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Wednesday, March 26, 2014

Crowd Funded Low-Tech Cyanide Mitigation, Anyone?


By Josh Kearns

Crowdsourcing is by now thoroughly established as an internet meme. How do I know this? Because I’m aware of it.

Compared to today’s hip and uber-connected Millennials, I’m a hopelessly antiquarian Gen-Xer. I do not and hope to never own a smart phone. (My career aspiration is to eventually go “full Wendell Berry” and refuse to even use a computer.) The only Rock I know is Classic; I don’t even know what “Emo” is (or was); anyway, these days I mostly dig on Bluegrass and Old-Time – you know, “both kinds of music.” I greatly prefer slow travel by train to blasting around the country (and world) stuffed into an airplane. I’ve vowed that my dearly loved ’89 Toyota pickup will be the last car I ever own. (It doesn’t have to last my whole lifetime – just until peak oil drives gas prices out of range of all but the one-percenters…) And I get all giddy whenever a new article comes out in Low Tech Magazine.

With that thumbnail sketch of my corn-pone backwardness, you can understand that by the time an internet trend reaches me, its cutting-edge has long since dulled.

One such contemporary internet meme for which I am late-as-usual to the party is: crowdsourcing support for scientific and research endeavors. I was excited to learn recently about sites such as experiment.com that provide a crowd-funding platform for research projects. This may turn out to be a viable support mechanism for “Chemistry Without Borders” projects, like those we undertake at Aqueous Solutions, which often are difficult to fund through conventional academic channels.

I would be interested to hear from any researchers who have experience with crowd funding their work – what do you think? Pros? Cons? Groovy? Or a total drag?

One thing about doing fieldwork is that practical and applied research projects seem to constantly throw themselves at you. I wrote about one in last week’s post, calling on the (Bio-) Chemists Without Borders community to help us hack a cheap-and-easy field E.coli water tests.

Another nugget (pun intended) I have been mulling over for a while now is how to develop a low-cost treatment system for village water sources impacted by gold mining effluents.

Burma is a country with a lot of mining operations and not a lot of environmental and public health protections.[1] Cyanide – a toxin so potent that it gets its own chapter in The Poisoner’s Handbook[2] – is by far the most common lixiviant (extraction agent) used in gold mining, accounting for about 90% of world production.[3] It’s also used in the recovery of base metal such as copper, lead, and zinc.


Gold mine in Burma.
Image source: http://thevelvetrocket.com/2011/02/23/photos-of-the-day-gold-mining-in-myanmrarburma/

A number of physical and chemical mechanisms influence the fate of cyanide released to the environment, including volatilization, sorption to sediments, oxidation, hydroloysis, photolysis, and biodegradation.[4] Cyanide reacts relatively quickly to for thiocyanate, which is less toxic but much more persistent.[5]

In my work and travels in SE Asia, I’ve encountered numerous individuals and communities concerned about their exposure to mining effluents. These have included complaints of symptoms consistent with exposure to thiocyanate, including skin, eye, and respiratory irritations, nausea and stomach ulcers, and possible neurological effects.

Without epidemiological surveys it is impossible to confirm exposure to cyanide or cyanate species, and the predominant exposure routes (occupational, food and drinking water, dermal exposure e.g. during bathing and clothes washing, etc.). But there is little doubt that mining in Burma heavily impacts water quality at the local and even regional scales, and that proper control measures on cyanide release to the environment are non-existent.

It turns out, though, that many garden-variety indigenous microbes are capable of uptake, conversion, sorption, and/or precipitation of the cyanide, cyanate, and thiocyanate.[3] Microbial species living in mine tailings piles can become acclimatized to elevated cyanide and thiocyanate. Some species, for example the ubiquitous Pseudomonas, are capable of using cyanide and thiocyanate as their source of carbon and nitrogen and are particularly effective at degradation.

A variety of fixed-bed bioreactors for cyanide/thiocyanate degradation have been developed and tested at the lab, pilot, and full scale with encouraging results.[5] One study found activated carbon to be a favorable biofilm support medium, due to its high porosity and surface area for microbial colonization, and its capacity for adsorption of cyanide and thiocyanate complexes.[6]

This has led me to wonder if we could develop a low-cost fixed-film bioreactor using locally generated adsorbent biochar as the support medium, and a cyanide-acclimated microbial inoculum harvested from local gold mill tailings.

It’s a tough question whether such a system could produce drinking-water-quality-water, especially in the case of source waters that are very heavily impacted by mining effluents and therefore are likely to contain also a host of toxic metals. Although, thiocyanate readily forms complexes with many transition metals, so some metals removal may also be achievable through co-precipitation. Furthermore, biochars have also been demonstrated as effective for some uptake of some heavy metals.[7]

Could the water be made safe for drinking and food preparation is thus a totally open – and difficult – question. In my experience, though, many affected communities have worked to secure alternative sources of water for consumption, but still rely on mining impacted waters for bathing, personal hygiene, and clothes washing. A cost-effective treatment system could, therefore, alleviate dermal exposures, or, for example, provide sufficiently detoxified water for raising fish or watering livestock.

Anyway, just some ideas that come up in day-to-day activities here in the village. I wonder if we should test the crowd-funded-science-research waters. What do you think? Anyone want to team up on this project?


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References

[1] At What Price? Gold Mining In Kachin State, Burma. Images Asia & Pan Kachin Development Society, November 2004. [http://www.ibiblio.org/obl/docs/gold%20pdf1.pdf]

Vrieze P, Naing Zaw H. In Tenasserim hills, rise in mining threatens communities. The Irrawaddy, Wednesday, February 5, 2014. [http://www.irrawaddy.org/feature/tenasserim-hills-rise-mining-threatens-communities.html]

[2] Blum D. The Poisoner’s Handbook: Murder and the Birth of Forensic Medicine in Jazz Age New York. Penguin, pubs. 2011. The book has also been made into a PBS film: http://www.pbs.org/wgbh/americanexperience/films/poisoners/

[3] Akcil A., Mudder T. Microbial destruction of cyanide wastes in gold mining: process review. Biotechnology Letters 25: 445–450, 2003.

[4] ATSDR Toxicological Profile for Cyanide. [http://www.atsdr.cdc.gov/toxprofiles/tp8-c6.pdf]

[5] Gould WD, King M, Mohapatra BR, Cameron RA, Kapoor A, Koren DW. A critical review on destruction of thiocyanate in mining effluents. Minerals Engineering 34 (2012) 38–47.

[6] Dictor MC, Battaglia-Brunet F, Morin D, Bories A, Clarens M. Biological treatment of gold ore cyanidation wastewater in fixed bed reactors. Environmental Pollution, Vol. 97, No. 3, pp.287-294.

[7] Mohan D, Sarswat A, Ok YS, Pittman CU. 2014. Organic and Inorganic Contaminants Removal from Water with Biochar, a Re- newable, Low Cost and Sustainable Adsorbent- a Critical Review. Bioresource Technology (in press).


3 comments:

  1. Josh this is really interesting! CN is still the preferred method of leaching in the 1st world but we have liners which (generally) catch the CN and prevent it from entering the soil/aquifers. How do they currently collect the gold-cyanide leachate (to get the gold) and then what do they do with the spent leachate, if anything? Generally in the US, which may or may not be similar in Burma, the largest health issues surrounding mining is the leaching of metals into the aquifers from the acidic "pit lakes" or holes that fill up with water. This is a hard problem to tackle and basically here we pray that there are some native carbonates which will buffer (yay precipitation!) the water before it hits our drinking water. So what I’m wondering is do you think this could be causing the health issues in Burma? Without investigation it may be hard to pick apart the culprit for the health effects. However, treating the gold-cyanide spent leachate will definitely be a step in the right direction. I think it’s a great idea. Let me know how I can help!

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  2. Hey, I don't have access to the sources you cited but sounds like a good idea. Even though you would want to make sure what exactly you are trying to remove - cyanides, thiocyanates or heavy metals. As well, here are some facts which are important to consider when applying a biological system in a rural area: A biological system needs to be running all the time - it´s not something you can turn of for a week or so. For that reason it is important to maintain a constant supply of food for the bacteria. As well you want to avoid peaks in pH, shock loadings/concentration peaks in toxic substances and excessive temperature changes.
    I'd have to consult literature for more detailed information on the concrete topic of biological cyanide removal. As far as I know, this is not the standard method in 1st world countries...


    Lg Phil

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  3. N. Kuyucak, A. Akcil, Cyanide and Removal Options from Effluents in Gold Mining and Metallurgical Processes. Minerals Engineering, 50-51, 13-29, 2013.

    Botz, M., Mudder, T., Akcil, A., Cyanide treatment: physical, chemical and biological processes (Chapter 28), Advances in Gold Ore Processing, ed. M. Adams, Elsevier Ltd., Amsterdam, pp.672-702, 2005.

    Akcil A., Destruction of cyanide in gold mill effluents: biological versus chemical treatments, Biotechnology Advances, Vol.21, No. 6, pp.501-510, 2003.


    Akcil A., Mudder T., Microbial destruction of cyanide wastes in gold mining: process review, Biotechnology Letters, Vol.25, No. 6, pp.445-450, 2003.

    ReplyDelete