School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China.
School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China.
Chemosphere. 2023 Nov;340:139957. doi: 10.1016/j.chemosphere.2023.139957. Epub 2023 Aug 24.
Lanthanum modified bentonite (LMB) is a widely used adsorbent for removing inorganic phosphorus from polluted water to prevent eutrophication. However, its efficiency can be affected by various environmental factors, including dissolved organic matter (DOM), which is still unclear. In this study, we systematically explored the influence of model DOMs, including HA, bovine serum albumin (BSA), and sodium alginate (SA), on phosphate adsorption by LMB, as well as to elucidate the underlying adsorption mechanisms. Our results showed that only HA had a significant effect on phosphate adsorption by LMB, causing inhibition. When three DOMs were mixed with phosphate in different proportions and DOM was mainly HA, the performance of phosphate adsorption on LMB became worse, while BSA can slightly offset this impact. The kinetics of HA and phosphate adsorption on LMB followed the pseudo-second-order kinetic model, and isotherms fitted the Langmuir model, with a maximum adsorption capacity of 5.7 mg g for P and 12 mg g for HA. However, when HA and phosphate were mixed based on their Qm, a C/P molar ratio of 5.35, LMB preferentially adsorbed phosphate. HA invasion was also disadvantageous for phosphate removal by LMB, in which P adsorption was less efficient at low-concentrations. However, during co-adsorption the adsorption capacity for HA was higher. With a secondary addition of higher levels of P, both pollutants were adsorbed more effectively. In the natural water experiment, phosphate concentration decreased with increasing shaking time, while the UV254 value showed a downward trend, indicating that LMB also adsorbed HA. Characterization results showed that La and phosphate formed LaPO precipitation, forming La-O-P inner-sphere complexes as the main mechanism of phosphate removal by LMB. La and HA formed La-HA complexes, with O-CO bonds from HA competing for lanthanum with phosphate. Despite HA obstructing pores from adsorbent, LMB still maintained a good binding ability with phosphate. It may form La-P-HA ternary complexes during adsorption to keep HA adsorption amount.
镧改性膨润土 (LMB) 是一种广泛用于从受污染的水中去除无机磷以防止富营养化的吸附剂。然而，其效率可能会受到各种环境因素的影响，包括溶解有机物 (DOM)，但这一点仍不清楚。在这项研究中，我们系统地研究了模型 DOM（包括 HA、牛血清白蛋白 (BSA) 和海藻酸钠 (SA)）对 LMB 吸附磷酸盐的影响，并阐明了潜在的吸附机制。我们的结果表明，只有 HA 对 LMB 吸附磷酸盐有显著影响，导致抑制作用。当三种 DOM 与磷酸盐以不同比例混合且 DOM 主要为 HA 时，LMB 对磷酸盐的吸附性能变差，而 BSA 可以轻微抵消这种影响。HA 和磷酸盐在 LMB 上的吸附动力学符合准二级动力学模型，等温线符合 Langmuir 模型，最大吸附容量分别为 5.7 mg g 对 P 和 12 mg g 对 HA。然而，当 HA 和磷酸盐按照 Qm 混合时，C/P 摩尔比为 5.35，LMB 优先吸附磷酸盐。HA 的入侵也不利于 LMB 去除磷酸盐，在低浓度下 P 吸附效率较低。然而，在共吸附过程中，HA 的吸附容量更高。随着二次添加更高水平的 P，两种污染物都能更有效地被吸附。在天然水实验中，随着摇床时间的增加，磷酸盐浓度降低，而 UV254 值呈下降趋势，表明 LMB 也吸附了 HA。表征结果表明，La 和磷酸盐形成 LaPO4 沉淀，形成 La-O-P 内球络合物是 LMB 去除磷酸盐的主要机制。La 和 HA 形成 La-HA 配合物，HA 中的 O-CO 键与磷酸盐竞争镧。尽管 HA 堵塞了吸附剂的孔，但 LMB 仍保持与磷酸盐的良好结合能力。在吸附过程中，可能会形成 La-P-HA 三元配合物，以保持 HA 的吸附量。
