Aerogel: Buffer Time
Week #10: Reducing Property Deficiencies In The Aerogel
My intentions for writing these articles are:
- Explain technical information about aerogels in simple terms (to the public)
- Store information and habits for my future self and others (in <7 minutes)
Coolio? Sweet. Enjoy the series :-)
Chemistry Modification Updates ⚛️
I realized there was a problem when mixing the base chemical, the carboxyl activator, the Ca2+ ions, and the cross-linkers.
The pH, chemical stability, water solubility, etc. of the aerogel were in jeopardy without a compound/molecule minimizing changes that would affect the adsorption properties. The molecule is called a buffer.
The other concern is that the filter will ionize the water and make it unsafe to drink without a buffer minimizing changes in the properties.
Enter Biological Buffers.
Biological buffers allow the pH of an aqueous solution to remain constant while the concentration of hydrogen ions changes.
They were made by Dr. Norman Good in 1966 to reduce damage to human cells and the environment caused by pH changes. These buffers are exactly what it needs to provide a healthier relationship with the people and nature without environmental consequences.
An example is acetic acid (vinegar) which will use to extract heavy metal ions from the filter.
Acetic acid and sodium acetate (acetate ion) is the acidic buffer.
There are two options in this reaction:
- The reaction goes to the left (to make acetic acid)
- The reaction goes to the right (to make acetate ions)
The reaction (direction) depends if the base (negatively charged, electron donor) or the acid (positively charged, electron receiver) is the chemical that is being added to the solution.
What did you mean by that, Carlos?
Let’s say you added an equal amount of acetic acid and sodium acetate to a glass beaker. What if you wanted the beaker to have more acetic acid than sodium acetate?
One would need to insert a strong acid (like H3O+) into the beaker so the sodium acetate (CH3COO-) can regain its missing proton (the lost proton was H+). The remainder of the acid is a water molecule! This creates the acetic acid and creates the desired outcome: Acetic Acid > Sodium Acetate
(H3O+ is a water molecule with an extra proton | H2O & H+)
But what if you wanted the beaker to have more sodium acetate than acetic acid?
One would need to insert a strong base (like OH-) into the beaker so the acetic acid gives up (donates) a proton (H+) and stabilizes the hydroxide group to make a water molecule! It is now sodium acetate (CH3COO-) and created the desired outcome: Sodium Acetate > Acetic Acid
(OH- is a hydroxide group that needs a proton to become a water molecule | HO + free electron)
Have you noticed something about both buffers? They both created a water molecule as a “leftover” group! The pH for both solutions did not change because:
- Both solutions resulted in the same “leftover” group!
- Both reactions quickly reacted & “consumed” the free protons & electrons!
The properties of both buffer solutions are nearly the same! Wild!
That Is The Power Of Buffers In Solutions.
Introducing MES Buffer! 🎉
MES is an abbreviation for the biological buffer: 2-(N-morpholino)ethanesulfonic acid
The reason I chose MES over 20+ options from Good’s Biological Buffers are as follows:
- MES pH stability range is from 5.2–7.1
- The melting point for MES is approximately 300°C
- Highly soluble in water
- pKa is 6.16 at 20°C
But why were these options crucial?
There are values that we must submit and defend when creating an impact on people and the environment.
- The world’s wastewaters have similar pH levels (pH 5.5–6.5)
- MES will not melt if water is boiled (Boiling point of H2O is 100°C)
- Being soluble allows MES to mix and bond to the aerogel
- pKa level is safe to add to the filter without environmental damage
(Add the boundaries of the pH stability range and divide by two to find the pKa of MES) | 5.2 + 7.1 / 2 ≈ 6.15
The Supplementary Chemicals For The Filter Are Complete.
© 2023 by Carlos Manuel Jarquín Sánchez. All Rights Reserved.