Combating Plastic Pollution on the Microscopic Level

             Polyethylene terephthalate (PET) is a type of plastic that is one of the most widely used plastics in the world. It is used in things such as running shirts, carpet fibers, curtains, solar panels, tennis balls, microwavable containers, and plastic bottles. The PET Resin Association says, “Virtually all single-serving and 2-liter bottles of carbonated soft drinks and water sold in the U.S. are made from PET.” The plastic is very popular amongst manufacturers and with good reason! It is an extremely durable, lightweight, safe, and is 100% recyclable. However, the recycling rate for PET in the United States has been on a decline in 2019, residing at a low 27.9%. The un-recycled PET plastics that remain in the landfills are extremely problematic for the same reasons that make PET a preferred material. According to the World Wildlife Fund, those plastic bottles listed earlier could take about 450 years to decompose. These plastics are in turn, killing wildlife and polluting the world ecosystem.

This is the chemical structure of PET.

             Researchers at Reed College, located in Oregon, are working on ways to break down PET using certain combinations of bacteria. However, “[PET’s] long tough strands of ethylene glycol and terephthalic acid monomers, all tangled up together. These strands lend PET its durability; they also make it virtually impervious to biological reaction.” Professor Jay Mellies had previously examined bacteria, using only plastics as their source of nutrition, with some bacterial species remaining alive at the end of his experiments. He assumed that because plastic was their only nutritional source, they must be able to break down plastic in some way. He was then given a grant to further explore the use of bacteria to break down these PET’s. The students looked at numerous colonies and after 8 weeks of trials, one sample was found to be working quite well. The sample of 5 different strains of bacteria had consumed 3 percent of the plastic’s mass. Under further inspection of the sample, tiny holes where the bacteria had ate the plastic could be seen under a microscope. The bacteria had formed a symbiotic relationship where some were breaking down the plastics into new forms that each other could digest. 

             Looking at how the bacteria do this; they naturally produce hydrolases. These are enzymes that the bacteria produce and use to digest their food. These hydrolases work like scissors that cut the bacteria’s food into smaller counterparts that they can eat. Even though PET is much larger and more complex than anything the bacteria would normally consume, the theory is that the bacteria would be able to adapt and produce more efficient enzymes to break down the PET. 

Above is the reaction of an esterase (a type of hydrolase) and how it breaks down into smaller components.

             Further experimentation is still going on where they are looking to boost and speed of the generation of these hydrolases that can break down PET. The genetic pathways are not fully understood in this situation, but Professor Mellies is confident that new genetic techniques can solve their problems. This research will be extremely beneficial in the case of pollution, as well as furthering the use of symbiotic bacteria. 

 

Read the article here.

Sources:

https://www.reed.edu/reed-magazine/articles/2021/reed-biologists-plastic-eating-bacteria.html

http://www.petresin.org/news_introtoPET.asp

https://www.wwf.org.au/news/blogs/the-lifecycle-of-plastics#gs.xnq6tn

Cleaning Up Steel Production

 

              Steel surrounds us in our daily lives; we use this alloy of iron, carbon, and other elements in cars, fridges, surgical instruments, and an incredible number of other products. However, for every ton of steel produced, nearly 2 tons of carbon dioxide are emitted and the extreme demand for steel has resulted in this process accounting for about 8 percent of global carbon dioxide emissions in 2018. This has resulted in many scientists striving for the decarbonization of steel through a couple different approaches.

One approach the scientists have been considering includes the use of hydrogen as a fuel source in order to heat the enormous blast furnaces and executives of steel plants indicate this may be the best solution in the future. Traditionally, this process has utilized liquid natural gas or coke, a derivative of coal, however, these conventional sources lead to the emission of significant amounts of carbon dioxide. Employing hydrogen as a fuel source would release only water as a by-product and would therefore be significantly more environmentally friendly. Unfortunately, the current sources of hydrogen include natural gas reforming and electrolysis, both of which employ fossil fuels as either feedstock or fuel and emit greenhouse gases. If hydrogen could be produced by electrolysis coupled to renewable energy sources such as solar or wind, this could provide a significantly more environmentally friendly avenue to steel synthesis.

Another potential solution suggested by experts includes the use of electric arc furnaces connected to sources of renewable power. Electric arc furnaces themselves are cleaner than the traditional blast furnaces as they do not require the continuous input of coke. Additionally, it is easier to control their internal temperature which increases their efficiency. Connecting these cleaner furnaces to renewable energy sources could allow for the production of low-carbon steel, thereby significantly decreasing the harmful emissions conventionally released.

            The final solution that is being suggested is using bacteria to transform carbon dioxide from the plant exhaust into ethanol. The biotech start-up LanzaTech identified this, or a similar bacterium, in the gut of rabbits that was able to produce ethanol through a process of gas fermentation. With ethanol constituting 10% of every gallon of gasoline sold in the US, this new supply of ethanol would allow for the crops (namely sugar cane, corn, or grasses) that generally provide this compound or the land that these crops grow on to be put to other uses. The fuel produced by these bacteria could be utilized by cars or jets, but it could also be converted to ethylene and then to polyethylene for use in plastic products, therefore allowing for a greener source of plastic. Overall, the implementation of these bacteria would also reduce carbon dioxide emissions and allow for a greener steel production process overall.

References:

https://www.nytimes.com/2021/03/17/business/steel-emissions-arcelor-mittal.html

https://www.mckinsey.com/industries/metals-and-mining/our-insights/decarbonization-challenge-for-steel#

https://www.worldsteel.org/about-steel.html

https://www.energy.gov/eere/fuelcells/hydrogen-fuel-basics#:~:text=Hydrogen%20is%20a%20clean%20fuel,fuel%20cell%2C%20produces%20only%20water.&text=Today%2C%20hydrogen%20fuel%20can%20be,solar%2Ddriven%20and%20biological%20processes

https://www.mbrashem.com/electric-arc-furnaces-vs-blast-furnaces/

https://www.en-former.com/en/hydrogen-revolution-steel-production/

https://www.cnbc.com/2018/07/27/lanzatech-turns-carbon-waste-into-ethanol-to-one-day-power-planes-cars.html

https://en.sysbiotech.at/articles/ralstonia-eutropha-soil-bacteria-with-big-potential/

Plastic Pollution and Its Solution.

 Plastic Pollution and Its Solution.

It is undeniable that plastic has completely changed our lives. Our current lives are closely related to plastic products. However, due to our excessive use of plastics and the lack of relevant recycling measures, plastic products have already had a serious negative impact on the ecosystem.

From 1950 to 2019, humans have produced 8.3 billion tons of plastic and 6.4 billion tons of waste, of which only 9% is recycled, 12% is incinerated, and 79% is landfilled. In fact, most plastics can be recycled.

Because of changes in the types of polymers we use, it is particularly important to develop new recycling methods. More and more products, such as cars, rely on the strength of composite materials made of fiberglass and carbon fiber. These materials cannot be melted and reshaped as easily as other plastics. Chemists have begun to study ways to recycle them in the laboratory. Others choose to develop plastics that are easier to recycle.

The road to recycling plastic is full of challenges, and not all plastics have the opportunity to be recycled. PET bottles and high-density polyethylene containers are the most valuable because these plastics are relatively clean materials. Other plastic waste, such as polypropylene plastics will end up being landfills. 

More and more people are beginning to pay attention to recyclable plastics. Despite the difficulties, chemists will continue to carry out unremitting research.

Sources:

1.    Tullo, A. H. Plastic Has a Problem; Is Chemical Recycling the Solution? C&EN Global Enterprise2019, 97(39), 29–34.

2.    Hub, I. Plastic: The problem and its impact – Impact Hub https://impacthub.net/plastic-the-problem-and-its-impact/ (accessed Mar 25, 2021).

Have You Seen this Color Before?

Blue dyes have been around since the days of crushing lapis lazuli: a silicate based inorganic mineral. But now, a new set of compounds, which was the subject of a recent article in the New York Times, has been added to a list of blue inorganic pigments which has not been altered in the last 200 years. The Y-In-Mn containing oxides, discovered by a team of materials science researchers headed by Mas Subramanian at Oregon State University, was an unexpected product of a high temperature reaction involving constituent metal oxides. This addition of an inorganic synthetic pigment presents an environmentally benign alternative to the current pigments used in industry for creating blue paints.

 The new compounds, with a general formula YIn_1-xMn_xO₃, were synthesized back in 2009 from a high temperature reaction of Y₂O₃, In₂O₃, and Mn₂O₃ and shows a range of blue hue depending, on the level of Mn content, i.e. the larger ratio of manganese in the compound, the more intense the blue color becomes. This is the first example of a manganese containing compound being involved in a synthetic dye. So, the question is, what is special about these compounds such that they have this characteristic blue color?

As it turns out, the compound highly absorbs light in the green and red regions of the electromagnetic spectrum, meanwhile there is little absorbance in the blue region. As a result, the compound appears blue to the eye. The absorbance in the red-green region is highly dependent on the manganese content, though, with higher Mn concentrations yielding greater and broader absorbance. Thus, the compounds with a lower Mn content appear to be a more navy-blue meanwhile those with higher amounts of Mn take on a vibrant blue. And this color remains highly stable, according to the researchers, with no indications that the color will degrade. This pigment was appropriately named after the element it contains (YInMn Blue) and was approved for industrial use in coatings and plastics in 2017 by the Environmental Protection Agency.

This series of compounds represents the first synthetic inorganic pigment that has been synthesized in 200 years and is a revolutionary finding for the paint/coating industry. Pigments like Cobalt Blue, Prussian Blue, and ultramarine, amongst others, have been the go to inorganic pigments for getting a blue color. But each of these have historically had drawbacks that this new YInMn Blue does not. Cobalt Blue, for instance, is a toxicity hazard being that in contains  cobalt. Prussian Blue is unstable under acidic conditions. And, not only is ultramarine unstable under heat, but also, the manufacturing of the pigment causes the release of harmful emissions into the environment. Thus, YInMn Blue provides the blue color without the potential toxicity, instability, and harmful emissions while also having a tuneability for its color. In other words, this new synthetic pigment provides a better alternative.

This YInMn oxide is now available for purchase by artists everywhere as a paint and was entered into the Forbes Pigment Collection at Harvard University. The compound's brilliant blue color has even attracted Crayola where a crayon shade is being devised with the name "Bleutiful." This surely provides an example of the broad impacts of chemistry as this discovery left its mark on the paint and coating industry all the way to children who are excited to draw with this new shade of blue. 

Sources:

https://www.nytimes.com/2021/02/05/style/blue-pigment-YInMn.html

Smith, A.; Mizoguchi, H.; Delaney, K.; Spaldin, N.; Sleight, A.; Subramanian, M. Mn3+In Trigonal Bipyramidal Coordination: A New Blue Chromophore. Journal of the American Chemical Society 2009, 131 (47), 17084-17086.

  

Recycling Nitrate Rich Runoff into Fertilizer

 The usage of nitrogen based fertilizer has allowed the farming industry to increase the overall capable yield therefore allowing more people to be fed per similar plot of land. It is estimated that around half of the world's food production is grown with the use of nitrogen based fertilizers allowing for food production to meet the ever growing world population demands. The use of this excessive amount of nitrogen based fertilizer results in water runoff rich in nitrates that leads to eutrophication allowing algae blooms that deplete water of natural oxygen therefore causing this ecosystem to suffocate. 

An article in SciTechDaily¹ discusses efforts that are focusing on converting this nitrate rich water runoff into ammonia so it can be used to create fertilizer or power fuel cells. The most recent promising study by Yu², is with the use of special strained Ru nanoclusters electrodes that promote the generation of hydrogen radicals, therefore accelerating the hydrogenation of nitrate reduction products leading to the desired ammonia. This end product may be familiar in the case of fertilizer since ammonia used to produce it comes from the famous Haber-Bosch process that would be in competition with this new discovered process. This new process does have advantages over its century old competitor process due to the fact that this process is able to run at ambient temperature and can source its electricity from green renewable energy sources such as solar and wind power. Electrolysis has another great advantage in which a large amount of ammonia does not have to be stored in containers helping in reducing accidental explosions like the incident in Beirut this past year. 

Before this process can be implicated into industry there are still a few hurdles to get over the main one the numerous plants that produce ammonia through the Haber-Bosch process that has mainly monopolized the way it's produced. Another factor in the study found was that directly using agricultural runoff did not have a high enough concentration of nitrates to be viable for this method, so a preceding process will be required for this to become a viable option to produce ammonia. This process is a step in the right direction of helping to eliminate eutrophication of our waterways as well as recycling materials easily accessible helping to reduce carbon emissions put into our atmosphere.

Sources:

1. “Polluted Water as a Source of Fertilizer.” SciTechDaily, 4 Feb. 2021, scitechdaily.com/polluted-water-as-a-source-of-fertilizer/.

2. “Efficient Ammonia Electrosynthesis from Nitrate on Strained Ruthenium Nanoclusters.” Journal of the American Chemical Society, pubs.acs.org/doi/abs/10.1021/jacs.0c00418. 

3. “Electrocatalytic Nitrate Reduction for Sustainable Ammonia Production.” Cell, 26 Jan. 2021, www.cell.com/joule/fulltext/S2542-4351(20)30624-3.

4. EPA damns itself with faint praise in response to Inspector General's Gulf Dead Zone report | NRDC

Chemistry of Water Corrosion in Flint, Michigan

       Everyone has seen in the news the water issues plaguing the city of Flint Michigan and the basis behind the contamination issues comes down to chemistry. 

    The issues arose when the city decided to switch their water supply from the Detroit River to the Flint River water in 2014. The new water was treated with the same chlorine disinfectant as the previous source, but lacked orthophosphate corrosion inhibitors that had been added to the Detroit River water previously used. Within months of switching problems began to occur.

Lead concentrations were found in the water to be ~50 times more than the EPA's standards. Olson et. al were concerned that the pipes were the possible culprits to be blames for the contamination.  Using inductively an inductively coupled plasma mass spectrometer (ICPMS) they were able to observe the metal content in various samples of lead service line pipes.  In most pipes build ups of various substances are expected throughout the pipes lifetime. In pipes from Flint Michigan, the build up was found to be composed of 12.4% lead, which was significantly lower than that of lead pipes from other areas which didn't use the Flint River water, which had values around 54%.

How does chemistry play into this issue?

The answer is the removed mineral preservation layer. Mineral preservation layers protect the pipes from corrosion by adding phosphate (PO₄^4-) ions to the water before it is distributed. This encourages the formation of a lead (II) phosphate (Pb₃₍PO₄)₂) crust inside the pipes, which prevents the lead in the pipes from undergoing a characteristic redox reaction, which oxidizes the lead from its neutral solid state and leaches itself into the water.

With phosphate not being added the mineral layer present in the pipes began to degrade and expose the metal lead in the pipes.

The study also found that the low pH (7-8 compared to 10 from other water systems) of the water exiting the facility was contributing to corrosion by increasing the solubility of the lead (II) carbonate (PbCO₃), which may also act as a protection layer in the pipes. When PbCO₃ dissolves it allows for the formation of carbon dioxide and releases free lead ions into the water, disrupting the equilibrium depicted below.

These chemical factors above caused the lead contamination issues above, but through recognizing the problem and switching back to Detroit’s water supply the city was able to begin to reverse their water chemistry. The problems however do highlight the issues surrounding the continued use of lead pipes and the importance of replacing and upgrading aging civil infrastructure. 

 

Sources:

https://www.pbs.org/newshour/science/study-confirms-lead-got-flints-water

https://www.michiganradio.org/post/flint-water-crisis-began-5-years-ago-city-better
 

 Environ. Sci. Technol. Lett. 2017, 4, 9, 356–361

https://www.acs.org/content/acs/en/education/resources/highschool/chemmatters/past-issues/2016-2017/december-2016/flint-water-crisis.html