Lingbin Lu

Heat insulation performance, mechanics and hydrophobic modification of cellulose-SiO2 composite aerogels.

Cellulose-SiO2 composite hydrogel was prepared by combining the NaOH/thiourea/H2O solvent system and the immersion method with controlling the hydrolysis-fasculation rate of tetraethyl orthosilicate (TEOS). The hydrophobic composite aerogels were obtained through the freeze-drying technology and the cold plasma modification technology. Composite SiO2 could obviously reduce the thermal conductivity of cellulose aerogel. The thermal conductivity could be as low as 0.026 W/(mK). The thermal insulation mechanism of the aerogel material was discussed. Composite SiO2 reduced hydrophilicity of cellulose aerogel, but environmental humidity had a significant influence on heat insulation performance. After hydrophobic modification using CCl4 as plasma was conducted, the surface of composite aerogel was changed from hydrophilic to hydrophobic and water contact angle was as high as 132°. The modified composite aerogel still kept good heat insulation performance. This work provided a foundation for the possibility of applying cellulose-SiO2 composite aerogel in the insulating material field.

Clean and rapid synthesis of double metal cyanide complexes using mechanochemistry

A novel and green chemistry technique is presented for the synthesis of double metal cyanide (DMC) complexes that are further used for the copolymerization of CO2 and propylene oxide. The catalytic activity and selectivity are improved by this strikingly efficient and practically applicable method. The mechanosynthesis of DMC reveals clear merits.

An environment-friendly and multi-functional absorbent from chitosan for organic pollutants and heavy metal ion.

Developing environment-friendly green absorbents for disposal of wastewater remains to be studied. In this paper, the cross-linked chitosan aerogel (CsA) as an environment-friendly absorbent was obtained by a simple method involving cross-linked process and freeze drying technique. Compared with conventional absorbents, the porous chitosan aerogel was provided with unique properties such as low density (0.0283g/cm(3)), high porosity (97.98%) and outstanding adsorption performance. The chitosan aerogel also displayed good reusability and excellent elasticity with a maximal thickness recovery up to 96.8% of the original thickness. The as-prepared absorbent exhibited preferable adsorption capacities for crude oil, diesel and copper ion (41.07g/g, 31.07g/g and 21.38mg/g, respectively). The aerogel can collect a wide range of organic solvents and oils with absorption capacities up to 40 times their own weight, depending on the density and viscosity of the liquids. The adsorption capacity for heavy metal ion was also considerable and the maximum adsorption capacity (qm) of the aerogel for copper ion was 35.08mg/g according to Langmuir isotherm model. Consequently, the chitosan aerogel with versatile adsorption properties has a good potential for wastewater treatment in environmental application.

On preparation, structure and performance of high porosity bulk cellulose aerogel

Abstract A novel approach has been applied in preparing cellulose aerogel foams by combining NaOH/ thiourea/ H2O solvent system and the freeze drying technology. The improvement involved adding 60°C ethanol during the formation process of cellulose hydrogel. The effects of the solvent system on the structure and heat insulation performance of aerogel were studied. The gelation time reduced 63% and the mechanical strength of hydrogel reinforced 2·3% with 60°C ethanol. The optimal ratio of the solvent system for cellulose was NaOH 9·5 wt-%, thiourea 4·5 wt-%. Under this condition, the obtained cellulose aerogel have a density range between 0·2 to 0·4 g cm−3, and the porosity up to 84·88%. Cellulose aerogel had good heat insulation performance with the lowest thermal conductivity only 0·029 W m K−1. This work provided an effective preparation method for high porosity bulk cellulose aerogel, and showed the application potential of cellulose aerogel as insulation materials in the medium low thermal insulation field.

Mechanical reinforcement of a cellulose aerogel with nanocrystalline cellulose as reinforcer

As an environmentally friendly aerogel with outstanding performances, the improvement of mechanical properties is urgently required for cellulose aerogel development. In this study, a cellulose aerogel with good mechanical properties was successfully fabricated using nanocrystalline cellulose (NCC) as reinforcer. Characterization results demonstrated that NCC was embedded well into the cellulose aerogel. Tests and evaluation showed that the compressive modulus of the NCC reinforced cellulose aerogel was significantly improved, about 6 times higher than that of the pure cellulose aerogel. Furthermore, after modification with trimethylchlorosilane via a cold plasma treatment, the NCC reinforced aerogel became hydrophobic but its oleophilic property remained. This aerogel showed good adsorption capacity, reached saturation rapidly and possessed good reusability. Reinforced mechanical properties with NCC make this cellulose aerogel a very promising material for highly efficient separation and extraction of organic pollutants and oils from water.

Converting untreated waste office paper and chitosan into aerogel adsorbent for the removal of heavy metal ions

The utilization of waste paper, an obsolete recyclable resource, helps to save resources and protect environment. In this paper, an aerogel was prepared to convert the waste paper into a useful material, which was used to adsorb heavy metal ions and handle water pollution. Combining waste office paper and chitosan, the aerogel obtained the enhanced mechanical strength, acid resistance and high adsorption capacity (up to 156.3 mg/g for Cu2+). This adsorption process obeyed the pseudo-second order model and the Langmuir model. The research showed that a coordination compound was formed between amino group and Cu2+ during the adsorption process. The adsorbent could be regenerated well in 0.1 M H2SO4 with up to 98.3% desorption efficiency. The low cost, environmental friendliness, excellent adsorption capacity and regeneration ability made this novel aerogel a promising adsorbent for heavy metal ions. And this conversion is an effective reuse way of waste paper too.

Excellent reusable chitosan/cellulose aerogel as an oil and organic solvent absorbent

Absorption is one of the most important methods for oil spill cleanup. An ideal absorbent is expected to possess advantages of low cost, green, high absorption capacity and excellent reusability. In this paper, a new kind of cellulose aerogel was successfully fabricated via cellulose oxidation, crosslinking, freeze drying and cold plasma modification. The obtained aerogel (water contact angle up to 152.8°) exhibited outstanding oil/water selectivity and high absorption capacity (13.77-28.20 g/g) for various oils and organic solvents. Whats more, this kind of aerogel could be reused by simple compression. The absorption-desorption process could be repeated for at least 50 cycles. Through the kinetic analysis, it was found that the pseudo-second order model was more appropriate for the aerogels oil absorption process. Owing to its low cost, hydrophobicity, high absorption capacity and excellent reusability, this kind of aerogel is expected to be used in oils and organic solvents spill cleanup and oil/water separation field.

Dual responsive intelligent aerogel made from thermo/pH sensitive graft copolymer ALG-g-P(NIPAM-co-NHMAM) for drug controlled release

Alginate was grafted with NIPAM and NHMAM successfully, and a new responsive copolymer, alginate-g-P(NIPAM-co-NHMAM), was obtained. A novel dual responsive polysaccharide-based aerogel with thermo/pH sensitive properties was designed from the copolymer as drug controlled release system. The chemical structure of the copolymer was characterized by FT-IR and 1H NMR. Lower critical solution temperature (LCST) of the copolymer covered a wide temperature range from 27.6 °C to 42.2 °C, which could be adjusted with changing the ratio between NIPAM and NHMAM. The dual responsive aerogel had a three-dimensional network structure. As a drug controlled release system, the aerogel was high responsive to both temperature and pH with drug loading efficiency up to 13.24%. Above LCST, the aerogel had a faster drug release, and drug was completely released in neutral environment, while the drug release was obstructed in acid environment. Furthermore, the drug release mechanism of the aerogel was illuminated. These results indicated that the dual responsive aerogel was a promising candidate for drug carriers.