Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Homemade diaphragms for electrolysis. New developments
Many electrochemical syntheses require a diaphragm. However, there is very little information on amateur simple, cheap and reliable diaphragms on the
Internet. I decided to fix this. Amateurs use clay pots as a diaphragm, but they are expensive, heavy and conduct electricity poorly
I read the instructions mysteriusbhoice and decided to develop my own diaphragms. The basic material for them is meltblown polypropylene fabric as
well as any CYLINDRICAL container made of polyethylene or polypropylene (bottles, glasses, cans, etc.) on which you will wind this fabric.
The basic manufacturing technique is as follows: Using an electric soldering iron, many holes are made in a circle in a plastic container, then the
container is sanded with sandpaper to remove irregularities. Next, you wind the polypropylene fabric in several layers. After that, you make ropes
from the same fabric and wrap this fabric on top with considerable force and fix it with a knot. This is very important. Without a strong fit, your
diaphragm will leak.
And so you got a raw diaphragm. In this state, it is not a diaphragm but rather a filter. There are several ways to make this a diaphragm.
The most universal way is to wrap with a separator from of lithium-ion batteries the container BEFORE wrapping with polypropylene fabric. I do not
recommend separators from automotive lead batteries. These separators have poor geometry and are difficult to seal hermetically.
You can use such a diaphragm for organic and inorganic electrosynthesis. Polypropylene is resistant to acids, alkalis and organic solvents.
The second way is to soak the polypropylene fabric with a polymer solution and remove the solvent with water. This is what did mysteriusbhoice. The
downside of this method is that even such a durable plastic as PVC can be destroyed by organic solvents. Other varnishes and polymers are much less
durable. I did it this way: The workpiece for the diaphragm with polypropylene fabric was impregnated with varnish from old paint with settled filler.
Afterwards, the workpiece was immersed in a bucket of warm water with washing powder while actively stirring. Then the wet workpiece was wrapped on
top with new ropes made of polypropylene fabric and dried
With these actions, you reduce the porosity of the diaphragm, but the polymer filler usually has lower chemical resistance than polypropylene.
The last way is inorganic fillers. You can soak the workpiece with sodium silicate and add any acid. This way you will get a diaphragm for working
with organic substances and an acidic medium. For an alkaline medium you can use sodium hydroxide with magnesium sulfate or calcium salts instead acid
for silicate percipation.
Inorganic fillers are resistant to any organic solvents and can be used for organic electrosynthesis. But they are sensitive to the pH of the
environment.
Diaphragm test. The diaphragm should conduct current in salt solutions and not leak. Pour water into the diaphragm and leave it for about 10 minutes.
It should not leak a significant amount of water. A small amount of liquid is acceptable. If too much water leaks, add ropes for fixation or soak it
with fillers again.
P.S. If you preparing sulfuric acid by electrolysis of gypsum, you can not modify the polypropylene fabric. The gypsum layer is a diaphragm in itself
[Edited on 13-9-2024 by Hexabromobenzene]
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Ion exchange resins are not discussed in this article. I have not found a way to make them from readily available materials. Non-crosslinked resins
will not be chemically stable and will not be suitable for organic solvents. Sulfonated polystyrene would work well in theory for inorganic syntheses
such as chlor-alkali cells. The manufacturing process is the same as with polymer filler.
Sample of workpiece on pic
[Edited on 13-9-2024 by Hexabromobenzene]
 
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
A more improved method for making porous diaphragm.
You no longer need solvents or adhesives anymore. Everything is very simple and cheap
You only need a polypropylene container and a piece of fabric meltblown. You can also make a container from a polypropylene pipe from the sewer
weldind bottom with an electric soldering iron
Polypropylene blank with holes is wrapped with a piece of polypropylene fabric. Thin iron sheet is wrapped on top. Blank with fabric is fixed with a
metal wire and heats up in the oven at 170-180 degrees for several minutes
Due to the temperature and pressure of the iron sheet, the layer of polypropylene becomes much less porous and is more like ceramics as we need.
Diaphragm is very light, chemically persistent and cheap
The porous layer of plastic gets wet, but the water does not leak significantly
  
[Edited on 28-9-2024 by Hexabromobenzene]
|
|
|
Pumukli
National Hazard
Posts: 708
Registered: 2-3-2014
Location: EU
Member Is Offline
Mood: No Mood
|
|
Looks promising. Hats off, Hexabromobenzene!
I like it when I see people use simple everyday things and assemble them a way no one tried before! This polypropylene wrap thingy looks exactly like
that.  The heat-treatment is also an interesting approach. Simple, cheap and with
the critical timing and temperature it might provide a useful "toy" for us hobbysts.
Now I would like to see the characterization attempts of this gadget!
E.g: fill the cell with a known concentration of acid then determine the acidity (leakage) in the outer container at 1 hour increments. Draw a graph
leaked acid versus time.  Or give us a number: leaked acid in an hour (in
millimol/hour)
Or fill the cells (both compartments) with a known (one molar maybe?) salt solution (NaCl) and measure the electric resistance of this assembly with a
DVM. This ohmic resistance value would be an interesting clue regarding the possible performance of the cell.
Or use this cell in a practical electrosynthesis and show us what can be achieved with such a "toy"!
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
I made the second according to the same technology. The temperature was increased to 180 degrees
The leak of water through the new backed diaphragm was 1 ml in 10 minutes. First noticeably more. Probably due to incorrect compression of an iron
sheet during baking.
For conducting an electrochemical test, stainless spoons were used as electrodes, a strong solution of sodium chloride and 2 batteries(3 volts) AA as
a source of current. Without diaphragm, the current of 400 mA. With backed diaphragm number 2 current about 30 mA.
The current of the first diaphragm was 3 mA. Current of another diaphragm without baking, but with a separator from lithium batteries was 2 mA
The volume of the diaphragms is 90ml.
A diaphragm without baking and without a separator from a post http://www.sciencemadness.org/talk/viewthread.php?tid=160566... with a volume of 400 ml shows a current of 20 mA
Definitely a working method, but more experiments are required.
During baking, the fabric is welded to the polypropylene container and you no longer need to fix it
Polypropylene is a wonderful material. Having an electric soldering iron, oven and electric stove can be made of various reactors, rectification
columns, distillators. Operating temperature of polypropylene up to 120 degrees
[Edited on 28-9-2024 by Hexabromobenzene]
|
|
|
BlueSwordM
Harmless
Posts: 3
Registered: 21-10-2024
Member Is Offline
|
|
If you're interested, I found a website blog discussing of many electrochemical subjects, but the most interesting part to me was related to cation
exchange membranes:
https://chemisting.com/2022/11/27/a-diy-cation-exchange-memb...
There's a whole series on this subject.
I've managed to replicate the first membrane and it works decently.
I'm slowly moving up the chain to replicate this results, but they're very promising.
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Yes, it is a PVA ion exchange membrane. It is not chemically stable
I was able to find some ion exchange resin for water purification in the form of small balls. I will bake layer it between polypropylene fabric. It
will be an analogue of ionic cement cement from mysteriusbhoice.
This ion exchange resin is very stable. It does not dissolve in dichloromethane and DMSO is resistant to alkalis and acids
|
|
|
semiconductive
Hazard to Others
Posts: 326
Registered: 12-2-2017
Location: Scappoose Oregon, USA.
Member Is Offline
Mood: Explorative
|
|
I'm curious; I found porous cups on ebay and bought one to try and fix a tin-plating problem. Background of issue, mentioned here:
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
How badly do membranes tend to clog in your experience?
This is the one I bought, for example:
Attachment: membrane.webp (13kB)
This file has been downloaded 94 times
It Sstarted out as white and had 2Amps of current flowing at 36Volts applied to the tin anode inside the cup with titanium dioxide, boric acid and
water in the anode compartment; Citric acid, and a steel target to plate were outside the cup, making the cathode portion (the bucket).
This does work, quite well. I can electroplate copper coins with tin, and get a very shiny smooth coating that's practically a mirror.
But, over the last week of use the current carrying capacity has dropped from 2Amps down to a measly 150 milliamps.
Increasing the conductivity of the solution by adding acid has no effect.
At first there were large white blocks of ceramic visible with small grey/black lines on it; I tried grinding them off and thinning the ceramic cup
wall thickness; but slowly the ceramic has turned to what's shown in the picture over a week.
I have been happy with the fact that the membrane does not leak water except very slowly. Maybe a teaspoon in a week's use. So there's no
degradation of the citric acid by electrolysis. Basically, I can wipe of a sponge of it from the ceramic filter and it keeps right on plating --
organics stay OUTSIDE the cup, ions pass through the cup, and I can use high anode voltages to get ions into solution.
But, how common is it to loose 92% of your current flow in a situation like I'm describing?
Since you're experimenting:
I bought some fish-tank bio-ceramic filters that have much larger pores, and was considering dissolving a little bit of cellulose acetate paper that I
got on ebay to turn them into a membrane so I could compare how they performed to my ceramic cup. Another thought that occurred to me was to dissolve
a bit of clear silicone caulk in a large quantity of ethyl acetate, in order to increase the chemical resistance/life of the cellulose acetate.
The plastics you are using -- do they completely block organic molecules from passing through; or are you just trying to mostly contain chemicals in
separate chambers with it?
Can the plastics you've experimented with be dissolved, or are the pores mechanical in nature and unable to be coated? I don't think it would be too
hard to wrap a bio-filter in plastic and cook at 180 in an oven. But, I'm curious as to how stable you think your membrane would be during tin
plating?
(I know very little chemistry. I'm a BSEE -- so this is all learn by bumps, crashes, and braile. ) But I enjoy experimenting.
|
|
|
BlueSwordM
Harmless
Posts: 3
Registered: 21-10-2024
Member Is Offline
|
|
Quote: Originally posted by Hexabromobenzene  | Yes, it is a PVA ion exchange membrane. It is not chemically stable
I was able to find some ion exchange resin for water purification in the form of small balls. I will bake layer it between polypropylene fabric. It
will be an analogue of ionic cement cement from mysteriusbhoice.
This ion exchange resin is very stable. It does not dissolve in dichloromethane and DMSO is resistant to alkalis and acids |
That is somewhat true, but further protocols designed membranes that are much tougher, as it seems the main bottleneck is in membrane chemical
resistance rather than PVA.
This doesn't fix the issue of low pH performance, so it limits PVA CEMs to mainly neutral/high pH environments.
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Polypropylene is resistant to solvents and you can't dissolve it in anything. Ion exchange resin is also resistant to solvents, even such as
dichloromethane, because it is a cross-linked polymer
Water flows through the diaphragm at a rate of 10-20 ml per hour. You can reduce this by simply adding another layer of polypropylene, but the
resistance will increase. Adding ion exchange resin will probably reduce the porosity and reduce the resistance. I hope.
The task of the diaphragm is organic and inorganic electrosynthesis. In my case, I just need to limit diffusion as much as possible without
significantly reducing the current. I do not like diaphragm electrolysis. It requires more voltage, but the process occurs with less current. But
sometimes there is no other choice.
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Diffusion test. A solution of melanoidin was poured into the container with the diaphragm. In the second container, pure water. In the photo, the
result of diffusion after 14 hours as well as a solution after direct mixing of the contents of 2 containers
The fluid level in 1 and in the 2nd vessel was the same.
The diaphragm is made by baking method
  
|
|
|
Pumukli
National Hazard
Posts: 708
Registered: 2-3-2014
Location: EU
Member Is Offline
Mood: No Mood
|
|
Looks promising.
Now, that you probably have something that would worth playing with, do you plan to use this membrane-setup for some sort of electro-synthesis?
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Preliminary test showed a current up to 0.7a with 12 volts in a solution of salt. Other diaphragms do not conduct electricity. Probably a plastic
layer is too thick
Apparently, the diaphragm leaks at the place of contact of porous plastic with the workpiece.
The addition of ion exchange resin did not improve conductivity but increased leaks.
The size of the pores in the meltblown fabric several micrometers but probably was reduced significantly when the plastic is flattened during backing
|
|
|
semiconductive
Hazard to Others
Posts: 326
Registered: 12-2-2017
Location: Scappoose Oregon, USA.
Member Is Offline
Mood: Explorative
|
|
I've tried some experiments;
1st attempt was to use biofilter ceramic filters with one level tablespoon of talc clay + 1 sheet of Cellulose DI (not tri) acetate paper. 8" x 12"
roughly.
I attempted to dissolve acetate paper in ethyl-acetate (MEK substitute), but it's extremely slow dissolving; so I added a small amount of acetone. I
added to this the talc, clay.
Then I simply poured it through the biofilter with the bottom plugged using silicone.
The next day I added about 1 cc of silicone to a cup of ethyl-acetate and made a re-enforcing rinse to block up large open pores.
I Poured this through the bio-filter several times allowing dry time in-between each pour. Each time I applied more sealant, the flow rate slowed
until the filter was able to hold liquid for 15 minutes.
I Allowed it to cure for two days.
As a test electrode I used a graphite bar that fit snugly inside the biofilter, 1 part boric acid, 2 parts titanium dioxide.
Even though this is a thick walled biofilter, it still conducted 0.8A at 36V and 0.25A at 12V.
I allowed it to run for about a week, but somewhere in the middle of the week the ceramic cracked in half spoiling the solution an wrecking the
filter.
Second attempt; I want to hardware store to see if I could get PP fabric, like you have. They didn't sell it, but they did sell paint strainer cloth.
Upon checking acetone resistance, it was good. After looking MSDS online, apparently this kind of netting is typically polyester.
I then put it in a sewing clamp to make it flat and tight. I mixed acetone + 2 sheets acetate, 1 teaspoon of TiO2. Made it fairly thin.
I then used a fan paintbrush 3cm wide, to paint liquid onto stretched netting. I coated it multiple times until I could see no more open netting
holes, and then once more coat to be safe.
I then wrapped a tin electrode bar with a ziplock bag, and that in the acetate cloth I had made. Putting a little silicone along the edges, I did my
best to seal the seams and wrapped the bar three times. There was excess netting sticking out after removing from the clamp, and it was convenient
for making a bottom seal with silicone and a top cylinder wall.
I then put zip-tie clamps around it to hold it fixed while it cured for several days. I think this is too much work; but it's very nice looking.
After removing the clamps, and working the tin bar loose, I took the manufactured cup and dipped it in water.
Unfortunately it has a pin hole somewhere as about 1CC of water fills it per minute when submerged to the next in a sink.
There are three layers of paper spiral wound, sealed at the top and bottom with silicone and along the final edge. Depending on where the leak is,
this might still be use-able. In theory, water will flow along the spiral -- but electricity will not follow the spiral, and instead will attempt to
take the shortest path which should be through the netting and cellulose acetate.
I'm debating whether to paint an extra coating of acetate on the outside to fully seal it, before trying it.
Third attempt:
I got polypropylene felt. This is from e-bay™, and meant to be used in Cars for covering speakers.
I used two sheets acetate, 1 teaspoon TiO2.
I cut a piece of cloth roughtly 6 inches high and 8 inches long. I saturated it with the acetate solution and TiO2. Then I rolled it into a tube
about 3/4 inch diameter with three to four full turns. Initially the felt wall looked to be about 3/16 inch thick. I then wrapped thread around it
to hold the tube closed and made a felt plug for the bottom.
It was not wrapped on a form. This was a very messy process, and I got quite a bit of acetate dried on my hands like paint.
I added one more acetate sheet to the remaining titanium in my mixing jar, and just enough acetone to dissolve it. Afterward I mixed in methanol, to
thin it. Then I used this as a rinse, pouring it into the tube and then dumping the solution back into the container I mixed it in. Giving a few
seconds to dry, I then repeated the process until the tube could hold the solution without dripping.
I then let it dry overnight. The longer it dried, the stiffer it became.
In the morning, I put it in a convection microwave oven and warmed it to 150 farenheight for a half hour. Then I set the temperature to 275 for 15
minutes.
I'm hoping this is hot enough to melt the polypropylene barely and cuase it to fill in any drying cracks in the acetate.
This produced an excellent stiff tube; roughly 1/8 inch thick. It's stiff enough that it doesn't need to have a form inside it once it's cooked.
Attempting to blow into it shows that it is nearly air-tight as well.
I think I may buy a glass rod or use hot water PVC pipe to make a form the next time I try this. It will make a straighter tube and allow me to
compress/thin the walls more.
After manufacture:
I filled it with 1 part H2BO3 to 2 parts TiO2 (roughly by volume.) And then inserted a graphite rod that is coated lightly with cellulose acetate --
but the bottom of it is scraped off. This is to make the rod preferably break down fastest at the bottom while reducing TiO2 to titanium ions, and
cause the electrode to be used up from the tip first for longest life.
The finished tube holds water, and drips about 2 drops per minute of water.
Unfortunately, the resistance is high. I only get 5mA of current at 12V.
But, with time, I hope some of the TiO2 in the acetate will be broken down by electricity passing, and the conductivity will rise.
But it is working, and I will run it at 36Volts for a week and see if it survives. Right now I'm plating tin with it. 30 mA from a tin electrode, and 10 mA from the titanium electrode, into a citric acid bath.
[Edited on 3-12-2024 by semiconductive]
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Polypropylene fabric is used to make reusable bags and it is also used to cover the back of furniture. Speaker fabric has a large fiber size and
therefore a large pore size. 135 degrees Celsius is not enough. Polypropylene begins to soften at 150 and melts at 160. I usually heat it up to
170-175. But be careful. If you overheat your diaphragm will stop conducting electricity. Also, when baking, compression force is needed to compress
the fiber
I also recently found a patent for hydrolysis of PMMA plastic in alkali with isopropanol. It can be completely hydrolyzed to a gel-like mass of
polyacrylic acid or partially hydrolyzed. PMMA plastic can be dissolved in many solvents and you can soak the fabric in a solvent of this plastic and
treat it with alkali
|
|
|
bearbot22
Harmless
Posts: 24
Registered: 10-4-2018
Member Is Offline
Mood: No Mood
|
|
Cell for Testing diaphragm materials
Hello Hexabromobenzene,
thanks for your inspiring posts about finding the perfect DIY diaphragm.
In the past I have also searched for good materials for diaphragms and ion exchange membranes.
I made a small electrochemical cell for quick and easy testing of materials. [Photos 1 and 2]
Its made from two 50ml square wide-mouth PVC jars with 20mm diameter holes drilled in the 35mm lids.
I sealed electrodes and plugs with silicone tubing.
An aluminum U-rail serves as a holder and an M8 screw is used to press the bottles against each other.
A material to be tested as diaphragm is cut to a 30 mm diameter and clamped under the lid of a bottle. Sealing rings are used if necessary.
Three Tests are performed using this cell :
1. Porosity (aka Drip Test)
One bottle is filled with 35 ml of water and closed with the test material. The cell is placed upright, the lower bottle initially being empty.
Measure how long it takes until the upper bottle is empty or how much water has dripped into the lower bottle after 24 hours.
2. Acid-Base exchange
One of the bottles is filled with 50 ml diluted sulphuric acid (H2SO4 0.3 molar) and the other with water. 1 ml sodium hydroxide
solution (NaOH 10%) is added to the water. Check ph every few minutes/hours whether the content of the water+alkali bottle has become acidic.
3. Current-Flow
Bottles are filled with 50 ml H2SO4 0.3 molar each and fitted with a copper electrode. Current is measured in mA at voltages
between 2 and 8 volts using an adjustable DC power source. Compared with the current flow without the diaphragm, the resistance of the diaphragm can
be calculated in ohms.
I have now tested non-woven polypropylene. I hot-pressed the material at different temperatures and the results confirm yours. Below 160°C, the
porosity is largely retained. At 180°, the fibers are fused into a dense film after 40 seconds. In between, you get more or less porous versions that
might be suitable as a diaphragm.
Tested Materials
a) Brown wrapping paper
From an Amazon packing bag, tested in organic reduction, did not work
b) Baking paper
No-name, unbleached, silicone-coated on both sides, not to be glued, difficult to seal
c) Solid NaCl solution
Water with 10% table salt, heated, 2.5% gelatine dissolved, then left to solidify for 48 hours to a 2mm sheet.
d) Parchment paper
This material is mentioned in the literature, e.g. “Organic Electrochemistry” [Link]
It is a cellulose-based paper that's treated with sulphuric acid which makes it transparent, grease-proof and permanently wet-proof. When soaked, it
tears easily, swells, wrinkles and is therefore difficult to seal.
Available as tracing paper for technical drawings, it is also used for the traditional packaging of butter or cheese.
Can be confused with other transparent materials that are also referred to as “parchment paper”. To test, genuine parchment paper:
- has a white crease
- is easy to tear (unlike synthetic paper-like wraps)
- can be wetted with water
- cannot be glued with paper glue (unlike glassine)
- can be written on with a felt-tip pen without it running off (unlike silicone-coated papers)
- is resistant to diluted acids and alkalis, even chlorine cleaner (2.47% hypochlorite) hardly attacks it
e) Non-Woven-165-20
PP non-woven cut out of a shopping bag, hot-pressed with low pressure at 165°C for 20 seconds between silicone baking foils.
f) Non-Woven-180-20
as e, but heated to 180°C
g) Non-Woven-180-40
as f, but for 40 seconds
Imho, the sintered non-woven PP performs well. It doesn't have the lowest electrical resistance, but other advantages:
The porosity can be variably controlled, it can be shaped as required, does not need any additional support structures and does not require any
special storage conditions. Does not swell in electrolyte. It is also highly chemically stable. And, Oh yes, it's also cheap as spit ;-)
Many other materials were tested this way and found to be unsuitable, e.g. because they are impermeable to water and electricity [plaster (standard),
concrete (standard), latex (condom)] because they decompose: [cellulose tissue, glassine, writing paper] or because they are hydrophobic [ tyvek,
filter fleece].
Test-Cell
Test-Cell disassembled
Copper Electrode 20mm long, with silicone tube sealing
Hot pressed non-woven PP, F.l.t.r.: 20 sec @ 150, 20 sec @ 165°, 20 sec @ 180°, 40 sec @ 180°
Test results
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Thank you for testing. As you can see, the problem with the non-woven diaphragm is leakage. I have not been able to solve this problem. Adding layers
of fabric dramatically reduces conductivity to almost zero. This is probably due to the fact that polypropylene is hydrophobic. Using different types
of fabric did not show any significant improvement in the result.
Wrapping the top layer of fabric helps a little. This probably fixes the fibers. Perhaps impregnation with an ion-exchange layer should help. But I
have not yet found an affordable and stable material
Use the thickest fabric possible to wrap fewer layers. More porous fabric has better conductivity after baking. Maybe if you find a very thick fabric
it will help you.
Here is a photo making diaphragm. Bottom of polypyropylene pipe is welded with a soldering iron, then wrapped in fabric, clamped with a steel sheet
with wire and baked in the oven at 175 degrees.
Without a diaphragm about 5A, the current with a diaphragm is 1.9A
     
[Edited on 17-12-2024 by Hexabromobenzene]
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
The process of making diaphragm volume about 1300 ml from polypropylene containers
Welding was carried out using an electric soldering iron. Holes were melted as well. Further grinding and backing at 175C
     
|
|
|
bearbot22
Harmless
Posts: 24
Registered: 10-4-2018
Member Is Offline
Mood: No Mood
|
|
Hi Hexabromobenzene!
I made further tests with non-woven PP.
The leakaing was greatly reduced by thickening the electrolyte. This worked better than I would have expected.
I therefore carried out the tests from my last post with non-woven PP and thickened liquids.
This time the non-woven PP was NOT heated or pressed, but used directly as I cut it out of the shopping bag.
As gelling agent, I added 0.2% xanthan gum to both the water for the drip test and the electrolyte.
Results for Test-Diaphragm: PP-Non Woven, 20mm diameter
Drip test: 5ml/24h
[35ml water with 0.2% xanthan gum]
Acid-Base Exchange: 240 min
[50ml H2SO4 0.3 molar with 0.2% xanthan gum vs. 50ml water + 1ml NAOH 10%]
Current-Flow at 2/ 3/ 4/ 5/ 6/ 7/ 8 Volts:
50/ 110/ 160/ 220/ 270/ 310/ 460 mA
[Electrolyte: 2x 50ml H2SO4 0.3 molar with 0.2% xanthan gum, Electrodes: 2x Cu 20mm
Current flow without diaphragm: 70/ 140/ 180/ 240/ 310/ 350/ 500 mA]
The current permeability is top. The acid-base balance is also delayed quite well with Non-Woven PP.
All in all, IMHO these are top values for a diaphragm and the only thing missing is a test electrolysis.
However, I don't know whether it is possible to work with thickened electrolyte for your electrolysis.
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Thank you for the test, but the use of thickener is very rarely possible. It will be destroyed during almost all electrochemical processes.
Untreated fabric can also be used. But only baking allows you to give the desired shape
For the diaphragm, you need the THICKEST fabric possible to reduce layers and leaks. You also need fabric with a MINIMUM fiber size for a minimum pore
size. And also MAXIMUM density to reduce the number of layers and a smaller pore size. Even after baking, the fabric partially retains the structure
of the original
The following very simple electrosyntheses can be carried out using a thisdiaphragm which are interesting:
Ferric chloride from iron and salt, chloroacetic aldehydes and acids from salt and alcohol, oxidation of chlorates to perchlorates on graphite or
other carbon anode, production of sulfuric acid from gypsum, chloralkali process
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
Are you sure that you can use fabric without baking? Even the dense samples are compressed 2-3 times when baking
A few more experiments were done. It was found that the conductivity of the diaphragm is very dependent on the number of layers of the fabric. 1 layer
in a vessel from a pipe of 40 mm show current 5 amperes, but with 2 layers only 1.5 - 2 amperes. The vessels are filled half.
Therefore, it is recommended to use the most thick and dense fabrics as the thin fabric melts during such treatment
Large diaphragm vessels 1300 ml (about 100mm diameter) in the photo above show very good conductivity even with 2 layers of fabric. At 12 volts, a
current of more than 5 amperes in 200+ gr \ liter of salt and this is half a liquid filling
Polypropylene diaphragms are much better than clay pots. But there is a serious problem with them. A very significant leak. This is probably due to
the plasticity of polypropylene fibers. It was proposed to thicken the solution. But this is the same as using ion exchange rubber. There is a problem
with chemical resistance.
A further development stage must be invented by an affordable and stable ion exchange resin. It is also possible to cover a polypropylene diaphragm
with something to give rigidity to the fibers. But do not forget about chemical resistance
[Edited on 18-1-2025 by Hexabromobenzene]
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
I think if you dip the diaphragm into an emulsion for example epoxy resin, it will settle on fibers by making them strong that will reduce the leakage
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
I know how to modify polypropylene diaphragm and reduce the leakage
When the solution is filtered through this tissue, the precipitate fills the pores and if the precipitate has a small size, it can almost stop
filtering.
You can grind the ion exchange resin to the size of a few micrometer, push into the fabric and then bake.
I think I have to try. During electrolysis, precipitation is often formed, which also reduce the leakage
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
This post is incorrect welding. https://www.sciencemadness.org/whisper/viewthread.php?tid=16...
It collapsed and I had to weld polypropylene again. In order for the welding connection of polypropylene to be strong you must use the same material,
there should always be additional material as a filler and you must also melt and mix both parts
For a new welding, the plug was made of the same pipe, straightened by heating and pressing and placed in blank for a depth of 5mm. These 5mm
matearial blanks are also act as filler during welding
The correct welding connection is stronger than the main material
In this post, the correct welding
https://www.sciencemadness.org/whisper/viewthread.php?tid=16...
[Edited on 27-1-2025 by Hexabromobenzene]
|
|
|
Hexabromobenzene
Hazard to Others
Posts: 149
Registered: 27-4-2021
Member Is Offline
|
|
I tested the diaphragm and the results were very good
1. Electrolysis of salt with an iron anode. A strong alkali and a bright green solution of iron chloride 2. Exact exits will be written soon in a
separate article. There was a lot of iron hydroxide in the anode chamber, but this did not affect the conductivity of the diaphragm
2. Electrolysis of the mixture of potassium sulfate and gypsum gave 8% sulfuric acid, but with a poor current yield. This is probably due to the fact
that a lot of potassium hydroxide has accumulated around cathode. The experience will be converted with a very diluted solution of potassium salts so
that only sulfate ions are in the solution. Wait for the report on the separated topic.
Due to the leakage of the diaphragm should be very quickly extracted from the solution after electrolysis. Any change in the fluid level in the
cathode and anode chamber is carried out to the leak
The most thick and dense reusable bag was also found. He allowed to bake the diaphragm in 1 layer without melting. This greatly increased conductivity
An attempt to add chopped ion exchange resin to the fabric during baking did not lead to success. This reduced its mechanical strength and was easily
washed out with water
[Edited on 27-1-2025 by Hexabromobenzene]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
