Stability improvement of carboxymethyl cellulose/chitosan complex beads by thermal treatment.

Carboxymethyl cellulose (CMC) and chitosan (CHI) are two well-known natural polymer derivatives, as such the CMC@CHI complex beads fulfill many requirements for bio-related and safety-required applications. However, poor mechanical properties of CMC@CHI beads hinder their applications. We managed to improve the beads stability by a simple thermal treatment during the bead preparation. The effects of temperature, changing from 25 °C to 75 °C, on the stability of the formed beads were investigated. The morphology, diameter, shell thickness and structure of the beads treated at different temperature were analyzed using SEM, XPS and FTIR. The mechanical test and swelling experiments showed that the thermal treatment enhanced the bead's ability to withstand pressure and swelling. The beads treated at 75 °C showed the best pressure resistance, while the beads treated at 55 °C exhibited the highest swelling capability without losing integrity. This method is convenient to implement, not only improves the stability, but also controls the swelling capacity and mechanical properties of the beads, which are important for their potential applications in adsorption and controlled release. More importantly, this work offered insights on the effects of thermal treatment on the complexation process of the two polysaccharide molecular chains.

The change from hydrophilicity to hydrophobicity of HEC/PAA complex membrane for water-in-oil emulsion separation: Thermal versus chemical treatment.

Recently, the growing environmental concerns and economic demands drive the need to develop effective solutions for the treatment of oily wastewater, especially for oil/water emulsions. In this work, hydroxyethyl cellulose (HEC) and poly(acrylic acid) (PAA) are selected to form a complex membrane on the surface of poly(ethylene terephthalate) (PET) nonwoven via layer-by-layer assembly for separation of water-in-oil emulsions. In order to obtain a hydrophobic surface, two post-treatment methods, thermally and chemically induced cross-linking, are applied to modify the hydrogen-bonded HEC/PAA complex membrane. The properties of the two treated HEC/PAA-PET membranes, including surface morphology, chemical structure, chemical composition, thermal stability, mechanical property, and membrane wettability are systematically studied and compared to each other. When the membranes are applied as oil filters to treat water-in-oil emulsions with different concentrations, both of the modified membranes show excellent separation efficiencies with a more than 99.4% rejection for all tested water-in-oil emulsions.

Complex Aerogels Generated from Nano-Polysaccharides and Its Derivatives for Oil-Water Separation.

The complex aerogel generated from nano-polysaccharides, chitin nanocrystals (ChiNC) and TEMPO-oxidized cellulose nanofibers (TCNF), and its derivative cationic guar gum (CGG) is successfully prepared via a facile freeze-drying method with glutaraldehyde (GA) as cross-linkers. The complexation of ChiNC, TCNF, and CGG is shown to be helpful in creating a porous structure in the three-dimensional aerogel, which creates within the aerogel with large pore volume and excellent compressive properties. The ChiNC/TCNF/CGG aerogel is then modified with methyltrichlorosilane (MTCS) to obtain superhydrophobicity/superoleophilicity and used for oil-water separation. The successful modification is demonstrated through FTIR, XPS, and surface wettability studies. A water contact angle of 155° on the aerogel surface and 150° on the surface of the inside part of aerogel are obtained for the MTCS-modified ChiNC/TCNF/CGG aerogel, resulting in its effective absorption of corn oil and organic solvents (toluene, n-hexane, and trichloromethane) from both beneath and at the surface of water with excellent absorption capacity (i.e., 21.9 g/g for trichloromethane). More importantly, the modified aerogel can be used to continuously separate oil from water with the assistance of a vacuum setup and maintains a high absorption capacity after being used for 10 cycles. The as-prepared superhydrophobic/superoleophilic ChiNC/TCNF/CGG aerogel can be used as a promising absorbent material for the removal of oil from aqueous media.

Manipulating the surface wettability of polysaccharide based complex membrane for oil/water separation.

The treatment of oily wastewater is a global challenge owing to its diverse repercussions on environment and human life. The nanoporous complex membrane consisted of cellulose nanocrystals (CNC), chitin nanocrystals (ChiNC) and chitosan (CH) is fabricated on top of the poly (ethylene terephthalate) (PET) nonwoven fabric via a vacuum-assisted filtration method. The interactions among CNC, ChiNC and CH cause the formation of the membrane which shows underoil superhydrophobic property. The CH is demonstrated to play a key role in contributing to the hydrophobicity of membrane. Without any further treatment, the CNC/ChiNC/CH membrane is capable to separate water from water-in-oil emulsion with a high rejection. The separation performance is affected by the thickness of the prepared membrane which directly relates to the concentrations of the complex solutions. Such polysaccharide-based complex membranes with facile fabrication and low cost are promising for use in the field of oil/water separation.

Cellulose derivative-lanthanide complex film by hierarchical assembly process.

Carboxymethylcellulose (CMC), quaternized cellulose (QC) and lanthanide (Ln) ion ternary complex thin film was fabricated by hierarchical assembly process. CMC is a weak anionic polyelectrolyte while QC is a cationic polyelectrolyte. Strictly controlling pH value and molar ratio, CMC and Ln ion were prepared into polymer-metal complex nano-particles (CMC@Ln) which exhibit negative charge on surface, and then the nano-particles were layer-by-layer (LbL) assembled with positively charged QC to prepare thin films. Three kinds of Ln ion, Ce3+, Eu3+, and Tb3+ were successfully incorporated into films separately, and the corresponding films showed blue, green and red fluorescence color. In addition, we can adjust the luminescence of the film with combination of CMC@Ce, CMC@Eu, and CMC@Tb complex nano-particles.