Laboratoire de Physico-chimie des Matériaux et Environnement, Faculté des Sciences Semlalia, Université Cadi Ayyad, B.P. 2390, Av. Pce My Abdellah, 40001, Marrakech, Morocco.
Environ Sci Pollut Res Int. 2018 Jul;25(20):19585-19604. doi: 10.1007/s11356-018-2196-7. Epub 2018 May 7.
Shrimp shells and waste of olive stones were used as feedstock for the preparation of chitosan and activated carbon. The adsorption of Cr and Cr species in aqueous solution by the materials prepared and their blend were studied by using the well-known kinetic and isotherm models, Fourier transform infrared spectroscopy and scanning electron microscope. It was demonstrated that the rates of adsorption were controlled by diffusion inside particles and throughout the liquid film, and adsorption occurred spontaneously (- 26 < ∆G° < - 15 kJ/mol) in the range of 298-333 K, except for that involving Cr species and activated carbon. The maximum amounts of Cr species retained by the composite (146 mg of Cr/g and 33 mg of Cr/g at 298 K) were three times greater than those of the basic constituents. Adsorption was markedly affected by temperature and pH, and Cr species were substantially desorbed in acid mediums, particularly in acetic acid solution. The recovery of Cr species varied according to the adsorbent and the solution used. The immobilization of Cr species (HCrO and CrO) and Cr species (Cr(OH) and Cr(OH)) by chitosan was accomplished by means of amine moieties and hydroxyls of D-glucosamine units of the biopolymer. The adsorption of Cr species on activated carbon involved π electrons of aromatic rings as well as oxygenated sites (C-OH, C=O, C-O-C). In such a condition, Cr was partially reduced into Cr. For the composite, the amino functional groups of chitosan and hydroxyls of both constituents were implicated in the linkage of the biopolymer and activated carbon, and the C-O-H and C-O-C functional groups of chitosan were involved in the retention of Cr species. For Cr species, adsorption occurred preferentially on hydroxyls of the components, and consequently, the chains of the biopolymer recovered some flexibility.
虾壳和橄榄石废料被用作壳聚糖和活性炭制备的原料。使用众所周知的动力学和等温线模型、傅里叶变换红外光谱和扫描电子显微镜研究了材料在水溶液中对 Cr 和 Cr 物种的吸附及其混合物的吸附。结果表明，吸附速率受颗粒内部和整个液膜扩散的控制，在 298-333 K 范围内，吸附是自发进行的（-26<∆G°<-15 kJ/mol），除了涉及 Cr 物种和活性炭的情况。复合材料（298 K 时，Cr 物种的最大保留量为 146 mg/g 和 33 mg/g）保留的 Cr 物种量是基本成分的三倍。吸附受温度和 pH 值的显著影响，Cr 物种在酸性介质中大量解吸，特别是在乙酸溶液中。Cr 物种的回收取决于吸附剂和使用的溶液。壳聚糖通过胺基和 D-葡萄糖胺单元的羟基将 Cr 物种（HCrO 和 CrO）和 Cr 物种（Cr(OH) 和 Cr(OH)）固定化。Cr 物种在活性炭上的吸附涉及芳香环的π电子以及含氧位点（C-OH、C=O、C-O-C）。在这种条件下，Cr 部分还原为 Cr。对于复合材料，壳聚糖的氨基官能团和两种成分的羟基都参与了生物聚合物和活性炭的连接，壳聚糖的 C-O-H 和 C-O-C 官能团参与了 Cr 物种的保留。对于 Cr 物种，吸附优先发生在组分的羟基上，因此，生物聚合物的链恢复了一些柔韧性。
