Aerogel: (Gel) Bath Time
Week 14: Calcium Chloride Or Calcium Nitrate?
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 :-)
TL;DR Of Gelation Bead Bath 🛁
Note: This week’s article will be a short one. Why? We will be finalizing chemical mechanisms & technology equipment to build the Aerogel Beads.
There’s a critical section of aerogel bead production:
The gelation bath!
It is vital because the beads must react with calcium ions (Ca2+) for ion exchange to occur between heavy metal ions.
There are two candidate materials you can use for the gelation bath:
But which one should you select? Let’s see their properties.
Calcium Chloride Vs. Calcium Nitrate ⚛️
Calcium Chloride is made up of one calcium ion (Ca2+) and two chlorine atoms (Cl-)
Calcium has two extra protons. Each chlorine ion has an extra electron.
The extra protons & electrons create ionic bonds. The electron will be closer to the calcium ion than the chlorine atoms. Calcium wants electrons to be near it (aka electrophile).
The most crucial properties are molecular weight & pH (acidity).
Molecular weight can determine the mechanical strength of a material. The mechanical properties are more robust when the molecular weight number is higher.
One can roughly think of a beginner at the gym vs a seasoned lifter. Low molecular weight is the beginner's (strength is average). The seasoned lifter has a high molecular weight (strength is superior).
The pH (power of hydrogen) determines if there are more hydrogen ions (H+, protons) or hydroxide ions (OH-); acidic means more (H+) ions & alkaline means more (OH-) ions.
The molecular weight is 147.01 g/mol & the pH is seven (when touches water).
Why is the pH of Calcium Chloride seven? It’s not acidic or alkaline?
Consider the reaction with water because the filter will be rinsed with distilled & deionized water. You must consider the reaction of the gel bath when it touches water.
The calcium in CaCl2 is replaced with Ca(OH)2 due to the material being a strong base/alkaline (contains a positive charge). The Cl2 now becomes HCl (hydrogen chloride) when reacted with water, and it has an anionic charge.
The chlorine atom tends to be more negative because it “took away” hydrogen’s electron to satisfy its outer shell with eight electrons.
The final reaction is made neutral by donating the Hydrogen atom/proton in HCl (H+) and letting it react with Ca(OH)2 to make water as a product, leaving behind Calcium Chloride.
Calcium Nitrate is made up of one calcium ion (Ca2+), two nitrogen atoms, and six oxygen atoms.
The calcium ion has a positive charge of two (Ca2+). It has two extra protons. Three oxygen atoms attach to one nitrogen atom. This is (NO3)- (nitrate ion).
A positive and negative charge cancel out. But Nitrate is left with a negative charge of one. This means that one nitrate molecule has one extra electron.
Calcium Nitrate has two Nitrate molecules. We have two extra electrons because of that.
The molecular weight of Calcium Nitrate is 236.15 g/mol & the pH is approximately 6.0 (slightly acidic, anionic).
Final Results 🔮
It depends on what you desire to optimize.
We’ll select Calcium Nitrate if you choose to optimize mechanical strength.
We’ll select Calcium Chloride if you choose to optimize health risk mitigation.
What is so bad about Calcium Nitrate?
Inhalation of Calcium Nitrate in a powder compound can cause coughing and soreness in the throat. Short-term side effects associated with exposure to this compound include dizziness, headaches, nausea, and vomiting.
The risk is lowered when it is used to make the filters. But you must take precautions when handling the material.
I recommend using Calcium Nitrate as a default. But don’t rule out Calcium Chloride. Test the beads and notice their differences in the laboratory.
Final Checks For The Gelation Bath Are Ready. ✔️
© 2023 by Carlos Manuel Jarquín Sánchez. All Rights Reserved.