#28: Banana Peels to Potassium Metal (Part 2)

In part one of this experiment, I collected, dried, burned, and boiled 40 banana peels to obtain potassium carbonate (K2CO3). Before attempting to isolate pure potassium, I needed to transform this chemical into a different potassium compound: potassium hydroxide (KOH). Here's how it happened:

1. To start, I created a saturated solution of calcium hydroxide (Ca(OH)2). I then filtered off any excess solute which hadn't been dissolved. 
2. Next, I added the potassium carbonate that I had obtained from banana peels. After thoroughly stirring the mixture, I let the beaker sit overnight as the following reaction took place: K2CO3 + Ca(OH)2 → CaCO3 + 2KOH. 
3. Initially, because the calcium hydroxide solution was saturated, there was no room to dissolve the potassium carbonate. However, as the reaction occurred, the newly formed potassium hydroxide became dissolved while the calcium carbonate was forced out of solution. 
4. When I returned the next morning, I found that the contents of the beaker had separated into two distinct layers. At the bottom lay a white slurry of calcium carbonate crystals—just as expected. 
5. By filtering the beaker's contents, I was able to remove the solid calcium carbonate. This left me with a solution of potassium hydroxide. 
6. The last step was to obtain the KOH's solid form. I started by boiling down the solution until there was nothing but wet crystals. I decided not to boil it dry for fear that the chemical would harden onto and/or corrode the beaker. 
7. Instead, I completed the dehydration process by placing the moist potassium hydroxide in a desiccator bag. A desiccator bag is basically an enclosed space containing a hydroscopic (water absorbing) substance. In my case, I added a larger container of sodium hydroxide. This would act as the desiccant by absorbing the water that evaporated from the potassium hydroxide. At the same time, the sealed bag kept the potassium hydroxide (also hydroscopic) from absorbing new water from the surrounding air. 
8. A few days later, I retrieved the fully dried potassium hydroxide. 

Stay tuned for part 3.

Potassium carbonate from banana peels (left) and calcium hydroxide (right).  

White calcium carbonate crystals falling out of potassium hydroxide solution. 

Solid potassium hydroxide after evaporation and desiccation.

#27: Banana Peels to Potassium Metal (Part 1)

It's common knowledge that bananas are a great source of potassium. What people don't know is that they contain much less of the mineral than many other foods such as beans or potatoes. Nonetheless bananas have a lot. Interestingly, the peel contains roughly 40% or 200 mg of the fruit's potassium content. This is high when you consider the peel's low volume and low weight. Upon learning these facts myself, I began to wonder if raw potassium could be obtained from banana peels. As usual, I asked the internet. To my astonishment, I found very little. The closest I got was a video that showed how to extract a small amount of potassium carbonate (K2CO3). While this wasn't exactly what I was looking for, it got me thinking. What if I could I go beyond potassium carbonate?

My challenge was to devise a series of chemical reactions that would eventually get me to pure potassium. Through research and reasoning, I developed a plan and put it into action. Here is the first installment of my fascinating experiment:

1. Over the course of two months, I collected peels. I forced my siblings to eat as many bananas as possible. I guess this made them my lab monkeys. 
2. As I received new peels, I placed them across a bamboo pole that I hung in the garage. Within a week or so, they turned brown and dried up. 
3. When I reached 40 dried banana peels, I removed them from their rack and placed them in a small brick oven that I made. Next, I burned them with a blowtorch. This was difficult because the peels did not burn easily. Eventually, I had reduced the pile of peels to a cup of ash. 
4. Back in the lab, I added the banana remains to a large beaker and poured in an equal volume of water. With my butane burner on high, I brought the mixture to a boil. As the liquid bubbled, the potassium, in carbonate form, dissolved in the water while the rest of the ash did not. 
5. Through repeated filtering, I removed the undissolved ash. This left me with a dilute solution of potassium carbonate, among other trace compounds.  
6. By boiling down the solution, I obtained impure potassium carbonate in solid form—the first step toward potassium metal. 

Stay tuned for part 2 of this experiment.

It's well known that bananas are high in potassium, the question is, can the potassium be extracted?

To dry the banana peels, I hung them over a bamboo pole in my garage. 

While it took quite a long time to burn all 40 banana peels, wielding a blowtorch is never boring.