Pathways of birnessite formation in alkali medium

作     者：FENG Xionghan1, TAN Wenfeng1, LIU Fan1, HUANG Qiaoyun1 & LIU Xiangwen2 1. College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China 2. Testing Center, China University of Geosciences, Wuhan 430074, China 

作者机构：College of Resources and Environment Huazhong Agricultural University Wuhan China Testing Center China University of Geosciences Wuhan China 

出 版 物：《Science China Earth Sciences》 (中国科学（地球科学英文版）)

年 卷 期：2005年第48卷第9期

页      面：1438-1451页

核心收录：

学科分类：081704[工学-应用化学] 07[理学] 08[工学] 0817[工学-化学工程与技术] 0708[理学-地球物理学] 0703[理学-化学] 0704[理学-天文学] 070301[理学-无机化学] 

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.40403009 and 40101017) by Research Fund for the Doctoral Program of Higher Education(Grant No.2002050411) 

主　　题：birnessite, pathway of formation, reaction process, Eh-pH diagram, hausmannite, feitknechtite. 

摘      要：Birnessite is a common weathering and oxidation product of manganese-bearing rocks. An O2 oxidation procedure of Mn(OH)2 in the alkali medium has been used to synthesize birnessite. Fast and powder X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), energy dispersed X-ray analysis (EDAX), infrared spectroscopy (IR) techniques and chemical composition analysis, Eh-pH equilibrium diagram approaches were employed to investigate the reaction process and pathways of birnessite formation. Results showed that the process of the birnessite formation could be divided into four stages: (1) forma- tion stage for hausmannite and feitknechtite, (2) stage of transformation of hausmannite and feitknechtite to buserite, (3) buserite crystal growing stage, and (4) stage of conversion of buser- ite into birnessite. Mn(OH)2 was mainly present as amorphous state only for a short initial time of oxidation reaction. In the oxidation process, buserite formed following two pathways by recrys- tallization after dissolution of the intermediates, and the transformations of the minerals de- pended on the Eh determined by the dissolved O2 concentration on their surfaces. The results are fundamental in further exploration on the mechanism of birnessite formation in the alkali medium. A great practical significance would also be expected with respect to the areas of mate- rial sciences.