All,
I boiled a sample of honeycomb material in sulfuric acid (1.64 spgr = 74%) for 30 minutes. The acid darkened , but did not test positive for any precious metals. I suspect the darkening was from the carbon residues on the honeycomb as I did not incinerate the sample first.
I then treated the washed sample with boiling AR. The material fizzed with bubbles as typical with AR reactions and turned ever so slightly yellow but did not test positive for PGMs.
The sample I tested was very small and this may account for the unsuccessful results.
Given an average total honeycomb mass of 2.273 kg (5 lbs) and estimated PGM content of 2 grams the overall concentration of PGMs is:
2 gm / 2273 gm = 0.0009 PGM concentration ratio
If the PGM content were 4 grams per converter the concentration ratio for an entire converter would be 0.0018.
These concentrations are very low and hence small samples may not yield measurable results without sophisticate test equipment.
From this experiment I can conclude that even if extraction from small samples was possible for the home refiner, the yields are so low as to be immeasurable. To achieve a measurable sample from a 2 gram per cat honeycomb, you need to process a minimum sample size of 285 gm to yield 0.2565 gm of PGMs.
This all tells me to achieve success on a scale and be cost effective you need to process large quantities of cats. The matter is complicated further by the excessive size of the material compared to the amount of acid required to digest the PGMs. Large scale reactions require larger labware, and the requirement of heating large volumes adds more complexity. Here's a photo of a 10 pound bag of honeycomb material:
Digestion of the substrate seems to be the logical method of achieving success, but digesting the substrate is indeed a problem. Direct AR attack of the metals would be very costly due to the larger volume of the substrate.
I'll post more when my beads arrive.
Steve
