腐殖酸对铜的吸附与解吸特征

The characteristics of adsorption and desorption of humic acids on copper

采用铜离子选择电极研究了铜在腐殖酸两组分(富里酸FA、胡敏酸HA)中的吸附-解吸特征,以及介质pH对这种吸附-解吸的影响。结果表明,腐殖酸对铜的吸附量为FA>HA,吸附强度为HA>FA,解吸量FA-Cu>HA-Cu。腐殖酸两组分对铜的吸附,当介质pH为4.00～7.00时,很好地符合Langmuir等温吸附方程;当pH<4.0时,符合Freundlich方程。FA、HA与铜作用的条件稳定常数与介质pH有关,pH提高则条件稳定常数增大;但在低pH段和高pH段,其增长规律不一致,当4.00<pH<7.00时,HA与铜作用的条件稳定常数大于FA与铜作用的条件稳定常数,而当pH<4.00时情况则相反。这表明FA、HA的表面特征和吸附机制在低pH和高pH条件下不同。

The characteristics of adsorption and desorption of the two humic acids (fumaric acid and humic acid) on copper were studied by using copper ion selective electrode. The results showed that the adsorptive capacity and the desorption amount of fumaric acid on copper (FA-Cu) are greater than that of humic acid on copper (HA-Cu), while the adsorptive strength of HA-Cu is higher than that of FA-Cu. In this study, the influence of medium pH on adsorption and desorption was also examined. It was found that the adsorption of the two humic acids on copper agrees well with Langmuir isothermal adsorption equation at 4.00≤pH≤7.00, while it accords with Freundlich adsorption equation when pH is lower than 4.00. Moreover, the conditional stability constant of Cu-humic acids complex augments with the increase of medium pH, but the increasing rule at low pH section differs from that at high pH section. The conditional stability constant of Cu-HA is greater than that of Cu-FA at 4.00<pH<7.00, and vise versa when pH is lower than 4.00. These results indicated that the surface property and adsorptive mechanism of FA are different from that of HA in the two pH sections.