Ascorbic acid-induced digenite (Cu9S5) formation: A strategy to enhance sulfidation efficiency for copper recovery from acidic wastewater
Year: 2025
Type: article
Abstract: Sulfide precipitation is an effective method for copper recovery from acidic wastewater. However, excessive use of sulfide reagents leads to secondary pollution, which poses a significant challenge. This study demonstrates that leveraging the reducing properties of ascorbic acid (AA) and adding Na 2 S to acidic copper-containing solutions (pH 2–4) at a Cu:S molar ratio of 1.6:0.8 enhances Cu(II) removal efficiency from 50 % to 100 %, doubling sulfide reagent utilization. Solution chemistry, electron microscopy, and X-ray spectroscopy analyses indicate that AA primarily promotes copper sulfide precipitation with higher copper content. Addition of AA at pH 2 at a Cu:S:AA molar ratio of 1.6:0.8:1 lowers the oxidation–reduction potential (ORP) from 0.5 V to 0.1 V, forming digenite (Cu 9 S 5 ). Compared to covellite (CuS) formed without AA, digenite exhibits a higher Cu oxidation state and a lower S oxidation state. Furthermore, coagulation kinetics studies show that solution pH, Na 2 SO 4 , and FeCl 2 concentrations influence copper sulfide aggregation. At pH 2, Cu 9 S 5 coagulates at least 4.2 times faster than CuS within 20 min. Cost analysis shows that the cost per ton of copper recovered from wastewater using this method is about one-third of the cost of conventional methods. More importantly, this study minimizes residual sulfide, offering a novel strategy for dose control in copper sulfide recovery.
Source: Water Research
Authors: Yihan Chen, Han Ye, Yingying Xie, Haiming Cai, Zhi Dang, Guining Lu
Language: English
Subfield: Environmental Chemistry
Field: Environmental Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,660
Awards: G2819465094, G4104198494
OpenAlex ID: W4409686526