不同浓度铜离子土壤的吸附-解吸行为——兼论弱专性吸附态的存在

BEHAVIORS OF COPPER IONS DIFFERENT IN CONCENTRATION IN SORPTION-DESORPTION BY SOILS—AND EXISTENCE OF WEAK-SPECIFIC-ADSORPTION STATE

研究了三种可变电荷土壤和两种恒电荷土壤不同铜离子浓度条件下的吸附-解吸行为。结果表明,不同铜离子浓度下土壤的pH-Cu2+吸附率曲线均在低pH段出现会合,且随着铜离子浓度升高,pH-Cu2+吸附率曲线有向右偏移的趋势。证实了可变电荷土壤中吸附性铜离子可被去离子水解吸,并存在解吸峰现象。针对解吸前后吸附体系pH值的变化研究结果显示,吸附时体系pH低于5.0时,解吸后pH上升;而吸附体系pH高于5.0时,解吸后pH下降,表明pH5.0可能是土壤吸附铜离子机理发生变化的又一个转折点。本文还对专性吸附中弱吸附态的存在和形成原因进行了初步探讨。

Behaviors of Cu^2＋ in adsorption-desorption in three variable charge soils and two constant charge soils as affected by its concentration were studied. It was found that the curves of pH and Cu^2＋ adsorption rate always intersected in the section of low pH, and the curves tendedd to lean towards the right when Cu^2＋ rose in concentration, and confirmed that in variable charge soils, adsorbed copper ions could be desorbed with deionized water and desorption peaks observed. The study on change in pH of the adsorption system as affected by desorption revealed that when the system adsorbing Cu^2＋ was lower than 5.0 in pH, its pH would rise after desorption of the ions, but when the system was higher than 5.0 in pH, ts pH would decline, which suggest that pH5.0 is probably another turning point where the mechanism of the soil adsorbing Cu^2＋ changes. Existence of weak adsorption state in specific adsorption and causes of its formation were also dis- cussed.