土壤有机质在镉的吸附和固定化中起着重要作用。由于不同的有机物成分对镉吸附过程的影响不同,选择正确的有机底物并知道如何应用它可以改善镉的修复。这项研究比较了两种不同的有机分子的影响;壳聚糖和柠檬酸,酸性Ultisol中镉的吸附和形态形成。壳聚糖对Ultisol的吸附显着增加了土壤的正电荷,而柠檬酸的吸附增加了土壤的负电荷。在pH5.0时,过量壳聚糖中镉的最大吸附量比过量柠檬酸中的最大吸附量大341%。在pH4.0时,约有73-89%和60-62%的吸附镉与Fe/Mn氧化物和有机物/硫化物结合,而在pH5.0时,柠檬酸和壳聚糖的这一比例分别为77-100%和57-58%。壳聚糖络合能力的降低与高pH对壳聚糖结构的不稳定作用有关。此外,壳聚糖的顺序,柠檬酸,和镉被添加到吸附系统中影响吸附曲线,这在pH梯度上是不同的。具体来说,与在pH3.0-6.5内预吸附壳聚糖相比,添加壳聚糖和镉一起增加了吸附。然而,对于柠檬酸,与pH6.5和7.5相比,添加顺序对pH3.0-4.0之间的镉吸附没有显着影响,过量的柠檬酸通常会抑制吸附。鉴于柠檬酸在土壤中的作用是短暂的,壳聚糖是一种很好的固定镉的土壤改良材料。
Soil organic matter plays an important role in cadmium adsorption and immobilization. Since different organic matter components affect cadmium adsorption processes differently, selecting the right organic substrate and knowing how to apply it could improve cadmium remediation. This study compares the effects of two contrasting organic molecules;
chitosan and citric acid, on cadmium adsorption and speciation in acidic Ultisol. The adsorption of
chitosan to Ultisol significantly increased the soil positive charge while adsorption of citric acid increased the soil negative charge. At pH 5.0, the maximum amount of cadmium adsorbed in excess chitosan was 341% greater than that in excess citric acid. About 73-89% and 60-62% of adsorbed cadmium were bound to Fe/Mn oxides and organic matter/sulfide at pH 4.0 while this fraction was 77-100% and 57-58% for citric acid and chitosan at pH 5.0, respectively. This decrease in the complexing ability of
chitosan was related to the destabilizing effect of high pH on
chitosan\'s structure. Also, the sequence through which chitosan, citric acid, and cadmium were added into the adsorption system influenced the adsorption profile and this was different along a pH gradient. Specifically, adding
chitosan and cadmium together increased adsorption compared to when
chitosan was pre-adsorbed within pH 3.0-6.5. However, for citric acid, the addition sequence had no significant effect on cadmium adsorption between pH 3.0-4.0 compared to pH 6.5 and 7.5, with excess citric acid generally inhibiting adsorption. Given that the action of citric acid is short-lived in soil, chitosan could be a good soil amendment material for immobilizing cadmium.