NO refiner, worth his salt, uses chemical methods to go after the PM's on circuit boards. They know that there's no money in it, due mainly to chemical costs, fume control, and waste disposal costs. They may hi-grade the boards for fingers and hi-grade IC's but, few other components, if any. The fingers are cyanide stripped and the IC's are put through aqua regia.
Here's how they all run the boards. They burn the material and then grind it up, usually in a ball mill. Then, they separate the dust (pulp, they call it) from most of the metallics with an 8 or 10 mesh screen. The metallics are melted, cast into bars, numbered, weighed, and drilled scientifically. The drillings are blended and assayed for all PM contents and copper. The pulps are blended, thief sampled (a tube is run down into the pulp), and assayed. The bars and pulps are then shipped to a huge refiner or a copper smelter. In the past, most of these places were in Europe, mainly in Belgium. In the U.S., ASARCO would take material in some of their plants but, it was an on again, off again proposition. These companies have great rates and slow payout, about 3 months, awhile back. They even pay for a major portion of the copper. Nickel over 5% draws a penalty. After sampling and assaying, the smelters advance money against recovery but, they charge interest. I haven't been involved with smelters for quite awhile. Some details might have changed since then.
The present trend for the amateurs to chemically process boards is, as far as I'm concerned, a sucker deal. I imagine this is the main thing that Scott Andrews has in mind in his aversion to refining by amateurs. I know that this stuff is fun to play with. However, when you gear up and try to make money, you will lose. The numbers just aren't there. Chemical costs and waste disposal are the biggest money eaters. It's easy to deal with small amounts of waste. When you get bigger, the amounts of heavy metal, acidic toxic waste will grow much faster than you realize. To dissolve a pound of base metals, it will take at least a gallon of 50% acid plus rinses. If you dump large amounts down the drain, you'll be caught in no time. In some states, you need a license to generate this waste.
There's a whole cottage industry bilking the public, selling info and chemicals to process boards. This all seemed to start with Shor International. I must admit, however, that Peter Shor's stuff keeps you as safe as possible and, it works. I can't say the same for a lot of the other stuff out there. I hate the sodium nitrate system since it gives people false hopes. If you seriously want to refine, it's a lot easier to get real nitric acid than you're led to believe.
The best way to make money with boards is to buy low, sell high, and don't refine them yourself. I'm not saying you shouldn't hi-grade them. It usually pays to sort the stuff into homogeneous lots rather then having a large mixed lot. Buyers and refiners lick their chops when they see a mixed lot. They know that you don't know. When taking a lot of boards to a refiner (I would suggest a ton, or more), accompany (most refiners allow this - it's called repping - representing your material) the lot and don't leave until the material is homogeneous and you have good samples in your hand - the more different samples - the merrier. You will have to schedule this with the refiner. Don't be lazy or let the refiner distract you or take you away from the material. Stay with it, when required, until you have samples. Even when the stuff is being burned, if you're not around to watch it, the refiner could throw in some barren burnables to reduce your values. Think of ways that the refiner can screw you and avoid these traps. Repping is a boring job and it may take 2 or 3 days. At the end of the day, try to make the refiner put the stuff into sealed drums, sealed with lead or plastic numbered tags. If you rep your own stuff correctly, it's less important to sort it. In any case, pull off the good gold ceramic IC's and deal with them separately. They won't burn or chop and are hard to grind. Even though they're the best stuff on the boards, they may not turn up in the samples. I'm not saying that all refiners are dishonest. However, enough of them are to make preparation always necessary.
Get your ducks in a row before taking the material to a refiner. It doesn't pay on real low grade stuff. Check on his charges. He may have a whole slough of them. There are processing charges, refining charges, assay charges, etc. Most refiners charge at least $2.50 a pound just for processing charges and, they deserve it. If your stuff is too low grade, you may end up owing him money.
What do you do with the samples? If you are big enough to generate a ton of good boards, you are big enough to set up fire assaying equipment and learn how to use it. You can send samples to a professional assayer but a good one will charge from $50 to $300 per sample. The higher rates include the platinum group. I would avoid most mining type assayers, although their rates are much less, unless they have a background in scrap. They are good in their field but scrap is a different deal.
This is only the tip of the iceberg on this subject. Ask questions.
