富啡酸对潮褐土吸附重金属离子的影响

Effects of Fulvic Acid on Sorption of Heavy Metal Ions in Meadow Cinnamon Soil

采用平衡吸附法,研究了不同浓度的富啡酸(FA)对土壤吸附重金属离子(Cu2+、Cd2+、Pb2+)的影响。结果表明,潮褐土对富啡酸的吸附作用很强;潮褐土对富啡酸的吸附随pH的升高先缓慢增大后迅速下降;潮褐土对重金属离子的吸附随pH的升高而增大,且在低pH值下,富啡酸促进潮褐土对Cu2+、Cd2+、Pb2+的吸附和Pb2+的次级吸附,抑制对Cu2+、Cd2+的次级吸附;在高pH值下,富啡酸抑制土壤对Cu2+的吸附和次级吸附,而促进Cd2+和Pb2+的吸附和次级吸附;在富啡酸浓度相同的条件下,潮褐土对重金属离子的吸附能力为:Pb2+>Cu2+>Cd2+。

Fulvic acid (FA), as an important complexing agent, has a great function in preventing the soil from heavy metal pollution, the effects of different concentrations of FA on Cu2+, Cd2+, Pb2+ sorption in meadow cinnamon soil (MCS) were studied by batch method. The results showed that maximum sorption of heavy metal ions on MCS decreased in the order: Pb2+>Cu2+>Cd2+. The fulvic acid was strongly absorbed by MCS, even when the concentration of FA was 6.3 mmol·L-1. It was found that maximum amount of FA adsorbed in the soil was depended on the composition and properties of both the soil and FA its self. The quantity of FA sorption initially increased slowly with increment of pH. When pH of the system was 6.5, the maximum amount of FA sorption occurred, and then the sorption decreased markedly. The quantity of FA on MCS was much greater at high concentration than that at the low concentration, but the percentage of FA sorption was slightly lower at high concentration than that at the low concentration. The percentage of heavy metal ions on MCS increased with pH increasing. The differences among effects of FA concentrations on Cu2+, Cd2+, Pb2+ sorption in MCS indicated that: at lower pH, sorption of Cu2+, Cd2+, Pb2+ were promoted in the presence of FA compared with the zero FA, and this kind of the promotion was gradually enhanced with rising FA concentration; at higher pH, while FA restrained Cu2+ sorption, promoted Cd2+ sorption, and made Pb2+ sorption to maximum quickly. Influence of concentrations of FA on Cu2+, Cd2+, Pb2+ sequential sorption in MCS were similar to that at higher pH and different from that at lower pH, which is FA restrained Cu2+ and Cd2+ sequential sorption and promoted Pb2+ sequential sorption. The inhibition for Cu2+ and Cd2+ weakened with the FA concentration. Under the condition of the same FA concentration, the sorption of heavy metal ions on MCS deceased in the order as Pb2+>Cu2+>Cd2+.