负载硼的针铁矿结构表征研究  

STRUCTURAL CHARACTERISTICS OF GOETHITE AND ITS B-LOADED OXIDES

作　　者：廖水姣[1] 王娟[1] 朱端卫[1] 任丽英[1] 周文兵[1] 丁家旺[1] 

机构地区：[1]华中农业大学微量元素研究中心

出　　处：《土壤学报》2006年第5期742-748,共7页Acta Pedologica Sinica

基　　金：国家自然科学基金项目(40371064)资助

摘　　要：人工合成了针铁矿(Goethite)及其负载硼的氧化物(硼吸附态针铁矿Ad-B-Goethite,硼包被态针铁矿Oc-B-Goethite),用IR、X射线衍射、TEM对其进行表征,测定了它的比表面积及其对锰离子的吸附性能。IR分析表明,负载硼的针铁矿较之普通针铁矿在888 cm-1处的Fe-OH-Fe表面羟基弯曲振动1、000 cm-1处的表面Fe-OH弯曲振动及3 100 cm-1处的游离羟基峰均减弱;硼吸附态针铁矿在458.5 cm-1处,硼包被态针铁矿在527.2 cm-1和476.5 cm-1处出现了与BO3和B(O,OH)4的弯曲振动有关的吸收峰。X射线衍射分析表明硼吸附态针铁矿的晶形与普通针铁矿相似,而硼包被态针铁矿的衍射吸收峰的位置、个数和相对强度都发生了变化。从TEM图上可看出硼包被态针铁矿的晶体明显要小些。实验测得3种矿物的比表面积分别是:普通针铁矿108.4 m2g-1,吸附态针铁矿88.69 m2g-1,包被态针铁矿120.5 m2g-1。对锰离子的吸附量为硼包被态针铁矿明显大于硼吸附态针铁矿大于普通针铁矿。结果表明:硼包被态针铁矿(Oc-B-goethite)中B进入了针铁矿的晶格,影响晶体的生长,使晶体的结晶性较差,晶体较小、比表面积增大,对锰离子的净吸附能力强。这也说明,土壤中的硼不仅起到植物营养的作用,其在形成负载硼的铁氧化物后有利于减轻土壤锰的毒害。Structures and morphologies of goethite and its two synthesized B-loaded oxides, Ad-B-Goethite and Oc-B- Goethite, were characterized with the aid of IR, XRD and TEM, and their specific surface areas and Mn^2＋-adsorption capacities were measured with the BET method. It was found from IR that as compared with goethite, the two B-loaded geothites decreased in the bands of Fe-OH-Fe in-plane bending at 888 cm^-1, the bands of Fe-OH in-plane bending at 1 000 cm^-1, and the bands of free OH at 3 100 cm^-1. The bands of bending modes of trigonal and tetrahedral boron were found at 458.5 cm^-1 with Ad-B- Goethite, and also at 527.2 cm^-1 and 476.5 cm^-1 with Oc-B-Goethite. XRD analysis showed that Ad-B-Goethite was still fine α-FeOOH and Oc-B-Goethite was differed from goethite, suggesting that Oc-B-Goethite is probably a new mineral. Judging from TEM graphs, the particle of Oc-B-Goethite was smaller than that of goethite. The specific surface area of goethite, Ad-B-Goethite and Oc-B-Goethite was 108.4 m^2 g^-1, 88.69 m^2 g^-1, and 120.5 m^2 g^-1, respectively. The increase in surface area means Oc- B-Goethite having more activity than normal goethite. This assumption is supported by the finding that the adsorption of Mn^2＋ on the surface of Oc-B-Goethite was the highest and that of goethite was the lowest in the three kinds of minerals. It was found that B in Oc-B-Goethite had replaced hydroxide ligands inside the crystal lattices, and inhibited crystal growth of goethite, thus result- ing in weak crystallizability. It was also found that Mn^2＋ adsorption increased with the presence of Ad-B-Goethite, especially of Oc-B-Goethite. It is suggested that boron applied into soil functions is not only as a nutrient for plant, but also as a buffer against Mn^2＋ toxicity to the plant in the soil by forming B-loaded iron oxides.

关 键 词：针铁矿 硼吸附态针铁矿 硼包被态针铁矿 结构 吸附 锰离子 

分 类 号：S153[农业科学—土壤学]