【作者】 张嵚； 冯雄汉； 刘凡；

【Author】 Zhang Qin~(1,2),Feng Xiong-han~2,Liu Fan~(2*) (1.College of Land Resource and Environment,Jiangxi Agricultural University,Nanchang; 2.College of Resources & Environment,Huazhong Agricultural University,Wuhan)

【机构】 江西农业大学国土资源与环境学院； 华中农业大学资源与环境学院；

【摘要】 水钠锰矿是土壤中广泛分布的层状氧化锰矿物,土壤中许多氧化锰矿物的形成与水钠锰矿关系密切,以水钠锰矿为母体直接或间接转化生成。依据层结构的对称性,水钠锰矿分为六方对称型水钠锰矿（简称"六方水钠锰矿"）和三斜对称型水钠锰矿（简称"三斜水钠锰矿"）,而天然水钠锰矿主要为六方对称型。目前关于水钠锰矿转化的研究多以三斜水钠锰矿为母体,且多偏向于苛刻物理化学条件下的矿物转化。因此,本项目以六方水钠锰矿为前驱物,在接近表生环境条件下研究表生环境(K⁺浓度、Mn²⁺浓度和回流温度)变化对其转化产物的影响。研究将更贴近土壤表生环境,对深入揭示锰氧化物的环境地球化学行为、丰富表生矿物学理论具有重要意义。主要研究结果为:（1）当溶液K⁺浓度为0和0.1 mol/L时,水钠锰矿回流3 h后完全转变为锰钾矿;当K⁺浓度增加至0.5和1.0 mol/L时,水钠锰矿回流1 h后完全转变为锰钾矿。尽管K⁺浓度的变化对反应产物的晶体结构没有影响,但随着K⁺浓度的增加水钠锰矿转变为锰钾矿所需要的时间也逐渐减小,这表明K⁺浓度的增加有利于水钠锰矿向锰钾矿转变。（2）当溶液Mn²⁺浓度为0mol/L时,酸性水钠锰矿回流12h后转变为锰钾矿;溶液Mn²⁺浓度增加至0.01 mol/L时,回流24 h后产物为拉锰矿和锰钾矿的混合物;溶液Mn²⁺浓度增加至0.1、0.5和1.0 mol/L时,水钠锰矿回流1 h后便完全转变为拉锰矿。这表明Mn²⁺浓度显著影响水钠锰矿的转变产物,Mn²⁺浓度的增加有利于水钠锰矿向拉锰矿转变。（3）当回流温度低于60℃时,酸性水钠锰矿回流7天未发生矿相转变;当温度高于80℃时,随着温度的升高,水钠锰矿向锰钾矿转变的速率增加。这表明回流温度不仅决定着水钠锰矿是否发生转变,还影响着水钠锰矿的转变速率。更多还原

【Abstract】 Birnessite,a layer structured manganese oxide,is widely distributed in earth surface environment.The formations of many other manganese oxides have close relations with birnessite,and many of them are formed directly or indirectly from birnessite.According to layer symmetry of birnessite, it can be divided into the hexagonal birnessite and triclinic birnessite,and natural birnessite always has hexagonal symmetry.So far most of studies focused on the transformation of triclinic birnessite or under certain harsh conditions.Hence,this project,under simulated surface environment,focuses the effect of earth surface environment conditions(concentration of K⁺ and Mn ²⁺,reflux temperatures) on mineral transformation.The results will contribute to reveal the environmental geochemical behaviors of manganese oxide,and enrich surface environment mineralogy theory.The main results are: （1） When the concentration of K+ is 0 and 0.1 mol/L,the birnessite converted to cryptomelane after refulx of 3 h.As the concentration of K+ increased to 0.5 and 1.0 mol/L,the birnessite converted to cryptomelane after refulx 1 h.Although the concentration of K+ impacted the crystal structure of the product,it reduced the time of phase transformation which implied that the increase of concentration of K+ facilities the transformation form birnessite to cryptomelane. （2） When the concentration of Mn²⁺ is 0 mol/L,birnessite transformed to cryptomelane after reflux of 12 h.When the concentration of Mn²⁺ increased to 0.01 mol/L,the products were the mixtures of cryptomelane and ramsdellite after reflux of 24h.As the concentration of Mn²⁺ increased to 0.1,0.5 and 1.0 mol/L,the porduct was only ramsdellite after reflux of 1 h.Above result indicated that the concentration of Mn²⁺ effectively impacted on the porduct,and the increase of concentration of Mn²⁺ facilities the transformation form birnessite to ramsdellite. （3） When the reflux temperature is below 60℃,birnessite did transofrmed even reflux of 7 days. However,when the temperature increased to 80℃,birnessite convert to cryptomelane,and the conversion rate incread with temperature.It could be deduced that the temperature not only determined the occurrence of phase conversion,but also affected the conversion rate.更多还原