In the field of gold beneficiation, there is a type of ore called "refractory gold ore" - they are like "stubborn stones", with gold particles tightly wrapped in sulfide minerals such as pyrite and arsenopyrite, which traditional processes are difficult to extract efficiently. With the gradual depletion of easily selected gold resources, how to overcome these "hard bones" has become a core issue facing the global gold mining industry.
Today, we will start fromSulfur arsenic separationandEnvironmental protection fundsTwo dimensions, in-depth analysis of the latest breakthroughs in difficult to process gold ore beneficiation technology.
The so-called difficult to process gold ore refers to gold ore that is encapsulated in sulfide minerals (mainly pyrite and arsenopyrite) in fine particles (even microscopic and submicroscopic levels), and has a low gold leaching rate (usually less than 80%) during conventional cyanide leaching.
Where is the difficulty? 主要有三大障碍：
Physical packageGold is tightly wrapped by sulfide minerals, and leaching agents cannot come into contact with the surface of gold particles
The 'Gold Robbery' EffectOrganic carbon in ores can adsorb dissolved gold, causing it to be "dissolved and then captured back"
Harmful element interferenceElements such as arsenic, antimony, and copper can consume chemicals or form passivation films
among which,arsenicOne of the most challenging issues is that high arsenic gold concentrate not only has a low selling price, but may even be rejected by smelters. Therefore, sulfur arsenic separation has become the core technical link for difficult to process gold ore beneficiation-4。
Pyrite (FeS ₂) and arsenopyrite (FeAsS) are the main carrier minerals of gold, but their physical and chemical properties are extremely similar, making separation extremely difficult. Traditional craftsmanship often adopts the method of "strong pressure and strong pulling", resulting in either incomplete separation or huge consumption of chemicals-4。
A new process that has been granted a national patent, the "gold ore flotation process based on sulfur arsenic stepwise separation," provides an innovative solution to this problem-4。
The technical roadmap is divided into five steps：
Step 1: Selective inhibition during the grinding stage
During the grinding process, a composite modifier composed of sodium carbonate, zinc sulfate, and sodium metabisulfite is added to selectively inhibit the mineral surface as soon as it is "cut open". The ratio of this combination is4:2:1The total dosage is 1500-2000g/t-4。
Step 2: Preliminary separation of sulfur and arsenic (e.g. floatable separation)
After grinding, add ethyl xanthate (40g/t), Z-200 (20g/t), and 2 # oil (20g/t) for preliminary flotation. The goal of this step is not to completely separate, but to float together sulfur and arsenic loaded gold minerals with similar floatability to obtain a "low arsenic gold concentrate"-4。
Step 3: Acid washing+deep separation of organic inhibitors
This is the "stroke of genius" of the entire process - washing low arsenic gold concentrate with dilute sulfuric acid first to break the adsorbed chemical film on the mineral surface; Add sodium humate and amino acid methyl phosphonic acid (mass ratio 2:1, total amount 100-200g/t) for deep separation. Finally, two types of products are obtained: low arsenic gold concentrate and high arsenic gold intermediate ore, which enter different smelting processes respectively-4。
Step 4: Enhanced flotation of high arsenic loaded gold ore
The "strong pulling" strategy is adopted for the initial separation of tailings - adding copper sulfate (200g/t), pentyl xanthate (150g/t), and butyl ammonium black powder (30g/t) to "clean" the residual high arsenic gold carrying minerals-4。
Step 5: Concentrate, grind and select again
Combine the high arsenic intermediate ores generated by various processes, grind them to -0.037mm, accounting for 70-90% (extremely fine), and perform enhanced flotation under low concentration (10-15%) conditions to ultimately obtain high arsenic gold concentrate-4。
The core value of this process lies inWe have achieved a "step-by-step enhanced separation" of sulfur and arsenic, avoiding the extensive operation of "one pot, one end", which not only improves the separation efficiency but also significantly reduces the consumption of reagents-4。
In addition to sulfur arsenic separation, researchers are also exploring new paths to overcome difficult to process gold mines.
Kazakh scientists have recently developed two innovative technologies-8：
Regarding oxidized mineralsPre treatment with hydrogen peroxide and/or sodium acetate before heap leaching can increase gold recovery by approximately 7%; When two reagents are used in combination, the recovery rate can be increased by up to10%-14%-8
Regarding sulfide oresBy using enriched gravity concentrate combined with enhanced cyanide treatment, sodium acetate can increase the recovery rate by about 4% and partially replace expensive traditional reagents, reducing production costs-8
A recent study explores surfactant modification technology for "dual refractory gold mines" containing organic carbon (gold encapsulated by sulfide minerals+carbonaceous gold robbing)-5。
The research team tested three types of surfactants: anionic, cationic, and nonionic. The results show thatThe best modification effect is achieved by anionic surfactant (SDS)——After treatment with 0.5mM SDS, the gold leaching rate increased from 53.1% to80.4%Mechanism studies have shown that surfactants preferentially occupy adsorption sites on carbonaceous surfaces through electrostatic and π - π interactions, thereby reducing the chance of gold cyanide complexes being "hijacked"-5。
This discovery provides a relatively simple pretreatment solution for "gold robbing" type refractory gold mines - without the need for high-temperature roasting or chemical oxidation, the recovery rate can be significantly improved through chemical modification alone.
In the process of conquering difficult to process gold mines, environmentally friendly beneficiation agents also play an important role.
A newly authorized patent (CN117085855B) discloses a low toxicity and environmentally friendly gold beneficiation method-2Its technical features include:
Sodium citrate assisted slurry adjustmentAdd sodium citrate before grinding to optimize the slurry environment
Preprocessing agent cracks packageA composite pretreatment agent composed of sodium persulfate, methyl isobutyl methanol, lower alcohols, and sodium dodecyl sulfate is used to solve the problem of difficult exposure of gold particles
Composite leaching agentUsing environmentally friendly composite leaching agents for gold leaching, replacing traditional sodium cyanide
The innovation of this method lies in:Combining chemical pretreatment with environmentally friendly leaching agentsSpecifically targeting the problem of difficult exposure of gold particles in refractory gold mines-2。
From the perspective of technological development in recent years, there are three major trends in the beneficiation of refractory gold mines:
1. The "combination punch" strategy has become mainstream
It is difficult to conquer complex and difficult to process gold mines solely relying on a certain agent or technology. Whether it is the combination of "inorganic salt adjuster+acid washing+organic inhibitor" in the stepwise separation of sulfur and arsenic, or the combination of "oxidation pretreatment+environmental leaching", they all reflect the idea of multiple technologies working together.
2. Precise and intelligent regulation
The traditional "experiential" dosing method is being replaced by data-driven approaches. By monitoring parameters such as slurry potential, pH value, and ion concentration online, real-time optimization of drug dosage can be achieved, which can improve indicators and reduce costs.
3. Green and low toxicity transformation
While conquering difficult to handle gold mines, the environmental red line is also tightening. Low toxicity and biodegradable agents are gradually replacing traditional highly toxic chemicals, even for difficult to process ores.
For enterprises facing difficulties in handling gold mines, the following points are worth paying attention to:
First, conduct research on process mineralogyThe types of difficult to handle gold mines vary greatly, and it is necessary to first clarify where the "difficulty" lies - whether it is encapsulation, gold robbery, or interference from harmful elements? This is a prerequisite for choosing a technological route.
Step by step separation is better than "one pot end"The case of sulfur arsenic separation shows that breaking down complex problems into multiple steps to solve them separately is often more efficient and economical than "strong pressure and strong pulling".
Pay attention to the progress of cutting-edge technologiesFrom surfactant modification to oxidation pretreatment, new technologies are constantly emerging. Maintaining technical sensitivity and introducing mature new processes in a timely manner may become a breakthrough for enterprises to reduce costs and increase efficiency.
Environmental protection and efficiency can be achieved at the same timeThe application of low toxicity and environmentally friendly beneficiation agents in the field of refractory gold mines proves that green transformation does not necessarily come at the cost of sacrificing efficiency.
Difficult to handle gold mines used to be a headache for mineral processing engineers. Nowadays, with breakthroughs in technologies such as sulfur arsenic stepwise separation, environmentally friendly leaching agents, and surfactant modification, these "hard bones" are being gnawed on piece by piece.
The evolution of difficult to process gold ore beneficiation technology, from "able to select" to "good selection", from "high toxicity" to "low toxicity", reflects the development logic of the entire gold mining industry from extensive to refined, from high pollution to green and sustainable. Overcoming difficult to handle gold mines is not only related to resource utilization, but also to the future competitiveness of the mining industry.
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