Preparation And Application Of Nanocellulose-based Superhydrophobic Materials

In nature,there are many superhydrophobic phenomena,which essentially require micro nano double rough structure and low surface energy substance.Therefore,the use of biomimetic principles to design and fabricate new superhydrophobic materials is one of the hot topics in recent years.In this work,nanocellulose based superhydrophobic multifunctional materials were prepared by using nanocellulose as the raw material due to superhydrophobic materials may have great application prospect in industry and daily life.It can provide a feasible way for high value utilization of nanocellulose.（1）Nanocellulose can be extracted from lignocellulosic biomass and before the extraction,lignin,which is a kind of biomass resource as well,should be separated as a precondition.Therefore,the application of lignin-based hydrogel and nanocellulose aerogels in wastewater treatment was studied.Firstly,the lignin hydrogel was prepared by using sodium lignosulfonate as raw material,and its adsorption behavior against MB was analyzed.The maximal equilibrium adsorption capacity of MB was up to 2013 mg?g^-1.The adsorption isotherm and kinetics fit the Freundlich model and the Pseudo-second-order model well,respectively.Secondly,nanocellulose-based aerogels with low density(2.0-16.7 mg?cm^-3)and high porosity（99.9%-98.9%）were prepared through the reconstruction of“three-dimensional network”by using the TEMPO-mediated oxidation nanocellulose（TOCN）as raw materials.And then the TOCN aerogels were silanized using methyltrimethoxysilane（MTMS）.The results showed that the static contact angle of MTMS-modified TOCN aerogels was146.3°-150.8°,and had good hydrophobic and lipophilic properties.MTMS-modified TOCN aerogels had high adsorption capacity for vacuum pump oil and olive oil,and their equilibrium adsorption capacities were as high as 140 g?g^-1 and 179.1 g?g^-1,respectively.The adsorption kinetics conformed to the Pseudo-2^nd-order kinetics model.The as prepared TOCN aerogels had good reusability,after 6 times of repeated use still maintain the original adsorption capacity.Thus,the TOCN hydrophobic aerogels are expected to be applied to oil-water separation,and be a new adsorbent for solving oil spill pollution（2）Magnetic-responsive TOCN aerogel（MGTOCN）was prepared in situ loading of Cu_xCo_1-xFe₂O₄ magnetic nanoparticles on the TOCN aerogels surface by hydrothermal method.And then the magnetic aerogels were hydrophobized by vapor deposition.The prepared MGTOCN aerogels showed good adsorption capacity for the treatment of oily wastewater,and organic solvent adsorption.These magnetic nanoparticles not only provide magnetic response properties,but also improve the roughness of the MGTOCN aerogel surface with water contact angle were greater than 150°,showing excellent hydrophobic properties.The equilibrium adsorption capacity of vacuum pump oil and olive oil were 49.8g·g^-1-73.5 g·g^-1 and 53.2 g·g^-1-81.4 g·g^-1,respectively.The experimental adsorption kinetics conformed to the Pseudo-2^nd-order kinetics model.Moreover,the MGTOCN aerogel showed excellent adsorption capacity for different types of oily substances and organic solvents,and had a good reusability.After 12 times repeated use still maintain the original adsorption capacity.（3）The cellulose membrane with carboxyl groups（TOCM-COOH）was prepared by TEMPO--mediated oxidation cellulose（TOC）.Then,the SiO₂ nanoparticles（SiO₂ NPs）were modified by KH550 and KH560 to obtained amino-functionalized silica nanoparticles（amino-SiO₂ NPs,260 nm diameter）and epoxy-functionalized silica nanoparticles（epoxy-SiO₂ NPs,30 nm diameter）,respectively.The amino-SiO₂ NPs grafted onto the TOCM surface through a standard amidation reaction between the amino groups of the SiO₂NPs and the carboxyl groups of the TOCM surface in the presence of EDC and NHS consequently forming a first layer of large（260 nm）nanoparticles.Subsequently,it was reacted with smaller（30 nm）epoxy-SiO₂ NPs.Continuous repetitions of these alternating sized silica NPs through a standard Lb L approach lead to a highly micro/nano-texturized TOCM,which was ultimately sealed with a layer of hydrophobic PFOTES（1H,1H,2H,2H-perfluorooctyltriethoxysilane）.It was found that at five layers deep of NPs,it became superhydrophobic as evidenced by a water contact angle of 151±2°and slide angle of 4°.It was also noted that these superhydrophobic-MNOCM materials displayed good self-cleaning.（4）TOCN-based micro-nano particles（TOCNmp）were prepared by reconstructing the micro-nano structure of TOCN by solid-liquid two-phase separation method.It was found that the prepared TOCNmp had a micro-size and nanometer fold,which was similar to that of rose petal structure.It was a kind of micro-nano dual structure particles.Then,the TOCNmp-superhydrophobic coatings were prepared by mixing TOCNmp with MTMS and PDMS（Polydimethylsiloxane）.The utility model TOCNmp-superhydrophobic coatings can endue the filter paper excellent super hydrophobic property with contact angle was up to 157°and slide angle of 10°.Meanwhile,the paper retained its own filtering function,can be applied to the oil-water separation process,and showed a good oil-water separation characteristic.Moreover,the TOCNmp-superhydrophobic coating was a kind of wear-resistant,acid resistant coating.This coating can also endue the surface of wood and glass superhydrophobic characteristics.Therefore,the superhydrophobic coatings prepared in this experiment had a wide range of applications.（5）The fluorescent-superhydrophobic bifunctional nanocellulose-based micro-nano particles（FTOCNmp）were successfully prepared.Firstly,the fluorescent-nanocellulose（FTOCN）were prepared by fluorescence modification of TOCN by 5-（4,6-dichlorotriazine）amino fluorescein（DTAF）.Then,FTOCN-based micro-nano particles were prepared（FTOCNmp）.The FTAR and XPS spectrum confirmed that DTAF was successfully grafted onto TOCN.The prepared FTOCNmp coating was not only a coating with fluorescent anti-counterfeiting function,but also a coating with superhydrophobic function.The FTOCNmp coating can produce fluorescence emission peaks at about 477 nm under the excitation of 455nm.Moreover,FTOCNmp coating can endue paper,wood chips and glass excellent superhydrophobic properties,and the contact angles were 159°,151°and 164°,respectively.