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Day 2 of LD anode test

Swede

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If you haven't been keeping up, (and if you care... :D ) I have been blogging fast and furious while the LD anode is undergoing its first real test. If you'd like, it might be worth going back about a week to catch up. This entry will be more pictures, less text.

 

Basically, a few of the warts on one edge had broken off and fallen to the bottom of the cell. While not catastrophic, this had me concerned, as it hinted that the integrity of the anode was not what I had hoped for. A greater concern was the voltage. To obtain a decent amperage of only 15 amps, the system was requiring almost 10V, which is simply too high. Usually 6 to 7 is about the maximum that you would normally see. Part of the problem was that I had selected a very small cathode; supposedly, the current density on the cathode should be high for best efficiency. Well, efficiency can kiss my a** when it takes 10V to run the cell. Excess voltage is never good for either a chlorate or a perchlorate cell... it tends to stress the anode and create more heat than it would otherwise.

 

Additionally, the anode was gathering significant amounts of crystalline perchlorate on the surface. Interestingly, the side of the anode AWAY from the cathode was the one gathering crystals... the side facing the cathode was clean. I decided to replace the dinky cathode with one a bit larger, and also have a cathode area on both sides of the anode. While the system was down, I could also take a look at the anode and try to find out what was going on with it, mechanically.

 

The first step was to create a titanium box that would act as a pair of cathodes:

 

http://www.5bears.com/ld1/ldbca020.jpg

 

After this was made, the test cell was taken apart, temporarily. This is the anode inside the cell, away from the cathode. Note the loss of several of the edge "warts" on the left side, and the accumulation of perchlorate crystals:

 

http://www.5bears.com/ld1/ldbca021.jpg

 

http://www.5bears.com/ld1/ldbca022.jpg

 

http://www.5bears.com/ld1/ldbca023.jpg

 

The anode was removed, washed in warm water, and then I gently manipulated the remaining warts to see if they were adhering well. The warts on the bottom were quite strong. Those on the sides popped free easily. I decided to go ahead and remove all of the side warts, and it didn't take long.

 

http://www.5bears.com/ld1/ldbca025.jpg

 

These nuggets of lead dioxide were interesting. They are very dense, and similar to pure lead in their mass.

 

http://www.5bears.com/ld1/ldbca028.jpg

 

They reminded me of fossil teeth. Arranged in their original pattern, they look a bit like molars!

 

http://www.5bears.com/ld1/ldbca029.jpg

 

The good news - wherever the LD had adhered to MMO, which included the faces of the anode, and the bottom edge, the adhesion was very strong. I tried about 3X the manipulation on the bottom warts, which had an MMO edge (as opposed to a sawcut edge) and they didn't budge, so I left them there. The system was reassembled with the box cathode:

 

http://www.5bears.com/ld1/ldbca026.jpg

 

With the power applied, I was very happy to see the voltage drop by about 1.5V for a given amperage. I set the unit up to deliver 15 amps, and for now it is humming along. The perchlorate is accumulating fairly quickly... for a given amount of current, the conversion of chlorate to perchlorate is more than twice as fast as chloride to chlorate.

 

http://www.5bears.com/ld1/ldbca027.jpg

 

The anode in its current state wasn't what I started with, but at least I verified one thing - the lead dioxide plated over the MMO areas yielded a strong adhesion which is very promising. If I had popped those warts free after the anode had been initially plated, it'd look as it does now. A bit neutered, but what remains appears strong and functional.

 

So the news is, I'd say, about 75% good, and 25% bad. Properly prepared, it appears that LD does in fact plate over MMO very effectively. The real test will come in a day or four. If there is no additional erosion at the edges, where the warts were popped free, then I'd say I have a smaller, but strong and functional LD anode that should give good service.

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WSM

Hi Swede,

 

It's been a month, is the perchlorate cell still running? How does everything look? I'm crossing my fingers and hoping the LD/MMO bond is maintaining its integrity. I'm also wondering how the O4 cell characteristics differ from the O3.

 

You mentioned the O3 to O4 conversion happening about twice as fast as the O0 to O3. Is that true throughout the run or do things shift as the run progresses? How often do you have to restock the cell with O3 and how often do you harvest the O4? As a batch process, I'm guessing things turn over fairly fast.

 

Please let us know how it's going when you get a chance. Thanks.

 

WSM

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Swede

Hi WSM - I am not using O3 to do anything - the scent (unmistakable) comes from the process itself. The very first time I used a Pt anode, I immediately noticed a scent of ozone coming from the vent, so perhaps generated O3 has something to do with the oxidation of chloate to perchlorate.

 

I let the cell run for perhaps 4 to 5 days. I sabotaged myself with poor electrode spacing that required a fairly high voltage which might have contributed to LD erosion. I gathered what perc it made, hot filtered the dissolved perc, the boiled it down to crystallization. I have not calculated total yield nor have I calculated efficiency. The whole setup was poorly executed. With the loss of the nuggets along the sides, the anode lost probably 15% of its total mass.

 

No big deal. I will never surrender. It is a matter of doing a good plating job on a properly-prepared substrate. On Science Madness, we have been discussing anode forms that will better support the plated LD.

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WSM

Hi Swede,

 

I should have been clearer; by O3 I meant KClO3 and KClO4 by O4. I do find it interesting that ozone is generated during the conversion (oxidation) of chlorate to perchlorate. It makes me wonder if ozone could be utilized to bypass the electrochemistry and make perchlorate from chlorate without current? :unsure:

 

Making chlorate is fairly well understood and routine. Amateur making of perchlorate with home made LD anodes is a pioneering effort and we have to develop the whole process and perfect it as we go. I need to set up a plating rig and duplicate your efforts. If I can do it, anyone can (with effort and motivation :D ). Thanks for all you've done and sharing the learned lessons with us.

 

WSM

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