Phase transformation of Cr(Ⅶ)-adsorbed ferrihydrite in the presence of Mn(Ⅱ):Fate of Mn(Ⅱ)and Cr(Ⅶ)

• 作者: Zecong Ding Guangzhao Sun Fenglian Fu Chujia Ye
• 来源期刊: 环境科学学报（英文版）
• 年，卷（期）: 2022,（3）
• 页码范围: 251-259
• 页数: 9页
• 语种: 英文

摘要

Ferrihydrite is an important sink for the toxic heavy metal ions,such as Cr(Ⅶ).As ferrihy-drite is thermodynamically unstable and gradually transforms into hematite and goethite,the stability of Cr(Ⅶ)-adsorbed ferrihydrite is environmentally significant.This study inves-tigated the phase transformation of Cr(Ⅶ)-adsorbed ferrihydrite at different pH in the pres-ence of aqueous Mn(Ⅱ),as well as the fate of Mn(Ⅱ) and Cr(Ⅶ) in the transformation process of ferrihydrite.Among the ferrihydrite transformation products,hematite was dominant,and goethite was minor.The pre-adsorbed Cr(Ⅶ) inhibited the conversion of fertihydrite to goethite at initial pH 3.0,whereas little amount of adsorbed Mn(Ⅱ) favored the formation of goethite at initial pH 7.0.After the aging process,Cr species in solid phase existed primarily as Cr(Ⅲ) in the presence of Mn(Ⅱ) at initial pH 7.0 and 11.0.The aqueous Mn concentration was predominantly unchanged at initial pH 3.0,whereas the aqueous Mn(Ⅱ) was adsorbed onto ferrihydrite or form Mn(OH)2 precipitates at initial pH 7.0 and 11.0,promoting the im-mobilization of Cr(Ⅶ).Moreover,the oxidation of Mn(Ⅱ) occurred at initial pH 7.0 and 11.0,forming Mn(Ⅲ/Ⅳ) (hydr)oxides.