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tianwei1332铁杆木虫 (著名写手)
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改变酸度和温度，合成正钒酸盐已有1人参与
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求解答下面三个问题，谢谢： pH在8～2范围内时,钒酸盐以“多钒酸盐”的形式存在与水溶液中。如果除去水，并在600℃焙烧，应该可以转化为正钒酸盐，是吧？ 另外，如果在上述pH范围内，对钒酸盐进行的水热合成（＞100℃），多钒酸盐也能转化为正钒酸盐，对吗？ 钨酸盐和磷酸盐也类似吧？ |
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硫酸盐的分解温度一般为多少？
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2楼2014-11-16 21:32:36
tianwei1332
铁杆木虫 (著名写手)
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请看一下下面这两种办法能得到正钒酸盐吗？谢谢指导 Pure t-LaVO4（水热法合成） was prepared through several steps using a hydrothermal method. First, a predetermined amount of La2O3 was dissolved in 6 M HNO3 solution. Then, the obtained La(NO3)3 solution was mixed with 0.4 M NH4VO3 at the V:La mole ratio of 1:1 to form a precipitate, followed by adjusting the pH of the new mixture to 7 with a 2 M NH3 solution and transferring it into a 100-mL Teflon-lined stainless-steel autoclave. The autoclave was sealed and maintained at 180°C for 24 h and then air-cooled to room temperature. The resulting products were filtered, washed with deionized water, and dried at 80°C for 12 h. Pure m-LaVO4（普通沉淀法） was prepared via a precipitation method. Specifically, 20 mL of0.4 M NH4VO3 and 20 mL of 0.4 M La(NO3)3 were used for the mixing and generation of a precipitate. The pH of the mixture was controlled at 5, using a 2 M NH3 solution. After aged at room temperature for 30 min, the precipitate was filtered, washed three times by deionized water, dried at 100 ℃ for 12 h and calcined at 600 °C for 4 h.The LaVO4/g-C3N4 composite catalysts were prepared as follows. LaVO4 and g-C3N4 with given ratios were mixed and ground in an agate mortar for 20 min, and then calcined at 450℃ for 2 h to obtain the LaVO4/g-C3N4 catalyst. The actual LaVO4 concentration was determined with thermogravimetry(TG) experiments (see Figure S1 in the Supporting Information). For simplification, the synthesized LaVO4/gC3N4 composites are denoted as xwt %t-LC or xwt %m-LC,in which xrepresents the LaVO4 concentration. |
3楼2014-11-17 10:39:13