Extraction of Gold from ores and concentrates by leaching with the use of cyanides and alternative reagents

Abstract

The problems associated with gold mining are considered from the standpoint of application of heap leaching, a method for gold recovery. Data on the kinetics and mechanism of gold dissolution in cyanide and alternative solvents [thiocarbamide solutions containing Fe(III) ions and hypochlorite-chloride bromine-bromide, iodine-iodide, and copper-thiosulfate solutions], which make it possible not only to improve the working efficiency in gold mining, but also to lessen the contamination of the environment with highly toxic compounds.The method of heap leaching (HL) is a geotechnological method for processing of low-grade goldcontaining ores and rejects of concentration plants. Alkaline solutions of cyanides are used in enormous amounts as solvents for gold [1,2], which gives rise to quite a number of ecological problems. From the standpoint of environment protection [3], it is unsafe to use the HL technique in countries with fertile soils and high population density. Therefore, an exceedingly important problem of the HL technique is that alternative solvents for gold are to be developed [3].In the HL of gold, special attention is given to taking into account the natural factors, absence of rifts, density of the surface layer of soil, presence of clay strata, and absence of compounds of such elements as arsenic, selenium, cadmium, thallium, lead, etc. in the ores. An exceedingly important specific feature of the HL technique is the possibility of processing of both moderate amounts of gold-containing ores and concentrates (tens and hundreds of thousands of tons) and enormous quantities of gold-containing raw materials of technological origin (tens and hundreds of millions of tons) [1,2]. At present, the HL of gold is the most cost-effective method for leaching of lowgrade gold-containing ores. However, despite the high economical efficiency of the HL of gold, proper attention is not, paradoxically, paid to the environment protection in gold-mining regions [3].The rise in gold output in many countries all over the world is clearly seen from the data in Fig. 1. A steep rise in the output of gold has been noted in Fig. 1. Output of gold, Q Au in some countries. (N ) Years; the same for Fig. 2.

Mining as the “Locomotive” of the Colombian Economy: It’s Real Cost

“…Significant occupational exposure to mercury occurs since 28% of the mercury used is precipitated on the zinc shavings and is lost to the atmosphere when the shavings are burned. Methods of extraction that are safer to health and the environment, and are economically competitive, include ammonium thiosulfate [30], thiocarbamide hypochlorite and halogen-halide solutions [31].…”

The Leaching of Gold-silver from Refractory Gold Concentrate by Chlorine-hypochlorite Solution

“…염소-차아염소산은 시안의 24시간보다, 그리고 티 오요소의 15분보다 gold를 매우 빠르게 용해시키 고, 또한 독성이 상대적으로 적기 때문에 시안의 대체 용매제로 사용된다 (Kozin and Melekhin, 2004;Hilson and Monhemius, 2006). 그러나 차아염소산 나트륨은 염산이나 황산과 반응하여 염소를 생성 시키며, 이때 생성된 염소 가스는 독성이 있으므로 접촉을 피해야 한다 (Hilson and Monhemius, 2006).…”

A kinetic model for the adsorption of gold from I2/I− solutions onto a porous polymer membrane

“…This indicated that such a formulation may have the potential to treat aqueous streams typically produced during leaching of gold from ore minerals. 14 In a subsequent paper, 15 the authors showed that the adsorption equilibrium of gold on the membrane at room temperature followed a Langmuir-type relationship:…”