Cleaning the environment!

Cleaning the environment!

ROMA – Lerata Mothepu is developing highly specialised materials to remove potentially dangerous pollutants from your environment.
Under the supervision of Dr Tebello Mahamo and Mrs Itumeleng Seotsanyana-Mokhosi, Mothepu is building materials he calls catalysts or complexes.
He uses these to target a specific and potentially problematic pollutant called nitrophenol (whatever that means).
By the way, brace for impact, as we enter the tricky territory of chemistry. Of course, we will demystify the chemistry for you. At least we will try. So don’t go away!
Let’s start.

You probably know what we mean by a catalyst. Eh hee! That thing which the high school teacher used to call “a material that speeds up a rate of reaction without taking part in the reaction!”
But don’t tell this to anyone, the teacher was not being totally right when she said, “without taking part in the reaction.” You see! You now recall catalysts!
So Lerata is making those things.

He is building the catalysts with copper and cobalt. You surely know copper is a metal, is that right? Cobalt is also a metal. Both are called transition metals — don’t ask why.
On their own, these metals don’t act as catalysts, at least in this particular case. So let Mothepu tell you the stealthy (secret) part, “when these metals react with ligands, they make complexes which we now call catalysts, organometallic catalysts.”

Don’t leave; we will struggle to tell you what that means. Probably you raised your eyebrows at the mention of the word ligand; what on earth is that? Suppose a molecule is attached to a metal ion, in which case the molecule shares both of its electrons with the metal in a bond. That contributing molecule is a ligand.
Sorry if you still don’t get it. And don’t worry. After all, it does not matter in the larger scheme of things.

You remember we said a thing or two about transition metals, copper and cobalt in this case. Why them? “Transition metals, have empty d-obitarls which are able to absorb electrons from the ligands, making what we call coordinate bonds,” Mothepu says as he branches into coordination chemistry. Now you probably see why we don’t ask Mothepu to talk much. Every time he talks, Oh boy! Can the guy speak Greek! So these ligands, he calls Schiff Bases. They come in many forms and he tested quite a few of them.
Once the catalysts are built, Mothepu now sets his sights on the culprit, nitrophenol, a pollutant he wants to wipe off. But don’t think destroying this chemical will be a walk in the park.
Actually, the catalysts do not attack the pollutant directly.

“I first use the catalysts to break hydrogen peroxide,” that is Mothepu, struggling to unravel his magic to a layman, “hydrogen peroxide, on its own, is a stable compound. However, if you bring the catalysts, it breaks into hydroxyl radicals.” The hydroxyl radicals, whatever they are, are the ones which break down the nitrophenols, changing them into simpler, less dangerous compounds (don’t worry, we will tell you what those compounds are later).

For those who want to know hydrogen peroxide, think about this. Water is hydrogen oxide, H2O, chemically speaking. But hydrogen peroxide is just slightly different, it is H2O2. Yep! You add extra oxygen and, what a difference you will make! But why is nitrophenol a culprit? First let’s see what it is (or what they are). We now talk in the plural because these compounds come in more than one version. Nitrophenols are man-made chemicals found in common compounds such as dyes, paints, rubber, drugs, and fungicides and so on.
So you probably bump across them on a daily basis, you just aren’t aware.

As you throw away those things, nitrophenols may get released from them, finally finding their way into water and soil and very little into the air.
And, as you may have guessed already, they finally get into you!
And that is the scary part!

While the nature of their effect on humans is under intensive studies, they have already been proven toxic to animals.
Back to the catalysts, how effective are they in helping to destroy the nitrophenols?
“I set to find out exactly that,” Mothepu said. “I used seven ligands for copper and seven ligands for cobalt to make copper and cobalt complexes.”
“I monitored absorbance of nitrophenols using UV-Vis. In the presence of catalysts, nitrophenols decrease with time. Compared in the space of an hour, cobalt complexes were more active than copper complexes.”

Mothepu had one more thing to add, “Once I am pleased with my complexes, I suspend them in supports made of keratin which I extract from chicken feathers. I dissolve feathers in sodium sulphide and when I add ammonium sulphate, keratin precipitates.”
Now you see why we don’t invite folks like Mothepu to this platform? Oh boy! Can they speak in tongues!

Own Correspondent

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