{"title":"Role of Cr(VI) in the efficient removal of Cd(II) from aqueous solutions using Fe3S4 in a Cd(II)/Cr(VI) binary system","authors":"Yaxin Qin , Fengfeng Zhou , Chao Wang , Wei Liu","doi":"10.1016/j.envres.2025.121404","DOIUrl":null,"url":null,"abstract":"<div><div>In this study, the synthesized magnetic greigite (Fe<sub>3</sub>S<sub>4</sub>) was utilized to simultaneously eliminate Cd(II) and Cr(VI) from aqueous solution. The removal efficiency (96.6 %) of Cd(II) in the binary (Cd(II)/Cr(VI)) system was superior to that (79.2 %) of the single (Cd(II)) system, accompanied by a negligible difference in the removal efficiency of Cr(VI) (∼100 %) between the single Cr(VI) and binary systems. The adsorption process of Cd(II) onto Fe<sub>3</sub>S<sub>4</sub> closely followed the pseudo-first order kinetic model and Freundlich isotherm, suggesting that the adsorption of Cd(II) primarily involved multi-molecular layer physical adsorption. Characterization results confirmed that the surface hydroxyl groups on Fe<sub>3</sub>S<sub>4</sub> played a significant role in the Cd(II) adsorption in the single system. In contrast, in the binary system, the adsorption of Cd(II) was predominantly attributed to surface sulfide groups at pH 3.8, while hydroxyl groups were the primary contributors to Cd(II) adsorption at pH 6.8. Additionally, at pH 5.3, both sulfide and hydroxyl groups contributed equally to Cd(II) adsorption. This pH-dependent mechanism for Cd(II) removal was resulted from the fact that Cr(VI) could not only influence the solution pH and adjust the isoelectric point of Fe<sub>3</sub>S<sub>4</sub> to enhance the electrostatic attraction between Cd(II) and Fe<sub>3</sub>S<sub>4</sub>, but also diminish the concentrations of Fe species to eliminate their competitive adsorption with Cd(II). This study is significantly important for understanding the enhanced removal mechanisms of Cd(II) in the presence of Fe<sub>3</sub>S<sub>4</sub>, particularly with the coexistence of Cr(VI), as well as for the simultaneous remediation of both cationic and anionic pollutants from wastewater using iron sulfides.</div></div>","PeriodicalId":312,"journal":{"name":"Environmental Research","volume":"275 ","pages":"Article 121404"},"PeriodicalIF":7.7000,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Environmental Research","FirstCategoryId":"93","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0013935125006553","RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
In this study, the synthesized magnetic greigite (Fe3S4) was utilized to simultaneously eliminate Cd(II) and Cr(VI) from aqueous solution. The removal efficiency (96.6 %) of Cd(II) in the binary (Cd(II)/Cr(VI)) system was superior to that (79.2 %) of the single (Cd(II)) system, accompanied by a negligible difference in the removal efficiency of Cr(VI) (∼100 %) between the single Cr(VI) and binary systems. The adsorption process of Cd(II) onto Fe3S4 closely followed the pseudo-first order kinetic model and Freundlich isotherm, suggesting that the adsorption of Cd(II) primarily involved multi-molecular layer physical adsorption. Characterization results confirmed that the surface hydroxyl groups on Fe3S4 played a significant role in the Cd(II) adsorption in the single system. In contrast, in the binary system, the adsorption of Cd(II) was predominantly attributed to surface sulfide groups at pH 3.8, while hydroxyl groups were the primary contributors to Cd(II) adsorption at pH 6.8. Additionally, at pH 5.3, both sulfide and hydroxyl groups contributed equally to Cd(II) adsorption. This pH-dependent mechanism for Cd(II) removal was resulted from the fact that Cr(VI) could not only influence the solution pH and adjust the isoelectric point of Fe3S4 to enhance the electrostatic attraction between Cd(II) and Fe3S4, but also diminish the concentrations of Fe species to eliminate their competitive adsorption with Cd(II). This study is significantly important for understanding the enhanced removal mechanisms of Cd(II) in the presence of Fe3S4, particularly with the coexistence of Cr(VI), as well as for the simultaneous remediation of both cationic and anionic pollutants from wastewater using iron sulfides.
期刊介绍:
The Environmental Research journal presents a broad range of interdisciplinary research, focused on addressing worldwide environmental concerns and featuring innovative findings. Our publication strives to explore relevant anthropogenic issues across various environmental sectors, showcasing practical applications in real-life settings.