2-deoxy-d-glucose This present study was initiated to evaluate the bleaching

This present study was initiated to evaluate the bleaching efficiency and energy reduction achieved by H2O2 bleaching with added ultrasonication. The ultrasonic frequency range is beyond the capacity of human hearing, that is, frequencies higher than 16kHz (1600 cycles per second) [11]. Ultrasound can be used to perform heat transfer in liquids, and the bubbles generated by ultrasound-induced cavitation are used in cleaning applications. In addition, such ultrasound-cavitation can facilitate particle disintegration. Ultrasonication can produce morphological changes in fibers that can contribute to increased flexibility and improved bonding of the fibers during paper formation [12,13] and efficient bleaching of pulp. Therefore, the aim of this study was to investigate the effect of ultrasonication during H2O2 bleaching.

Materials and methods

Results and discussion

Conclusion
Ultrasonication was used included in a H2O2 bleaching process to improve the bleaching efficiency by adjustment of temperature and reaction time. In addition, MgSO4·7H2O was used as a bleaching stabilizer to prevent 2-deoxy-d-glucose degradation. The best pulp bleaching efficiency was obtained for a combined H2O2/ultrasonication (20kHz) bleaching system at 45°C for 30min. The ISO brightness of the bleached pulp increased by 1.9%, although the yield was slightly reduced to 1.5% as compared with that of the pulp bleached using H2O2 without ultrasonication. The optimum viscosity and yield for the bleached pulp were obtained at 2% MgSO4·7H2O consistency. Thus, the use of ultrasonic energy in bleaching systems has a positive effect: it reduces the treatment time and temperature of the bleaching and improves the optical properties of the pulp.

Acknowledgements

Introduction
Superparamagnetic iron oxide nanoparticles (SPION) are material of interest for biomedical research and related applications such as magnetic resonance imaging (MRI) contrast agent, biocatalyst, biomarker, biosensor, drug delivery and hyperthermia therapy [1–4]. For these functions, stable SPION is required [5]. However, owing to energetic surface of SPION, the nanoparticles usually agglomerate in ionic medium [6]. Surface modification of SPION with biocompatible material is one of the methods used to control problems related to agglomeration of SPION [7]. Silica nanoparticle is among the preferred inorganic materials employed to modify the surface of SPION. Silica surfaces are chemically stable, biocompatible and can be easily functionalized for bioconjugation purpose [8].
Recently, many routes such as sol–gel, microemulsion, combination of microemulsion and sol–gel, reverse micelles, wet impregnated and hydrothermal method [9–14] were used to synthesize iron oxide/silica composite nanoparticles. As shown in Table 1, the high saturation magnetization () value of the SPION is drastically reduced after their surface modification with silica.

Materials and method
Ferric chloride hexahydrate (FeCl2·4H2O 99%), Ferrous chloride (98%), ammonium hydroxide (25wt.%), sodium chloride salts, sodium hydroxide, 1-butanol (99%), triethoxyvinylsilane (TEVS 97%), and 1-Decanethiol (99%) were bought and used directly without any further purification from Sigma–Aldrich. The ultrasonic irradiation was carried out using 20kHz Vibra-Cell ultrasonic with 13mm diameter horn.

Result and discussion
It is well known that ultrasonic irradiation of liquid generates acoustic cavitation (formation, growth and collapse of bubbles in the liquid). The cavitation creates a unique interaction between energy and matter, with temperature, pressure and cooling rate of approximately 5000K, 1000atm and 1010Ks−1, respectively [21]. These extraordinary conditions permit access to wide range of chemical reactions and synthesis varieties of unusual nanostructured materials [22].
The dynamics of the growth and the collapse of cavity are dependent on local environment. The environment can either be homogenous liquid or heterogeneous solid–liquid interface. In homogenous liquid, spherical cavity is formed. Acoustic cavitation in homogenous liquid generates implosive bubble plus shock waves [23]. The shock waves produce high pressure with amplitudes exceeding 10kbar [24].