Chitosan-polyvinyl alcohol-diatomite hydrogel removes methylene blue from water.

Dye pollution in the aquatic environment can harm ecosystems and human health. Here, we developed a new green adsorbent by applying an improved drying process. Diatomite was embedded in a network structure formed between chitosan and polyvinyl alcohol without using any crosslinking agent to prepare chitosan-polyvinyl alcohol-diatomite hydrogel beads through alkali solidification. The beads were tested for removing a cationic dye (methylene blue (MB)) from water. The structure of the adsorbent beads was analysed using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The adsorption capacity was investigated, and the results indicated excellent MB adsorption properties. The adsorbents had a rough surface and high swelling capacity of 66.9 g/g. The maximum MB adsorption capacity was 414.70 mg/g, and the adsorption followed the Freundlich isothermal and quasi-second-order kinetic models. The adsorption was an endothermic spontaneous process governed by both intra-particle and external diffusion processes. The proposed adsorption mechanisms involved hydrogen bonding and electrostatic interactions. These adsorbent beads have considerable application potentials owing to their high adsorption capacity, green composition, and non-polluting nature.

On the investigation of composite cooling/heating set gel systems based on rice starch and curdlan.

In pursuit of advancing the understanding of composite gel systems, this study delves into the intricate realm of rheology, structural elucidation, and mechanical attributes. Specifically, it scrutinizes the symbiotic interplay between rice starch, a cooling-set gel, and curdlan, a thermo-irreversible heating-set gel. A higher curdlan content enhances the inter-chain hydrogen bonding between rice starch and curdlan, resulting in a denser gel structure and thus increased moduli, solid-like behavior, and mechanical properties, and reduced frequency-dependence, especially at high temperatures (>65 °C). For example, with 50 % curdlan incorporation, G' (90 °C) improved by 252 %. Notably, thermal treatment can compromise the structural integrity of the rice starch gel, reducing strength and softening texture. However, this textural degradation can be effectively mitigated with, for example, 30 % curdlan incorporation, resulting in a 55-fold hardness increase at 85 °C. The knowledge gained from this work offers valuable guidance for tailoring starch-based gel products to specific properties.

Ultralight and highly efficient oil-water selective aerogel from carboxymethyl chitosan and oxidized ß-cyclodextrin for marine oil spill cleanup.

Biomass-based aerogels for oil spill cleanup have attracted tremendous research interests due to their feasibility in oil-water separation. However, the cumbersome preparation process and toxic cross-linking agents hinder their application. In this work, a facile and novel method to prepare hydrophobic aerogels is reported for the first time. Da-ß-CD/CMCS aerogel (DCA), Da-ß-CD/CMCS/PVA aerogel (DCPA), and hydrophobic Da-ß-CD/CMCS/PVA aerogel (HDCPA) were successfully synthesized via the Schiff base reaction between carboxymethyl chitosan (CMCS) and dialdehyde ß-cyclodextrin (Da-ß-CD). Meanwhile, polyvinyl alcohol (PVA) acted as reinforcement and hydrophobic modification was conducted via chemical vapor deposition (CVD). The structure, mechanical properties, hydrophobic behaviors and absorption performance of aerogels were comprehensively characterized. The results indicated that the DCPA containing 7 % PVA exhibited excellent compressibility and elasticity even at a compressive strain of ε = 60 %, however, the DCA without PVA showed incompressibility, suggesting that the important role played by PVA in improving compressibility. Moreover, HDCPA possessed excellent hydrophobicity (water contact angle up to 148.4°), which could be well maintained after experiencing wear and corrosion in harsh environments. HDCPA also possesses high absorption capacities (24.4-56.5 g/g) towards different oils with satisfied recyclability. These advantages endow HDCPA with great potential and application prospects in offshore oil spill cleanup.

Sugarcane cellulose-based composite hydrogel enhanced by g-C3N4 nanosheet for selective removal of organic dyes from water.

The effective removal of toxic dyes from aqueous solution is of great significance for environmental protection. Herein, an eco-friendly sugarcane cellulose (SBC)/sodium carboxymethylcellulose (CMC-Na) adsorbent reinforced with carbon nitride (g-C3N4) was successfully prepared via a facile sol-gel method. The resulting gel-like adsorbent or composite hydrogel was comprehensively characterized with FTIR, SEM, EDS, TGA analysis. The adsorption behaviors of the adsorbent in the removal of methylene blue (MB) were systematically investigated. Results showed the pseudo-second-order kinetic model and Langmuir model described adsorption process accurately with the maximum adsorption capacity of 362.3 mg g-1, indicating that adsorption behavior is a monolayer chemical adsorption. Moreover, the composited hydrogel displayed excellent adsorption selectivity on MB/MO or MB/RhB mixed dyes. In addition, adsorbent showed great stability and reusability with almost no loss in adsorption capacity after 7 cycles. Due to the facile preparation process and outstanding mechanical properties, as well as high recyclability, g-C3N4@SBC/CMC has great potential in wastewater treatment.

Cellulose-based antimicrobial films incroporated with ZnO nanopillars on surface as biodegradable and antimicrobial packaging.

Biodegradable and antimicrobial films without antibiotics are of great significance for the application associated with food packaging meanwhile minimizing the negative impact on environments. In this work, cellulose-based films with the surface tailor-constructed with ZnO nanopillars (ZnO NPs@Zn2+/Cel films) were prepared via chemical crosslinking in conjunction with a hydrothermal process for in-situ growth of ZnO NPs. As a packaging material, ZnO NPs@Zn2+/Cel films possess excellent mechanical properties, oxygen and water vapor barrier, food preservation, biodegradability and low Zn2+ migration. Moreover, ZnO NPs@Zn2+/Cel films show remarkable antimicrobial activity, especially for Staphylococcus aureus (gram-positive bacteria) and Escherichia coli (gram-negative bacteria). The antimicrobial mechanism of ZnO NPs@Zn2+/Cel films is studied using the controlled variable method, and results showed that the film without UV pretreatment killed bacterial cells mainly by mechanical rupture, while the film with UV pretreatment killed bacterial cells mainly via the synergistic effect of photocatalytic oxidation and mechanical rupture.

Novel multi-responsive and sugarcane bagasse cellulose-based nanogels for controllable release of doxorubicin hydrochloride.

Nanogel based on polysaccharides has attracted the tremendous interest due to its unique performance as drug carrier for in vivo release. In this work, the multi-responsive nanogels were developed based on the tailor-modified sugarcane bagasse cellulose (SBC). In the presence of crosslinking agent cystamine bisacrylamide (CBA), the in-situ free radical copolymerization of methacrylated monocarboxylic sugarcane bagasse cellulose (MAMC-SBC) and N-isopropylacrylamide (NIPAM) in aqueous phase was conducted, thus leading to redox, pH and thermal-responsive nanogels. The results obtained from FT-IR, SEM and particle sizer showed that the nanogels were highly stable with the desired particle size ranging from 90 to 180 nm and contained targeted polymeric segments and linkage for multi-responsivity. Doxorubicin hydrochloride (DOX) as a model drug was effectively loaded into the nanogels, partly driven by strong electrostatic association; and the loading efficiency reached up to 82.7%. Moreover, the drug release could be readily manipulated by the addition of reducing agent, pH and temperature, which is attributed to the multi-responsive behavior of nanogels as carrier and synergetic effects. The performance of nanogels was also governed by the ratio of reactive MAMC-SBC and NIPAM during polymerization; and the ratio at 1:1(wt) led to the optimal structure of nanogels.

Green-Based Antimicrobial Hydrogels Prepared from Bagasse Cellulose as 3D-Scaffolds for Wound Dressing.

Developing the ideal biomaterials for wound dressing still remains challenging nowadays due to the non-biodegradable features and the lack of antimicrobial activity of conventional synthetic polymer-based dressing materials. To tackle those problems, a novel and green-based antimicrobial hydrogel dressing was synthesized in this work via modifying sugarcane bagasse cellulose with guanidine-based polymer, followed by crosslinking antimicrobial-modified cellulose with unmodified one at various ratios. The resulting hydrogels were comprehensively characterized with swelling measurements, compression test, Fourier transform infrared spectroscopy, and scanning electron microscopy. The results indicated that the dressing possessed the degree of swelling up to 2000% and the compress strength as high as 31.39 Kpa, at 8:2 ratio of pristine cellulose to modified cellulose. The antibacterial activities of the dressing against E. coli were assessed using both shaking flask and ring diffusion methods. The results demonstrated that the dressings were highly effective in deactivating bacterium without leaching effect. Moreover, these hydrogels are biocompatible with live cell viability responses of (NIH3T3) cells above 76% and are very promising as wound dressing.

Novel cellulose/montmorillonite mesoporous composite beads for dye removal in single and binary systems.

Fine aminated cellulose/montmorillonite mesoporous composite beads (ACeMt) were prepared as green-based adsorbent via a novel approach utilizing ultra-fine calcium carbonate as a pore-forming agent to increase the porosity and specific surface area of ACeMt. The resulting bioadsorbent was characterized by means of SEM, FTIR and BET analysis and used for dye removal. Adsorption experimental data were fitted with various isotherm and kinetic models. The results indicated that chemical adsorption was the rate-limiting step. The maximum adsorption capacities of ACeMt, better described by Langmuir model, were much higher than those of conventional adsorbents, particularly for the removal of Auramine O dye (up to 1336.2 mg/g at 55 °C). The adsorptions at equilibrium were better correlated with Redlich-Peterson model and uncompetitive Langmuir isotherm model in single and binary system, respectively. Overall, ACeMt is a promising bioadsorbent and highly efficient in the removal of dyes for water clarification.

Dual-responsive IPN hydrogel based on sugarcane bagasse cellulose as drug carrier.

In this work, the stepwise synthesis of interpenetrating polymer network (IPN) strategy was developed in an attempt to fabricate novel hydrogels consisting of sugarcane bagasse cellulose (SBC), carboxymethylcellulose (CMC) and poly (N-isopropylacrylamide) (PNIPAm) as a dual-responsive drug carrier. The pretreated and dissolved SBC was pre-crosslinked using epichlorohydrin in the presence of CMC, followed by in-situ free-radical polymerization of NIPAm in the presence of N,N'-Methylene-bis(acrylamide) as a crosslinking agent. The carboxyl groups in CMC and PNIPAm chains rendered the resulting hydrogel pH and thermal responsive. The results from scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis and mechanical property testing demonstrated the successful formation of the IPN with proper structure and mechanical strength. The swelling experiments at different temperatures and pH showed the dual-sensibility of the hydrogels. Moreover, bovine serum albumin (BSA) was used as a model drug and loaded in the hydrogel; and the drug release behavior was revealed in phosphate buffer solution (PBS) and simulated gastric fluid (SGF). The results indicated that the dual-responsive IPN hydrogel is of great potential for the controlled release of drug.

Single and binary adsorption of heavy metal ions from aqueous solutions using sugarcane cellulose-based adsorbent.

A high efficient and eco-friendly sugarcane cellulose-based adsorbent was prepared in an attempt to remove Pb2+, Cu2+ and Zn2+ from aqueous solutions. The effects of initial concentration of heavy metal ions and temperature on the adsorption capacity of the bioadsorbent were investigated. The adsorption isotherms showed that the adsorption of Pb2+, Cu2+ and Zn2+ followed the Langmuir model and the maximum adsorptions were as high as 558.9, 446.2 and 363.3mg·g-1, respectively, in single component system. The binary component system was better described with the competitive Langmuir isotherm model. The three dimensional sorption surface of binary component system demonstrated that the presence of Pb2+ decreased the sorption of Cu2+, but the adsorption amount of other metal ions was not affected. The result from SEM-EDAX revealed that the adsorption of metal ions on bioadsorbent was mainly driven by coordination, ion exchange and electrostatic association.

Preparation of Copolymer-Based Nanoparticles with Broad-Spectrum Antimicrobial Activity.

Polyacrylate and guanidine-based nanoparticles which involve acrylate monomers and glycidyl methacrylate modified oligo-guanidine were prepared by a seeded semi-continuous emulsion polymerization. The results from transmission electron microscope and dynamic light scattering measurements showed that the nanoparticles were spherical in shape and the particle size was in the range of 80⁻130 nm. Antimicrobial experiments were performed with two types of bacteria, Gram-negative (Escherichia coli, ATCC 8739) and Gram-positive (Staphylococcus aureus, ATCC 6538). The as-synthesized cationic nanoparticles exhibited effective antimicrobial activities on Escherichia coli and Staphylococcus aureus with the minimal inhibitory concentrations at 8 µg/mL and 4 µg/mL, respectively. The mechanism of action of the resulted nanoparticles against these bacteria was revealed by the scanning electron microscopic observation. In addition, the films consisting of latex nanoparticles are non-leaching antimicrobial materials with excellent antimicrobial activity, which indicates the polymers could preserve their antimicrobial activity for long-term effectiveness.

Cellulose fibers modified with nano-sized antimicrobial polymer latex for pathogen deactivation.

Antimicrobial cellulose fibers and paper products are of great importance for various applications. In this work, novel core-shell antimicrobial latexes based on hydrophobic acrylate monomers and antimicrobial macromonomer (GPHGH) were successfully prepared via a seeded semi-continuous emulsion copolymerization in the presence of a cationic surfactant. The surface properties as well as size of latex were tailored by varying the amount of GPHGH incorporated during the copolymerization. The resulting cationic nano-sized latexes showed the strong adsorption and formed monolayer on the surfaces of bleached sulfite fibers, thus rendering the cellulose fibers antimicrobial. An excellent antimicrobial activity (>99.99% inhibition) of modified fiber toward Escherichia coli was achieved at 0.3wt% of latex dosage (on dry fibers). Results of transmission electron microscopy (TEM) observation confirmed that the particles obtained indeed possessed a desired core-shell structure. The latexes themselves exhibited high antimicrobial activities against E. coli with the minimum inhibitory concentration (MIC) as low as 6.25ppm (similar to that of pure guanidine-based polymer). Moreover, the mechanical strength of the hand-sheets made from latex-modified cellulose fibers was also improved due to the filming of the latex on fiber surfaces.