College of Chemistry and Materials Engineering, Zhejiang A&F University, Hangzhou, Zhejiang, 311300, People's Republic of China.
Environ Sci Pollut Res Int. 2023 Sep;30(41):94185-94194. doi: 10.1007/s11356-023-29085-5. Epub 2023 Aug 1.
Hydrochar is an environmentally friendly and cheap adsorbent, but its adsorption amounts for anions is very limited. The functionalized hydrochar can overcome this shortcoming. Herein, polyethyleneimine-modified hydrochar (PEI-HC) was synthesized from hydrothermal carbonization (HTC) of methyl acrylate and bamboo after addition of initiator ammonium persulfate, and then modified by polyethyleneimine (PEI), which was used to treat Cr(VI). PEI-HC was tested by XANES, EXAFS, SEM-EDS, XPS, FTIR, N sorption isotherms, zeta potential, and elemental analyses. The characterizations showed that PEI was successfully grafted onto hydrochar, and the PEI-HC was rich in N and O functional groups, which presented high Cr(VI) sorption ability (528.41 mg·g at pH 2). The bath experiments found the pseudo-second-order kinetic and Freundlich equations can well describe the adsorption kinetics and isotherm of the Cr(VI) adsorption onto PEI-HC, respectively. Electrostatic interaction, reduction, complexation, and H-bonding are the main removal mechanisms as supported by XANES, EXAFS, XPS, and FTIR. This study provides a strategy of combining HTC and free radical graft polymerization to convert agricultural and forestry wastes into functionalized hydrochar, showing highly efficient removal of Cr(VI).
水凝胶是一种环保且廉价的吸附剂，但对阴离子的吸附量非常有限。功能化水凝胶可以克服这一缺点。本文通过在引发剂过硫酸铵存在下将甲基丙烯酰胺和竹子进行水热碳化，合成了聚乙烯亚胺改性水凝胶（PEI-HC），然后用聚乙烯亚胺（PEI）对其进行改性，用于处理 Cr(VI)。通过 XANES、EXAFS、SEM-EDS、XPS、FTIR、N 吸附等温线、zeta 电位和元素分析对 PEI-HC 进行了测试。表征结果表明，PEI 成功接枝到水凝胶上，PEI-HC 富含 N 和 O 官能团，对 Cr(VI)具有高吸附能力（pH 2 时为 528.41 mg·g）。间歇实验发现，拟二级动力学和 Freundlich 方程可以分别很好地描述 Cr(VI)在 PEI-HC 上的吸附动力学和等温线。XANES、EXAFS、XPS 和 FTIR 表明，静电相互作用、还原、络合和氢键是主要的去除机制。本研究提供了一种将农业和林业废物转化为功能化水凝胶的结合水热碳化和自由基接枝聚合的策略，展示了高效去除 Cr(VI)的能力。
