锰铬掺杂对氧化铁的形成、表面性质及吸附硒的影响
发布时间：2018-09-08 19:26
【摘要】：水热条件下制备了纯针铁矿、赤铁矿和不同比例的锰、铬掺杂氧化铁,采用现代测试技术分析了样品的微观结构和表面性质,通过等温吸附实验研究了样品对不同价态硒的吸附特性,并探讨了其吸附机制。取得的主要结果有:(1)在合成针铁矿的体系中,低比例锰掺杂(R=0.1~0.2,R为掺杂金属与铁的摩尔比)促进了针铁矿的形成;随着掺杂比例的升高,产物的形貌变得越细长。锰掺杂比例较高时(R=0.3~0.5),随着掺杂比例的升高,产物的结晶度不断降低,颗粒尺寸逐渐变短;当R=0.5时,产物中出现了形貌不规则的掺锰磁铁矿。在合成赤铁矿的体系中,锰的掺杂比例R从0.1增加至0.5时,产物中赤铁矿的结晶度不断减弱,颗粒尺寸也不断变小;当R=0.5时,产物主要为掺锰磁铁矿。铬的掺杂比例R=0.1~0.5时,针铁矿和赤铁矿的形成都受到了明显的抑制作用,且产物中没有形成其它结晶物质;随着掺杂比例的升高,产物中针铁矿和赤铁矿的结晶度不断减弱,其颗粒尺寸逐渐减小;当掺杂比例R=0.5时,产物中出现了大量非晶形颗粒物。(2)样品的氮气等温吸附/脱附分析显示,针铁矿(Goe)和R=0.2时的锰、铬掺杂产物(G-Mn0.2和G-Cr0.2)的比表面积分别为46.25、83.45和101.33 m2·g-1;3种样品的平均孔径分别为23.63、14.29和2.43 nm。赤铁矿(Hem)和R=0.2时的锰、铬掺杂产物(H-Mn0.2和H-Cr0.2)的比表面积分别为12.29、169.62和99.55 m2·g-1;它们的平均孔径分别为6.75、0.75和0.97 nm。锰、铬掺杂对针铁矿和赤铁矿的表面分形度(SFD)的影响较小,其中Goe及其掺杂产物的SFD在2.43~2.54间,Hem及其掺杂产物的SFD在2.56~2.73间。(3)Goe、G-Mn0.2和G-Cr0.2的Zeta电位零点分别为7.36、6.58和4.74,Hem、H-Mn0.2和H-Cr0.2的Zeta电位零点分别为6.41、5.42和5.71。可见,锰、铬掺杂都明显降低了氧化铁的表面电位零点。激光粒度分析显示,Goe、G-Mn0.2和G-Cr0.2的颗粒平均粒度分别为630、915和765 nm,Hem、H-Mn0.2和H-Cr0.2的平均粒度分别为1025、534和523 nm。可见,掺杂比例R=0.2时,锰、铬掺杂针铁矿的颗粒粒度增加,而掺杂赤铁矿的粒度却明显减小。(4)样品对不同价态硒的等温吸附实验表明,同种样品对Se(Ⅳ)的吸附容量明显高于对Se(Ⅵ)。锰、铬掺杂升高了针铁矿和赤铁矿对Se(Ⅳ)和Se(Ⅵ)的吸附容量,其中对吸附Se(Ⅳ)的影响更明显。当Se(Ⅳ)的初始浓度为80 mg·g-1时,Goe、G-Mn0.2和G-Cr0.2对Se(Ⅳ)的吸附容量分别约为10、16和25 mg·g-1;Hem、H-Mn0.2和H-Cr0.2对Se(Ⅳ)的吸附容量分别约为6、23和24 mg·g-1。可见,掺杂比例R=0.2时,铬掺杂针铁矿和赤铁矿对Se(Ⅳ)的吸附容量都高于锰掺杂产物。(5)初始p H=4.0时,Goe、G-Mn0.2和G-Cr0.2吸附Se(Ⅳ)以后体系的p H值分别升高至5.6、5.7和5.9,吸附Se(Ⅵ)以后的p H分别为4.3、4.9和5.2;Hem、H-Mn0.2和H-Cr0.2吸附Se(Ⅳ)以后的p H分别为4.3、5.4和5.3,吸附Se(Ⅵ)以后的p H分别为4.4、5.0和5.1。Zeta电位分析表明,各种样品吸附Se(Ⅳ)和Se(Ⅵ)以后,样品的Zeta电位零点都有所降低;Goe、Hem和铬掺杂产物吸附Se(Ⅳ)以后的Zeta电位零点略低于吸附Se(Ⅵ)以后的值,锰掺杂产物吸附Se(Ⅳ)以后的Zeta电位零点反而高于吸附Se(Ⅵ)以后的值。这表明静电引力、阴离子交换、表面配位等作用是样品吸附Se(Ⅳ)和Se(Ⅵ)的重要机制,其中样品对Se(Ⅳ)的配位吸附以双齿配位作用为主,而对Se(Ⅵ)的配位吸附以单齿配位作用为主。
[Abstract]:Goethite, hematite and manganese and chromium-doped ferric oxide were prepared under hydrothermal conditions. The microstructure and surface properties of the samples were analyzed by modern testing techniques. The adsorption characteristics of different valence selenium on the samples were studied by isothermal adsorption experiments, and the adsorption mechanism was discussed. In iron ore system, low proportion of manganese doping (R = 0.1-0.2, R is the molar ratio of doped metal to iron) promotes the formation of goethite; with the increase of the doping ratio, the morphology of the product becomes more slender and longer. When the ratio of manganese doping is higher (R = 0.3-0.5), with the increase of the doping ratio, the crystallinity of the product decreases and the particle size gradually shortens; when R = 0.5 In the system of hematite synthesis, the crystallinity of hematite decreases from 0.1 to 0.5, and the size of hematite particles decreases continuously. When R = 0.5, the product is mainly manganese-doped magnetite. When the doping ratio of chromium is between 0.1 and 0.5, goethite and hematite are the main products. The crystallinity of goethite and hematite decreases gradually with the increase of doping ratio, and a large number of amorphous particles appear in the product when the doping ratio R=0.5. (2) Nitrogen isothermal adsorption/desorption of the sample. The results show that the specific surface areas of Mn and Cr-doped products (G-Mn 0.2 and G-Cr0.2) at Goethite (Goe) and R=0.2 are 46.25, 83.45 and 101.33 m2.g-1, respectively; the average pore sizes of the three samples are 23.63, 14.29 and 2.43 nm, respectively. Hematite (Hem) and Mn at R=0.2, and the specific surface areas of Cr-doped products (H-Mn 0.2 and H-Cr0.2) are 12.29, 169.62 and 99.55 m2, respectively. Their average pore diameters are 6.75, 0.75 and 0.97 nm, respectively. The influence of chromium doping on surface fractal degree (SFD) of goethite and hematite is small. Among them, the SFD of Goe and its doped products ranges from 2.43 to 2.54, the SFD of Hem and its doped products ranges from 2.56 to 2.73. (3) Zeta potential zeros of Goe, G-Mn0.2 and G-Cr0.2 are 7.36, 6.58 and 4.74, Hem, Hem, and their doped products are 7.56 to 2.73, respectively. Zeta potential zeros of H-Mn 0.2 and H-Cr0.2 are 6.41, 5.42 and 5.71, respectively. It can be seen that both Mn and Cr doping significantly reduce the surface potential zeros of ferric oxide. Laser particle size analysis shows that the average particle sizes of Goe, G-Mn 0.2 and G-Cr0.2 are 630, 915 and 765 nm, Hem, H-Mn 0.2 and H-Cr0.2 are 1025, 534 and 523 nm, respectively. (4) The adsorption capacity of the same sample for Se (IV) was significantly higher than that for Se (VI). Manganese and chromium doping increased the adsorption capacity of goethite and hematite for Se (IV) and Se (VI). The adsorption capacity of Goe, G-Mn0.2 and G-Cr0.2 for Se(IV) is about 10,16 and 25 mg (4) The adsorption capacity of the system was higher than that of the manganese-doped products. (5) When the initial P H=4.0, the P H values of the system after Goe, G-Mn0.2 and G-Cr0.2 adsorption of Se (IV) were increased to 5.6, 5.7 and 5.9, respectively, and the P H values after adsorption of Se (VI) were 4.3, 4.9 and 5.2, respectively; and the p H values after adsorption of Hem, H-Mn0.2 and H-Cr0.2 were 4.3, 5.4 and 5.3, respectively.3, and 5.3 after adsorption of Se (IV) respectively. Zeta potential analysis showed that Zeta potential zero point of all samples decreased after adsorption of Se (IV) and Se (VI); Zeta potential zero point of Goe, Hem and chromium doped products after adsorption of Se (IV) was slightly lower than that after adsorption of Se (VI); Zeta potential zero point of manganese doped products after adsorption of Se (IV) was higher than that of adsorption of Se (VI). These results indicate that electrostatic attraction, anion exchange and surface coordination are important mechanisms for the adsorption of Se (IV) and Se (VI). Bidentate complexation is dominant for the coordination adsorption of Se (IV) and monodentate complexation is dominant for the coordination adsorption of Se (VI).
【学位授予单位】：湖北民族学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O647.3
本文编号：2231467
[Abstract]:Goethite, hematite and manganese and chromium-doped ferric oxide were prepared under hydrothermal conditions. The microstructure and surface properties of the samples were analyzed by modern testing techniques. The adsorption characteristics of different valence selenium on the samples were studied by isothermal adsorption experiments, and the adsorption mechanism was discussed. In iron ore system, low proportion of manganese doping (R = 0.1-0.2, R is the molar ratio of doped metal to iron) promotes the formation of goethite; with the increase of the doping ratio, the morphology of the product becomes more slender and longer. When the ratio of manganese doping is higher (R = 0.3-0.5), with the increase of the doping ratio, the crystallinity of the product decreases and the particle size gradually shortens; when R = 0.5 In the system of hematite synthesis, the crystallinity of hematite decreases from 0.1 to 0.5, and the size of hematite particles decreases continuously. When R = 0.5, the product is mainly manganese-doped magnetite. When the doping ratio of chromium is between 0.1 and 0.5, goethite and hematite are the main products. The crystallinity of goethite and hematite decreases gradually with the increase of doping ratio, and a large number of amorphous particles appear in the product when the doping ratio R=0.5. (2) Nitrogen isothermal adsorption/desorption of the sample. The results show that the specific surface areas of Mn and Cr-doped products (G-Mn 0.2 and G-Cr0.2) at Goethite (Goe) and R=0.2 are 46.25, 83.45 and 101.33 m2.g-1, respectively; the average pore sizes of the three samples are 23.63, 14.29 and 2.43 nm, respectively. Hematite (Hem) and Mn at R=0.2, and the specific surface areas of Cr-doped products (H-Mn 0.2 and H-Cr0.2) are 12.29, 169.62 and 99.55 m2, respectively. Their average pore diameters are 6.75, 0.75 and 0.97 nm, respectively. The influence of chromium doping on surface fractal degree (SFD) of goethite and hematite is small. Among them, the SFD of Goe and its doped products ranges from 2.43 to 2.54, the SFD of Hem and its doped products ranges from 2.56 to 2.73. (3) Zeta potential zeros of Goe, G-Mn0.2 and G-Cr0.2 are 7.36, 6.58 and 4.74, Hem, Hem, and their doped products are 7.56 to 2.73, respectively. Zeta potential zeros of H-Mn 0.2 and H-Cr0.2 are 6.41, 5.42 and 5.71, respectively. It can be seen that both Mn and Cr doping significantly reduce the surface potential zeros of ferric oxide. Laser particle size analysis shows that the average particle sizes of Goe, G-Mn 0.2 and G-Cr0.2 are 630, 915 and 765 nm, Hem, H-Mn 0.2 and H-Cr0.2 are 1025, 534 and 523 nm, respectively. (4) The adsorption capacity of the same sample for Se (IV) was significantly higher than that for Se (VI). Manganese and chromium doping increased the adsorption capacity of goethite and hematite for Se (IV) and Se (VI). The adsorption capacity of Goe, G-Mn0.2 and G-Cr0.2 for Se(IV) is about 10,16 and 25 mg (4) The adsorption capacity of the system was higher than that of the manganese-doped products. (5) When the initial P H=4.0, the P H values of the system after Goe, G-Mn0.2 and G-Cr0.2 adsorption of Se (IV) were increased to 5.6, 5.7 and 5.9, respectively, and the P H values after adsorption of Se (VI) were 4.3, 4.9 and 5.2, respectively; and the p H values after adsorption of Hem, H-Mn0.2 and H-Cr0.2 were 4.3, 5.4 and 5.3, respectively.3, and 5.3 after adsorption of Se (IV) respectively. Zeta potential analysis showed that Zeta potential zero point of all samples decreased after adsorption of Se (IV) and Se (VI); Zeta potential zero point of Goe, Hem and chromium doped products after adsorption of Se (IV) was slightly lower than that after adsorption of Se (VI); Zeta potential zero point of manganese doped products after adsorption of Se (IV) was higher than that of adsorption of Se (VI). These results indicate that electrostatic attraction, anion exchange and surface coordination are important mechanisms for the adsorption of Se (IV) and Se (VI). Bidentate complexation is dominant for the coordination adsorption of Se (IV) and monodentate complexation is dominant for the coordination adsorption of Se (VI).
【学位授予单位】：湖北民族学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O647.3
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