Abstract

Removal of low content of Cr(VI) from water is a critical challenge for water environment protection. Herein, an acrylamide-thiosemicarbazide cellulose aerogels (ATC) was designed by dissolving, grafting and freeze-drying to introduce thiosemicarbazide onto acrylamide-cellulose aerogels (AMC) via Schiff based reaction. The resultant ATC was further employed as an efficient adsorbent to remove low content of Cr(VI) from wastewater by adsorption and reduction. The SEM, FT-IR, and BET results showed that the ATC was composed of well-developed pore structure and owned functional groups such as –NH₂, C–S and C=S groups. Experimental results indicated that ATC exhibited excellent removal efficiency for 99% under low initial concentration (0.1–10 mg/L). The adsorption isotherms demonstrated ATC adsorbent according to a monolayer adsorption behavior following the Langmuir model with a calculated maximum adsorption capacity of 83.40 mg/g at pH 3, and the adsorption kinetics well obeyed the pseudo-first-order kinetic model. Importantly, the maximum effluent concentration of Cr(VI) was lower than 0.045 mg/L, meeting the standard of WHO (50 μg/L). Furthermore, the main removal mechanisms involved the synergistic effect of electrostatic interactions, reduction and chelation between the positively charged functional groups of adsorbent and the anionic Cr(VI) ions.

Graphic Abstract

中文翻译：

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改性纤维素气凝胶的吸附/还原行为以去除低含量的Cr（VI）

摘要

从水中去除低含量的Cr（VI）是水环境保护的关键挑战。本文中，通过溶解，接枝和冷冻干燥来设计丙烯酰胺-硫代氨基脲纤维素气凝胶（ATC），以通过席夫（Schiff）基反应将硫代氨基脲引入丙烯酰胺-纤维素气凝胶（AMC）上。所得的ATC进一步用作有效的吸附剂，通过吸附和还原从废水中去除低含量的Cr（VI）。SEM，FT-IR和BET结果表明，ATC由发达的孔结构和–NH ₂等自有官能团组成，CS和C = S组。实验结果表明，在较低的初始浓度（0.1-10 mg / L）下，ATC的去除效率高达99％。吸附等温线表明，根据Langmuir模型，单层吸附行为符合ATC吸附剂，在pH 3下计算的最大吸附容量为83.40 mg / g，吸附动力学完全符合拟一级动力学模型。重要的是，Cr（VI）的最大流出物浓度低于0.045 mg / L，符合WHO的标准（50μg/ L）。此外，主要的去除机理涉及静电相互作用，吸附剂带正电荷的官能团与阴离子Cr（VI）离子之间的还原和螯合的协同效应。

图形摘要