National Engineering Research Center for Efficient Utilization of Soil and Fertilizer Resources, College of Resources and Environment, Shandong Agricultural University, Tai'an, Shandong 271018, China.
National Engineering Research Center for Efficient Utilization of Soil and Fertilizer Resources, College of Resources and Environment, Shandong Agricultural University, Tai'an, Shandong 271018, China.
Sci Total Environ. 2023 Jul 10;881:163457. doi: 10.1016/j.scitotenv.2023.163457. Epub 2023 Apr 14.
Clay minerals are effective sorbents for toxic metal immobilization in contaminated soils and waters. However, their Cd immobilization efficiency is unclear when they are loaded with organics. In this study, sodium montmorillonite (Na-M) was successfully loaded with potassium humate, chitosan, and glycine to adsorb Cd(II) in solution. Potassium humate loaded Na-M (Na-M-HA), which had the highest specific surface area and cation exchange capacity (CEC), showed the highest Cd(II) adsorption capacity (73.7 mg g), 22.5 % and 81.8 % higher than that of chitosan loaded Na-M (Na-M-CTS) and glycine loaded Na-M (Na-M-G), respectively. The pseudo-second-order kinetic model best described (R > 0.98) the adsorption kinetics of Cd(II) on the three Na-Ms, indicating that the adsorption processes were of chemisorption nature. The adsorption isotherm of Cd(II) on Na-M-HA was of the Freundlich type, suggesting multilayer adsorption. In contrast, the isothermal adsorption of Cd(II) on Na-M-CTS (R = 0.99) and Na-M-G (R = 0.89) was better described by the Langmuir model, suggesting the dominance of monolayer adsorption in the adsorption process. High temperature, high pH, low background ionic strength, and low valence competing cations favored Cd(II) adsorption on Na-M-HA. The underlying mechanisms of Cd(II) sorption on Na-M-HA were electrostatic attraction, ion exchange and complexation. Na-M-HA was applied to a Cd polluted soil planted with lettuce (Lactuca sativa L.). in a pot experiment. Compared to the control with no adsorbent application, Na-M-HA application at 2 % effectively reduced the available Cd content in soil and Cd accumulation in plant by 36.0 % and 56.8 %, respectively. This work demonstrated that Na-M-HA is a green, low-cost and excellent adsorbent for Cd stabilization, and that its application in Cd-polluted soils can efficiently reduce Cd bioavailability and thereby Cd transfer along the food chain and eventually reduce the threat of Cd pollution to human health.
粘土矿物是固定污染土壤和水体中有毒金属的有效吸附剂。然而，当它们负载有机物时，其对 Cd 的固定效率尚不清楚。本研究成功地将钾腐殖酸、壳聚糖和甘氨酸负载到钠蒙脱石（Na-M）上，以吸附溶液中的 Cd(II)。具有最高比表面积和阳离子交换容量（CEC）的钾腐殖酸负载 Na-M（Na-M-HA）表现出最高的 Cd(II)吸附容量（73.7mg/g），分别比壳聚糖负载 Na-M（Na-M-CTS）和甘氨酸负载 Na-M（Na-M-G）高 22.5%和 81.8%。准二级动力学模型（R>0.98）最好地描述了 Cd(II)在三种 Na-Ms 上的吸附动力学，表明吸附过程是化学吸附性质。Cd(II)在 Na-M-HA 上的吸附等温线为 Freundlich 型，表明为多层吸附。相比之下，Cd(II)在 Na-M-CTS（R=0.99）和 Na-M-G（R=0.89）上的等温吸附更符合 Langmuir 模型，表明吸附过程中单层吸附占主导地位。高温、高 pH 值、低背景离子强度和低价竞争阳离子有利于 Cd(II)在 Na-M-HA 上的吸附。Na-M-HA 对 Cd(II)的吸附机制为静电吸引、离子交换和络合。Na-M-HA 被应用于生菜（Lactuca sativa L.）种植的 Cd 污染土壤中进行盆栽实验。与不添加吸附剂的对照相比，2%的 Na-M-HA 有效降低了土壤中有效 Cd 含量和植物 Cd 积累量，分别降低了 36.0%和 56.8%。这项工作表明，Na-M-HA 是一种绿色、低成本、优良的 Cd 稳定剂，其在 Cd 污染土壤中的应用可以有效地降低 Cd 的生物有效性，从而减少 Cd 沿食物链的迁移，并最终降低 Cd 污染对人类健康的威胁。
