Key Takeaways & Executive Findings
- •• TJ-215, a novel composite thionocarbamate collector, demonstrates superior selectivity for chalcocite over pyrite at pH>8 compared to Z-200, enabling effective flotation separation in low-alkaline conditions. • The enhanced performance of TJ-215 is attributed to the synergistic coordination of NH—C=S and C=N—OH groups, which form stronger Cu-S, Cu-N, and Cu-O bonds with chalcocite surfaces, as confirmed by zeta potential analysis. • TJ-215 offers a cost-effective alternative to Z-200 due to its low-cost raw materials and short synthetic route, potentially reducing reagent costs and environmental impact in industrial copper-sulfur separation. • The findings provide practical guidance for replacing Z-200 with TJ-215 in the flotation of secondary copper ores, improving separation efficiency and economic viability under weak alkaline conditions.
Abstract
The flotation separation of high pyrite content secondary copper ores faces challenges including elevated pH levels, poor xanthate selectivity, and higher costs associated with its combination with Z-200. In this work, a composite thionocarbamate collector (TJ-215), with low-cost raw materials and a short synthetic route, showed a better selectivity for chalcocite than Z-200 when pH>8. Zeta potential analysis indicated a stronger interaction between TJ-215 and chalcocite. These results were achieved through the synergistic coordination of NH—C=S and C=N—OH in TJ-215 molecule, compared with the single thiourea group, NH—C=S, in Z-200 molecule. At low-alkaline condition, the NH—C=S in TJ-215 formed Cu—S, Cu—N bonds with Cu atoms, and the C=N—OH combined with Cu to form a Cu—O bond. The results of this study provide guidance on the replacement of Z-200 by TJ-215 in the separation of chalcocite from pyrite in weak alkaline conditions.
1. Introduction
Secondary copper ore is an indispensable and important raw material in the copper metallurgy industry, and its theoretical copper content is usually higher than that of primary copper ore, which has extremely high utilization value. Taking chalcocite (Cu2S) as an example, the theoretical copper content is 79.86%, much higher than that of chalcopyrite (CuFeS2) in primary copper mines, with about 34.56% theoretical copper content [1]. The high-grade nature of secondary copper deposits originates from the selective enrichment of copper during secondary enrichment processes in their formation. This enrichment not only enhances the economic value of ore but also significantly improves its surface chemical activity. Therefore, secondary copper ore shows obvious advantages in floatability compared with primary copper ore.
However, chalcocite is usually accompanied with pyrite, which significantly affects the separation efficiency. Copper ions release during the grinding of secondary copper sulfide ores. Numerous previous studies [2, 3] have demonstrated that Cu2+ ions in solution adsorb onto the surface of pyrite and form hydrophobic copper-containing products (such as CuS, Cu2S, or Cu(OH)2 adsorbed layers) through ion exchange or electrochemical reduction processes, activate pyrite surfaces, and promote unintended flotation [4, 5]. Furthermore, as the proportion of pyrite in the ore increases, the dissolution of iron from pyrite accelerates the oxidation of xanthate to dixanthogen [6]. When the pyrite content exceeds a certain threshold, the grade of the flotation concentrate often decreases, thereby intensifying the challenges associated with selective separation [4, 5]. These results compelled the plant to increase the pulp pH to meet the copper concentrate grade specifications [7]. The high-alkaline environment facilitates the formation of hydrophilic iron hydroxide film on the pyrite surface, suppressing its floatability. However, the use of excessive lime frequently causes pipeline scaling and equipment wear while also increases reagent and wastewater treatment costs. The flotation of chalcocite at over-high pH was undesirable [8].
Consequently, although xanthate has become the preferred collector for secondary copper ore flotation owing to its significant cost-effectiveness and strong collecting power [9, 10], the requisite high-alkalinity conditions substantially diminish the plant's overall economic benefits. Thionocarbamate collectors have the advantages of good selectivity, less pollution, less dosage, and stable chemical properties [11, 12], with Z-200 as the most widely used in low-alkaline pH pulp [13]. But limited by the high synthesis cost, a combination of xanthate and thionocarbamate is often used in industry to balance economic efficiency and separation performance through a synergistic effect. Unfortunately, it fails to fundamentally solve the cost problem, which restricts its wide application in large-scale industrial flotation operations to a certain extent.
The development of collectors provides more options for the separation of secondary copper mines. FENG et al [14] found that XK-103 was better than Z-200 in collecting chalcocite under weak alkaline conditions and could be used for copper-sulfur separation. The S atoms in XK...
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ZHAO Xin-miao, YAO Xiang, WU Yan-ming, YANG Yuan-kun, YU Sheng-li, OUYANG Chong-zhong, LÜ Bing-chao, GU Guo-hua, WANG Yan-hong (2026). Selectivity of composite thionocarbamate collector in flotation separation of chalcocite from pyrite in low-alkaline pH pulp. Journal of Central South University. https://doi.org/10.1007/s11771-026-6235-0
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Frequently Asked Questions
What is the main advantage of the composite thionocarbamate collector TJ-215 over Z-200?
TJ-215 exhibits better selectivity for chalcocite over pyrite at pH>8, and it is synthesized from low-cost raw materials with a short synthetic route, making it a cost-effective alternative to Z-200.
How does TJ-215 achieve selective separation of chalcocite from pyrite?
TJ-215 contains both NH—C=S and C=N—OH groups, which synergistically coordinate with copper atoms on chalcocite surfaces, forming Cu-S, Cu-N, and Cu-O bonds. This stronger interaction enhances selectivity compared to Z-200, which only has a single thiourea group.
What is the significance of the study for industrial flotation?
The study provides guidance for replacing Z-200 with TJ-215 in the flotation separation of chalcocite from pyrite under weak alkaline conditions, potentially reducing reagent costs and improving separation efficiency in secondary copper ore processing.
What methods were used to investigate the adsorption mechanism?
Zeta potential analysis was used to indicate a stronger interaction between TJ-215 and chalcocite, and the adsorption mechanism was inferred from the molecular structure and bonding analysis.
What are the environmental benefits of using TJ-215?
TJ-215 is a thionocarbamate collector, which generally has less pollution and lower dosage requirements compared to xanthates. Its use in low-alkaline conditions reduces the need for excessive lime, thereby decreasing wastewater treatment costs and environmental impact.
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