There are a number of alternatives that have been tried by the industry - thiosulfate, thiourea, various types of halides and so on. Although new processes are being proposed on a regular basis, there have in fact been no dramatic changes in metallurgical techniques for gold extraction since the introduction of the cyanide process in late 1800s.
There was somework done on evaluating different graphite depressants in a polymetallic sulphide flotation circuit at Hindustan Zinc's Rampura Agucha Mine. The primary evaluation criteria were quality (grades) of lead and zinc concentrates, their recoveries (%) and graphite rejection (%) in tailings. Nigrosine as a benchmark showed 94.3% rejection of graphite carbon. Details of the work are given in the following paper https://www.sciencedirect.com/science/article/pii/S209526861730054X
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There are a number of alternatives that have been tried by the industry - thiosulfate, thiourea, various types of halides and so on. Although new processes are being proposed on a regular basis, there have in fact been no dramatic changes in metallurgical techniques for gold extraction since the introduction of the cyanide process in late 1800s.