黄河沉积物对稀土元素的吸附特性研究

Study on the adsorption characteristics of REE on the Yellow River sediment

针对自然水体的实际情况,开展了黄河沉积物对La3+,Ce3+,Nd3+,Sm3+等4种离子的吸附竞争及其特性研究.结果表明,在较宽的初始浓度范围内(2～11mg·L-1),4种离子之间处于弱吸附竞争或无吸附竞争状态;当初始浓度较高,泥沙浓度较低时,4种离子之间的竞争吸附才得以体现,此时有Sm3+>Nd3+≥La3+>Ce3+的初步吸附竞争能力序列;黄河沉积物对4种离子的吸附受控于pH值,随pH的增加4种离子吸附量逐渐增大,但弱碱性或碱性更有利于吸附;当初始浓度较低(<11mg·L-1)时,主要环境因子对4种离子的吸附竞争影响均不明显;当初始浓度较高(>11mg·L-1)时,各环境因子对4种离子的吸附竞争均有显著影响,总体上,降低离子强度、去除有机质、减小颗粒物粒度,均使Sm3+,Nd3+,La3+等3种离子与Ce3+表现不同的吸附行为.

La3+, Ce3+, Nd3+, Sm3+ and sediments were taken as the adsorbate and sorbent respectively and experiments were carried out under conditions similar to those of the Baotou section of the Yellow River. Competitions among cations, adsorption characteristics, as well as factors that affect adsorption were studied. The experimental results show that competition among La3+, Ce3+, Nd3+and Sm3+is not significant when the initial concentration of absorbents are lower (2～11?mg·L-1) and it become evident when higher initial concentration (11～20?mg·L-1) and low content of absorbate were applied (5?g·L-1). The experiments give a competition capacity order of Sm3+> Nd3+≥La3+>Ce3+. The adsorption is pH-dependent and increases with increasing pH. Adsorption is favorable under alkaline and week alkalie conditions. Under lower initial concentration, influences of the major environmental factors on adsorption is not obvious. However when the initial concentrations are higher, the influences of environmental factors on adsorption become significant. In general, lower ion strength, removal of organic matter, and reduce the particle size will result in the different adsorption behaviors of Sm3+,Nd3+,La3+ from that of Ce3+.