Department of Chemical, Materials and Production Engineering, University of Naples Federico II, Piazzale Tecchio 80, 80125 Napoli, Italy.
Departments of ChiBioFarAm and MIFT-Section of Industrial Chemistry, University of Messina, CASPE-INSTM, V.le F. Stagno d'Alcontres 31, 98166 Messina, Italy.
Int J Mol Sci. 2021 May 24;22(11):5535. doi: 10.3390/ijms22115535.
Chitosan (CS) is largely employed in environmental applications as an adsorbent of anionic dyes, due to the presence in its chemical structure of amine groups that, if protonated, act as adsorbing sites for negatively charged molecules. Efficient adsorption of both cationic and anionic dyes is thus not achievable with a pristine chitosan adsorbent, but it requires the combination of two or more components. Here, we show that simultaneous adsorption of cationic and anionic dyes can be obtained by embedding Linde Type A (LTA) zeolite particles in a crosslinked CS-based aerogel. In order to optimize dye removal ability of the hybrid aerogel, we target the crosslinker concentration so that crosslinking is mainly activated during the thermal treatment after the fast freezing of the CS/LTA mixture. The adsorption of isotherms is obtained for different CS/LTA weight ratios and for different types of anionic and cationic dyes. Irrespective of the formulation, the Langmuir model was found to accurately describe the adsorption isotherms. The optimal tradeoff in the adsorption behavior was obtained with the CS/LTA aerogel (1:1 weight ratio), for which the maximum uptake of indigo carmine (anionic dye) and rhodamine 6G (cationic dye) is 103 and 43 mg g, respectively. The behavior observed for the adsorption capacity and energy cannot be rationalized as a pure superposition of the two components, but suggests that reciprocal steric effects, chemical heterogeneity, and molecular interactions between CS and LTA zeolite particles play an important role.
壳聚糖（CS）由于其化学结构中存在胺基，这些胺基质子化后可作为带负电荷分子的吸附位点，因此被广泛应用于环境领域作为阴离子染料的吸附剂。然而，未经修饰的壳聚糖吸附剂无法高效吸附阳离子和阴离子染料，需要结合两种或更多种成分。在这里，我们展示了通过将 Linde 型 A（LTA）沸石颗粒嵌入交联壳聚糖基气凝胶中，可以实现同时吸附阳离子和阴离子染料。为了优化杂化气凝胶的染料去除能力，我们将交联剂浓度作为目标，使得交联主要在 CS/LTA 混合物快速冷冻后的热处理过程中激活。对于不同的 CS/LTA 重量比和不同类型的阴离子和阳离子染料，都获得了吸附等温线。无论配方如何，均发现 Langmuir 模型能够准确描述吸附等温线。在 CS/LTA 气凝胶（1:1 重量比）中获得了最佳的吸附行为折衷，对于该气凝胶，靛蓝胭脂红（阴离子染料）和罗丹明 6G（阳离子染料）的最大吸附量分别为 103 和 43 mg g。观察到的吸附容量和能量行为不能简单地归结为两种成分的纯叠加，而是表明 CS 和 LTA 沸石颗粒之间的相互空间位阻、化学异质性和分子相互作用起着重要作用。
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