Cellulose Esterification with Octanoyl Chloride and its Application to Films and Aerogels

Homogeneous esterification of cellulose with octanoyl chloride (a long-chain fatty acid) was investigated in lithium chloride/N,N-dimethyl acetamide (LiCl/DMAc) medium. Cellulose was readily esterified by the octanoyl chloride, as shown by 1H NMR analysis. The effects of the ratio of octanoyl chloride to cellulose hydroxyl groups, the reaction temperature, and the reaction time on the yield and degrees of substitution (DS) of cellulose esters (CEs) were investigated. CEs with high DS (2.2) were achieved after 8 h at 100 °C with a 1.6 to 1.8 of molar ratio of octanoyl chloride to cellulose hydroxyl groups. Furthermore, hydrophobic, fully transparent CE films and aerogels were prepared using CE tetrahydrofuran (THF) solutions. The CE aerogels exhibited high porosity and were formed with evenly distributed porosity, as revealed by scanning electron microscopy (SEM)

Graphene Oxide-Based Fe–Mg (Hydr)oxide Nanocomposite as Heavy Metals Adsorbent

A novel adsorbent for divalent metal cations was prepared as nanocomposite of Fe–Mg (hydr)­oxide with graphene oxide by one-step coprecipitation. This material showed adsorption selectivity of Pb²⁺ > Cu²⁺ > Ag⁺ > Zn²⁺ ≫ Co²⁺, Ni²⁺, Cd²⁺ with high adsorption capacity of 100–600 mg/g for Pb²⁺, Cu²⁺, Ag⁺, and Zn²⁺. Distribution coefficient (<i>K</i>_d) was as high as ∼10⁷ mL/g for Pb²⁺ and Cu²⁺. The adsorption isotherms for Pb²⁺, Cu²⁺, Ag⁺, and Zn²⁺ followed the Langmuir model, indicating monolayer adsorption. The adsorption kinetics for Pb²⁺, Cu²⁺, Ag⁺, and Zn²⁺ followed pseudo-second-order model, suggesting chemisorption. Removal of 50 ppm Pb²⁺ or Cu²⁺ from 100 mL solution by 0.1 g of the nanocomposite was over 99.7%. The thermodynamics studies implied that the adsorption process toward heavy metals was spontaneous and endothermic. Together with recyclability through magnetic separation, this adsorbent would be useful in polluted water processing

Extraordinary Reinforcement Effect of Three-Dimensionally Nanoporous Cellulose Gels in Poly(ε-caprolactone) Bionanocomposites

Three-dimensionally nanoporous cellulose gels (NCG) were prepared by dissolution and coagulation of cellulose from aqueous alkali hydroxide-urea solution, and used to fabricate NCG/poly­(ε-caprolactone) (PCL) nanocomposites by in situ ring-opening polymerization of ε-CL monomer in the NCG. The NCG content of the NCG/PCL nanocomposite could be controlled between 7 and 38% v/v by changing water content of starting hydrogel by compression dewatering. FT-IR and solid-state ¹³C NMR showed that the grafting of PCL onto cellulose are most likely occurred at the C6-OH groups and the grafting percentage of PCL is 25 wt % for the nanocomposite with 7% v/v NCG. ¹H NMR, XRD, and DSC results indicate that the number-average molecular weight and crystal formation of PCL in the nanocomposites are remarkably restricted by the presence of NCG. AFM images confirm that the interconnected nanofibrillar cellulose network structure of NCG are finely distributed and preserved well in the PCL matrix after polymerization. DMA results show remarkable increase in tensile storage modulus of the nanocomposites above glass transition and melting temperatures of the PCL matrix. The percolation model was used to evaluate the mechanical properties of the nanocomposites, in which stress transfer among the interconnected nanofibrillar network is facilitated through strong intermolecular hydrogen bonding and entanglement of cellulose nanofibers