植酸对碳酸盐绿锈转化的影响

Effects of myo-inositol hexakisphosphate on the transformation of carbonate green rust

为研究植酸(IHP)对绿锈转化过程及机制的影响,通过空气氧化法合成碳酸盐绿锈[GR1(CO_(3)^(2-))],并利用X射线衍射、衰减全反射-傅里叶变换红外光谱、高分辨透射电子显微镜、扫描电子显微镜和能量色散X射线能谱对体系中的固体产物进行分析表征。研究表明:不存在IHP时GR1(CO_(3)^(2-))在5 h左右完全转化为针铁矿,而存在IHP时GR1(CO_(3)^(2-))的转化会受到抑制。在0~0.5 mmol·L^(-1)的IHP浓度范围内,GR1(CO_(3)^(2-))的转化产物为针铁矿,而当IHP浓度高于1.0 mmol·L^(-1)时,GR1(CO_(3)^(2-))的转化产物为针铁矿和高铁绿锈。IHP对GR1(CO_(3)^(2-))转化机制的影响与其浓度有直接关系,在低浓度IHP(0~0.5 mmol·L^(-1))条件下,GR1(CO_(3)^(2-))转化过程只涉及溶解-氧化-沉淀(DOP)机制;而高浓度IHP(1.0~5.0 mmol·L^(-1))体系中,固态氧化(SSO)机制占主导地位,在其转化过程中,一部分GR1(CO_(3)^(2-))通过溶解再沉淀机制转化为针铁矿,一部分GR1(CO_(3)^(2-))通过原位脱质子反应转化为高铁绿锈。此外,在GR1(CO_(3)^(2-))转化过程中,IHP在GR1(CO_(3)^(2-))及其转化产物表面会形成内圈络合物和植酸(亚)铁沉淀。总体而言,IHP会抑制GR1(CO_(3)^(2-))的溶解再沉淀转化机制,阻碍针铁矿的结晶和晶体生长,且抑制作用与IHP浓度呈正相关。

Green rust exists widely in paddy soil,sediment,groundwater,and other environments,and its transformation is affected by various environmental geochemical factors.Carbonate green rust[GR1(CO_(3)^(2-))]was synthesized by air oxidation,and the effect of organic phosphorus(myo-inositol hexakisphosphate,IHP)on the transformation process and mechanism of green rust was investigated.The solid products in the system were characterized by X-ray diffraction,attenuated total reflection Fourier-transform infrared spectroscopy,highresolution transmission electron microscopy,scanning electron microscopy,and energy dispersive X-ray spectroscopy.The results showed that GR1(CO_(3)^(2-))was completely converted to goethite in approximately 5 h in the absence of IHP,while the transformation of GR1(CO_(3)^(2-))was inhibited in the presence of IHP.In the presence of 0-0.5 mmol·L^(-1) IHP,the transformation product of GR1(CO_(3)^(2-))was goethite,while GR1(CO_(3)^(2-))was transformed into goethite and ferric green rust when the concentration of IHP was above 1.0 mmol·L^(-1).The effect of IHP on the conversion mechanism of GR1(CO_(3)^(2-))was directly related to its concentration.In a system with a low concentration of IHP(0-0.5 mmol·L^(-1)),the conversion process of GR1(CO_(3)^(2-))only involved the dissolution-oxidation-precipitation(DOP)mechanism.However,in a system with a high concentration of IHP(1.0-5.0 mmol·L^(-1)),the solid-state oxidation(SSO)mechanism dominated,and GR1(CO32-)was partially converted into goethite through a dissolution reprecipitation mechanism,and GR1(CO_(3)^(2-))was partially transformed into ferric green rust via an in situ deprotonation reaction.In addition,during the transformation of GR1(CO_(3)^(2-)),IHP formed inner-sphere complexes or(ferro)ferric phytate precipitates on the surface of GR1(CO_(3)^(2-))and its transformation products.Overall,IHP inhibites the dissolutionreprecipitation transformation mechanism of GR1(CO_(3)^(2-))and hinderes the crystallization and crystal growth of goethite,and the inhibition is positively correlated with the concentration of IHP.