Category Archives: Inorganic

Environmental Hazard to Reusable Material: Converting Plastics and CO2 into Fuel

Plastic waste management has become a serious issue over the last few decades. In 2019, the total amount of plastic produced since 1950 totaled just over 9.5 billion tons, and plastic production hasn’t slowed down, as 400 million tons were added to that in 2020.

The chemical bonds that make up plastics are hard to break and do not degrade in the environment quickly. This makes plastic waste challenging to deal with, leading to a large amount of plastic being discarded or incinerated.

While people have been recycling since the late 1980s, only about 6% of annual waste is recycled, and only a further 20% of that stays recycled.  Current recycling methods consist of mechanical recycling, a process by which the plastic is ground or melted down into a new product, or chemical recycling, a process by which chemical additives break down the plastic into more manageable pieces to be used as raw material. However, both methods are not environmentally friendly or cheap, leading to a high volume of plastics that are not recycled (see below).

The final fate of plastics over 65 years. only 1.72% of plastics remain recycled.

Finding new ways to deal with plastic waste is a heavy focus for environmental scientists, leading to catalysis, electrochemistry, and photochemistry developments. One such method, developed by Dr. Resier and his team at the University of Cambridge, has found a way to deal with this waste in an environmentally clean way. Using a perovskite (PVK) based photocathode and a copper-palladium alloy anode in combination with a CO2 reduction catalyst, they transformed PET plastics and CO2 into a variety of useable fuels and by-products, such as carbon monoxide, hydrogen gas, and glycolic acid.

Electrochemical pathway of CO2 reduction into CO and byproducts.

The photoelectrochemical system works upon sunlight exposure under zero applied voltage and generates products 10-100 times faster than other catalytic methods. Further, the catalyst system is not sensitive to the introduction of bio-organic molecules; in fact, the presence of small amounts of food products could increase the activity of the system.

However, this process is anything but cheap. The copper-palladium alloy anode is not cheap to fabricate, and the materials required are rare, palladium being over 15 times rarer than platinum. This increases startup costs, which is not favorable to most companies who could instead dump the waste.

While advancements in this technology are still needed, there is a positive outlook for the future of plastics and environmental contaminants. We may yet be able to save our fragile, yet vital planet from our own advancement.

 

Tristan Ruigrok

The Gore-Tex Enigma

Gore-Tex is a highly versatile material that has garnered a lot of publicity in recent years.

It is a magical material in many respects. Water simply glides off it, leaving it bone dry. Being also very breathable and light, it is no surprise that it is the ideal material for water resistant clothing.

First invented in 1968 by Wilbert and Robert Gore, it is made of polytetrafluoroethylene, more commonly known as Teflon. Not the hard stuff though. It’s basically Teflon that has been stretched… a lot.

With the likes of Adidas and Nike incorporating it into their outdoor wear products, its worldwide use and popularity has called into question the manufacturing process and its environmental impacts.

Teflon is a very durable material that does not degrade easy and lasts for a long, long time. This is a good thing right? Well, yes… But what happens when that fifteen year old jacket you own is discarded or lost, and finds itself buried in the dirt outside an abandoned parking lot?

It persists. And doesn’t degrade. For centuries.

 

PFC’s or perfluorinated compounds are those that contain only carbon and fluorine atoms. Teflon is made from these compounds.

Chemical structure of Teflon: repeating units of carbon and fluorine atoms

The problem with PFC’s is that they tend to accumulate within our bodies and the environment. They are difficult to break down as they are quite unreactive.

A class action lawsuit at a DuPont Teflon plant found a very strong association between working with PFC’s and two types of cancer. Since then, many other studies have found a correlation between exposure to certain PFC’s and negative health outcomes.

To be clear, it isn’t the wearing of Gore-Tex products that is concerning. Also, not all PFC’s are harmful. However, the manufacturing process dispels many harmful PFC’s into the environment.

Gore-Tex jackets are also near impossible to recycle. They are made in complex ways, and the design process involves multiple layers, glues, and components.

Gore-Tex must not be completely written off though. Gore and company have assured investors and the public that they are stopping the use of many harmful PFC’s in their manufacturing process. However, the effects of this are yet to be seen.

There are also other, more intriguing applications of this remarkable material.

What is not talked about nearly enough is the role of Gore-Tex in medicine. It has shown to be ideal for use inside our bodies.

Being so unreactive, it allows the body’s cells and tissues to grow through it without any side effects. This makes it a viable material for many medical applications.

Like most technologies, Gore-Tex is complicated in many ways. Its strengths in one regard prove to be its downfall in another. It seems the jury is still out on this one

– Salik Rushdy

A green future for ammonia

Chemists from the University of California, Berkley (UCB) have designed a new material that could reduce the energy requirements of the Haber-Bosch process.  The group hopes their research, published January 11th 2023, will conserve energy and lead to a “greener” future for ammonia and fertilizer production.

Current infrastructure needed to maintain the pressure and temperature required for the Haber-Bosch process source

The Haber-Bosch process has been the main method for producing ammonia since its invention over 100 years ago.  It is widely considered one of the most important scientific discoveries of the 20th century. Yet, despite its important role producing ammonia for agricultural fertilizer, its industrial synthesis continues to be energy inefficient.

High temperatures and pressures are needed to produce ammonia which must then be extracted to be used. Conventionally, the reaction mixture is cooled from 500℃ to -20℃. This condenses the synthesized ammonia and separates it from the remaining chemicals. However, cooling the mixture while maintaining the pressure of 300 atmospheres accounts for a large proportion of the processes’ energy loss.

Benjamin Snyder, who leads the UCB research group, said it was this extraction step that his team sought to improve by “finding a material where you can capture and then release very large quantities of ammonia, ideally with a minimal input of energy”.

These requirements led the research group to create a metal-organic framework (MOF) material.  The MOF had a crystal structure made from copper atoms linked to cyclohexane dicarboxylate molecules.  The crystalline structure gave the material unique properties suited for its use in ammonia extraction.

Structure of the cyclohexane dicarboxylate molecule used to make the MOF source

When exposed to ammonia the material changes its structure from a rigid crystal to a loosely packed and porous polymer. The polymer form can readily store a large amount of ammonia within it which can then be released with cooling. The result is that ammonia can be extracted 195℃ above the temperature required by current methods and at half the pressure.

Not only would the MOF save energy in the extraction process but, interestingly, after releasing the ammonia “the polymer somehow weaves itself back into a three-dimensional framework” says Snyder. This mechanism, which is still being studied, allows the MOF to be used repeatably.

With the Haber-Bosch process using 1% of the world’s energy, the research done by Snyder and his group is an important step in producing a greener future for ammonia.