. Copper-Lead Separation Methods
The floatability of galena and copper minerals such as chalcopyrite is similar. In processing copper-lead-zinc ores, it is common to first produce a copper-lead bulk concentrate, followed by copper-lead separation. Two approaches are typically used: floating copper while depressing lead, or floating lead while depressing copper. The traditional method uses sodium dichromate to depress galena and float chalcopyrite, or cyanide to depress chalcopyrite and float galena. Due to environmental concerns with both reagents, extensive research has been conducted in recent years on cyanide-free, chromium-free, or reduced-chemical methods, with significant progress made. According to incomplete statistics, about 60% of concentrators in China processing complex sulfide ores use no cyanide at all, while 20% use small amounts (e.g., 10 g/t), and the remaining 20% still use cyanide. However, these plants are transitioning toward eliminating cyanide or chromate. Several copper-lead separation methods used in practice include:
(1) Oxysulfite Method
This method uses SO₂ or sulfites combined with various depressants to depress galena and float chalcopyrite. It strongly depresses galena, slightly activates chalcopyrite, and does not dissolve precious metals.
Common depressant combinations include:
① SO₂ (or sulfite) + starch;
② Sulfite + sodium sulfide;
③ Sodium thiosulfate + ferric chloride;
④ Sodium carbonate + ferrous sulfate.
(2) Cyanide Method
Although toxic, cyanide is still used due to its effective separation performance. To reduce cyanide consumption, it is often combined with other depressants.
(3) CMC + Sodium Silicate (or Sodium Pyrophosphate) Method
At one mine, a mixture of CMC and sodium silicate (1:100 by mass) or CMC and sodium pyrophosphate (1:10 by mass) was used to separate copper-lead bulk concentrate, achieving good results. The main minerals in the ore were galena, marmatite, sphalerite, pyrrhotite, pyrite, and chalcopyrite. The head grade was Pb 1.82%, Zn 2.36%, Cu 0.1–0.15%, S 5%, and Fe 10–15%. Using a copper-lead bulk flotation process, separation was carried out with sodium silicate (200 g/t) and CMC (10 g/t) to depress lead and float copper. The copper concentrate graded 21.36% Cu with 45.83% recovery; the lead concentrate graded 68.48% Pb with 87.2% recovery. The tailings from copper-lead bulk flotation were treated with copper sulfate for zinc flotation, producing a zinc concentrate grading 46.8% Zn with 88.64% recovery. Practice shows that CMC strongly depresses galena but also affects the floatability of copper minerals. Sodium silicate has a weaker depressing effect on galena and less impact on copper minerals, leading to higher copper recovery. Combining the two leverages their respective strengths to achieve copper-lead separation.
(4) Heating Method
This method was developed to eliminate pollution and improve metallurgical performance. The copper-lead bulk concentrate is heated to approximately 60°C with steam. In acidic or neutral pulp, chalcopyrite becomes more floatable while galena is depressed. No additional reagents are needed, and the copper concentrate is high-grade with low Pb and Zn content. The mechanism involves selective desorption of collectors from the galena surface and surface oxidation leading to hydrophilicity. Some operations also add depressants during heating. For example, at one concentrator, steam heating was combined with Na₂CrO₄ (1.5 kg/t) as a depressant, under conditions of 60°C and pH 7.5–8.
Post time: Jun-01-2026
