还原态蒙脱石结构Fe(Ⅱ)催化水铁矿转化特性及影响因素  

Characteristics and Influencing Factors of the Catalytic Transformation of Ferrihydrite by the Structural Fe(Ⅱ)in Reduced Montmorillonite

作　　者：廖文娟 彭薇 吴聪 宁雅琪 王帅 崔浩杰 LIAO Wenjuan;PENG Wei;WU Cong;NING Yaqi;WANG Shuai;CUI Haojie(College of Resources and Environment,Hunan Agricultural University,Changsha 410128,China)

机构地区：[1]湖南农业大学资源环境学院,长沙410128

出　　处：《土壤学报》2023年第2期469-478,共10页Acta Pedologica Sinica

基　　金：国家自然科学基金项目(41771272,41702040);湖南省自然科学基金项目(2021JJ40256);湖南农业大学“双一流”建设项目(SYL2019043)共同资助。

摘　　要：还原条件下土壤中Fe(Ⅱ)催化水铁矿转化在调控营养元素和污染物的生物地球化学过程中具有重要作用。然而,作为土壤中Fe(Ⅱ)存在的主要形态之一,蒙脱石结构中Fe(Ⅱ)催化水铁矿转化的特性及其影响因素目前尚不清楚。以化学还原的蒙脱石为研究对象,探究还原态蒙脱石(rSWy-2)结构中Fe(Ⅱ)催化水铁矿转化的特性及其影响因素。结果表明,贫铁的蒙脱石结构中Fe(Ⅱ)可催化水铁矿向纤铁矿转化,反应96 h后水铁矿转化量达到83.3%。X射线衍射(XRD)、高分辨透射(HRTEM)、球差电镜(STEM)和表面吸附态Fe(Ⅱ)含量分析表明,rSWy-2结构Fe(Ⅱ)催化水铁矿转化主要经历矿物间固相吸附、电子传递和水铁矿转化三个阶段,形成的纤铁矿呈板状纳米片,尺寸大小为100~200 nm。溶液中Na^(+)和Cl^(-)离子对rSWy-2催化水铁矿转化影响较弱,而Ca^(2+)、SO_(4)^(2-)、有机质和As(Ⅲ)均对水铁矿转化具有明显的抑制作用。【Objective】Fe(Ⅱ)-induced transformations of amorphous ferrihydrite to more crystalline iron oxide phases is a widely occurring geochemical process in soils under reduced conditions,and play an important role in regulating the biogeochemical processes of nutrient elements and pollutants.As one of the main species of Fe(Ⅱ)in soils,Fe(Ⅱ)-containing clay minerals are ubiquitous in soils under reduced conditions.However,the catalytic properties of structural Fe(Ⅱ)in clay minerals for ferrihydrite transformation and its influencing factors are still not fully understood.【Method】In this study,the transformation of ferrihydrite induced by the structural Fe(Ⅱ)in reduced montmorillonite(rSWy-2),which was produced by a chemical method,were investigated at neutral pH under anoxic conditions.Also,the influencing factors including types of cations and anions,organic matter,and As(Ⅲ)on the transformation were studied.【Result】The X-ray diffraction(XRD)and chemical extraction analyses results showed that the structural Fe(Ⅱ)in rSWy-2 with low Fe content can catalyze the transformation from ferrihydrite to more crystalline lepidocrocite,and 83.3%of initial ferrihydrite converted to lepidocrocite after mixing reaction for 96 h.XRD,high-resolution transmission electron microscope(HRTEM),scanning transmission electron microscopy(STEM)and surface adsorbed Fe(Ⅱ)content analyses showed that the processes of ferrihydrite transformation induced by the structural Fe(Ⅱ)in rSWy-2 mainly included three stages:Firstly,positively charged ferrihydrite nanoparticles adsorption on negatively charged rSWy-2 surface through electrostatic interaction.Secondly,interfacial electron transfer from the structural Fe(Ⅱ)in rSWy-2 to the adsorbed ferrihydrite and partly reducing Fe(Ⅲ)to surface adsorbed Fe(Ⅱ).Finally,the surface adsorbed Fe(Ⅱ)catalyzed the transformation of ferrihydrite to more crystalline lepidocrocite phases.HRTEM analyses showed that the formed lepidocrocite phases presented nanoplates with a size ran

关 键 词：蒙脱石 水铁矿 结构Fe(Ⅱ) 电子传递 矿物转化 

分 类 号：S158.5[农业科学—土壤学]