Fe-Al改性硅藻土的制备及其对土壤Cd污染固定化效果

Preparation of Iron-Aluminum Modified Diatomite and Its Immobilization in Cadmium-Polluted Soil

为了提高硅藻土对土壤镉污染的原位固定化效果,采用羟基Fe-Al对硅藻土进行改性,通过土壤培养实验研究了Fe/Al摩尔比、OH/cation摩尔比、陈化时间、(Fe+Al)/硅藻土比、反应温度、老化时间对土壤镉污染固定化效果的影响,同时采用扫描电镜(SEM)和傅里叶红外光谱(FTIR)分析了改性前后硅藻土理化特征的变化.结果表明,改性硅藻土最佳制备工艺条件为Fe/Al摩尔比1∶8、OH/cation摩尔比2.0~2.2、陈化时间2 d、(Fe+Al)/硅藻土比10 mmol·g-1、反应温度60℃、老化时间2 d.改性硅藻土显著降低了土壤中可交换态镉的含量,硅藻土改性前后对交换态Cd含量的降低率由11.83%提升到39.52%.SEM与FTIR分析表明,通过改性增加了硅藻土的比表面积和Si—O—H基团,并且羟基铁铝被成功置入硅藻壳体内部,形成了有效柱体,增大了孔道间距,增强了硅藻土的表面活性.因此,羟基铁铝改性能有效地促进硅藻土对土壤镉的固定效果.提供的改性方法和实验结果,为硅藻土固定土壤重金属提供了新的技术手段和理论依据.

To improve the in-situ immobilization effect of diatomite on cadmium （ Cd）-contaminated soil, diatomite was modified by hydroxyl iron-aluminum （Fe-Al）. The soil incubation experiments were carried out to investigate the effect of Fe/Al molar ratio, OH/ cation of molar ratio, pillaring agent aging time, （Fe ＋ AI）/diatomite ratio, pillaring temperature, and pillaring product aging time on the immobilization of Cd in soils. The changes in properties of diatomite before and after modification were analyzed by scanning electron microscopy （SEM） and Fourier transform infrared spectroscopy （FTIR）. The results showed that： the optimal preparation conditions for modification were： Fe/Al molar ratio = 1 ： 8, OH/cation molar ratio 2.0-2.2, pillaring agent aging time = 2 d, （ Fe ＋ Al）/diatomite ratio = 10 mmol·g-1 , pillaring temperature = 60℃, pillaring product aging time = 2 d. The hydroxyl-Fe-Al-modified diatomite significantly reduced the content of exchangeable Cd in soil, and the modification reduced soil exchangeable Cd from 11.83% to 39.52%. The SEM and FTIR analyses of hydroxyl-Fe-Al-modified diatomite revealed increase in the specific surface area of diatomite and the amount of the Si-O-H groups. After modification, the hydroxyl-Fe-Al successfully exchanged into the diatom shell forming available pillars, thus increasing channel spacing and enhancing the microporous surface activity. The modification with hydroxyl-Fe-Al increased the immobilization effect of diatomite on Cd in soil. The modification methods and data from this study will help increase the application of diatomite materials for the immobilization of soil containing heavy metals.