改性蒙脱石吸附降解硝酸根离子的研究

STUDY OF USING MODIFIED SMECTITE TO ADSORB AND DEGRADE NITRATE

水体中硝酸根离子可以导致人体患多种疾病,并且引起一系列的环境问题,因此仍然需要对硝酸根离子去除方法进行研究。本研究的目的是评价含铁粘土矿物去除水体中硝酸根离子的能力。实验所用粘土矿物为含铁蒙脱石,采自美国华盛顿州Grant county。利用聚二烯丙基二甲基氯化铵交换蒙脱石层间阳离子得到改性蒙脱石,化学方法还原蒙脱石结构三价铁离子至结构二价亚铁离子,测定了不同氧化态的未改性蒙脱石吸附降解硝酸根离子的能力,氧化态改性蒙脱石在不同带电条件下吸附硝酸根离子的水平,还原态改性蒙脱石降解硝酸根离子的能力,采用ζ电位测定,X射线衍射(XRD),傅氏转换红外线光谱(FTIR)和扫描电子显微镜(SEM)分析表征改性蒙脱石特性。实验结果表明:氧化态未改性蒙脱石几乎不能吸附与还原降解硝酸根离子;还原态未改性蒙脱石可以吸附大约0.0054mmole/g的硝酸根离子,产生极少量的低价态硝族产物,这种阻滞是由于电负性未改性蒙脱石与电负性硝酸根离子之间存在库仑斥力。蒙脱石改性后由电负性转变为电正性,原有库仑斥力得以消除,氧化态改性蒙脱石能够吸附高达0.23mmole/g的硝酸根离子,其吸附能力随着层间聚合阳离子浓度的增大而升高;还原态改性蒙脱石还原降解硝酸根离子的能力较未改性蒙脱石提高了13至39倍。结合还原态改性蒙脱石结构二价亚铁再氧化的趋势,探讨了电子的转移方式以及多种可能的降解产物。

Research carries out to use polydiallyldimethylammonium chloride to intercalate into the interlayer of smectite and exchange with cations, g-potential, XRD, FTIR and SEM was uti- lized for experiment measurement. The capacity of nitrate absorbed and reduced was measured be- fore and after smectite modified in different oxidation state. It showed thatξ-potential of modified smectite converted from negative to positive, polymer cations intercalated into the interlayer of smectite successfully, and R-NH3 ＋ was reacted with smectite. The surface of smectite significant- ly changed after modification and the nature smectite cannot adsorb or reduce nitrate. Modified smectite can enhance nitrate adsorption to 0. 0054 mmole/g, reduced and modified smectite en- hances the capacity of nitrate reduction from 13 to 39 times, and the structural ferrous ion oxidized accordingly. This research may inspire a new research trend in the field of nitrate pollution treat- ment.