a b s t r a c tCellulose nanocrystals (CNs) were extracted from different sources by acid hydrolysis using H 2 SO 4 and HCl. The thermal decomposition of resulting CNs was studied by thermogravimetric analysis (TGA). The kinetic parameters were determined using the Flynn-Wall-Ozawa (FWO) and Kissinger methods. CNs were also characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM), elemental analysis (EA), Zeta Potential (ZP) and degree of polymerization (DP). The results of the XRD analysis showed different profiles, making it possible to differentiate cellulose I from cellulose II. The results obtained by the FWO method showed that cellulose II CNs had an increased activation energy (E a ) with conversion (˛), while in CNs of cellulose I the E a remained constant or decreased slightly. This difference between E a values for the thermal decomposition of CNs was mainly attributed to different crystalline arrangements of cellulose I and cellulose II, and to the type of acid employed.
The
work presented here aims to study and compare the performance
of a polyvinylidene fluoride (PVDF) electrospun membrane, unmodified
cellulose nanofiber (CNF) based PVDF membrane, and Meldrum’s
acid (2,2-dimethyl-1,3-dioxane-4,6-dione) modified CNF-based PVDF
membranes against the Fe2O3 nanoparticle filtration
and crystal violet (CV) dye adsorption. Herein, we introduced a facile
method to produce a unique green adsorbent material from cellulose
nanofibers (CNFs) via a nonsolvent assisted procedure using Meldrum’s
acid as an esterification agent to enhance the adsorption toward positively
charged crystal violet dyes. Most of the surface modifications of
cellulose nanofibers have been done using toxic organic solvents like
pyridine, dimethyl acetate, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl
(TEMPO), etc. So far, this is the first report on the surface modification
of cellulose nanofibers via a nonsolvent assisted procedure. Both
CNF-based PVDF membranes were prepared by successive coating of modified
and unmodified CNFs on to the surface of a PVDF electrospun membrane.
All the demonstrated membranes showed high filtration capacity against
the Fe2O3 nanoparticles. With the 10 mg/L of
crystal violet (CV) aqueous solution, CV adsorption of PVDF electrospun
membrane, and unmodified CNF-based PVDF membrane was around 1.368
and 2.948 mg/g of the membrane respectively, whereas it was 3.984
mg/g of the membrane by Meldrum’s acid CNF-based PVDF membrane.
The demonstrated Meldrum’s acid modified CNF-based PVDF membrane
was proven to be the efficient media that can concurrently eliminate
the Fe2O3 nanoparticles and CV dyes from the
water. The investigation into the surface chemistries of cellulose
nanofibers beyond the adoption of toxic solvents can enhance the economic
usefulness of the process and also yield a new ecofriendly adsorbent
material that is agreeable to adsorbing various toxic pollutants.
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