Abstract：
Agricultural biomass wastes are an abundant feedstock for biorefineries. However, most of these wastes are not treated in the right way. Here, corn stalks (CSs) were assigned as the raw material to produce cellulose nanofibers (CNFs) via in situ Fenton oxidation treatment. In order to probe the formation mechanism of an in situ Fenton reactor, the bonding interaction of hydrated Fe2+ ions and fiber has been systemically studied based on adsorption experiments, IR spectroscopy, density functional theory (DFT) calculations, and Raman spectroscopy. The results indicate that the coordination of the hydrated Fe2+ ion to the fiber generates a quasi-octahedral-coordinated sphere around the Fe center. The Jahn-Teller distortion effect of the Fe center promotes the Fe-O2H2 bonding interaction via reduction of the energy gap of the dz2 orbital of the Fe center and π2py/π2pz orbitals of the H2O2 molecule. The oxidation treatment of the pretreated CS by the in situ Fenton process shows the formation of a new carboxyl group on the fiber surface. The scanning electron microscopy image shows that the Fenton-treated fiber was scattered into the nanosized CNFs with a diameter of up to 50 nm. Both experimental and theoretical studies show that the pseudo-first-order kinetic reaction could describe the in situ Fenton kinetics well. Moreover, the proposed catalytic cycle shows that the large thermodynamic barrier is the cleavage of the O-O bond of H2O2 to generate the •OH radical, and the whole catalytic cycle is found to be spontaneous at room temperature.
摘要：
农业生物质废物是生物炼制的丰富原料。然而,这些废物中的大多数没有得到正确的处理。这里,以玉米秸秆（CSs）为原料，通过原位Fenton氧化处理生产纤维素纳米纤维（CNFs）。为了探讨原位Fenton反应器的形成机理,基于吸附实验，系统地研究了水合Fe2+离子与纤维的键合相互作用，红外光谱，密度泛函理论(DFT)计算，和拉曼光谱。结果表明，水合Fe2离子与纤维的配位在Fe中心周围产生了准八面体配位球。Fe中心的Jahn-Teller畸变效应通过减少Fe中心的dz2轨道的能隙和H2O2分子的π2py/π2pz轨道来促进Fe-O2H2键合相互作用。通过原位Fenton工艺对预处理的CS进行氧化处理表明在纤维表面上形成了新的羧基。扫描电子显微镜图像显示Fenton处理的纤维被分散到直径高达50nm的纳米尺寸的CNF中。实验和理论研究都表明，伪一级动力学反应可以很好地描述原位Fenton动力学。此外，提出的催化循环表明，大的热力学障碍是H2O2的O-O键断裂产生·OH自由基，发现整个催化循环在室温下是自发的。
