Preparation Of Nanofibrillated Cellulose-based Hydrogel Loaded With Ni/Fe Bimetallic Nanoparticles And Its Dechlorination Performance On O-Dichlorobenzene Degradation

With the depletion of nonrenewable resources,cellulose as natural recyclable materials are obtaining more and more attention and application.Nanofibrillated cellulose（NFC）prepared by a variety of treatment methods has large specific surface area and excellent enhancements,and has been widely used in medicine packaging,membrane materials,electronics and wastewater treatment.In this paper,bamboo pulp was pretreated by NaIO₄-NaClO₂ oxidation system and neutral TEMPO / NaClO / NaClO₂ microwave oxidation system,and NFC with high carboxyl content was prepared by ultrasonic mechanical process.Then nanofibrillated cellulose-based hydrogel was crosslinked by mixing NFC with carboxymethyl cellulose（CMC）,which was used as substrate.CMC/NFC-L-Ni/Fe catalyst was in situ prepared by chemical reduction method,and Ni/Fe bimetallic was loaded on the hydrogel.The resulting CMC/NFC-L-Ni/Fe catalyst was used to degrade o-dichlorobenzene,and explore the effects of various reaction conditions on the degradation efficiency of o-dichlorobenzene（DCB）.An UV spectroscopy method for simultaneous determination of DCB,chlorobenzene（CB）and benzene（B）was established,in which the spectral interference from the nanoparticles could be effectively avoided.Besides,the method can be used to evaluate the reduction performance of the CMC/NFC-L-Ni/Fe catalyst.The optimum conditions of NaIO₄-NaClO₂ oxidation system were listed: reaction temperature 40℃,20mmol/g of NaClO₂ dosage,15mmol/g of acetic acid dosage（compared to never-dried bamboo pulp）,1 hour of reaction time.The FTIR,XRD and TEM analysis of NFC showed that the bamboo fiber after chemical oxidation pretreatment and ultrasonic treatment kept the basic crystal form of bamboo pulp and carboxyl group was introduced into the macromolecule chain of cellulose.The length of NFC is 100-200 nm and the width is 5 ± 2 nm,which showed large aspect ratio.CMC/NFC hydrogel was prepared by aldol condensation reaction.The results of TEM showed that CMC/NFC hydrogel was a successful carrier material,which played a good role in dispersing and preventing oxidation.The results of SEM show that there are many large pore structures in the CMC/NFC hydrogel.Then,the CMC/NFC-L-Ni/Fe catalyst was prepared in situ by chemical reduction in liquid phase.The SEM images showed that the Ni/Fe bimetallic particles were uniformly separated by hydrogel,the results of XRD showed that the CMC/NFC hydrogel still maintained the crystal structure of cellulose I,and the XRD pattern of CMC/NFC-L-Ni/Fe catalyst showed that NZVI has been successfully loaded on CMC/NFC hydrogel.Based on the quint-wavelength UV spectroscopy,a spectral method for simultaneous determination of DCB,CB and B was established,which avoided the spectral interference caused by the nano-bimetallic particles.So it determined the concentration of DCB,CB and B accurately in the solution for the dechlorination process of DCB reduced by nanoscale zero-valent Fe/Ni bimetal.CMC/NFC-L-Ni/Fe catalyst was used to dechlorinate o-DCB in simulated wastewater,The optimum reaction conditions of the reaction were listed: hydrogel loaded with Ni/Fe dosages 0.16 g/27 m L,Ni 9 wt%,pH 4-7.The experimental results showed that the initial concentration of o-DCB has little effect on the degradation rate,moreover,the higher reaction temperature can lead higher degradation efficiency.Besides,increasing the times of cyclic reactions can decrease the reaction activity of CMC/NFC-L-Ni/Fe catalyst.