以水滑石和类水滑石为前体, 通过煅烧法制备了两种双金属氧化物, 对比研究了它们对溶液中亚砷酸根的吸附作用. 在室温条件下, Mg-Al-LDO和Mg-Fe-LDO对As(III)的吸附容量分别为83.2和87.45mg/g. 从整个时间系列来看, Mg-Fe-LDO对As(III)吸附能力明显要高于Mg-Al-LDO, 尤其是在吸附反应初期. 观测到Mg-Al-LDO在吸附As(III)过程中溶液pH值上升, 这与化学反应方程式一致; 而Mg-Fe-LDO在吸附As(III)过程中pH值先升后降, 可以解释为Fe(III)与As(III) 的反应所致. 将反应介质加热能有效抑制溶解CO2的干扰, 并大幅提高LDO对As(III)的吸附容量.
Mg-Al-HT (Hydrotalcite) and Mg-Fe-HTLcs (Hydrotalcie-like compounds) were used as precursor. Calcined at 550℃ and 380℃ for 2h, they were transformed into Mg-Al-LDO (Layered Double Oxide) and Mg-Fe-LDO respectively. Both of them have strong tendency of obtaining anion and water from ambient to recover their primary crystal structure of HT and HTLcs. At room temperature, arsenous absorption capacity is 83.2mg/g for Mg-Al-LDO, and 87.45mg/g for Mg-Fe-LDO. It is found that pH values increase while arsenous anion is absorbed by Mg-Al-LDO, which is predicted by the equation that describes the chemical reaction between Mg-Al-LDO and arsenous solution. During the reaction of Mg-Fe-LDO with the same solution, pH ascends first and then descends. It is believed that there is another reaction besides arsenous absorbed by Mg-Fe-LDO, i.e., arsenous anion will be deposited by Fe(III) in the LDO. Theoretic absorption capability of the LDOs on arsenous anion calculated from the chemical equation is 219.3mg/g for Mg-Al-LDO and 187.5mg/g for Mg-Fe-LDO, much higher than their real performance at room temperature. In believing that it is due to the competition from dissolved CO2 with arsenous anion, the system is heated to 90℃ to expel
CO2 from the solution. Absorption capability on arsenous anion at 90℃ is 114.9mg/g for Mg-Al-LDO, and 199mg/g for Mg-Fe-LDO. Heating has double effects for the later in the system: the competition from dissolved CO2 is eliminated, and the deposition of arsenous by Fe(III) in LDO is enhanced.
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