Newly Discovered Bacterium Rids Problematic Pair of Toxic Groundwater Contaminants

Date: October 9, 2018
Source: New Jersey Institute of Technology
Summary: Researchers have detailed the discovery of the first bacterium known capable of simultaneously degrading the pair of chemical contaminants -- 1,4-Dioxane and 1,1-DCE.

Image of DD4 cells.
Credit: NJIT, Mengyan Li

Known as a chemical manufacturing by-product of many cosmetics and home cleaning products, the industrial solvent 1,4-Dioxane is now considered by the Environmental Protection Agency to be an "emerging contaminant" and "likely human carcinogen" that can be found at thousands of groundwater sites nationally -- potentially representing a multi-billion dollar environmental remediation challenge.

However, it is the contaminant's frequent co-existence with another toxic chemical -- 1,1-Dichloroethylene (1,1-DCE) -- that has been found to aid in 1,4-dioxane's resistance to certain remediation strategies, including degradation by naturally-occurring microbes.

Now, New Jersey Institute of Technology (NJIT) researchers have detailed the discovery of the first bacterium known capable of simultaneously degrading the pair of chemical contaminants -- 1,4-Dioxane and 1,1-DCE. The study, published in Environmental Science & Technology Letters, also showcases the efficiency of the microbe, called Azoarcus sp. DD4 (DD4), in reducing 1,4-dioxane and 1,1-DCE levels in co-contaminated groundwater samples.

"Nationwide, researchers have found that more than 80% of the groundwater sites contaminated with 1,4-dioxane also contain 1,1-DCE," said Mengyan Li, assistant professor of chemistry and environmental science at NJIT. "This pair of chemicals are toxic and costly to remove from the environment because the pair have very different properties that typically require separate treatment solutions. Biodegradation by DD4 is the first biological method we have found for treating both compounds concurrently, and it is also environmentally-friendly and cost-efficient."

Li's research team initially discovered the DD4 microbe from activated sludge samples collected from a municipal wastewater treatment facility. In the lab, Li's team was able to isolate and analyze DD4's ability to degrade 1,4-dioxane and 1,1-DCE simultaneously in contaminated groundwater samples over a two-week period.

Applying the microbe to the field samples, Li's team observed that concentration of 1,4-dioxane was degraded from 10 parts-per-million (10 ppm) -- or 3,000 times the limit of the EPA's guidance level of 0.35 parts-per-billion (0.35 ppb) -- to under 0.38 ppb. The lab also found 1,1-DCE concentration levels reduced from over 3 ppm to below 0.02 ppm.

Notably, DD4 displayed resistance to cellular toxicity produced by the metabolites of 1,1-DCE, which typically inhibit the ability of other bacteria capable of degrading 1,4-dioxane. Li's team observed that although DD4 was partially inhibited in its ability to degrade 1,4-dioxane when excessive amounts of 1,1-DCE were artificially spiked in the water samples, 1,4-dioxane degradation capability immediately recovered once the microbe had depleted 1,1-DCE.

"Overall, we were impressed by the performance of DD4," said Li. "We did not add nutrients like ammonia for the microbe to feed on, or other facilitators that might enhance the bacterium's activity. This demonstrated to us the potential of this bacterium for future use in the field."

In an analysis of the genetic makeup of DD4, Li's lab identified a potentially key gene related to the microbe's chemical degradation activity. Li says that the gene encodes for an enzyme, called soluble di-iron monooxygenase (SDIMO), with versatile capabilities of breaking down chemical pollutants. "We want to characterize it (this enzyme) further to see if we can better learn the mechanism underlying how DD4 degrades these contaminants." said Li.

Along with DD4's 1,1-DCE-resistance and ability to degrade the co-contaminants concurrently, Li says the bacterium possesses several other key traits that make it conducive as a potential bioremediation solution at contaminated groundwater sites -- such as its ability to disperse freely through water to remediate larger areas of contamination, rather than aggregating like other bacterial treatments. The microbe can also be cultured rapidly and can sustain for extended periods with limited nutrient source.

"We tested the bacterium in normal refrigerated temperature over three days and its viability remained above 80%," said Li. "After a week, half were still alive. This makes it even more desirable because it would be able to survive the delivery time from the lab to contaminated sites."

Li's lab is now conducting further tests of the bacterium in the lab to better understand how DD4 might perform at contaminated water sites. With feasibility tests already underway, Li says his team could begin field demonstrations of DD4 as a water treatment solution for 1,4-dioxane and 1,1-DCE contamination sites as early as next year.

"Ideally, we may inject the bacteria into the center of a contamination zone, or try growing them on the surface of bio-barriers that help stop spread of contamination," said Li. "First, we'd like to do more tests and possibly develop a gene marker that helps us assess the bacteria's performance. Then, we would like to move into the field."

Story Source:
New Jersey Institute of Technology. "Newly discovered bacterium rids problematic pair of toxic groundwater contaminants." ScienceDaily. ScienceDaily, 9 October 2018. https://www.sciencedaily.com/releases/2018/10/181009115019.htm

Heavy Metals in Water Meet Their Match

Reusable, Carbon Nanotube-Reinforced Filters Clean Toxins from Water, study shows

Date: July 27, 2017
Source: Rice University
Summary: A high school student's project removes more than 99 percent of heavy metal toxins from water. A new article demonstrates its potential for water remediation in developing nations around the world.

Plain quartz fiber, top, gains the ability to remove toxic metals from water when carbon nanotubes are added, bottom. The filters absorbed more than 99 percent of metals from test samples laden with cadmium, cobalt, copper, mercury, nickel and lead. Once saturated, the filters can be washed and reused.
Credit: Barron Research Group/Rice University

Carbon nanotubes immobilized in a tuft of quartz fiber have the power to remove toxic heavy metals from water, according to researchers at Rice University.

Prize-winning filters produced in the lab of Rice chemist Andrew Barron by then-high school student and lead author Perry Alagappan absorb more than 99 percent of metals from samples laden with cadmium, cobalt, copper, mercury, nickel and lead. Once saturated, the filters can be washed with a mild household chemical like vinegar and reused.

The researchers calculated one gram of the material could treat 83,000 liters of contaminated water to meet World Health Organization standards -- enough to supply the daily needs of 11,000 people.

The lab's analysis of the new filters appears this month in Nature's open-access Scientific Reports.

The robust filters consist of carbon nanotubes grown in place on quartz fibers that are then chemically epoxidized. Lab tests showed that scaled-up versions of the "supported-epoxidized carbon nanotube" (SENT) filters proved able to treat 5 liters of water in less than one minute and be renewed in 90 seconds. The material retained nearly 100 percent of its capacity to filter water for up to 70 liters per 100 grams of SENT, after which the metals contained could be extracted for reuse or turned into a solid for safe disposal.

While the quartz substrate gives the filter form and the carbon nanotube sheath makes it tough, the epoxidation via an oxidizing acid appears to be most responsible for adsorbing the metal, they determined.

Alagappan, now an undergraduate student at Stanford University, was inspired to start the project during a trip to India, where he learned about contamination of groundwater from the tons of electronic waste -- phones, computers and the like -- that improperly end up in landfills.

"Perry contacted me wanting to gain experience in laboratory research," Barron said. "Since we had an ongoing project started by Jessica Heimann, an undergraduate who was taking a semester at Jacobs University Bremen, this was a perfect match."

Barron said the raw materials for the filter are inexpensive and pointed out the conversion of acetic acid to vinegar is ubiquitous around the globe, which should simplify the process of recycling the filters for reuse even in remote locations. "Every culture on the planet knows how to make vinegar," he said.

"This would make the biggest social impact on village-scale units that could treat water in remote, developing regions," Barron said. "However, there is also the potential to scale up metal extraction, in particular from mine wastewater."

Alagappan's research won a series of awards while he was still a high school student in Clear Lake, a Houston suburb, as well as a visiting student in Barron's Rice lab. First was the top prize for environmental sciences at the Science and Engineering Fair of Houston in 2014. That qualified him to enter the Intel International Science and Engineering Fair in Los Angeles the next year, where he also took the top environmental award.

He booted that into the top prize at the 2015 Stockholm Junior Water Prize, where the crown princess of Sweden presented him with the honor.

"It's been a tremendous honor to be recognized on an international level for this research, and I am grateful for the opportunity to work on this project alongside such a talented group of individuals," Alagappan said. "I also especially appreciated being able to meet with other young researchers at the Intel International Science Fair and the Stockholm Junior Water Prize, who inspired me with their firm commitment to elevate society through science and technology."

Story Source: Rice University. "Heavy metals in water meet their match: Reusable, carbon nanotube-reinforced filters clean toxins from water, study shows." ScienceDaily. ScienceDaily, 27 July 2017. www.sciencedaily.com/releases/2017/07/170727083159.htm

More Environmentally-Friendly Concrete Made Using Sugar Cane Residue

Date: January 4, 2016
Source: Asociación RUVID
Summary: A new type of concrete has been developed that is cheaper and much less polluting to the environment. Researchers have swapped in sugar cane straw ash, a crop residue typically discarded as waste, as a substitute for Portland cement.

Researchers from the Universitat Politècnica de València (Polytechnic University of Valencia, UPV) and San Paolo State University (Unesp) have developed a new type of concrete that is cheaper and much less polluting to the environment. They have done so by swapping in sugar cane straw ash, a crop residue typically discarded as waste, as a substitute for Portland cement.

Currently pursued at laboratory scale only, the results of this work have been published in the Construction and Building Materials journal. They also form part of Brazilian student João Cláudio Bassan de Moraes's master's dissertation, directed by lecturer Mauro Tashima, who completed his PhD at the UPV and is currently lecturing at Unesp.

Talking to us about the project, Jordi Payá, researcher at the Concrete Science and Technology Institute (ICITECH) at the UPV, explains: "The harvester strips the cane, discarding the tops and leaves as waste. This is the raw material we work with, sugar cane straw." In total around 650 million tonnes of sugar cane are harvested in Brazil every year. Of this, between 15 and 20% corresponds to sugar straw, which is left on the field and either burned or left to decay naturally.

So far, the international research team has been able to obtain concrete using 30% less Portland cement, substituting it with the ashes obtained from burning the sugar cane straw.

"The cement itself is the most expensive and most polluting ingredient of concrete, which makes the benefits [of this new method] as much economic as environmental. We are also making use of a by-product that is currently unexploited, with all the benefits that this entails" (Payá).

Process

To burn the waste, UPV and Unesp researchers have designed a bespoke combustion burner, into which the raw material must be fed following a strict procedure. "Through this process we obtain ashes that are very reactive to the cement, a quality that is very important to the mechanical performance of the resulting concrete, to its resistance to compression, for instance" (Payá).

Work has focused primarily on the microstructural analysis of the concrete. "In the lab we analyse the chemical compounds of the ashes and of the compounds produced during the reaction with the cement, in order to assess their performance in the final product," explains Payá. Future work would include studying indicators related to the durability of mass and reinforced concrete.

The ICITECH research team also studies the use of other agricultural waste as a cement substitute, including the bamboo leaf.


Story Source: The above post is reprinted from materials provided by Asociación RUVID.

New Salt Compounds Challenge the Foundation of Chemistry

Dec. 19, 2013 — All good research breaks new ground, but rarely does the research unearth truths that challenge the foundation of a science. That's what Artem R. Oganov has done, and the professor of theoretical crystallography in the Department of Geosciences will have his work published in the Dec. 20, 2013 issue of the journal Science.

The paper, titled "Unexpected stable stoichiometries of sodium chlorides," documents his predictions about, and experiments in, compressing sodium chloride -- rock salt -- to form new compounds. These compounds validate his methodology for predicting the properties of objects -- a methodology now used worldwide for computational material discovery -- and hold the promise of novel materials and applications.

"I think this work is the beginning of a revolution in chemistry," Oganov says. "We found, at low pressures achievable in the lab, perfectly stable compounds that contradict the classical rules of chemistry. If you apply the rather modest pressure of 200,000 atmospheres -- for comparison purposes, the pressure at the center of the Earth is 3.6 million atmospheres -- everything we know from chemistry textbooks falls apart."

Standard chemistry textbooks say that sodium and chlorine have very different electronegativities, and thus must form an ionic compound with a well-defined composition. Sodium's charge is +1, chlorine's charge is -1; sodium will give away an electron, chlorine wants to take an electron. According to chemistry texts and common sense, the only possible combination of these atoms in a compound is 1:1 -- rock salt, or NaCl.

"We found crazy compounds that violate textbook rules -- NaCl3, NaCl7, Na3Cl2, Na2Cl, and Na3Cl," says Weiwei Zhang, the lead author and visiting scholar at the Oganov lab and Stony Brook's Center for Materials by Design, directed by Oganov. "These compounds are thermodynamically stable and, once made, remain indefinitely; nothing will make them fall apart. Classical chemistry forbids their very existence. Classical chemistry also says atoms try to fulfill the octet rule -- elements gain or lose electrons to attain an electron configuration of the nearest noble gas, with complete outer electron shells that make them very stable. Well, here that rule is not satisfied."

This opens all kinds of possibilities. Oganov posited that, if you mix NaCl with metallic sodium, compress in a diamond anvil cell, and heat, you will get sodium-rich compounds like Na3Cl. He likewise theorized that, if you take NaCl, mix it with pure chlorine, and compress and heat, you will get chlorine-rich compounds such as NaCl3. This is exactly what was seen in the experiments, which were performed by the team of Alexander F. Goncharov of Carnegie Institution of Washington, confirming Oganov's predictions. "When you change the theoretical underpinnings of chemistry, that's a big deal," Goncharov says. "But what it also means is that we can make new materials with exotic properties."

Among the compounds Oganov and his team created are two-dimensional metals, where electricity is conducted along the layers of the structure. "One of these materials -- Na3Cl -- has a fascinating structure," he says. "It is [composed of] layers of NaCl and layers of pure sodium. The NaCl layers act as insulators; the pure sodium layers conduct electricity. Systems with two-dimensional electrical conductivity have attracted a lot of interest."

Like much of science, Oganov's pursuit began with curiosity -- and obstinacy.

"For a long time, this idea was haunting me -- when a chemistry textbook says that a certain compound is impossible, what does it really mean, impossible? Because I can, on the computer, place atoms in certain positions and in certain proportions. Then I can compute the energy. 'Impossible' really means that the energy is going to be high. So how high is it going to be? And is there any way to bring that energy down, and make these compounds stable?"

To Oganov, impossible didn't mean something absolute. "The rules of chemistry are not like mathematical theorems, which cannot be broken," he says. "The rules of chemistry can be broken, because impossible only means 'softly' impossible! You just need to find conditions where these rules no longer hold."

Oganov's team harnessed their own energy to bring the research to fruition. "We have a fantastic team," he says. "The theoretical work was done here at Stony Brook; the experimental work took place at the Geophysical Laboratory in the Carnegie Institution of Washington."

Additionally, Oganov's team utilized the NSF-funded Extreme Science and Engineering Discovery Environment (XSEDE) by running USPEX code -- the world-leading code for crystal structure prediction -- on Stampede, a supercomputer at the Texas Advanced Computing Center at the University of Texas at Austin. USPEX was developed by Oganov's lab and he estimates over 1,500 researchers use it worldwide.

His discovery may have application in the planetary sciences, where high-pressure phenomena abound. It may explain results of other experiments, where researchers compressed materials and got puzzling results. His computational methodology and structure-prediction algorithms will help researchers predict material combinations and structures that exhibit desired properties and levels of stability.

"We have learned an important lesson -- that even in well-defined systems, like sodium chloride, you can find totally new chemistry, and totally new and very exciting materials," Oganov says. "It's like discovering a new continent; now we need to map the land. Current rules cannot cope with this new chemistry. We need to invent something that will."

Original article posted at: http://www.sciencedaily.com/releases/2013/12/131219142138.htm