Recovery of chalcopyrite from galena using ellagic acid as a lead-selective and environmentally friendly inhibitor: Experimental and mechanistic insights

Abstract

This study explores the selective application of an environmentally friendly organic inhibitor, ellagic acid (EA), in the flotation separation of galena from chalcopyrite. Single-mineral flotation experiments revealed that the galena flotation recovery significantly decreased from approximately 95% to 6.16% following the addition of EA, whereas chalcopyrite maintained a high recovery of approximately 95%. In artificial mixed-ore flotation, effective separation was achieved under optimized conditions. This yielded a Cu concentrate with a Cu grade of 29.73% and recovery of 95.67%, and a Pb grade of 8.39% with a recovery of 8.62%, resulting in a separation index of 15.30. Comprehensive analyses were conducted using various techniques including X-ray photoelectron spectroscopy, density functional theory calculations, zeta potential measurements, time-of-flight secondary ion mass spectrometry, xanthate adsorption capacity measurements, and contact angle measurements. These analyses suggested that selective EA adsorption on the galena surface is the key mechanism underlying the separation. Under alkaline conditions, the deprotonated phenolic hydroxyl groups in EA preferentially interact with Pb sites on galena, increasing the surface hydrophilicity via the formation of –OH groups, oxides, and sulfur oxides. These interactions effectively occupied the active sites on the galena surface, inhibiting xanthate adsorption. However, EA exhibited minimal influence on the surface chemistry of chalcopyrite and its interaction with collectors, thereby enhancing the wettability difference between the two minerals. These results demonstrated the feasibility of effectively separating these minerals using the proposed approach.

1. Introduction

Cu and Pb are critical elements for national infrastructure and economic development. These metals have primarily been acquired through the smelting of sulfide ores [1–2]. Cu is mainly sourced from chalcopyrite, whereas Pb predominantly occurs in galena [3–4]. Notably, chalcopyrite and galena are frequently associated. Furthermore, during Cu smelting in blast furnaces, high Pb levels can be obtained from Pb oxides or other compounds that adsorb onto sintered ore or pellets, thereby reducing the sintering temperature. Under oxygen-rich, high-temperature conditions, elemental Pb is oxidized to form Pb oxide particles, which can enter soot, dust, and slag. Pb vapor also pollutes the prefurnace environment and poses health risks to workers [5]. Therefore, reducing the Pb content in Cu concentrates is essential for safe and efficient smelting. Flotation has emerged as a relatively effective technique for the separation of Cu–Pb minerals [6]. This process reduces the mutual contamination between Cu and Pb minerals, thereby minimizing hazards during the Pb–Cu smelting phase. Additionally, effective flotation-based separation of chalcopyrite from galena not only enhances the process safety but also increases the overall economic feasibility of Cu smelting.

In the flotation recovery process, untreated galena and chalcopyrite exhibit similar floatability, complicating their separation [7]. To enhance the wettability differences between these minerals, it is crucial to select appropriate inhibitors or highly selective collectors [8]. Among these, inhibitors are more commonly used than collectors [9]. Traditional Cu–Pb flotation separation methods utilize inorganic inhibitors such as dichromate, sulfites, phosphates, and silicates to effectively suppress galena [10–12]. These inhibitors are known for their high selectivity and effectiveness for the separation of Cu and Pb sulfide ores. However, they have notable drawbacks. For example, potassium dichromate is environmentally hazardous, and its interaction with minerals can be slow [13–14]. Other inhibitors may require stringent flotation conditions, which can compromise process reliability. Consequently, developing highly selective and eco-friendly organic inhibitors is a key research area for achieving Cu–Pb separation [15].

Historically, mineral processing researchers have sought effective depressants to separate chalcopyrite from galena. Theoretical studies have identified common organic inhibitors such as lignin, dextrin, carboxymethyl cellulose, and alginate gum as potential inhibitors in Cu–Pb flotation separation [16–17]. Typically, these depressants contain hydroxyl and carboxyl functional groups that interact with Pb ions to form hydrophilic complexes, thereby hindering the adsorption of subsequent collectors. This reduces the floatability of the galena surface, thereby enabling the separation of the two minerals. Additionally, galena depressants have been developed by either modif...