Aurum Scaurum as you know reports to Carbon 12 or 14 depending on how atavistic you are. That is the basis for the infamous carbon in pulp process which works perhaps best as the carbon in solution process. Or perhaps not.
*Electrically* activated charcoal of cocoanut husks will extract gold nicely under ideal conditions and then, when backwashed with an adsorbing electrolyte of alcohol and sodium hydroxide will give up its gold to the more concentrated solution. An overvoltage of 36 volts to stainless steel wool will deposit the gold onto the nickel iron for smelting.
I have an even better way where the gold can be directly electro deposited on the carbon when dissolved by the hydronium ion, chlorine gas or cyanide. It still requires a backwash, but this form of deposition is controlled by current directly in very, very dilute solutions. It does not require a strong electrolyte to do the primary deposition. I have an idea that it will produce better recovery than CIL or CIP as it is more positive. It would work with seawater as well to a degree of perhaps 10% recovery. Interesting point, I realize. Economics may be unfavourable but it would make an interesting test for academic purposes. The problem with seawater is taking out the undissolved or colloidal gold, not the dissolved species. This may not work entirely but its worth a try. You also have to put up with tons of magnesium and other crud and do a separation on the metals later, which is a tad pricey for the amount of precious you might get ~ 5 cents per ton. Still, it's fascinating.
Carbon is a good natural sink for gold. All gold deposits are located in carbon rich environments ( manifested as crstalline CaCO3 and MgCO3.) As you get closer to the gold deposits traversing the metasediments and metavolcanics, which are relics of the hiatus in the near shore subaqeuous volanic regimes, your HCL test of the shear zones gets progressively more active and bubbly. And you wondered why geologists carried little bottles of 10% HCL. In the Algal seashore mats of the Asian southwest continent some organic sea swamp biomass runs .10 ounces per ton gold. They have no practical way of extraction of the gold as any solution method has to compete with the natural carbon which acts as a "pregnant solution robber" and defeats the process. Attempts to ash the substance are fraught with difficulties of harvesting and drying and lead to high colloidal and volatiles losses. There are probably ways to deal with this last problem by precip methods such as liquid treatment, scrubbing or cottrel plants, but it so far has not been piloted. Colloidals requires some form of wash and recovery precip. The above mentioned process may work here but has an unkown effect with suspensions.
A birch tree above a gold deposit west of Timmins was tested to 3.0 parts per million gold in a biogeochemical survey for the metal. That is wood containing 1/10 of a troy ounce per ton. This is the highest recorded biogeochem of gold recorded. Biogeochemical surveys for gold in A horizon soil detritus of plants worked well in the Puskasaw projects for some mining companies in the 1980's. You need a residually developed soil of some one or more feet to develop an anomaly horizon. Archean moss covered terrane does not always qualify. A new australian technique called enzyme leach is not biogeochem but compares well with another new technique from australia, of "dissolved mobile metal-ion extraction" (I thinks its acronym is MMI or something like that) which depends on the A horizon for its precip sampling zone. Aussies are the kings of geochem as their soils are mostly residual and map rocks and metals accurately by these methods.
Organic acids to recover gold from all sorts of substance are a good idea to experiment with as they may be less troublesome than cyanide or aqua-regia. Some are not funny either. You can use some benign substances to create cyanide in solution such as thiourea, but if you don't keep the Ph above 10 you will get HCN gas evolution. Not nice.
You can create weak aqua regia with salts of nitre, iron aluminum sulfate, sodium chloride (all obtainable at your drug store) and maybe some battery acid. Heat to room temp in glass jar for five days. If you use battery acid perhaps 2 days is enough. Ventilate exclusively to the outdoors or you will get emphysema and all your metal fixtures will fall apart in weeks. Bring to 7.0 Ph with baking soda or lime. Burnish copper plate with steel wool and scratch it with a nail all over. Clean copper with dilute acid till it shines. Use a fume hood and be careful. Immerse copper plate in solution and boil. When gold stops plating on copper, remove plate and scrape off gold. Smelt to taste. To smelt gold, put in a clay crucible with some flux and heat in a ceramic oven to 2100 degrees or until a bright white-yellow heat. This may take one hour or more in an electric furnace. Use iron tongs, glasses and a reflective apron to remove crucible. Pour into ceramic clay molds or iron. It takes a long time to cool. If you have dissolved gold with some sulfuric acid in the presence of copper you may get unwanted copper too. To separate the copper requires redissolving to a sulfate and plating.
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