been carefully watched throughout their lives, and had their life histories and social status recorded. Meyer and Cassidy found that infected wolves were 11 times more likely than uninfected ones to leave their birth family to start a new pack, and 46 times more likely to become pack leaders — often the only wolves in the pack that breed...

...Wolves are known for killing cougars, however, so even bold, risk-taking wolves infected with the parasite are not likely to end up as lunch for the cats, Meyer says. He speculates that in the past, infected wolves could have been more likely to be preyed on by American lions (Panthera atrox), massive feline predators weighing around 200 kilograms, which prowled North America until they went extinct over 11,000 years ago.

The full original article is definitely open sourced:

Meyer, C.J., Cassidy, K.A., Stahler, E.E. et al. Parasitic infection increases risk-taking in a social, intermediate host carnivore. Commun Biol 5, 1180 (2022).

Note that this behavior is slightly different than in American politics. In 2016, a minority of American citizens managed to promote a parasite into a de facto leader, with the result that the country was almost eaten by wolves.

A little different, I think.

I hope you're enjoying the holiday break.

I had a video call with an old friend in France, with whom I haven't spoken for about 20 years...

...or more. We reconnected on Linkedin and made arrangements to connect by Zoom.

He married a German woman, but confessed he forgot how to speak German (as have I).

He was a excellent business associate - we worked together on many important projects in drug development. Beyond business grew into a great friend; I actually had a jam session with his band when they were playing American rock songs in a Paris bar filled with Japanese tourists (who knew all the songs). Somehow though, we fell out of touch.

It was really a joyous moment to connect again; just like all these years hadn't passed, that my sons, babies when we last met, were not men, and his daughter, for whom we bought (unavailable in France back then) baby socks wasn't now a 27 year old woman, his younger son now an IT professional.

It was a wonderful morning; very happy.

I should visit France again sometime before I die. I loved that country.

NERC Warns of Tight Generation Resources, Fuel Supply Issues This Winter

I'm on the Power Magazine news feed and this article came up yesterday:

NERC Warns of Tight Generation Resources, Fuel Supply Issues This Winter (Sonal Patel, November 17, 2022, Power Magazine.)

An excerpt:

Power shortfalls could be rife over the next three months across a large portion of the North American bulk power system (BPS), particularly during extreme and prolonged cold conditions, the North American Electric Reliability Corp. (NERC) has warned.

The nation’s designated Electric Reliability Organization (ERO) in its latest Winter Reliability Assessment, issued on Nov. 17, said several regions face risks of insufficient electricity supplies during peak winter conditions owing to higher peak-demand projections and inadequate weatherization. The reliability watchdog also prominently highlighted fuel supply risks for coal, natural gas, and oil, and it underscored risks related to natural gas infrastructure constraints.

According to NERC’s evaluation of the generation resource and transmission system adequacy to meet projected peak demand, several regions may be highly vulnerable to extreme weather this winter and could require load-shedding procedures. These include the Electric Reliability Council of Texas (ERCOT); the Midcontinent Independent System Operator (MISO); SERC-East—a region that includes North Carolina and South Carolina; WECC-Alberta; and the Northeast Power Coordinating Council (NPCC) Maritimes, a region that comprises the Canadian provinces of New Brunswick, Nova Scotia, and Prince Edward Island, and the northern portion of Maine...

This topic is covered ably in my friend Meredith Angwin's increasingly discussed book Shorting the Grid. The Hidden Fragility of Our Electrical Grid.

Her book focuses on the arcane dealings of the New England ISO, which according to the map provided in the Power Article, is potentially threatened with rolling blackouts this winter if a polar vortex drives South, something made increasingly likely by climate change but often utilized by Trump Scale idiots to deny that climate change is real.

A map from the article of the regions considered most at threat:

Who knows, maybe we'll get lucky and the wind will blow in the period just after the winter solstice, but I wouldn't bet on avoiding energy poverty for those who can least afford it. Winter is a likely time for Dunkelfluate.

Welcome to antinuke heaven, a world dependent on access dangerous fossil fuels.

I trust you will have a pleasant and happy Thanksgiving.

A Rather Witty T-Shirt I Might Buy for My Son.

It's from the American Nuclear Society:

Regrettably it's out of stock:


On almost any grid in the world, power demand typically peaks in the late afternoon/early evening, generally between 5:30 PM and 8 PM, you know around or after sunset.

Nature Editorial: Overhyping hydrogen as a fuel risks endangering net-zero goals

Nature has the highest impact factor of any scientific journal in the world. I'll bet the editors know all about the second law of thermodynamics.

The Editorial: Overhyping hydrogen as a fuel risks endangering net-zero goals (EDITORIAL 16 November 2022)


Hydrogen is touted as a wonder fuel for everything from transport to home heating — but greener and more efficient options are often available.

It should be open sourced, but an excerpt:

As governments across the world scramble to find ways to reform energy systems to meet climate commitments, hydrogen looms large. The fuel is now seen as a pillar of most net-zero emissions scenarios. Production is expected to at least quintuple by mid-century.

On one level, the enthusiasm is understandable. If hydrogen were freely available, it would be something of a decarbonization wonder. It can make carbon-free fuels for transportation and heating, and power some energy-intensive industries that can’t easily be electrified, such as the manufacture of steel or fertilizer (see Feature).

The problem is that hydrogen is not freely available. On Earth, it exists mostly in molecules bound to other elements, from which it must be extracted at huge energetic cost. Policymakers should beware potential unintended negative consequences for both people and the planet from an overwrought dash for hydrogen.

Most hydrogen is currently made by processes — such as steam reformation of natural gas (methane) — that produce large amounts of CO2 as a by-product. Although ‘green’ hydrogen can be made by using electricity from renewable sources to split water molecules, this process is costly compared with more conventional production methods.

It can also be an inefficient use of renewable resources. Using green electricity to make hydrogen at times of peak demand, when that energy could be feeding the grid and displacing electricity generated from fossil fuels, could result in higher overall emissions than intended. Making hydrogen with electricity generated from unabated use of fossil fuels would be even worse.

All this means that hydrogen should be used judiciously, to address emissions that can’t be eliminated in other ways. Many of the uses being touted do not tick that box. For example, some groups are advocating burning hydrogen to heat homes, as an alternative to natural gas, but this is much less efficient than using electricity directly. Most immediately, this means higher costs for consumers. But it also means that using even truly green hydrogen to heat homes displaces a smaller chunk of current CO2 emissions than would using it for other tasks, for which there are no alternatives...

It's pretty much what I say frequently in this space, but the hydrogen hydra, which has been carrying on for half a century refuses to die its deserved death.

There is a path to relatively clean hydrogen as a captive intermediate, but it industrial nowhere on Earth. This is thermochemical hydrogen. It should be industrial and I believe it could be industrial, but right now it isn't.

Consumer hydrogen even were it possible to make bulk hydrogen cleanly - electrolysis powered by the useless solar and wind industries won't cut it - would be a terrible idea, all the cartoons to the contrary notwithstanding.

I hope your holiday preparations are going well.

Review of "Solar Power: Technology, Innovation and Environmental Justice."

While wandering around in the literature this evening, I came across this review: Schlosser, K., Review of Solar Power: Technology, Innovation and Environmental Justice. Hum Ecol 47, 479–480 (2019).

The book reviewed is this one:

Dustin Mulvaney. Solar Power. Innovation, Sustainability, and Environmental Justice. Oakland, University of California Press 2019. ISBN 978-0-520-28817-1, Price $29.65 (paperback). 322

Here's a few excerpts of the review:

Dustin Mulvaney’s Solar Power: Innovation, Sustainability, and Environmental Justice provides a thorough overview of the California solar power industry. Mulvaney makes the purpose of such an overview clear at the outset: a transition to solar (among other renewable energy technologies) is underway, but this is not necessarily a just transition unless we make it so. In order to facilitate a just transition, certain questions must be answered. For Mulvaney, these include: “…who bears the burdens? Where might collateral effects manifest? How can these aspects be integrated into energy policy, planning, and practice?” (pp. 3–4). These are important questions in the realms of environmental and climate justiceFootnote1 and Mulvaney’s contribution towards addressing them is timely and useful.

Solar Power is densely packed with a wide range of information on solar power in California. The first four chapters of the book cover details of the industry, including technology, raw materials, the Silicon Valley start-ups and venture capital involved, government investment programs, and NGOs. Readers get an occasional excursion into more theoretical terrain, such as a discussion of the tension between justice and sustainability or debates about whether technology can be inherently political, but Mulvaney generally remains focused on the technology and industrial organization...

...From chapter five onward, however, Mulvaney begins to connect the industry overview to thornier policy questions a bit more explicitly. For instance, chapter five (Green Civil War) lays out four possible explanations for why solar projects might be resisted at the local level. These include a lack of consulting with communities on project implementation (‘democratic deficit’), the likelihood that views about solar projects are more nuanced than surveys can capture, an ‘insider-outsider’ dynamic wherein Big Solar is demonized, and the well known Not In My Back Yard phenomenon. Chapter six explores the U.S. federal government’s Western Solar Plan to identify potential solar energy zones (SEZs) to be converted into solar farms. The chapter provides excellent information on the potential ecological impacts of solar farms and a critical evaluation of the concepts of ‘solar debt’ and ‘GHGFootnote2 return on investment.’ In chapter seven (‘Breakthrough Technologies and Solar Trade Wars’) Mulvaney discusses federal policies to support risk-taking in solar power innovation and this is probably the most analytically nuanced portion of the book, as he situates these policies within debates about green developmentalism and eco-modernism. In short, Mulvaney points to the failure of a federal energy policy that is based on a laissez-fair, market approach with the government assuming the role of venture capitalist. Mulvaney does argue for public investment in clean energy, but in different (and rather underspecified) ways. He concludes the chapter by outlining three primary reasons why ARRA and DOE investment programs resulted in the Solyndra fiasco, and not more sufficient gains in solar power transition. First, they have emphasized pre-commercial technologies and a ‘black swan’ approach (in which a high number of projects are supported in hopes that even a small percentage of them are truly transformative), rather than improving upon solar technology that is already commercial. Second, Mulvaney suggests that these programs “assumed that ‘disruptive technologies’ had agency and would survive on their own in the market” (p. 243), as if solar panels were the same as iPads or flat screen televisions...

The review seemed interesting so I accessed the book.

I'm hardly going to find the time to read the whole thing, especially as it's about an industry I believe is useless and an expensive and ecologically dubious affectation with unwarranted public enthusiasm and popularity, but I was rather struck in a section about bird mortality at what is a personal bête noire, the solar thermal tragedy at Ivanpah, a huge plant over a large area that produces trivial energy and burns gas to pretend to be economically viable.

(In this text USSE refers to "Utility Scale Solar Energy." )

The text:

USFWS biologists coined the term “streamers” to describe birds singed by solar flux at the Ivanpah site, which is particularly problematic when it is above the power tower receiver while the plant is in standby mode. Later research from Ivanpah raised the bird death totals upwards, with just under half of the deaths due to the heat flux.20 One public letter, submitted by a USFWS chief biologist, asked that the CEC not approve any more solar power towers until data could be collected on the impacts of power towers on avian ecology. Unlike the challenges with tortoises, which can be avoided by siting projects on non-habitat, the solar power towers’ impacts on birds may be unavoidable.21...

... A wide variety of bird types have died at USSE plants.24 Two endan-gered Yuma clapper rails (Rallus longirostris yumanensis), a population with only a thousand living individuals, were killed at the Desert Sunlight facility in Desert Center, California. At two solar power plants in the California desert (one photovoltaic farm and one parabolic-trough CSP), over 20 birds associated with aquatic habitat—yellow-headed blackbirds (Xan-thocephalus xanthocephalus), great blue herons (Ardea herodias), eared grebes (Podiceps nigricollis), western grebes (Aechmophorus occidentalis), pied-billed grebes (Podilymbus podiceps), surf scoters (Melanitta perspi-cillata), red-breasted mergansers (Mergus serrator), buffleheads (Bucephala albeola), black-crowned night herons (Nycticorax nycticorax), double crested cormorants (Phalacrocorax auritus), American coots (Fulica americana), and brown pelicans (Pelecanus occidentalis)—were found dead, apparently due to colliding with panels and mirrors, far from any sources of water.25 Other species known to have avian-solar mortality include migratory birds such as the yellow warbler (Setophaga coronate), Vaux’s swift (Chaetura vauxi), and loggerhead shrike (Lanius ludovicianus), and raptors such as the American kestrel (Falco sparverius), red-tailed hawk (Buteo jamicensis), golden eagle (Aquila chrysaetos), northern harrier (Circus cyaneus), and peregrine falcon (Falco peregrinus). Some USSE sites have on-site ponds that may attract such birds.

Polarized-light cues cause aquatic insects to lay their eggs on photovoltaic modules rather than in water, prompting some to argue for more research into how polarized light might affect insect, bat, and bird behavior near USSE installations, since water bodies are the only sources of polarized light in nature.26 Many renewable energy advocates minimize the consequences of USSE bird mortality by comparing it to other sources such as cats, buildings, and automobiles, but this comparison seems incommensurate given that the impacts are cumulative, not tradeoffs, and it does not distinguish between mortality of different types of birds...

I certainly don't know if modern day "environmentalism" finds birds to be all that important anymore, with the rush to industrialize the wilderness to charge up Elon Musk's Powerwall® products and Tesla cars so we can all drive around showing how "green" we are.

I dissent.

I find birdlife to be valuable, and once, in this space referenced a very insightful book, now in my files, called Why Birds Matter (Subtitle: Avian Ecological Function and Ecosystem Services; Edited by Çagan H. Sekercioglu, Daniel G. Wenny, and Christopher J. Whelan) because somehow we live in times that this has to be explained to us.

I love the evocative cover of the book, which evokes some of the reasons birds matter:

I referenced this book in a post a few years back: A Minor Problem For Sound Science of the Effect of Offshore Windfarms on Seabirds: There Isn't Any.

There's a lot of "Watt" talk in Mulvaney's solar energy book, using units of peak power that solar plants never actually reach, except for perhaps a few minutes on a cloudless sunny day near the summer solstice, the intellectually dishonest units use to hype the solar (and wind) industry, but I was pleased to find a unit of energy appearing in the text, which reports that solar PV USSE require about 36 square kilometers to produce 1 TWh of electricity, in SI units, 3600 X 10^12 Joules, where a Joule is a unit of energy (as is the derived unit, TWh).

The Diablo Canyon nuclear plant, the last nuclear plant in California, produced in 2021, on a footprint of 12 acres, (0.049 square kilometers) including the parking lot, 16.477 TWh.

Go figure.

I think Mulvaney's book is valuable inasmuch as it asks questions that aren't asked, but should be asked, as we rush headlong into a fantasy land that has no hope of addressing climate change.

I trust your preparations for the upcoming holiday are going well.

Well, in theory we could make the silicon semiconductor industry "clean."

Here's a cutting edge paper in the current issue of Environmental Science & Technology from scientists in the country where most of our solar cells are made:

Recovery of Fluoride-Rich and Silica-Rich Wastewaters as Valuable Resources: A Resource Capture Ultrafiltration–Bipolar Membrane Electrodialysis-Based Closed-Loop Process, Yangbo Qiu, Long-Fei Ren, Lei Xia, Changmei Zhong, Jiahui Shao, Yan Zhao, and Bart Van der Bruggen Environmental Science & Technology 2022 56 (22), 16221-16229.

From the introductory text, which describes the current practice for these "clean energy" jobs in China:

1. Introduction

Wastewater is increasingly considered a renewable resource linked to the industry–resource–environment nexus. (1) Recovery of valuable resources from wastewater not only contributes to solving an ecological crisis but also gives additional economic benefits. (2) Traditionally, a variety of technologies such as precipitation, adsorption, and electrochemical systems have been developed for the removal of pollutants from wastewater. (3−5) However, the looming concerns of the generation and disposal of secondary pollutants such as waste solids cannot be ignored. (6) Commonly, traditional technologies focus on the removal of typical pollutants from one type of wastewater (e.g., fluoride removal from fluoride-rich wastewater). Few techniques focus on the recovery of valuable ionic resources from various wastewaters. If a variety of wastewaters can be recovered simultaneously, wastewater treatment capacity can be significantly improved.

For the semiconductor industry, large amounts of fluoride-rich and silica-rich wastewaters are discharged. The fluoride-rich wastewater with a high fluoride concentration (e.g., 1–50 g L–1) causes severe crises for human health, (7−9) while the fluoride emission discharge is limited to a median value of 15 mg L–1. (10,11) Silica is a typical waste in silica-rich wastewater. (12) The high concentration of nanosized silica particles (around 2.6 g L–1 SiO2) in wastewater causes environmental issues such as the production of hazardous oxyradicals. (13−15) Traditionally, the treatment methods such as precipitation and coagulation–flocculation are applied to treat the fluoride and silica in semiconductor wastewaters separately. (16,17) However, the waste solid (e.g., calcium fluoride and silica slurry) generation will cause secondary pollution to the environment. On the contrary, capturing fluoride and silica from different wastewaters (e.g., fluoride-rich wastewater and silica-rich wastewater) as well as recovery of the ionic products such as sodium silicofluoride (Na2SiF6) will eliminate pollutants from the environment and bring economic values simultaneously. Na2SiF6 is an odorless and white hexagonal structure crystalline salt, which has been widely used in water fluoridation, as well as the photovoltaic and frosted glass industry. (18) Previous studies have reported that the chemical reaction of hydrofluoric acid (HF) and silica generates silicofluoride (SiO2 + 6HF → SiF62– + 2H2O + 2H+). (19) Moreover, the precipitation reaction of silicofluoride with sodium ions can be used to produce Na2SiF6 (SiF62– + 2Na+ → Na2SiF6?. (20) Due to the fluoride ions being transformed into HF at lower pH (pH < 3.16), (21) it is possible to acidify the fluoride-rich wastewater to form HF using a strong acid. Then, the HF in fluoride-rich wastewater can react with SiO2 to generate Na2SiF6 using silica-rich wastewater. Based on these reactions, a corresponding efficient and sustainable separation system could be designed for resource recovery from the fluoride-rich and silica-rich wastewaters.

In view of sustainability and superior separation efficiency, membrane technology is preferential for consideration in a closed-loop process for zero liquid discharge of wastewater. In particular, ultrafiltration (UF) shows a unique advantage in removing macromolecules from wastewater with high water flux and low energy consumption. (22) For example, Liu et al. achieved over 99% rejection rate of calcium fluoride particles by UF during the treatment of fluoride-rich wastewater. (23) Ohanessian et al. carried out a crossflow UF for silica-rich wastewater treatment due to its efficient rejection of silica particles. (14) Therefore, it can be inferred that UF is feasible to recover Na2SiF6 macrocrystals by capturing the fluoride and silica from the mixed fluoride-rich and silica-rich wastewaters. However, the generation of Na2SiF6 requires the use of an acid and a base, thus limiting the large-scale production of Na2SiF6. Bipolar membrane electrodialysis (BMED) can be used to generate H+ and OH– through the dissociation of water molecules in a bipolar membrane (BM). Then, the cation/anion will migrate through cation/anion-exchange membranes (CEMs/AEMs) to form a base/acid, respectively, under an electric field. (24−26) Therefore, BMED could be designed to produce acid and base for the continuous generation of HF in fluoride-rich wastewater. (27)

In this study, a closed-loop process based on resource capture ultrafiltration–bipolar membrane electrodialysis (RCUF-BMED) was designed to recover fluoride and silica as Na2SiF6 from fluoride-rich and silica-rich wastewaters, and the feasibility of the RCUF-BMED system was demonstrated. Two key parts are essential for the RCUF-BMED system: (1) capture of the fluoride and silica to generate Na2SiF6 in an acid environment, and recovery of the Na2SiF6 using a base by the UF system and (2) acid/base generation and freshwater recovery by the BMED system...

The scariest day in my professional career by the way, was when some guys working for me allowed liquid HF to spill all over the hood. (I threw them out of the lab and cleaned it up myself, but it was scary, even fully suited up.)

They recovered 72% of the waste according to the conclusion, stated in "percent talk."

Don't worry. Be happy. It's all "green."

Well, I thought about it, but didn't go there and lived to laugh about the thought.

The idea seemed outrageous, I'm sure, in 1958, less so in 1968, and even less in 1978.
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