升温速率对活体硅藻壳提纯的影响

选用一种舟形藻作为实验材料，研究了不同升温速率下硅藻壳的形态和成分变化。首先，对从该种硅藻得到的细胞壳进行酸洗处理，以去除金属离子和其它无机盐；之后，分别以1，3，5 和7℃/min的速率将硅藻壳升温至600℃，并保温2 h。然后，使用扫描电子显微镜、能量色散X射线分析和傅里叶变换红外分析3种手段对不同阶段和不同处理条件下的硅藻壳进行分析表征。实验显示：生物SiO₂的含量随着升温速率的降低而升高，以1℃/min升温到600℃并保温2 h的硅藻壳的SiO₂含量最高，其质量分数可达到90%，并且该硅藻壳能保持完整的原始形态。结果表明：由于硅藻的生物SiO₂结构具有较好的隔热性，热传导速度慢，故较快的升温速率很难使生物有机质充分分解，而过高的温度或保温时间又会对硅藻壳形态造成新的威胁。所以，较为缓慢的升温速率有益于有机质的充分去除和保证硅藻壳外观的完整性。

Effects of heating rate on biosilica structure purification of living diatoms

The morphology and composition of living diatoms were explored at different heating rates, in which the marine diatom Navicula sp. was selected as experimental materials. First, the frustules from living diatoms were cleaned by hydrochloric acid to remove metal oxide and other inorganic salts. After that, chemically purified frustules were heated to 600℃ at the heating rates of 1℃/min, 3℃/min, 5℃/min and 7℃/min for 2 h. The morphology and composition of diatom frustules at different stages were characterized by Fourier Transform Infrared Spectra (FTIR), Scanning Electronic Microscopy (SEM), and Energy Dispersive X-ray Analysis (EDS). Obtained results show that the SiO₂ contents increase with the slowdown of the heating rate. The highest SiO₂ content in the diatom frustules is obtained when they are baked at 600℃ at a heating rate of 1℃/min for 2 h, reached about 90%, and they will maintain a shape perfectly with few impurities. These results mean that organic matter is difficult to be removed with a fast heating speed because the biosilica structures of frustules are characterized by good thermal insulator and slower heat transfer. Moreover, higher temperatures and longer maintaining temperature will effect the morphology of diatom frustules. Therefore, it suggests that the slower heating rate is beneficial to removing organic matters and ensuring the integrity of diatom appearance.