酸雨和有机配体(EDTA)对已污染红壤中稀土元素释放的研究

选用不同污染程度的红壤,采用化学成分模拟自然雨水,加入有机配体(EDTA),并调节pH值(5.6、4.0、3.0),作为萃取剂,研究了酸雨和有机配体(EDTA)对已污染红壤中稀土元素释放的影响。结果表明,相同pH值下,萃取率随着EDTA的浓度升高而升高;EDTA浓度一定时,随着萃取溶液的pH值降低,萃取率降低。在相同条件下,萃取率大小的顺序为Nd>Pr>Ce>La,与EDTA及4种稀土元素的条件络合常数大小顺序相同。

Extraction of Rare Earth Elements (REEs) from Polluted Soil Under Different Environmental Conditions

We examined the ability of acid rain-EDTA as a leaching solution to extract REEs from three contaminated soils in this study. The acid rainwater used in our test was prepared according to chemical composition of the rainwatercontaining appropriate amounts of EDTA in Nanjing area. The leaching solution was adjusted to pH 3.0, 4.0, 5.6. A red soil, a typical acid soil in Southern China, was collected from Jiangxi Province, China. The red soil was covered with distilled water, mixed with different amounts of REE solutions, then air-dried, ground, and sieved (2 mm) to simulated REE polluted soils. The effect of EDTA concentrations and pH values of the leaching solution were studied. The results showed that removal of REEs was improved when EDTA concentrations increased and the percentage of REE recovery was increased when pH values of the leaching solution increased. The log conditional formation constant was an important factor that influenced the REE recovery. By extraction, this order of the percentage of REE recoveries was Nd>Pr>Ce>La. This order was similar to the order of the value of the log conditional formation constant for REEs-EDTA. We also found that REErecovery changed little for the three increasing levels of soil pollution.