As an important type of difficult-to-process gold ore resources, the sorting problem of high-arsenic gold ore has long restricted the development and utilization of gold resources. In this type of ore, gold is often embedded in sulfide minerals such as arsenopyrite and pyrite in the form of fine particles, forming a complex encapsulation structure, and the recovery rate of traditional cyanide leaching is less than 40%. With the tightening of environmental protection policies and the advancement of beneficiation technology, the sorting of high-arsenic gold ore has broken through traditional ideas and formed a multi-technical collaborative solution.

 1. Technical challenges of high-arsenic gold ore sorting

The difficult-to-process characteristics of high-arsenic gold ore are due to its special mineralogical characteristics. Electron probe analysis shows that more than 80% of the gold particles are less than 10 microns in size and are mainly found in arsenopyrite lattices (AsFeS). The presence of arsenic not only poses environmental risks, but also forms a passivation film during the leaching process, which seriously hinders the dissolution of gold. Organic carbonaceous substances commonly found in ores can also produce a "gold-robbing effect", causing dissolved gold to be re-adsorbed and precipitated.

2. Analysis of modern separation process system

Pretreatment technology shows a diversified development trend: the biological oxidation tank can increase the sulfide oxidation rate to more than 95% at 45°C through acidophilic bacteria; the microwave roasting system uses selective heating characteristics to achieve arsenopyrite structure dissociation at 600°C, and the arsenic solidification rate can reach 98%. A gold mine adopts a two-stage roasting process (one stage 450°C dearsenication and the second stage 650°C desulfurization), and the gold leaching rate is increased from 27% to 89%.

In terms of flotation technology innovation, the new inhibitor DMA (dimethyl dithiocarbamate) has a three-fold higher selectivity for arsenopyrite inhibition than the traditional lime method, and combined with nanobubble flotation technology, the arsenic grade of the concentrate can be reduced to less than 0.8%. A certain concentrator uses electrochemically controlled flotation to achieve efficient separation of arsenopyrite and pyrite by controlling the pulp potential at -200mV.

The combined process route has become the mainstream configuration, and the typical process is: raw ore → AI photoelectric sorting → ultrafine grinding → flotation enrichment → pressure oxidation → resin adsorption. A gold mine in South Africa uses a combined process of biological oxidation-carbon pulp to treat ore with an arsenic content of 8.2%, and the gold recovery rate reaches 91.3%. The arsenic solidification product is melted at high temperature to form a glass body, which meets the hazardous waste landfill standard.

3. Frontier of green sorting technology development

Breakthroughs have been made in clean production technology innovation: the persulfate oxidation system can achieve efficient decomposition of sulfides at room temperature, saving 60% energy compared with traditional roasting; the selectivity coefficient of ionic liquid extraction technology for gold reaches 10^4 level, which can replace cyanide leaching. A pilot plant uses supercritical CO2 extraction technology to achieve one-step gold recovery at a pressure of 30MPa, and there is no wastewater discharge in the whole process.

The artificial intelligent photoelectric sorting system and XRT sensors to identify gold-containing arsenopyrite particles in real time. After a Finnish concentrator installed an intelligent sorting machine, the grade of the selected ore increased by 5 times, and the arsenic content of the tailings was reduced to 0.15%. The circular economy model promotes the development of wastewater deep treatment technology. The combined process (chemical precipitation + biological adsorption + reverse osmosis) can make the wastewater reuse rate reach 95%, and the arsenic concentration is stable below 0.01mg/L.