土壤中球孢枝孢对铀(Ⅵ)的吸附

Sorption of Uranium by Cladosporium Sphaerospermum Isolated From Soil

从拟作为低放射性废物处置填埋场土壤中分离出一种霉菌,经过鉴定为链孢霉目黑霉科球孢枝孢,并考察该菌对UO22+的吸附行为。实验结果表明:铀初始质量浓度为10mg/L,加入5g/L的新鲜湿菌体,其吸附平衡时间约为24h,最终吸附率约94.1%,吸附符合准二级动力学模型;吸附最适宜pH=5～9,当pH≤2时,菌体几乎不吸附UO22+;铀初始质量浓度为2～10mg/L时,吸附率均在90%左右;吸附近似符合Langmuir吸附经验公式;菌体累积吸附6次吸附量可达6.6mg/g;Ca2+会降低微生物对铀的吸附;柠檬酸、硝酸和EDTA对吸附的铀均具有一定的解吸能力,其中柠檬酸最高为67%。采用红外吸收光谱分析,显示吸附后出现UO22+的吸收峰,表明铀主要以UO22+的形式被菌体吸附。

A kind of fungus, which was identified by molecular biology technology as cladosporium sphaerospermum, was isolated from the soil in a potential site for disposal of low radioactive waste. The sorption behavior of uranium by this living fungus was investigated. When the initial concentration of uranyl ion is 10 mg/L, the sorption efficiency for uranium is 94.1G. Sorption equilibrium time is about 24 h. The experimental data can be described with the pseudo-second order equation with much high regression coefficient. The uranium adsorbability is closely in connection with its pH value of which the best range is from 5 to 9. When pH the thalli scarcely adsorb uranium. The relationship between sorption capacities and concentration of uranium in aqueous solutions can be described by the Lang- muir adsorption equation. The accumulating adsorbing capacities finally reach to about 6.6 mg/g. Except Ca2＋ , coexistent ions such as Na＋ , K＋ , HCO;- , CO and SO- scarcelyinhibite the sorption of uranium on the fungus. Three desorption agents was investigated. Citric acid is found to be the best desorbent with a desorption rate of up to 67 , followed by HNOa about 60%, and lastly EDTA about 40%. Additionally, the bacteria were observed by infrared spectroscopy. The results show that uranium is absorbed in the form of UO2＋.