土壤腐殖酸的提取及其对^(241)Am的吸附

Adsorption of ^(241)Am on the extracted humic acid from soil

用稀碱法从核废物填埋场的土壤中提取腐殖酸,并用此腐殖酸对241Am进行吸附实验.结果表明,当241Am初始浓度为0.26~2.7×10-7mol/L,溶液pH为2~3时,腐殖酸对241Am有明显的吸附,其吸附率达90%以上;接触时间4h基本达到平衡,241Am浓度与吸附量之间的关系符合Langmuir经验公式;0℃~40℃范围内,温度对吸附无显著影响;Fe3+、EDTA和柠檬酸根等离子或基团能使腐殖酸对241Am的吸附率显著降低,而Ca2+、PO43-和SO42-等离子或基团对吸附无明显影响;溶液中Eu3+和Nd3+的浓度为241Am的2500倍或更高时,也能使腐殖酸对241Am的吸附明显降低.

Humic acid （HA） was extracted from the soil as the procedure recommeded by Interrnational Humic Substance Society （IHSS） with minor modification. Then the adsorption behavior of 241^Am on the extracted HA, especially, the effects of the various experimental conditions on the adsorption were investigated by the static experimental method. The results showed that the HA is an efficient adsorbent for 241^Am. More than 90% of the total 241^Am in solutions could be adsorbed by humic acid of 5 mg at pH 2-3. The adsorption equilibrium was achieved within 4 hour and 241^Am uptake on humic acid was a pH-dependent process. The relationship between concentration of 241^Am in aqueous solutions and adsorption capacities of 241^Am can be described by the Langmuir adsorption equation. Nd^3 ＋, Eu^3 ＋, Fe^3 ＋, Mg^2 ＋, Al^3 ＋, Lemon anion and EDTA can inhibit the adsorption of 241^Am on humic acid, while no significant differences on 241^Am adsorption were observed at 0 ℃-40℃ and in solutions containing Ca^2＋ ,PO4^3- ,Cl^- or SO4^2-.