砷超富集植物的热解特征及其与砷含量的关系

Pyrolysis characteristic of arsenic hyperaccumulators and its relation to arsenic content

不同热解气氛和升温速率的比较研究表明,在空气气氛条件和25℃.min-1的升温速率下,砷超富集植物的热解曲线特征明显且实验速度适中,因此,是适用于砷超富集植物的热解实验条件.在该实验条件下,不同含砷浓度的蜈蚣草(Pteris vittata L.)和大叶井口边草(P.cretica L.)的热解温度主要集中在200～500℃之间.与低砷蜈蚣草相比,高砷蜈蚣草在300℃附近热解减弱,而在450℃附近热解加剧,蜈蚣草体内的砷有促使其热解过程向高温方向偏移的趋势;而大叶井口边草体内的砷则促使其在300℃附近热分解程度加剧,而对450℃附近的热解程度影响不明显.

In order to get appropriate pyrolysis condition, different atmosphere and heating rates were compared during pyrolysis of two arsenic hyperaccumulators, Pteris vittata L. and P. cretica L. According to thermogravimetry （TG）, derivative thermogravimetry （DTG） and differential thermal analysis （DTA） curves, the results show that the existence of O2 in the atmosphere could make the characteristic curves of pyrolysis appear more obvious than N2atmosphere and made the samples release more quantity of heat, and be decomposed more completely. Under the heating rates of 25℃·min ^-1, fine thermal analysis curves were obtained, pyrolysis course was relatively focused and completed time was feasible. Therefore, air atmosphere and a heating rate of 25℃ ·min^-1 were selected as appropriate conditions to study the pyrolysis of As-hyperaccumulators. Under above conditions, the two Ashyperaccumulators were decomposed rapidly between 200 and 500℃. Compared with the P. vittata L. of low As concentration, the P. vittata L. with high As concentration decreased the thermal decomposition around 300℃, and increased decomposition around 450℃. An increase in arsenic of P. nervosa L. might increase the thermal decomposition around 300℃ and did not influence obviously the decomposition around 450℃.